Optimizing glutamine concentration enhances ex vivo expansion of natural killer cells through improved redox status

Amino acids are vital components of the serum-free medium that influence the expansion and function of NK cells. This study aimed to clarify the relationship between amino acid metabolism and expansion and cytotoxicity of NK cells. Based on analyzing the mino acid metabolism of NK-92 cells and Design of Experiments (DOE), we optimized the combinations and concentrations of amino acids in NK-92 cells culture medium. The results demonstrated that NK-92 cells showed a pronounced demand for glutamine, serine, leucine, and arginine, in which glutamine played a central role. Significantly, at a glutamine concentration of 13 mM, NK-92 cells expansion reached 161.9 folds, which was significantly higher than 55.5 folds at 2.5 mM. Additionally, under higher glutamine concentrations, NK-92 cells expressed elevated levels of cytotoxic molecules, the level of cytotoxic molecules expressed by NK-92 cells was increased and the cytotoxic rate was 68.42%, significantly higher than that of 58.08% under low concentration. In view of the close relationship between glutamine metabolism and intracellular redox state, we investigated the redox status within the cells. This study demonstrated that intracellular ROS levels in higher glutamine concentrations were significantly lower than those under lower concentration cultures with decreased intracellular GSH/GSSG ratio, NADPH/NADP+ ratio, and apoptosis rate. These findings indicate that NK-92 cells exhibit improved redox status when cultured at higher glutamine concentrations. Overall, our research provides valuable insights into the development of serum-free culture medium for ex vivo expansion of NK-92 cells.

Fluid shear force and hydrostatic pressure jointly promote osteogenic differentiation of BMSCs by activating YAP1 and NFAT2

Natural bone tissue features a complex mechanical environment, with cells responding to diverse mechanical stimuli, including fluid shear stress (FSS) and hydrostatic pressure (HP). However, current in vitro experiments commonly employ a singular mechanical stimulus to simulate the mechanical environment in vivo. The understanding of the combined effects and mechanisms of multiple mechanical stimuli remains limited. Hence, this study constructed a mechanical stimulation device capable of simultaneously applying FSS and HP to cells. This study investigated the impact of FSS and HP on the osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) and examined the distinctions and interactions between the two mechanisms. The results demonstrated that both FSS and HP individually enhanced the osteogenic differentiation of BMSCs, with a more pronounced effect observed through their combined application. BMSCs responded to external FSS and HP stimulation through the integrin-cytoskeleton and Piezo1 ion channel respectively. This led to the activation of downstream biochemical signals, resulting in the dephosphorylation and nuclear translocation of the intracellular transcription factors Yes Associated Protein 1 (YAP1) and nuclear factor of activated T cells 2 (NFAT2). Activated YAP1 could bind to NFAT2 to enhance transcriptional activity, thereby promoting osteogenic differentiation of BMSCs more effectively. This study highlights the significance of composite mechanical stimulation in BMSCs' osteogenic differentiation, offering guidance for establishing a complex mechanical environment for in vitro functional bone tissue construction.

Characterization of cellular responses and cell lysis to elevated hydrodynamic stress from benchtop perfusion bioreactors

The effective design of perfusion cell culture is currently challenging regarding balancing the operating parameters associated with the hydrodynamic conditions due to increased system complexity. To address this issue, cellular responses of an industrial CHO cell line to different types of hydrodynamic stress in benchtop perfusion bioreactors originating from agitation, sparging, and hollow fibers (HF) in the cell retention devices were systematically investigated here with the analysis of cell lysis. It was found that cell lysis was very common and most associated with the sparging stress, followed by the HF and lastly the agitation, consequently heavily impacting the estimation of process descriptors related to biomass. The results indicated that the agitation stress led to a reduced cell growth with a shift toward a more productive phenotype, suggesting an energy redirection from biomass formation to product synthesis, whereas the sparging stress had a small impact on the intracellular metabolic flux distribution but increased the cell death rate drastically. For HF stress, a similar cell maintenance profile was found as the sparging while the activity of glycolysis and the TCA cycle was significantly impeded, potentially leading to the lack of energy and thus a substantial decrease in cell-specific productivity. Moreover, a novel concept of volume average shear stress was developed to further understand the relations of different types of stress and the observed responses for an improved insight for the perfusion cell culture.

Development of a Me2SO-free cryopreservation medium and its long-term cryoprotection on the CAR-NK cells

Cryopreservation is a crucial step in the supply process of off-the-shelf chimeric antigen receptor engineered natural killer (CAR-NK) cell products. Concerns have been raised over the clinical application of dimethyl sulfoxide (Me2SO) due to the potential for adverse reactions following infusion and limited cell-specific cytotoxic effects if misapplied. In this study, we developed a Me2SO-free cryopreservation medium specifically tailored for CAR-NK cells to address this limitation. The cryopreservation medium was formulated using human serum albumin (HSA) and glycerol as the base components. Following initial screening of seven clinically-compatible solutions, four with cryoprotective properties were identified. These were combined and optimized into a single formulation: IF-M. The viability, phenotype, and function of CAR-NK cells were evaluated after short-term and long-term cryopreservation to assess the effectiveness of IF-M, with Me2SO serving as the control group. The viability and recovery of CAR-NK cells in the IF-M group were significantly higher than those in the Me2SO group within 90 days of cryopreservation. Moreover, after 1 year of cryopreservation the cytotoxic capacity of CAR-NK cells cryopreserved with IF-M was comparable to that of fresh CAR-NK cells and significantly superior to that of CAR-NK cells cryopreserved in Me2SO. The CD107a expression intensity of CAR-NK cells in IF-M group was significantly higher than that of Me2SO group. No statistical differences were observed in other indicators under different cryopreservation times. These results underscore the robustness of IF-M as a suitable replacement for traditional Me2SO-based cryopreservation medium for the long-term cryopreservation and clinical application of off-the-shelf CAR-NK cells.

