As an immunodepressant, anti-CD25 monoclonal antibody has a huge market with wide prospect and economic value. We developed a low protein serum-free medium for large-scale GS-NS0 myeloma cell culture and anti-CD25 monoclonal antibody... more
As an immunodepressant, anti-CD25 monoclonal antibody has a huge market with wide prospect and economic value. We developed a low protein serum-free medium for large-scale GS-NS0 myeloma cell culture and anti-CD25 monoclonal antibody production. Further study focused on the characteristics of GS-NSO cell growth, glucose and amino acid metabolism, and antibody production. In the serum-free medium, the maximal viable cell density and antibody concentration reached above 3x10(6) cells/mL and 300 mg/L in batch culture. Compared with the commercial serum-free medium (Excell 620 + 0.2% Primatone), the maximal viable cell density doubled and the maximal antibody concentration increased 46%. Results also showed the specific growth rate decreased when the glucose concentration was lower than 6 mmol/L. And the production of lactate increased when glucose concentration was excessively high (> 30 mmol/L). These results were important to provide technique and theory basis for developing optim...
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Additional file 2: Fig. S1. Effects of uridineâ s feed concentration on cell growth and cell viability. a Viable cell density; b cell viability. Blank diamond control cultures; Blank circle 0.6 mM uridine fed; Blank triangle 6 mM uridine... more
Additional file 2: Fig. S1. Effects of uridineâ s feed concentration on cell growth and cell viability. a Viable cell density; b cell viability. Blank diamond control cultures; Blank circle 0.6 mM uridine fed; Blank triangle 6 mM uridine fed; Blank square 30mM uridine fed. The error bars indicate the standard deviations from three independent experiments.
Additional file 1: Table S1. Reactions in the simplified biochemical network. Table S2. Kinetic results in different cultures.
In recent years, there are tremendous economic and social losses across the world because of virus-related diseases. It is well known that Madin-Darby canine kidney (MDCK) cells are easily handled, quickly amplified and efficiently... more
In recent years, there are tremendous economic and social losses across the world because of virus-related diseases. It is well known that Madin-Darby canine kidney (MDCK) cells are easily handled, quickly amplified and efficiently infected with influenza virus. Therefore, they are considered as one of the most important cell lines for the production of influenza vaccine. In this work, we first developed a serum-free adherent culture process for MDCK cells with an in-house prepared serum-free medium MDCK-SFM. Next, we derived a cell line named ssf-MDCK, which was amenable for single-cell suspension culture in the serum-free medium. We found that during serum-free batch culture of MDCK cells, the peak viable cell density and maximum specific growth rate were 3.81 x 10(6) cells/mL and 0.056 h(-1), respectively; 3.6- and 1.6-fold increase compared with those in serum-containing adherent batch culture. In addition, we compared growth and metabolic characteristics of MDCK cells in serum-...
Research Interests: Technology, Biology, Medicine, Biological Sciences, Dogs, and 2 moreAnimals and Influenza vaccines(Animals and Influenza vaccines)
(Animals and Influenza vaccines)
Dissolved oxygen (DO) and shear stress have pronounced effects on hyaluronic acid (HA) production, yet various views persist about their effect on the molecular weight of HA. Accordingly, this study investigated the effects of DO and... more
Dissolved oxygen (DO) and shear stress have pronounced effects on hyaluronic acid (HA) production, yet various views persist about their effect on the molecular weight of HA. Accordingly, this study investigated the effects of DO and shear stress during HA fermentation. The results showed that both cell growth and HA synthesis were suppressed under anaerobic conditions, and the HA molecular mass was only (1.22+/-0.02) x 106 Da. Under aerobic conditions, although the DO level produced no change in the biomass or HA yield, a high DO level favored the HA molecular mass, which reached a maximum value of (2.19+/- 0.05) x 106 Da at 50% DO. Furthermore, a high shear stress delayed the rate of HA synthesis and decreased the HA molecular weight, yet had no clear effect on the HA yield. Therefore, a high DO concentration and mild shear environment would appear to be essential to enhance the HA molecular weight.
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Stirred culture offers a number of advantages over static systems as it maintains a stable, homogeneous culture environment and is easy to scale-up. This paper focused on the development and application of stirred tank bioreactor to... more
Stirred culture offers a number of advantages over static systems as it maintains a stable, homogeneous culture environment and is easy to scale-up. This paper focused on the development and application of stirred tank bioreactor to culture hematopoietic cells. Preliminary study of stirred culture of hematopoietic cells was carried out in cord blood mononuclear cells culture in spinner flask. The results showed that the amplification rates of total cell, CFU-GM and BFU-E, with the exception of CFU-Mk, were greater in spinner flask than T-flask. The number of total cells increased 20 fold after 14 days incubation in spinner flask. The amplification rates of CFU-GM, CFU-Mk and BFU-E reached maximum at 10th day, 10th day and 7th day respectively, and the maximal amplification rates were 9.2-fold, 5.5-fold and 2.4-fold respectively, whereas the rate of CD34+ cells in spinner flask was (6.7 +/- 4.0)-fold at day 10. These results indicated that the stirred culture system is better than th...
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Epigallocatechin-3-gallate (EGCG) is a kind of flavonoids and has the ability to promote differentiation of mesenchymal stem cells (MSCs) into osteoblasts. However, the EGCG is easily metabolized by cells during cell culture, which... more
Epigallocatechin-3-gallate (EGCG) is a kind of flavonoids and has the ability to promote differentiation of mesenchymal stem cells (MSCs) into osteoblasts. However, the EGCG is easily metabolized by cells during cell culture, which reduces its bioavailability. Therefore, in this paper, EGCG-loaded chitosan nanoparticles (ECN) were fabricated and entrapped into chitosan/alginate (CS/Alg) scaffolds to form CS/Alg-ECN scaffolds for improving the bioavailability of EGCG. The human umbilical cord mesenchymal stem cells (HUMSCs) were cultured on CS/Alg-ECN scaffolds to induce osteogenic differentiation. The results indicated that the CS/Alg-ECN scaffolds continuously released EGCG for up to 16 days. Besides, these results suggested that CS/Alg-ECN scaffolds promoted osteoblast differentiation through activating Wnt/β-catenin signaling pathway. Collectively, this study demonstrated that the entrapment ECN into CS/Alg scaffolds was a promising strategy for promoting osteogenesis of MSCs.
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Tyrosine (Tyr) is crucial to the maintenance of the monoclonal antibody (mAb) titers and quality attributes in fed-batch cultures of recombinant Chinese hamster ovary (rCHO) cells. However, the relation between tyrosine and these aspects... more
Tyrosine (Tyr) is crucial to the maintenance of the monoclonal antibody (mAb) titers and quality attributes in fed-batch cultures of recombinant Chinese hamster ovary (rCHO) cells. However, the relation between tyrosine and these aspects is not yet fully defined. In order to further elucidate such a relation, two groups of fed-batch experiments with high tyrosine (H-T) or low tyrosine (L-T) additions producing an IgG1 monoclonal antibody against CD20 were implemented to investigate the intracellular and extracellular effects of tyrosine on the culture performance. It was found that the scarcity of tyrosine led to the distinctive reduction in both viable cell density and antibody specific production rate, hence the sharply reduced titer, possibly related to the impaired translation efficiency caused by the substrate limitation of tyrosine. In addition, alterations to the critical quality attributes were detected in the L-T group, compared to those in the H-T condition. Notable decrease in the contents of intact antibody was found under the L-T condition because of the elevated reductive level in the supernatant. Moreover, the aggregate content in the L-T condition was also reduced, probably resulting from the accumulation of extracellular cystine. In particular, the lysine variant content noticeably increased with tyrosine limitation owing to the downregulation of two carboxypeptidases, i.e., CpB and CpH. Overall, understanding the role of tyrosine in these aspects is fundamental to the increase of product titers and control of critical quality attributes in the monoclonal antibody production of rCHO cell fed-batch cultures. • Tyrosine is essential in the maintenance of product titers and the control of product qualities in high cell density cultivations in rCHO cell. • This study revealed the bottleneck of decreased qmAbupon the deficiency of tyrosine. • The impact of tyrosine on the critical product qualities and the underlying mechanisms were also thoroughly assessed.
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H9N2 subtype avian influenza virus poses a constant threat to the poultry industry and the control of the disease leans upon the use of effective vaccines. As an alternative to the conventional chicken embryonated eggs, animal cell... more
H9N2 subtype avian influenza virus poses a constant threat to the poultry industry and the control of the disease leans upon the use of effective vaccines. As an alternative to the conventional chicken embryonated eggs, animal cell culture could overcome the limitations of egg supplies and upgrade the manufacturing of avian influenza vaccines for poultry. Development of serum-free suspension cell culture could allow even higher virus productivity, where a suspension cell line with good growth and production performance is required. In this work, an adherent MDCK cell line was adapted to suspension growth to cell concentration up to 12 × 106 cells/mL in a serum-free medium in batch cultures. Subsequently, the influenza virus propagation in this MDCK cell line was evaluated and was improved with the medium exchange at time of infection as well as optimization of infection conditions in terms of MOI and cell concentration for infection. Furthermore, various feed strategies were tested ...
Abstract Bioartificial liver (BAL) comprising a functional bioreactor represents a promising treatment, bridging patients with acute liver failure (ALF) to liver transplantation. In this research, a packed-bed (PB) bioreactor by utilizing... more
Abstract Bioartificial liver (BAL) comprising a functional bioreactor represents a promising treatment, bridging patients with acute liver failure (ALF) to liver transplantation. In this research, a packed-bed (PB) bioreactor by utilizing galactosylated poly(ethylene terephthalate) microfibrous carrier (PET-Gal) was fabricated and evaluated in vitro. Human induced hepatocytes (hiHeps) were dynamically seeded into a PET-Gal loaded bioreactor and cultured for 10 days. During perfusion culture, the effects of bioreactor scaffold on hepatocyte seeding, growth and functionality (albumin secretion and urea production) were determined, compared with that of control with non-modified PET carrier. Afterwards, drug metabolism and detoxification ability of hiHeps were measured. Results demonstrated that the seeding rate and proliferation fold within PET-Gal loaded bioreactor were significantly higher than that of control, resulting in a cell density of (8.17 ± 0.52)×107 cells/cm3. In contrast to flattened morphology observed in the control, hiHeps cultured in PET-Gal based bioreactor displayed as three-dimensional (3D) cell aggregates with close cell-matrix and cell-cell interactions and high cell viability, leading to higher albumin secretion and urea production. Besides, there were high levels of phase I drug metabolism and ammonia elimination for PET-Gal cultured cells. Therefore, the PET-Gal based PB bioreactor fabricated herein supports high-density hepatocyte growth and meanwhile preserves hepatic functionality, showing great potential in BAL systems application.
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The miRNA-based strategy has been used to develop live attenuated influenza vaccines. In this study, the nucleoprotein (NP) genome segment of the influenza virus was inserted by different perfect miRNA-192-5p target sites, and the virus... more
The miRNA-based strategy has been used to develop live attenuated influenza vaccines. In this study, the nucleoprotein (NP) genome segment of the influenza virus was inserted by different perfect miRNA-192-5p target sites, and the virus was rescued by standard reverse genetics method, so as to verify the virulence and protective efficacy of live attenuated vaccine in cells and mice. The results showed there was no significant attenuation in 192t virus with one perfect miRNA-192-5p target site, and 192t-3 virus with three perfect miRNA target sites. However, 192t-6 virus with 6 perfect miRNA target sites and 192t-9 virus with 9 perfect miRNA target sites were both significantly attenuated after infection, and their virulence were similar to that of temperature-sensitive (TS) influenza A virus (IAV) which is a temperature-sensitive live attenuated influenza vaccine. Mice were immunized with different doses of 192t-6, 192t-9, and TS IAV. Four weeks after immunization, the IgG in serum ...
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As the composition of animal cell culture medium becomes more complex, the identification of key variables is important for simplifying and guiding the subsequent medium optimization. However, the traditional experimental design methods... more
As the composition of animal cell culture medium becomes more complex, the identification of key variables is important for simplifying and guiding the subsequent medium optimization. However, the traditional experimental design methods are impractical and limited in their ability to explore such large feature spaces. Therefore, in this work, we developed a NRGK (nonparametric regression with Gaussian kernel) method, which aimed to identify the critical components that affect product titres during the development of cell culture media. With this nonparametric model, we successfully identified the important components that were neglected by the conventional PLS (partial least squares regression) method. The superiority of the NRGK method was further verified by ANOVA (analysis of variance). Additionally, it was proven that the selection accuracy was increased with the NRGK method because of its ability to model both the nonlinear and linear relationships between the medium components...