Development of a novel tyrosine-based selection system for generation of recombinant Chinese hamster ovary cells

Efficiently expanding Chinese hamster ovary (CHO) cells, which serve as the primary host cells for recombinant protein production, have gained increasing industrial significance. A significant hurdle in stable cell line development is the low efficiency of the target gene integrated into the host genome, implying the necessity for an effective screening and selection procedure to separate these stable cells. In this study, the genes of phenylalanine hydroxylase (PAH) and pterin 4 alpha carbinolamine dehydratase 1 (PCBD1), which are key enzymes in the tyrosine synthesis pathway, were utilized as selection markers and transduced into host cells together with the target genes. This research investigated the enrichment effect of this system and advanced further in understanding its benefits for cell line development and rCHO cell culture. A novel tyrosine-based selection system that only used PCBD1 as a selection marker was designed to promote the enrichment effect. Post 9 days of starvation, positive transductants in the cell pool approached 100%. Applied the novel tyrosine-based selection system, rCHO cells expressing E2 protein were generated and named CHO TS cells. It could continue to grow, and the yield of E2 achieved 95.95 mg/L in a tyrosine-free and chemically-defined (CD) medium. Herein, we introduced an alternative to antibiotic-based selections for the establishment of CHO cell lines and provided useful insights for the design and development of CD medium.

Suspension culture promoted the expansion of NK-92 cells ex vivo by enhancing the expression of IL-2 receptor

Vigorous ex vivo expansion of NK-92 cells is a pivotal step for clinical adoptive immunotherapy. Interleukin-2 (IL-2) is identified as a key cytokine for NK-92 cells, and it can stimulate cell proliferation after binding to the IL-2 receptor (IL-2R). In this work, the differences in IL-2 consumption and IL-2R expression were investigated between the two culture modes. The results showed that suspension culture favored ex vivo expansion of NK-92 cells compared with static culture. The specific consumption rate of IL-2 in suspension culture was significantly higher than that in static culture. It was further found that the mRNA levels of the two IL-2R subunits remained unchanged in suspension culture, but the proportion of NK-92 cells expressing IL-2Rβ was increased, and the fluorescence intensity of IL-2Rβ was remarkably enhanced. Meanwhile, the proportion of cells expressing IL-2R receptor complex also increased significantly. Correspondingly, the phosphorylation of STAT5, a pivotal protein in the downstream signaling pathway of IL-2, was up-regulated. Notably, the expression level and colocalization coefficient of related endosomes during IL-2/IL-2R complex endocytosis were markedly elevated, suggesting the enhancement of IL-2 endocytosis. Taken together, these results implied that more IL-2 was needed to support cell growth in suspension culture. Therefore, the culture process was optimized from the perspective of cytokine utilization to further improve the NK-92 cell's expansion ability and function. This study provides valuable insight into the efficient ex vivo expansion of NK-92 cells.

Development of a serum-free medium for myoblasts long-term expansion and 3D culture for cell-based meat

Cell-based meat technology provides an effective method to meet the demand for meat, while also posing a huge challenge to the expansion of myoblasts. It is difficult to develop serum-free medium suitable for long-term culture and large-scale expansion of myoblasts, which causes limited understanding of myoblasts expansion. Therefore, this study used C2C12 myoblasts as model cells and developed a serum-free medium for large-scale expansion of myoblasts in vitro using the Plackett-Burman design. The serum-free medium can support short-term proliferation and long-term passage of C2C12 myoblasts, while maintaining myogenic differentiation potential well, which is comparable to those of growth medium containing 10% fetal bovine serum. Based on the C2C12 myoblasts microcarriers serum-free culture system established in this study, the actual expansion folds of myoblasts can reach 43.55 folds after 7 days. Moreover, cell-based meat chunks were preliminarily prepared using glutamine transaminase and edible pigments. The research results provide reference for serum-free culture and large-scale expansion of myoblasts in vitro, laying the foundation for cell-based meat production. PRACTICAL APPLICATION: This study developed a serum-free medium suitable for long-term passage of myoblasts and established a microcarrier serum-free culture system for myoblasts, which is expected to solve the problem of serum-free culture and large-scale expansion of myoblasts in cell culture meat production.

Enhancing mesenchymal stem cells cultivated on microcarriers in spinner flasks via impeller design optimization for aggregated suspensions

During the ex vivo expansion of umbilical cord-derived mesenchymal stem cells (hUCMSCs) in a stirred tank bioreactor, the formation of cell-microcarrier aggregates significantly affects cell proliferation and physiological activity, making it difficult to meet the quantity and quality requirements for in vitro research and clinical applications. In this study, computational fluid dynamic (CFD) simulations were used to investigate the effect of an impeller structure in a commercial spinner flask on flow field structure, aggregate formation, and cellular physiological activity. By designing a modified impeller, the aggregate size was reduced, which promoted cell proliferation and stemness maintenance. This study showed that increasing the stirring speed reduced the size of hUCMSC-microcarrier aggregates with the original impeller. However, it also inhibited cell proliferation, decreased activity, and led to spontaneous differentiation. Compared to low stirring speeds, high stirring speeds did not alter the radial flow characteristics and vortex distribution of the flow field, but did generate higher shear rates. The new impeller's design changed the flow field from radial to axial. The use of the novel impeller with an increased axial pumping rate (Qz) at a similar shear rate compared to the original impeller resulted in a 43.7% reduction in aggregate size, a 37.4% increase in cell density, and a better preservation of the expression of stemness markers (SOX2, OCT4 and NANOG). Increasing the Qz was a key factor in promoting aggregate suspension and size reduction. The results of this study have significant implications for the design of reactors, the optimisation of operating parameters, and the regulation of cellular physiological activity during MSC expansion.

Suction rectal biopsy (SRB) in Hirschsprung's Disease: Is a single macroscopically adequate sample sufficient?