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Background and Aims Bioartificial livers (BALs) have attracted much attention as potential supportive therapies for liver diseases. A serum-free microcarrier culture strategy for the in vitro high-density expansion of human-induced... more
Background and Aims Bioartificial livers (BALs) have attracted much attention as potential supportive therapies for liver diseases. A serum-free microcarrier culture strategy for the in vitro high-density expansion of human-induced hepatocyte-like cells (hiHeps) suitable for BALs was studied in this article. Methods hiHeps were transdifferentiated from human fibroblasts by the lentiviral overexpression of FOXA3 , HNF1A , and HNF4A . Cells were cultured on microcarriers, their proliferation was evaluated by cell count and CCK-8 assays, and their function was evaluated by detecting liver function parameters in the supernatant, including urea secretion, albumin synthesis, and lactate dehydrogenase levels. The expressions of hepatocyte function-associated genes of hiHeps were measured by qRT-PCR in 2D and 3D conditions. The expression of related proteins during fibronectin promotes cell adhesion, and proliferation on microcarrier was detected by western blotting. Results During microcarrier culture, the optimal culture conditions during the adherence period were the use of half-volume high-density inoculation, Cytodex 3 at a concentration of 3 mg/mL, a cell seeding density of 2.0 × 10 5 cells/mL, and a stirring speed of 45 rpm. The final cell density in self-developed, chemically defined serum-free medium (SFM) reached 2.53 × 10 6 cells/mL, and the maximum increase in expansion was 12.61-fold. In addition, we found that fibronectin (FN) can promote hiHep attachment and proliferation on Cytodex 3 microcarriers and that this pro-proliferative effect was mediated by the integrin-β1/FAK/ERK/CyclinD1 signaling pathway. Finally, the growth and function of hiHeps on Cytodex 3 in SFM were close to those of hiHeps on Cytodex 3 in hepatocyte maintenance medium (HMM), and cells maintained their morphology and function after harvest on microcarriers. Conclusions Serum-free microcarrier culture has important implications for the expansion of a sufficient number of hiHeps prior to the clinical application of BALs.
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The insufficient vascularization is a major challenge in bone tissue engineering, leading to partial necrosis of the implant. Pre-vascularization is a promising way via in vitro cells co-culture strategies using osteogenic cells and... more
The insufficient vascularization is a major challenge in bone tissue engineering, leading to partial necrosis of the implant. Pre-vascularization is a promising way via in vitro cells co-culture strategies using osteogenic cells and vasculogenic cells, and the cross-talk of cells is essential. In the present study, the effect of rat bone-marrow derived mesenchymal stem cells (BMSCs) on angiogenic capability of human umbilical vein endothelial cells (HUVECs) in growth medium (GM) and osteogenic induction medium (OIM) was investigated. It was demonstrated that cells co-cultured in OIM showed high efficiency in osteogenesis but failed to form capillary-like structure while the results of co-culture in GM were the opposite. By comparing the angiogenic capacity of co-cultures under GM and OIM, chemokine (C-X-C motif) ligand 9 (Cxcl9), secreted by BMSCs in OIM, was identified to be an angiostatic factor to counter-regulate vascular endothelial growth factor (VEGF) and prevent its binding to HUVECs, which abrogated angiogenesis of MSCs-ECs co-culture. Moreover, Cxcl9 was proved to suppress the osteogenic differentiation of BMSCs monoculture. The molecular mechanism of Cxcl9 activation in BMSCs involved mTOR/STAT1 signaling pathway. Therefore, blocking this signaling pathway via rapamycin addition resulted in the inhibition of Cxcl9 and improvement of osteogenic differentiation and angiogenic capacity of co-culture in OIM. These results reveal that Cxcl9 is a negative modulator of angiogenesis and osteogenesis, and its inhibition could promote pre-vascularized of bone tissue engineering.
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Tyrosine (Tyr), as one of the least soluble amino acids, is essential to monoclonal antibody (mAb) production in recombinant Chinese hamster ovary (rCHO) cell cultures since its roles on maintaining the specific productivity (qmAb) and... more
Tyrosine (Tyr), as one of the least soluble amino acids, is essential to monoclonal antibody (mAb) production in recombinant Chinese hamster ovary (rCHO) cell cultures since its roles on maintaining the specific productivity (qmAb) and avoiding Tyr sequence variants. To understand the effects of Tyr on cell performance and its underlying mechanisms, rCHO cell–producing mAbs were cultivated at various cumulative Tyr addition concentrations (0.6 to 5.5 mM) in fed-batch processes. Low Tyr concentrations gave a much lower peak viable cell density (VCD) during the growth phase and also induced rapid cell death and pH decrease during the production phase, resulting in a low efficient fed-batch process. Autophagy was initiated following the inhibition of mTOR under the Tyr starvation condition. Excessive autophagy subsequently induced autophagic cell death, which was found as the major type of cell death in this study. Additionally, the results obtained here demonstrate that the decrease in culture pH under the Tyr starvation condition was associated with the autophagy and such pH drop might be attributed to the lysosome acidification and cell lysis.
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Sialylation affects circulating half-life, charge distribution, and other biochemical properties of therapeutic glycoproteins. Loss of protein sialylation during glycoprotein-producing bioprocesses could lead to a low final protein... more
Sialylation affects circulating half-life, charge distribution, and other biochemical properties of therapeutic glycoproteins. Loss of protein sialylation during glycoprotein-producing bioprocesses could lead to a low final protein sialylation level and bring negative effects on subsequent clinical efficacy. In this work, an Fc-fusion protein-producing Chinese hamster ovary cell fed-batch culture process was studied and insights into the loss of protein sialylation during the Fc-fusion protein production phase (days 5 to 13) were presented. The results showed that the decreased total sialic acid content was 13.84 μg/mg during the production phase, which accounted for 24% of the total sialic acid content on day 5. The lost sialic acids were predominantly from α 2-3 sialylation on N- and O-glycans. Through cell-free incubation and kinetics studies, it was found that the decreased sialic acid content caused by extracellular sialic acid degradation and incomplete glycan biosynthesis were 7.79 μg/mg and 6.05 μg/mg, respectively. The two processes had a nearly equal contribution to the loss of final product sialylation. Detailed characterizations revealed that decreases in sialic acid content were due either to extracellular sialic acid degradation via hydrolysis of α 2-3 sialic acids probably by released cytosolic sialidase or to a lack of galactosylated glycan availability for sialylation during late-stage glycosylation. Our work provides a better understanding of losses in protein sialylation during glycoprotein manufacturing.