Hirschsprung's Disease (HD) is a congenital disorder causing severe constipation in infants and children. Suction rectal biopsy (SRB) is the preferred technique for obtaining tissue samples for histopathological evaluation. In low-resource settings like Malaysia, cost-effective diagnostic approaches are necessary, making single sample SRB valuable. This study evaluates the diagnostic accuracy and sufficiency of a single macroscopically adequate sample in suction rectal biopsies for the histopathological confirmation of HD. We conducted a retrospective study of children who underwent suction rectal biopsies for the diagnosis of HD at Hospital Raja Perempuan Zainab II (HRPZII), Kota Bharu, Kelantan. A total of 68 patients were included in the study. The inadequacy rate for bedside SRB was 14%, comparable to current literature. Our study found no statistically significant association between sample inadequacy and gestational age, gender, birth weight, or weight at biopsy. Complication rates were 0%, consistent with literature reports. Calretinin staining, an additional technique, was performed in 23 biopsy episodes, with a 4.3% inadequacy rate, compared to 20% in specimens not subjected to calretinin staining. The cost of SRB almost doubled with each additional sample taken, significant in low-resource environments. In conclusion, single sample SRBs can be adequately diagnostic and cost-effective in low-resource settings, providing valuable insights for healthcare facilities in Malaysia and other developing countries. The use of adjunctive techniques such as calretinin staining may improve diagnostic accuracy while maintaining cost-effectiveness. Further prospective studies with larger sample sizes are needed to validate these findings.

Fiber reinforced hydrated networks recapitulate the poroelastic mechanics of articular cartilage

The role of poroelasticity on the functional performance of articular cartilage has been established in the scientific literature since the 1960s. Despite the extensive knowledge on this topic there remain few attempts to design for poroelasticity and to our knowledge no demonstration of an engineered poroelastic material that approaches the physiological performance. In this paper, we report on the development of an engineered material that begins to approach physiological poroelasticity. We quantify poroelasticity using the fluid load fraction, apply mixture theory to model the material system, and determine cytocompatibility using primary human mesenchymal stem cells. The design approach is based on a fiber reinforced hydrated network and uses routine fabrication methods (electrohydrodynamic deposition) and materials (poly[ɛ-caprolactone] and gelatin) to develop the engineered poroelastic material. This composite material achieved a mean peak fluid load fraction of 68%, displayed consistency with mixture theory, and demonstrated cytocompatibility. This work creates a foundation for designing poroelastic cartilage implants and developing scaffold systems to study chondrocyte mechanobiology and tissue engineering. STATEMENT OF SIGNIFICANCE: Poroelasticity drives the functional mechanics of articular cartilage (load bearing and lubrication). In this work we develop the design rationale and approach to produce a poroelastic material, known as a fiber reinforced hydrated network (FiHy™), that begins to approach the native performance of articular cartilage. This is the first engineered material system capable of exceeding isotropic linear poroelastic theory. The framework developed here enables fundamental studies of poroelasticity and the development of translational materials for cartilage repair.

Low CO2 partial pressure steers CHO cells into a defective metabolic state

PURPOSE

The accumulation of carbon dioxide during large-scale culture of animal cells brings adverse effects, appropriate aeration strategies alleviate CO2 accumulation while improper reactor operation may lead to the presence of low CO2 partial pressure (pCO2) condition as occurs in many industrial cases. Thus, this study aims to reveal the in-depth influence of low pCO2 on Chinese Hamster Ovary (CHO) cells for providing a reference for design space determination of CO2 control with regard to the Quality by Design (QbD) guidelines.

METHODS AND RESULTS

The headspace air over purging caused the ultra-low pCO2 (ULC) where the monoclonal antibody production as well as the aerobic metabolic activity were reduced. Intracellular metabolomics analysis indicated a less efficient aerobic glucose metabolic state under ULC conditions. Based on the increase of intracellular pH and lactate dehydrogenase activity, the shortage of intracellular pyruvate could be the cause of the deficient aerobic metabolism, which could be partially mitigated by pyruvate addition under ULC conditions. Finally, a semi-empirical mathematical model was used to better understand, predict and control the occurrence of extreme pCO2 conditions during the cultures of CHO cells.

CONCLUSION

Low pCO2 steers CHO cells into a defective metabolic state. A predictive relation among pCO2, lactate, and pH control was applied to get new insights into CHO cell culture for better and more robust metabolic behavior and process performance and the determination of QbD design space for CO2 control.

Investigating CT head diagnostic reference levels based on indication-based protocols - a single site study

INTRODUCTION

This study aimed to provide clinically-relevant insights into establishing CT DRLs based on indication-based protocols in Ireland, focusing on CT head examinations performed at a neurology centre of excellence hospital.

METHODS

Dose data were collected retrospectively. Typical values for six CT head indication-based protocols were established using a sample size of 50 patients for each protocol. Typical values for each protocol were set as the median of the distribution curve. Dose distributions for each protocol were calculated and compared using non-parametric median test (k-samples) to ascertain significant dose differences between the typical values.

RESULTS

Most typical values pairings showed significant differences (p < 0.001) except between stroke/non-vascular brain, stroke/acute brain, and acute brain/non-vascular brain pairings. This was expected due to similar scan parameters. The typical value for stroke (3-phases angiogram) was 52% lower than the typical value for stroke. Dose levels of the male populations recorded were higher than female populations for all protocols. Statistical comparison showed significant differences for dose quantities and/or scan length between both genders in five protocols.

CONCLUSION

Proposed values for DLP were up to 63% and 69% lower than the EU and Irish national DRLs respectively. Establishment of CT stroke DRLs should be based on the scan performed instead of number of scan acquisitions. Lastly, gender-based CT DRLs for specific protocols within the head region require further investigation.

IMPLICATIONS FOR PRACTICE

With increasing CT examinations worldwide, radiation dose optimisation is key. The value of indication based DRLs is to enhance the required patient protection so image quality can be maintained, however with relevant DRLs for varying protocols. Establishment of CT typical values and site specific DRLs for procedures beyond the national DRLs can drive dose optimisation locally.