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Ex vivo expansion is an effective strategy to acquire cytokine-induced killer (CIK) cells needed for clinical trials. In this work, the effects of dynamic suspension culture, which was carried out by shake flasks on a shaker, on CIK cells... more
Ex vivo expansion is an effective strategy to acquire cytokine-induced killer (CIK) cells needed for clinical trials. In this work, the effects of dynamic suspension culture, which was carried out by shake flasks on a shaker, on CIK cells were investigated by the analysis of expansion characteristics and physiological functions, with the objective to optimize the culture conditions for ex vivo expansion of CIK cells. The results showed that the expansion folds of total cells in dynamic cultures reached 69.36 ± 30.36 folds on day 14, which were significantly higher than those in static cultures (9.24 ± 1.12 folds, P < 0.05), however, the proportions of CD3+ cells and CD3+CD56+ cells in both cultures were similar, leading to much higher expansion of CD3+ cells and CD3+CD56+ cells in dynamic cultures. Additionally, expanded CIK cells in two cultures possessed comparable physiological functions. Notably, significantly higher percentages of CD25+ cells and CD69+ cells were found in dynamic cultures (P < 0.05). Besides, much higher glucose consumption rate of cells (P < 0.05) but similar YLac/gluc were observed in dynamic cultures. Further, cells in dynamic cultures had better glucose utilization efficiency. Together, these results suggested that dynamic cultures improved cell activation, then accelerated glucose consumption rate, which enhanced cell expansion and promoted glucose utilization efficiency of cells.
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To explore the impact of taurine on monoclonal antibody (mAb) basic charge variants in Chinese hamster ovary (CHO) cell culture. In fed-batch culture, adding taurine in the feed medium slightly increased the maximum viable cell density... more
To explore the impact of taurine on monoclonal antibody (mAb) basic charge variants in Chinese hamster ovary (CHO) cell culture. In fed-batch culture, adding taurine in the feed medium slightly increased the maximum viable cell density and mAb titers in CHO cells. What's more, taurine significantly decreased the lysine variant and oxidized variant levels, which further decreased basic variant contents from 32 to 27%. The lysine variant content in the taurine culture was approximately 4% lower than that in control condition, which was the main reason for the decrease in basic variants. Real-time PCR and cell-free assay revealed that taurine played a critical role in the upregulation of relative basic carboxypeptidase and stimulating extracellular basic carboxypeptidase activities. Taurine exhibits noticeable impact on lower basic charge variants, which are mainly due to the decrease of lysine variant and oxidized protein variants.
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A packed-bed (PB) bioreactor for bioartificial liver (BAL) was fabricated based on an optimum two-stage culture strategy and evaluated in vitro in this research. Human induced hepatocytes (hiHeps) were first expanded using Cytodex 3... more
A packed-bed (PB) bioreactor for bioartificial liver (BAL) was fabricated based on an optimum two-stage culture strategy and evaluated in vitro in this research. Human induced hepatocytes (hiHeps) were first expanded using Cytodex 3 microcarriers and the choice of microcarrier concentration and fetal bovine serum (FBS) content was optimized. Then, the cells expanded under the optimum expansion condition were perfused into a perfusion system containing Fibra-Cel (FC) disks to fabricate a PB bioreactor. Operating parameters including flow rate and seeding density for perfusion culture were optimized, respectively. Results indicated that during suspension culture, rapid cell proliferation and favorable amino acid metabolism were achieved at 3 mg/mL microcarriers combined with 1% FBS. While for the perfusion culture, the most effective flow rate and seeding density were 2 mL/min and 1 × 10 cells/mL, respectively. Under this optimum perfusion condition, hiHeps showed good proliferation a...
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To explore the influence of ultra-low carbon dioxide partial pressure (pCO) on the monoclonal antibody (mAb) N-glycosylation profile in Chinese hamster ovary (CHO) cell culture. In fed-batch bioreactor cultures, lowering the pCO in the... more
To explore the influence of ultra-low carbon dioxide partial pressure (pCO) on the monoclonal antibody (mAb) N-glycosylation profile in Chinese hamster ovary (CHO) cell culture. In fed-batch bioreactor cultures, lowering the pCO in the medium (< 25 mmHg) via increasing headspace aeration decreased the cell viability and mAb production in CHO cells. Additionally, mAb galactosylation under low pCO was approximately 27.45 ± 2.13%, noticeably higher than that observed under normal pCO (21.36 ± 1.66%) at harvest. However, all of the relevant intracellular nucleotide sugar concentrations were dramatically decreased to approximately 50% of the levels found under normal pCO on day 7. Real-time PCR revealed that the upregulation of galactosylation-related glycosyltransferase genes and substrate transporter genes played a critical role in the improved galactosylation under the ultra-low pCO condition. In the bioreactor culture processes, ultra-low pCO demonstrated a positive effect on mAb ...
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For successful engineering of pre-vascularized bone tissue , understanding the interactions between vasculogenic cells and bone-forming cells is a prerequisite. Mounting evidence indicates that microRNAs can serve as intercellular signals... more
For successful engineering of pre-vascularized bone tissue , understanding the interactions between vasculogenic cells and bone-forming cells is a prerequisite. Mounting evidence indicates that microRNAs can serve as intercellular signals that allow cell-cell communication. Here, the role of the transfer of the microRNA miR-200b between vasculogenic and osteogenic cells was explored in a co-culture system. Rat bone-marrow derived mesenchymal stem cells (BMSCs) formed functional gap junctions composed of connexin 43 (Cx43, also known as GJA1) with human umbilical vein endothelial cells (HUVECs), through which miR-200b could transfer from BMSCs to HUVECs to regulate osteogenesis and angiogenesis. As a negative regulator, the decrease in miR-200b level in BMSCs derepressed the expression of VEGF-A, leading to increased osteogenic differentiation. Once inside HUVECs, miR-200b reduced the angiogenic potential of HUVECs through downregulation of , , and Additionally, TGF-β was found to tr...