Development of stable HEK293T cell pools expressing CSFV E2 protein: A potential antigen expression platform

Large quantities of antigens are required since protective antigens, such as classical swine fever virus (CSFV) E2 protein, are widely used in diagnostic reagents and subunit vaccines. Compared to clonal cell lines and transient gene expression, stable cell pools provide a potential alternative platform to rapidly produce large amounts of antigens. In this work, firstly, Human embryonic kidney 293 T (HEK293T) cell pools expressing E2 protein were developed by transduction of lentiviral vectors. On the one hand, the SP7 was selected from 7 well-performing signal peptides to remarkably increase the production of E2 protein. On the other hand, it was found that high MOI could improve the expression of E2 protein by increasing gene copy numbers. Moreover, the HEK293T cell pools were evaluated for stability by passages and batch cultures, demonstrating that the cell pools were stable for at least 90 days. And then, the performance of the cell pools in batch, fed-batch, and semi-perfusion was studied. Among them, the titer of E2 protein was up to 2 g/L in semi-perfusion, which is currently the highest to the authors' knowledge. Finally, the aggregations and immunogenicity of the E2 protein were analyzed by SDS-PAGE and immunization of mice, respectively. There was no significant difference in aggregations and antibody titers of E2 protein in three culture methods. These results suggest that stable HEK293T cell pools are a promising and robust platform for rapid and efficient production of recombinant proteins.

Vitamin combination promotes ex vivo expansion of NK-92 cells by reprogramming glucose metabolism

Robust ex vivo expansion of NK-92 cells is essential for clinical immunotherapy. The vitamin B group is critical for the expansion and function of immune cells. This study optimized a vitamin combination by response surface methodology based on an in-house designed chemically defined serum-free medium EM. The serum-free medium EM-V4 with an optimal vitamin combination favoured ex vivo expansion of NK-92 cells. The characteristics of glucose metabolism of NK-92 cells in EM-V4 and the relationships between cell expansion and metabolism were investigated. NK-92 cells in EM-V4 underwent metabolic reprogramming. An elevated ratio of glucose-6-phosphate dehydrogenase/phosphofructokinase (G6PDH/PFK) indicated that NK-92 cells shifted towards the pentose phosphate pathway (PPP). An increase in the ratio of pyruvate dehydrogenase/lactate dehydrogenase (PDH/LDH) suggested that the cells shifted towards the Krebs (TCA) cycle, i.e., from glycolysis to aerobic metabolism. The enhanced ratio of oxygen consumption rate/extracellular acidification rate (OCR/ECAR) indicated that NK-92 cells were more reliant on mitochondrial respiration than on glycolysis. This shift provided more intermediate metabolites and energy for biosynthesis. Thus, EM-V4 accelerated biomass accumulation and energy production to promote NK-92 cell expansion by regulating the metabolic distribution. Our results provide valuable insight for the large-scale ex vivo expansion of clinically available NK-92 cells.

A novel magnetically controlled bioreactor for ex vivo expansion of NK-92 cells

The application of natural killer (NK) cells as potential antitumor effector cells appears to be valuable for immunotherapies. However, the clinical use of NK cells is limited because the technical difficulties associated with mass production NK cells at sufficiently high numbers represents a great challenge. Ex vivo expansion of NK cells is a key technology for cell therapy. Bioreactor systems can generate homogeneous culture condition and modulate the environmental and biochemical cues. In this study, a novel magnetically controlled bioreactor was developed for supporting NK cells ex vivo expansion. Using synthetic magnetic beads, the stirring device of the magnetically controlled bioreactor generated reduced shearing force. The intermittent magnetic field was applied for magnetic beads movement to homogenize the culture system. NK-92 cells were cultured in the magnetically controlled bioreactor and the expansion and function of expanded cells were investigated on day 8. The results showed that the expansion of NK-92 cells in the bioreactor was 67.71 ± 10.60-fold, which was significantly higher than that of the T25 culture flask (P < 0.05). Moreover, the proportions of CD3-CD56+ cells and cell killing activity of expanded cells in the bioreactor did not reveal any differences compared to T25 flasks. Taken together, this study demonstrated the possibility of magnetically controlled bioreactor as a potent strategy in NK cells production for facilitating cancer immunotherapy.

The chitosan/carboxymethyl cellulose/montmorillonite scaffolds incorporated with epigallocatechin-3-gallate-loaded chitosan microspheres for promoting osteogenesis of human umbilical cord-derived mesenchymal stem cell

Epigallocatechin-3-gallate (EGCG) is a plant-derived flavonoid compound with the ability to promote the differentiation of human bone marrow-derived mesenchymal stem cells (MSCs) into osteoblasts. However, the effect of EGCG on the osteogenic differentiation of the human umbilical cord-derived mesenchymal stem cells (HUMSCs) is rarely studied. Therefore, in this study, the osteogenic effects of EGCG are studied in the HUMSCs by detecting cell proliferation, alkaline phosphatase (ALP) activity, calcium deposition and the expression of relevant osteogenic markers. The results showed that EGCG can promote the proliferation and osteogenic differentiation of the HUMSCs in vitro at a concentration of 2.5-5.0 μM. Unfortunately, the EGCG is easily metabolized by cells during cell culture, which reduces its bioavailability. Therefore, in this paper, EGCG-loaded microspheres (ECM) were prepared and embedded in chitosan/carboxymethyl cellulose/montmorillonite (CS/CMC/MMT) scaffolds to form CS/CMC/MMT-ECM scaffolds for improving the bioavailability of EGCG. The HUMSCs were cultured on CS/CMC/MMT-ECM scaffolds to induce osteogenic differentiation. The results showed that the CS/CMC/MMT-ECM scaffold continuously released EGCG for up to 22 days. In addition, CS/CMC/MMT-ECM scaffolds can promote osteoblast differentiation. Taken together, the present study suggested that entrainment of ECM into CS/CMC/MMT scaffolds was a prospective scheme for promotion osteogenic differentiation of the HUMSCs.

Three-Dimension Co-culture of Hematopoietic Stem Cells and Differentiated Osteoblasts on Gallic Acid Grafted-Chitosan Scaffold as a Model of Hematopoietic Stem Cells Niche

The existing approaches of hematopoietic stem cells (HSCs) expansion in vitro were difficult to meet the needs of clinical application. While in vivo, HSCs efficiently self-renew in niche where they interact with three dimension extracellular matrix and stromal cells. Osteoblasts (OBs) are one of most significant stromal cells of HSCs niche. Here, we proposed a three-dimensional environment based on gallic acid grafted-chitosan (2c) scaffold and OBs differentiated from human umbilical cord mesenchymal stem cells (HUMSCs) to recapitulate the main components of HSCs niche. The results of alkaline phosphatase staining and alizarin red staining demonstrated that HUMSCs were successfully induced into OBs. The results showed that the expansions of CD34⁺cells, CD34⁺CD38^- cells and CD34⁺CD38^-CD45RA^-CD49f⁺CD90⁺ cells (primitive hematopoietic stem cells, pHSCs) harvested from the biomimetic HSCs niche based on 2c scaffold and OBs (IV) group were larger than those harvested from other three culture groups. Importantly, it was found that the CD34⁺ cells harvested from IV group had better secondary expansion capability and colony forming potential, indicating better self-renewal ability. In addition, the biomimetic HSCs niche based on 2c scaffold and OBs protected HSCs apoptosis and promoted HSCs division. Taken together, the biomimetic HSCs niche based on 2c scaffold and OBs was an effective strategy for ex vivo expansion of HSCs in clinical scale.

MEK1 activation enhances the ex vivo proliferation of haematopoietic stem/progenitor cell

Haematopoietic stem/progenitor cell (HSPC) integrates intracellular signal network from growth factors (GFs) and utilizes its proliferation feature to generate high yields of transplantable cells upon ex vivo culture. However, the molecular basis for HSPC activation and proliferation is not completely understood. The goal of this study was to investigate proliferation regulator in the downstream of GFs and develop HSPC expansion strategy. Microarray and Ingenuity Pathway Analysis were performed to evaluate differentially expressed genes in cytokine-induced CD34⁺ cells after ex vivo culture. We identified that MEK1 was a potential HSPC proliferation regulator, which represented indispensable roles and MEK1 silence attenuated the proliferation of HSPC. Notably, 500 nM MEK1 agonist, PAF C-16, increased the numbers of phenotypic HSPC and induced cell cycling of HSPC. The PAF C-16 expanded HSPC demonstrated comparative clonal formation ability and secondary expansion capacity compared to the vehicle control. Our results provide insights into regulating the balance between proliferation and commitment of HSPC by targeting the HSPC proliferation-controlling network. This study demonstrates that MEK1 critically regulates HSPC proliferation and cell production in the ex vivo condition for transplantation.

Trehalose glycopolymers for cryopreservation of tissue-engineered constructs

The development of an effective cryopreservation method to achieve off-the-shelf and bioactive tissue-engineered constructs (TECs) is important to meet the requirements for clinical applications. The trehalose, a non-permeable cryoprotectant (CPA), has difficulty in penetrating the plasma membranes of mammalian cells and has only been used in combination with other cell penetrating CPA (such as DMSO) to cryopreserve mammalian cells. However, the inherent cytotoxicity of DMSO results in increasing risks with respect to cryopreserved cells. Therefore, in this study, permeable trehalose glycopolymers were synthesised for cryopreservation of TECs. The trehalose glycopolymers exhibited good ice inhibiting activities and biocompatibilities. Furthermore, the viability and function of TECs after cryopreservation with 5.0 wt% S2 were similar to those of the non-cryopreserved TECs. We developed an effective preservation strategy for the off-the-shelf availability of TECs.

1459 Intravesical Chemohyperthermia Versus Bacillus Calmette-Guerin Instillation for Intermediate- And High-Risk Non-Muscle Invasive Bladder Cancer: A Systematic Review and Meta-Analysis

Introduction

Traditional intravesical chemotherapy instillations under room temperature post trans-urethral resection (TUR) of non-muscle invasive bladder cancer (NMIBC) have lower efficacies than maintenance BCG installations. Intravesical chemo-hyperthermia (CHT) at higher temperatures is developed to improve the efficacy of chemotherapy instillation. This systematic review aims to compare the use of CHT and BCG instillation post-TUR.

Method

The protocol of this review is registered on PROSPERO(CRD42020223277). A comprehensive literature search was performed on Medline, EMBASE, and Cochrane CENTRAL to identify studies comparing CHT and BCG post-TUR for intermediate- or high-risk NMIBC. Primary outcomes include recurrence-free survival (RFS) and progression-free survival (PFS). Secondary outcomes include adverse events (AE).

Results

From 2,375 identified records, four randomised control trials incorporating 327 patients were included for meta-analysis. The use of CHT was found to be non-inferior to BCG in RFS, PFS and AEs (Grades 1-3) (p &gt; 0.05). Sensitivity analysis, excluding patients with BCG failures, show 24-36 months recurrence rate to be significantly lower in CHT group (RR 0.64, 95% CI 0.42-0.98, p = 0.04) compared to the BCG group. In patients without carcinoma in situ (CIS), RFS is also significantly better in CHT patients (HR 0.52, 95% CI 0.32- 0.85, p &lt; 0.01). Safety profile remains non-inferior to the BCG group in sensitivity analyses. Quality of evidence across all outcomes ranged from moderate to low.