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Hydrolysates play important roles in enhancing the productivity of recombinant proteins in mammalian cell cultures. Lacking of detailed understanding of the mechanisms, hydrolysate is commonly regarded as an unstable factor which should... more
Hydrolysates play important roles in enhancing the productivity of recombinant proteins in mammalian cell cultures. Lacking of detailed understanding of the mechanisms, hydrolysate is commonly regarded as an unstable factor which should be used with cautions. A yeast extract (YE) was approved to improve the Fc-fusion protein productivity in a recombinant Chinese hamster ovary (CHO) cell line. To elucidate the responses of cells to hydrolysates, we further elaborate their physiological changes during the processes in the presence and absence of YE. Firstly, cell sizes and the cellular components including dry cell weight, cellular fatty acid, and total cellular protein were increased in the presence of YE. Then, by comparing the extracellular and intracellular concentrations of the main metabolites and their consumption rates, we excluded the possibility of nutrient depletion in the absence of YE and observed a distinct improvement on the net consumption rates of metabolites in the p...
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Human amniotic membrane-derived mesenchymal stem cells (hAMSCs) draw great interests for regenerative medicine due to convenient availability and low immunogenicity. However, suboptimal culture conditions limit their application. In... more
Human amniotic membrane-derived mesenchymal stem cells (hAMSCs) draw great interests for regenerative medicine due to convenient availability and low immunogenicity. However, suboptimal culture conditions limit their application. In recent years, small molecules have proven powerful in regulating stem cell fates and can be applied to stimulate their function. In the present study, the impacts of sodium butyrate (NaBu), a histone deacetylase inhibitor (HDACi), on hAMSCs were investigated. It was shown that NaBu at a low concentration inhibited cell proliferation by arresting cell cycle at G0/G1 rather than inducing apoptosis. When NaBu was supplemented at a concentration of <1.0 mM for 3 days during osteogenic induction, significantly more mineralized nodules were generated and the expression of osteogenesis-related genes (ALP, Runx2, Opn, and Ocn) and proteins (Col1a1, OPN, OCN, Runx2, and TAZ) were both significantly enhanced. However, a higher concentration (1.0 mM) and longer ...
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Charge variation is one of the most important heterogeneities during monoclonal antibody (mAb) manufacturing and this study presents insights into the generation of acidic charge variants during cell culture processes. Since acidic... more
Charge variation is one of the most important heterogeneities during monoclonal antibody (mAb) manufacturing and this study presents insights into the generation of acidic charge variants during cell culture processes. Since acidic variants generate both intracellularly and extracellularly, main charge fraction collected by weak cation exchange chromatography (WCX) was incubated in harvested cell supernatant (HCS) to simulate and investigate the extracellular process firstly. It is found that the main fraction was degraded rapidly into acidic variants rather than basic variants extracellularly, and the degradation sites were located in both Fab and Fc fragments indicated by papain digestion. Besides, certain process parameters were investigated as their potential roles in the extracellular process. As a result, media composition showed significant influence on degradation while culture time point did not, suggesting that the extracellular process was a spontaneous process without en...
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Abstract Leptospirillum ferriphilum ( L . ferriphilum ) is a widely used microorganism in the commercial biooxidation process. Its ability to adhere to sulfide ores when grown in sulfide mineral substrates is very important for the entire... more
Abstract Leptospirillum ferriphilum ( L . ferriphilum ) is a widely used microorganism in the commercial biooxidation process. Its ability to adhere to sulfide ores when grown in sulfide mineral substrates is very important for the entire biooxidation process. However, few studies have investigated the ore adhesion properties of L . ferriphilum . In this paper, the effects of temperature, pH and the passive layer of the sulfide ore surface on the ore adherence properties and biooxidation capacities of L . ferriphilum LJ02, which was screened by our laboratory, were investigated. The results of these experiments showed that both the contact and non-contact leaching mechanism were evident during the sulfide biooxidation process. L . ferriphilum LJ02 preferred the contact leaching mechanism to the non-contact leaching mechanism. Within the experimental range of temperatures from 36 °C to 46 °C, the OAR (ore adhesion ratio) of L . ferriphilum LJ02 increased initially and then decreased with the temperature. The optimum OAR was 0.84 at 41 °C. Within the experimental pH range of 1.1 to 2.0, the OAR of L . ferriphilum LJ02 decreased with pH. The optimum OAR was 0.87 at pH 1.1. It was also found that the OAR of L . ferriphilum LJ02 could be reduced by the passive layer on the surface of the sulfide ore, which was generated during the biooxidation process. Moreover, it seems that the OAR of L . ferriphilum LJ02 was proportional to the sulfide biooxidation efficiency.
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Coculture between mesenchymal stem cells (MSCs) and chondrocytes has significant implications in cartilage regeneration. However, a conclusive understanding remains elusive. Previously, we reported that rabbit bone marrow-derived MSCs... more
Coculture between mesenchymal stem cells (MSCs) and chondrocytes has significant implications in cartilage regeneration. However, a conclusive understanding remains elusive. Previously, we reported that rabbit bone marrow-derived MSCs (rbBMSCs) could downregulate the differentiated phenotype of rabbit articular chondrocytes (rbACs) in a non-contact coculture system for the first time. In the present study, a systemic investigation was performed to understand the biological characteristics of chondrocytes in coculture with MSCs. Firstly, cells (MSCs and chondrocytes) from different origins were cocultured in transwell system. Different chondrocytes, when cocultured with different MSCs respectively, consistently demonstrated stimulated proliferation, transformed morphology and declined glycosaminoglycan secretion of chondrocytes. Next, cell surface molecules and the global gene expression of rbACs were characterized. It was found that cocultured rbACs showed a distinct surface molecule profile and global gene expression compared to both dedifferentiated rbACs and rbBMSCs. In the end, cocultured rbACs were passaged and induced to undergo the chondrogenic redifferentiation. Better growth and chondrogenesis ability were confirmed compared with control cells without coculture. Together, chondrocytes display comprehensive changes in coculture with MSCs and the cocultured rbACs are beneficial for cartilage repair.