Conclusions

In well-selected patients, intravesical CHT has superior oncological outcomes and non-inferior safety profile when compared to BCG maintenance therapy for patients with intermediate- and high-risk NMIBC. CHT is a possible alternative treatment during BCG shortage.

Human umbilical cord-derived mesenchymal stem cells affect urea synthesis and the cell apoptosis of human induced hepatocytes by secreting IL-6 in a serum-free co-culture system

BACKGROUND

Bioartificial livers (BALs) are emerging as a potential supportive therapy for liver diseases. However, the maintenance of hepatocyte function and viability is a major challenge. Mesenchymal stem cells (MSCs) have attracted extensive attention for providing trophic support to hepatocytes, but only few studies have explored the interaction between human MSCs and human hepatocytes, and very little is known about the underlying molecular mechanisms whereby MSCs affect hepatocyte function, especially in serum-free medium (SFM).

CONCLUSION

The SFM co-culture strategy showed major advantages in maintaining hiHep function and viability, which is of great significance for the clinical application of hiHeps in BALs. This article is protected by copyright. All rights reserved.

Towards integrated production of an influenza A vaccine candidate with MDCK suspension cells

Seasonal influenza epidemics occur both in northern and southern hemispheres every year. Despite the differences in influenza virus surface antigens and virulence of seasonal subtypes, manufacturers are well-adapted to respond to this periodical vaccine demand. Due to decades of influenza virus research, the development of new influenza vaccines is relatively straight forward. In similarity with the ongoing coronavirus disease 2019 pandemic, vaccine manufacturing is a major bottleneck for a rapid supply of the billions of doses required worldwide. In particular, egg-based vaccine production would be difficult to schedule and shortages of other egg-based vaccines with high demands also have to be anticipated. Cell culture-based production systems enable the manufacturing of large amounts of vaccines within a short time frame and expand significantly our options to respond to pandemics and emerging viral diseases. In this study, we present an integrated process for the production of inactivated influenza A virus vaccines based on a Madin-Darby Canine Kidney (MDCK) suspension cell line cultivated in a chemically defined medium. Very high titers of 3.6 log₁₀ (HAU/100 µl) were achieved using fast-growing MDCK cells at concentrations up to 9.5 × 10⁶ cells/ml infected with influenza A/PR/8/34 H1N1 virus in 1 L stirred tank bioreactors. A combination of membrane-based steric-exclusion chromatography followed by pseudo-affinity chromatography with a sulfated cellulose membrane adsorber enabled full recovery for the virus capture step and up to 80% recovery for the virus polishing step. Purified virus particles showed a homogenous size distribution with a mean diameter of 80 nm. Based on a monovalent dose of 15 µg hemagglutinin (single-radial immunodiffusion assay), the level of total protein and host cell DNA was 58 µg and 10 ng, respectively. Furthermore, all process steps can be fully scaled up to industrial quantities for commercial manufacturing of either seasonal or pandemic influenza virus vaccines. Fast production of up to 300 vaccine doses per liter within 4-5 days makes this process competitive not only to other cell-based processes but to egg-based processes as well.

Magnetic-driven dynamic culture promotes osteogenesis of mesenchymal stem cell

Effective nutrient transport and appropriate mechanical stimulation play important roles in production of tissue-engineered bone grafts. In this study, an experimental set-up for magnetic-driven dynamic culture of cells was designed to mimic the microenvironment of the bone tissue. Here, its ability to contribute to osteogenic differentiation was investigated by inoculating human umbilical cord mesenchymal stem cells (HUMSCs) on magnetic scaffolds. The cytocompatibility of the developed magnetic scaffolds was verified for HUMSCs. Magnetic scaffolds seeded with HUMSCs were exposed to magnetic fields. The results showed that magnetic fields did not affect cell activity and promoted HUMSCs osteogenic differentiation. The magnetic scaffolds were magnetically driven for dynamic culture in the experimental set-up to evaluate the influence of HUMSCs osteoblast differentiation. The results indicated that magnetic-driven dynamic culture increased cell alkaline phosphatase (ALP) activity (p < 0.05) and calcium release (p < 0.05) compared with static culture. The effect was demonstrated in the expression of bone-associated genes. Overall, this study showed that magnetic-driven dynamic culture is a promising tool for regenerative bone engineering.

Reducing TGF-β1 cooperated with StemRegenin 1 promoted the expansion ex vivo of cord blood CD34+ cells by inhibiting AhR signalling

OBJECTIVE

As an inhibitor of the AhR signalling pathway, StemRegenin 1 (SR1) not only promotes the expansion of CD34⁺ cells but also increases CD34^- cell numbers. These CD34^- cells influenced the ex vivo expansion of CD34⁺ cells. In this work, the effects of periodically removing CD34^- cells combined with SR1 addition on the ex vivo expansion and biological functions of HSCs were investigated.

MATERIALS AND METHODS

CD34^- cells were removed periodically with SR1 addition to investigate cell subpopulations, cell expansion, biological functions, expanded cell division mode and supernatant TGF-β1 contents.

RESULTS

After 10-day culture, the expansion of CD34⁺ cells in the CD34^- cell removal plus SR1 group was significantly higher than that in the control group and the SR1 group. Moreover, periodically removing CD34^- cells with SR1 addition improved the biological function of expanded CD34⁺ cells and significantly increased the percentage of self-renewal symmetric division of CD34⁺ cells. In addition, the concentration of total TGF-β1 and activated TGF-β1 in the supernatant was significantly lower than those in the control group and the SR1 group. RT-qPCR results showed that the periodic removal of CD34^- cells with cooperation from SR1 further reduced the expression of AhR-related genes.

CONCLUSIONS

Periodic removal of CD34^- cells plus cooperation with SR1 improved the expansion of CD34⁺ cells, maintained better biological function of expanded CD34⁺ cells and reduced the TGF-β1 contents by downregulating AhR signalling.