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Cellular behaviors can be affected by both surface chemistry and topography of biomaterials substrates. The object of the present study was to investigate how pore structure and bioactive molecules regulate the adhesion and proliferation... more
Cellular behaviors can be affected by both surface chemistry and topography of biomaterials substrates. The object of the present study was to investigate how pore structure and bioactive molecules regulate the adhesion and proliferation of rabbit bone marrow-derived mesenchymal stem cells (rMSCs) in synergy. Poly(ε-caprolactone) (PCL) films with a honeycomb-like porous structure were fabricated via a breath-figure method, and then further coated with bioactive molecules including four combinations of polyelectrolytes (GEL/CS, GEL/HA, CHI/CS and CHI/HA) via a layer-by-layer self-assembly (LBL) process. rMSCs were seeded on these films to evaluate both adhesion and proliferation. It was shown that a uniform honeycomb-like porous structure with a pore size of 18.87±3.25μm was obtained in the films. Bioactive molecules were proven to be successfully deposited on the films, the amount of which increased with the number of assembled layer. Both surface pore structure and assembled molecu...
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Slow vascularization often impedes the viability and function of engineered bone replacements. Prevascularization is a promising way to solve this problem. In this study, a new process was developed by integrating microcarrier culture and... more
Slow vascularization often impedes the viability and function of engineered bone replacements. Prevascularization is a promising way to solve this problem. In this study, a new process was developed by integrating microcarrier culture and coculture to fabricate pre-vascularized bone microtissues with mesenchymal stem cells (MSCs) and human umbilical vein endotheli-al cells (HUVECs). Initially, coculture medium and cell ratio between MSCs and HUVECs were optimized in tissue culture plates concerning cell proliferation, osteogenesis and angiogenesis. Subsequently, cells were seeded onto CultiSpher S microcarriers in spinner flasks and subjected to a two-stage (prolifera-tive-osteogenic) culture process for 4 weeks. Both cells proliferated and functioned well in chosen medium and a 1 : 1 ratio between MSCs and HUVECs was chosen for better angiogenesis. After 4 weeks of culture in spinner flasks, the mi-crotissues were formed with high cellularity, evenly distributed cells and tube form...
Research Interests: Chemistry, Biotechnology, Industrial Biotechnology, Medicine, Environmental Biotechnology, and 10 moreBone Regeneration, Cell Differentiation, Humans, Medical Biotechnology, Osteogenesis, Cell Proliferation, Bone and Bones, Mesenchymal Stromal Cells, coculture techniques, and Human Umbilical Vein Endothelial Cells
Charge variants, especially acidic charge variants, of recombinant monoclonal antibodies are the major critical quality attributes in the biotechnology industry due to their potential influence on stability and biological activity. The... more
Charge variants, especially acidic charge variants, of recombinant monoclonal antibodies are the major critical quality attributes in the biotechnology industry due to their potential influence on stability and biological activity. The chemical properties of the acidic charge variants have been challenging to fully characterize, and it is critical for process development and optimization. To completely understand the multiple sources of acidic charge variants, the major charge forms of an IgG1 monoclonal antibody were firstly isolated and then analyzed by a battery of characterization tools. It was found that various degrees of disulfide bond reduction, the deamination of HC-T8 Asn84 and HC-T35 Asn388 and aggregation account for the majority of acidic charge heterogeneity and the terminal galactosylation content was in relation to the acidic charge heterogeneity. The correlation between acidic charge heterogeneity and galactosylation content was further explored by weak cation excha...
Research Interests: Mass Spectrometry, Multidisciplinary, Animals, Surface plasmon resonance, Monoclonal Antibodies, and 9 moreHigh Pressure Liquid Chromatography, Applied Microbiology and Biotechnology, Monoclonal Antibody, Recombinant Proteins, Hydrogen-Ion Concentration, Enzyme Linked Immunosorbent Assay, immunoglobulin G, CHO cells, and Cricetinae
Coculture between mesenchymal stem cells (MSCs) and articular chondrocytes (ACs) represents a promising strategy for cartilage regeneration. This study aimed at elaborating how ACs were regulated by MSCs. Rabbit ACs (rACs) and rabbit MSCs... more
Coculture between mesenchymal stem cells (MSCs) and articular chondrocytes (ACs) represents a promising strategy for cartilage regeneration. This study aimed at elaborating how ACs were regulated by MSCs. Rabbit ACs (rACs) and rabbit MSCs (rMSCs) were seeded separately in a Transwell system to initiate non-contact coculture in growth medium without chondrogenic factors. Cell morphology, cell proliferation, production of extracellular matrix (ECM), and gene expression of rACs were characterized. Upon coculture, rACs underwent a morphological transition from a rounded or polygonal shape into a fibroblast-like one and proliferation was provoked simultaneously. Such effects were dependent on the amount of rMSCs. Along with these changes, ECM production and gene expression of rACs were also perturbed. Importantly, when a ROCK inhibitor (Y27632) was supplemented to coculture, the effects except that on cell proliferation were inhibited, suggesting the involvement of RhoA/ROCK signaling. B...
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Charge variants, especially acidic charge variants, in recombinant monoclonal antibodies are critical quality attributes, which can affect antibodies' properties in vitro and in vivo. Meanwhile, charge variants are cumulative effects... more
Charge variants, especially acidic charge variants, in recombinant monoclonal antibodies are critical quality attributes, which can affect antibodies' properties in vitro and in vivo. Meanwhile, charge variants are cumulative effects of various post-translational modifications and chemical degradations on antibody. In this work, to investigate the effect of lowering culture pH in the stationary phase on acidic charge variant contents in fed-batch cultures and its mechanism, cell culture experiments in 2-L bioreactors were firstly performed to explore the changes in the charge distribution under the pH downshift condition using weak cation exchange chromatography. It is found that acidic charge variant contents were significantly decreased by pH downshift. Then, to reveal the mechanism by which the content of acidic charge variants is reduced under pH downshift condition, the variation of post-translational modifications and chemical degradations under the pH downshift condition ...