High cell density perfusion process for high yield of influenza A virus production using MDCK suspension cells

Similar to the recent COVID-19 pandemic, influenza A virus poses a constant threat to the global community. For the treatment of flu disease, both antivirals and vaccines are available with vaccines the most effective and safest approach. In order to overcome limitations in egg-based vaccine manufacturing, cell culture-based processes have been established. While this production method avoids egg-associated risks in face of pandemics, process intensification using animal suspension cells in high cell density perfusion cultures should allow to further increase manufacturing capacities worldwide. In this work, we demonstrate the development of a perfusion process using Madin-Darby canine kidney (MDCK) suspension cells for influenza A (H1N1) virus production from scale-down shake flask cultivations to laboratory scale stirred tank bioreactors. Shake flask cultivations using semi-perfusion mode enabled high-yield virus harvests (4.25 log₁₀(HAU/100 μL)) from MDCK cells grown up to 41 × 10⁶ cells/mL. Scale-up to bioreactors with an alternating tangential flow (ATF) perfusion system required optimization of pH control and implementation of a temperature shift during the infection phase. Use of a capacitance probe for on-line perfusion control allowed to minimize medium consumption. This contributed to a better process control and a more economical performance while maintaining a maximum virus titer of 4.37 log₁₀(HAU/100 μL) and an infectious virus titer of 1.83 × 10¹⁰ virions/mL. Overall, this study clearly demonstrates recent advances in cell culture-based perfusion processes for next-generation high-yield influenza vaccine manufacturing for pandemic preparedness. KEY POINTS: • First MDCK suspension cell-based perfusion process for IAV produciton was established. • "Cell density effect" was overcome and process was intensified by reduction of medium use and automated process control. • The process achieved cell density over 40 × 10⁶ cells/mL and virus yield over 4.37 log₁₀(HAU/100 μL).

Highly efficient production of an influenza H9N2 vaccine using MDCK suspension cells

The use of H9N2 subtype avian influenza vaccines is an effective approach for the control of the virus spread among the poultry, and for the upgrading of vaccine manufacturing, cell culture-based production platform could overcome the limitations of conventional egg-based platform and alternate it. The development of serum-free suspension cell culture could allow even higher virus productivity, where a suspension cell line with good performance and proper culture strategies are required. In this work, an adherent Mardin–Darby canine kidney (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 H9N2 influenza virus propagation in this MDCK cell line was evaluated with the optimization of infection conditions in terms of MOI and cell concentration for infection. Furthermore, various feed strategies were tested in the infection phase for improved virus titer and a maximum hemagglutinin titer of 13 log2 (HAU/50 μL) was obtained using the 1:2 medium dilution strategy. The evaluation of MDCK cell growth and H9N2 virus production in bioreactors with optimized operating conditions showed comparable cell performance and virus yield compared to shake flasks, with a high cell-specific virus yield above 13,000 virions/cell. With the purified H9N2 virus harvested from the bioreactors, the MDCK cell-derived vaccine was able to induce high titers of neutralizing antibodies in chickens. Overall, the results demonstrate the promising application of the highly efficient MDCK cell-based production platform for the avian influenza vaccine manufacturing.

β-mercaptoethanol promotes osteogenesis of human mesenchymal stem cells via sirt1-ERK pathway

Human umbilical cord-derived mesenchymal stem cells (hUMSCs) hold strong self-renewal capacity and low immunogenicity, which have attracted attention as potential candidates for bone repair and regeneration. However, insufficient osteogenic differentiation markedly hinders the clinical applications of hUMSCs. In the present study, the effect of β-mercaptoethanol (BME), a small molecule antioxidant which has been identified to regulate cell proliferation and differentiation, on osteogenic differentiation of hUMSCs and underlying signaling mechanism were investigated. The results indicated that under osteogenic induction conditions, BME treatment increased the alkaline phosphatase (ALP) activity and promoted calcium mineralization in hUMSCs. The gene and protein expression of osteogenesis-related markers such as ALP, osteopontin (OPN), osteocalcin (OCN) and collagen type I (COLI) were also significantly up-regulated. Besides, BME promoted the protein expression of silent information regulator type 1 (sirt1) and stimulated the activation of extracellular signal-related kinase (ERK), contributing to increased Runx2 expression. Furthermore, blocking the expression of sirt1 attenuated BME-enhanced ERK phosphorylation and osteogenic differentiation of hUMSCs. These results indicated that BME accelerated osteogenic differentiation of hUMSCs by activating the sirt1-ERK signaling pathway, thereby providing insights into the development of MSCs-based bone regeneration strategies.

Expansion of Transdifferentiated Human Hepatocytes in a Serum-Free Microcarrier Culture System

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 × 10⁵ 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 × 10⁶ 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.

Investigation into the impact of tyrosine on the product formation and quality attributes of mAbs in rCHO cell cultures

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. KEY POINTS: • 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 q_mAbupon the deficiency of tyrosine. • The impact of tyrosine on the critical product qualities and the underlying mechanisms were also thoroughly assessed.

Protective efficacy of anti-neuraminidase monoclonal antibodies against H7N9 influenza virus infection

The H7N9 influenza virus has been circulating in China for more than six years. The neuraminidase (NA) has gained great concern for the development of antiviral drugs, therapeutic antibodies, and new vaccines. In this study, we screened seven mouse monoclonal antibodies (mAbs) and compared their protective effects against H7N9 influenza virus. The epitope mapping from escape mutants showed that all the seven mAbs could bind to the head region of the N9 NA close to the enzyme activity sites, and four key sites of N9 NA were reported for the first time. The mAbs D3 and 7H2 could simultaneously inhibit the cleavage of the sialic acid of fetuin protein with large molecular weight and NA-XTD with small molecule weight in the NA inhibition experiment, prevent the formation of virus plaque at a low concentration, and effectively protect the mice from the challenge of the lethal dose of H7N9 virus.