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Physiochemical properties of biomaterials play critical roles in dictating types of cell behaviour. In this study, a series of poly(ε-caprolactone) (PCL)-derived polymers bearing different small chemical groups was employed as a platform... more
Physiochemical properties of biomaterials play critical roles in dictating types of cell behaviour. In this study, a series of poly(ε-caprolactone) (PCL)-derived polymers bearing different small chemical groups was employed as a platform to evaluate chondrogenesis of different cell types. Thin films were prepared by spin-coating PCL derivatives. Rabbit articular chondrocytes (rACs) and rabbit bone marrow-derived mesenchymal stem cells (rMSCs) were seeded on to the films, and cell adhesion, proliferation, extracellular matrix production and gene expression were evaluated. The presence of hydrophilic groups (-NH2 , -COOH, -OH and -C=O) promoted adhesion and proliferation of primary rACs and rMSCs. On these polymeric films, chondrogenesis of primary rACs depended on culture time. For passaged cells, re-differentiation was induced on these films by chondrogenic induction, but less for cells of passage 5 compared to passage 3. While films with hydrophilic groups favoured chondrocytic gen...
Research Interests: Chemistry, Cell Adhesion, Medicine, Extracellular Matrix, Cell Differentiation, and 12 moreAnimals, Glycosaminoglycans, Articular Cartilage Wear, Chondrocytes, Chondrogenesis, Cell Proliferation, Rabbits, Polyesters, Biocompatible Materials, Mesenchymal Stromal Cells, Biochemistry and cell biology, and Tissue Scaffolds
Oxygen tension is an important factor that regulates hematopoietic stem cells (HSCs) in both in vivo hematopoietic microenvironment and ex vivo culture system. Although the effect of oxygen tension on ex vivo expansion of HSCs was... more
Oxygen tension is an important factor that regulates hematopoietic stem cells (HSCs) in both in vivo hematopoietic microenvironment and ex vivo culture system. Although the effect of oxygen tension on ex vivo expansion of HSCs was extensively studied, there were no clear descriptions on physiological function and gene expression analysis of HSCs under different oxygen tensions. In this study, the effects of oxygen tension on ex vivo expansion characteristics of human umbilical cord blood (UCB)-derived CD34+ cells were evaluated. Moreover, the physiological function of expanded CD34+ cells was assessed by secondary expansion ability ex vivo and hematopoietic reconstitution ability in vivo. Also, genetic profiling was applied to analyze the expression of genes related to cell function. It was found that low oxygen tension favored expansion of CD34+CD38- cells. Additionally, CD34+ cells expanded under low oxygen tension showed better secondary expansion ability and reconstitution abili...
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Biomaterial properties play significant roles in controlling cellular behaviors. The objective of the present study was to investigate how pore size and surface chemistry of three-dimensional (3D) porous scaffolds regulate the fate of... more
Biomaterial properties play significant roles in controlling cellular behaviors. The objective of the present study was to investigate how pore size and surface chemistry of three-dimensional (3D) porous scaffolds regulate the fate of mesenchymal stem cells (MSCs) in vitro in combination. First, on poly(ε-caprolactone) (PCL) films, the hydrolytic treatment was found to stimulate the adhesion, spreading and proliferation of human MSCs (hMSCs) in comparison with pristine films, while the aminolysis showed mixed effects. Then, 3D porous PCL scaffolds with varying pore sizes (100-200μm, 200-300μm and 300-450μm) were fabricated and subjected to either hydrolysis or aminolysis. It was found that a pore size of 200-300μm with hydrolysis in 3D scaffolds was the most favorable condition for growth of hMSCs. Importantly, while a pore size of 200-300μm with hydrolysis for 1h supported the best osteogenic differentiation of hMSCs, the chondrogenic differentiation was greatest in scaffolds with a pore size of 300-450μm and treated with aminolysis for 1h. Taken together, these results suggest that surface chemistry and pore size of 3D porous scaffolds may potentially have a synergistic impact on the behaviors of MSCs.
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Development of serum-free suspension cell culture processes is very important for influenza vaccine production. Previously, we developed a MDCK suspension cell line in a serum-free medium. In the present study, the growth kinetics of... more
Development of serum-free suspension cell culture processes is very important for influenza vaccine production. Previously, we developed a MDCK suspension cell line in a serum-free medium. In the present study, the growth kinetics of suspension MDCK cells and influenza virus production in the serum-free medium were investigated, in comparison with those of adherent MDCK cells in both serum-containing and serum-free medium. It was found that the serum-free medium supported the stable subculture and growth of both adherent and suspension cells. In batch culture, for both cell lines, the growth kinetics in the serum-free medium was comparable with those in the serum-containing medium and a commercialized serum-free medium. In the serum-free medium, peak viable cell density (VCD), haemagglutinin (HA) and median tissue culture infective dose (TCID50) titers of the two cell lines reached 4.51×106 cells/mL, 2.94Log10(HAU/50 μL) and 8.49Log10(virions/mL), and 5.97×106 cells/mL, 3.88Log10(HA...
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ABSTRACT
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Metabolic analysis for medium optimization represents a very useful strategy in the process development of production of vaccines in cells. During influenza vaccine production, viruses hijack host cells and take advantage of host's... more
Metabolic analysis for medium optimization represents a very useful strategy in the process development of production of vaccines in cells. During influenza vaccine production, viruses hijack host cells and take advantage of host's metabolism. As a consequence, the nutritional demand of host cells should undergo a profound change, and usually more nutrients such as glucose and amino acids should be consumed. As such, the maintaining media used in virus production processes often cannot provide sufficient nutrients, and novel methods are urged to be established to address this severe issue of nutritional limitation. A detailed study on impacts of influenza virus on cell death and metabolism, with a profound analysis of nutritional requirements during virus production process, followed by a rational medium optimization is expected to be the most straightfoward and effective strategy. This would ensure a balanced and adequate nutritional supply, which should minimize cell death and...
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Stem cell factor (SCF) is essential in the haematopoietic stem cells (HSCs) niche, and is therefore used extensively in haematopoietic stem and progenitor cells (HSPCs) ex vivo expansion. However, in the literature, dose and schedule of... more
Stem cell factor (SCF) is essential in the haematopoietic stem cells (HSCs) niche, and is therefore used extensively in haematopoietic stem and progenitor cells (HSPCs) ex vivo expansion. However, in the literature, dose and schedule of SCF feeding varies widely. We previously proposed a novel SCF feeding regimen with proven effectiveness for HSPCs expansion; however, physiological function of expanded cells with this SCF feeding regimen required further research. CD34(+) cells were cultured with or without SCF supplementation in serum-free medium for 10 days. Expanded cells were transplanted into sublethally irradiated non-obese diabetic/severe combined immune-deficient (NOD/SCID) mice. Engraftment and multilineage reconstitution of transplanted cells were determined. Also, clonogenic potential of engrafted cells was analysed. Cells, both cultured with and without SCF supplementation, successfully engrafted and reconstituted blood cell lineages in NOD/SCID mice. However, level of e...
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Sialic acid levels of therapeutic glycoprotein play an important role in plasma half-life. An undesirable decrease of sialic acid content was observed when we increased Fc-fusion protein productivity fourfold in a GS-CHO cell line by... more
Sialic acid levels of therapeutic glycoprotein play an important role in plasma half-life. An undesirable decrease of sialic acid content was observed when we increased Fc-fusion protein productivity fourfold in a GS-CHO cell line by bioprocess optimization. We investigated the potential mechanism for the sialic acid content reduction. We found that limited nucleotide sugar precursor and the extracellular sialidase were not responsible for the reduction of the sialic acid content after titer improvement. Oligosaccharide analysis revealed that the lack of protein galactosylation was the potential cause for the reduction of sialic acid content. Thus we validated this notion by evaluated galactose supplementation in 2 L bioreactors. Cell culture performance was not impacted by addition of up to 40 mM galactose except for the glucose consumption rate. Addition of 20 mM galactose to the bioreactor resulted in the increase of 44 % for total sialic acid content and 20.3 % for sialylated glycans. These data were further validated when the process was run on 200 L scaled bioreactor. These data together show that the galactosylation plays an apparent role in sialylation in our current system.
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The mononuclear cells were cultivated in stirred flasks at different agitation speeds of 30 rpm, 45 rpm, 60 rpm and 80 rpm. At the agitation speed of 30 rpm, total cells achieved higher expansion folds and the CFC density increased. When... more
The mononuclear cells were cultivated in stirred flasks at different agitation speeds of 30 rpm, 45 rpm, 60 rpm and 80 rpm. At the agitation speed of 30 rpm, total cells achieved higher expansion folds and the CFC density increased. When at higher agitation speed of 60 rpm or 80 rpm, the number of cells dropped rapidly and characteristics of hematopoietic stem/progenitor cells (HSPCs) were not maintained. Moreover, the culture duration of 6-9 days was better for HSPCs ex vivo expansion. These data indicated that HSPCs should be cultured at relatively low agitation speed and for a short-term period when cultured in stirred suspension system.
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To investigate the effects of ex-vivo expansion on proliferative ability, pluripotentiality and other biologic characteristics of human bone marrow mesenchymal stem cells(MSCs). MSCs were isolated from human costal bone and passaged under... more
To investigate the effects of ex-vivo expansion on proliferative ability, pluripotentiality and other biologic characteristics of human bone marrow mesenchymal stem cells(MSCs). MSCs were isolated from human costal bone and passaged under the same culture conditions. At each passage, the characteristics of proliferation kinetics, osteogenic, chondrogenic, adipogenic differentiation potential were analyzed, and cell morphology, surface markers and cell cycle were investigated as well. The proliferative ability and osteogenic, adipogenic differentiation potential decreased during culture expansion, while chondrogenic differentiation potential had no significant changes. MSCs maintained their multiple differentiation potential during their life-span. For each passage, the positive ratio of CD29, CD44, CD105 were all above 90% and the negative ratio of CD14, CD34, CD45 were below 4%. Culture expansion causes MSCs to gradually lose their stem cell properties. During ex-vivo expansion of ...
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To explore the ex vivo expansion characteristics of selected CD(34)(+) cells and mononuclear cells (MNC). CD(34)(+) cells were isolated from umbilical cord blood MNC by MiniMACS system, expanded under the same conditions as that for MNC.... more
To explore the ex vivo expansion characteristics of selected CD(34)(+) cells and mononuclear cells (MNC). CD(34)(+) cells were isolated from umbilical cord blood MNC by MiniMACS system, expanded under the same conditions as that for MNC. The effects of re-isolation and the MNC supernatant (MNC-SN) on the selected CD(34)(+) cells were investigated. And the CD(34)(-) cells of MNC were cultured ex vivo. In the culture of selected CD(34)(+) cells, both the colony density and the proportion of the CD(34)(+) cells declined continuously with the culturing, although they presented a high proliferation potential. However, in the culture of the MNC, from day 0 to day 7, the colony density and the proportion of CD(34)(+) cells were increased from 412 +/- 167/10(5) cells and (1.12 +/- 0.42)% to 1 162 +/- 566/10(5) cells and (4.17 +/- 1.44)%, respectively. It was found that both the total cells and the CD(34)(+) cells restored expansion potential by re-isolating. CD(34)(-) cells of MNC had the a...
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The effect of antioxidants on the in vitro life span of mouse keratinocytes was investigated in this work. It was found that the life span of the keratinocytes cultured in the medium supplemented with antioxidants was extended... more
The effect of antioxidants on the in vitro life span of mouse keratinocytes was investigated in this work. It was found that the life span of the keratinocytes cultured in the medium supplemented with antioxidants was extended significantly. The most beneficial antioxidant used in this work was the mercaptoethanol, followed by the catalase and SOD. However, the growth rates of keratinocytes in vitro under all the experimental conditions still declined with the culture time. It was also found that the antioxidants added in the medium were also helpful to enhance the keratinocyte colony formation. In addition, the aging kinetics of the mouse epidermal keratinocytes in vitro were analyzed, and finally the aging rate constants corresponding to antioxidants used were calculated.
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The effect of trypsin on the separation an subculture of the keratinocytes was investigated in this work. It was found that when 0.25% trypsin was employed for 5 minutes to separate keratinocytes, the number of active keratinocytes and... more
The effect of trypsin on the separation an subculture of the keratinocytes was investigated in this work. It was found that when 0.25% trypsin was employed for 5 minutes to separate keratinocytes, the number of active keratinocytes and the cells capable of forming colony were higher than those of other experimental conditions. The maximum attached ratio of primary keratinocytes was obtained when skin tissues were treated at 0.05% concentration of trypsin. With the increase of the trypsin concentrations, the attached ratio, attachment rate constant, and colony forming efficiency were all increased. Thus, 0.25% concentration of trypsin was recommended for separating and subculturing the keratinocytes.