A novel method based on nonparametric regression with a Gaussian kernel algorithm identifies the critical components in CHO media and feed optimization

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 and titres. The application of this NRGK method provides new perspectives for the more precise identification of the critical components that further enable the optimization of media in a shorter timeframe.

Enhancing Immune Response and Heterosubtypic Protection Ability of Inactivated H7N9 Vaccine by Using STING Agonist as a Mucosal Adjuvant

Influenza vaccines for H7N9 subtype have shown low immunogenicity in human clinical trials. Using novel adjuvants might represent the optimal available option in vaccine development. In this study, we demonstrated that the using of the STING agonist cGAMP as a mucosal adjuvant is effective in enhancing humoral, cellular and mucosal immune responses of whole virus, inactivated H7N9 vaccine in mice. A single dose of immunization was able to completely protect mice against a high lethal doses of homologous virus challenge with an significant dose-sparing effect. We also found that intranasal co-administration of H7N9 vaccine with cGAMP could provide effective cross protection against H1N1, H3N2, and H9N2 influenza virus. Furthermore, cGAMP induced significantly higher nucleoprotein specific CD4⁺ and CD8⁺ T cells responses in immunized mice, as well as upregulated the IFN-γ and Granzyme B expression in the lung tissue of mice in the early stages post a heterosubtypic virus challenge. These results indicated that STING agonist cGAMP was expected to be an effective mucosal immune adjuvant for pre-pandemic vaccines such as H7N9 vaccines, and the cGAMP combined nasal inactivated influenza vaccine will also be a promising strategy for development of broad-spectrum influenza vaccines.

Transforming growth factor-β1 stimulates mesenchymal stem cell proliferation by altering cell cycle through FAK-Akt-mTOR pathway

Background: Mesenchymal stem cells (MSCs) are promising for cell therapy and regenerative medicine. An increased need for expanding of MSCs under serum-free condition to achieve a sufficient quantity for therapeutic applications is inevitable. Transforming growth factor-β1 (TGF-β1) is widely used for expanding clinical-grade MSCs in vitro. This work focuses on the influence of TGF-β1 on proliferation in rat bone marrow-derived MSCs (BMSCs) and the underlying mechanism. Materials and Methods: BMSCs were isolated and cultured with or without TGF-β1 in a serum-free medium and Cell Counting Kit-8 assay was used to detect BMSCs proliferation. Cell cycle transition was also analyzed. Further, the expression levels of cyclin D1, phosphorylated focal adhesion kinase, and downstream effectors in Akt-mTOR-S6K1 signaling pathway were examined by western blotting. Results and Conclusion: TGF-β1 triggered proliferation via accelerating G1/S cell cycle transition in BMSCs. The addition of TGF-β1 can activate Akt-mTOR-S6K1 pathway. Additionally, FAK was found to be involved in the process. Upon adding the FAK inhibitor, both the activation of Akt-mTOR-S6K1 and TGF-β1-induced cell proliferation were abrogated. Together, an insight understanding of how TGF-β1 influences BMSCs proliferation is achieved. This study provides a possible strategy of supplementing TGF-β1 in serum-free medium for in vitro expansion, which eventually would advance the production of clinical-grade MSCs for regenerative medicine.

Insight into the roles of tyrosine on rCHO cell performance in fed-batch cultures

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 (q_mAb) 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.

Simultaneous detection of nicotinamide adenine nucleotides and adenylate pool to quantify redox and energy states in mAb-producing CHO cells by capillary electrophoresis

Chinese hamster ovary (CHO) cells are predominant in the production of therapeutic proteins to treat various diseases. Characterization and investigation of CHO cell metabolism in a quick and simple way could boost process and cell line development. Therefore, a method to simultaneously detect seven redox- and energy-related metabolites in CHO cells by capillary electrophoresis has been developed. An on-line focusing technique was applied to improve the peak shape and resolution by using a 50 μm × 44 cm uncoated fused silica capillary. Key parameters and their interactions were investigated by design of experiments (DoE) and optimized conditions were determined by desirability function as follows: 24 °C, 95 mM, and pH 9.4 of BGE. The method was validated to ensure sensitivity, linearity, and reproducibility. The limits of detection (LODs) ranged from 0.050 to 0.688 mg/L for seven metabolites, and correlation coefficients of linearity were all greater than 0.996. The relative standard deviations (RSD) of migration time and peak area were smaller than 0.872% and 5.5%, respectively, except for NADPH, and the recoveries were between 97.5 and 101.2%. The method was successfully applied to analyze the extracts from CHO cells under two different culture conditions. Graphical abstract.

Enhanced metabolic activities for ATP production and elevated metabolic flux via pentose phosphate pathway contribute for better CIK cells expansion

Objective

Ex vivo expansion is an effective way to produce cytokine‐induced killer (CIK) cells needed for clinical trials. Here, ex vivo expansion and metabolism characters of CIK cells in static and dynamic cultures and the relationship between cell expansion and metabolism were investigated.

Materials and methods

Oxygen transfer efficiency was assessed by computational fluid dynamics technique. Cell phenotype, apoptosis and of transporter expression were determined by flow cytometry and Western blotting. Metabolites and enzyme activities were assessed by biochemical methods.

Results

Dynamic cultures favoured better CIK cell expansion without impairing their phenotype and cytotoxicity, enhanced oxygen transfer efficiency. The glucose metabolism flux of cells in dynamic cultures was enhanced by upregulating surface glucose transporter 1 expression and phosphofructokinase activity. Moreover, pentose phosphate pathway (PPP) metabolic flux was enhanced through upregulating glucose‐6‐phosphate dehydrogenase activity. Glutaminolysis was also accelerated via boosting glutamine transporters expression, glutaminase (GLS) and glutamate dehydrogenase activities. Together with higher oxygen consumption rate and extracellular acidification rate, it was suggested that cells in dynamic cultures were in a more vigorous metabolic state for ATP production.

Conclusion

Dynamic cultures accelerated glucose and glutamine metabolic flux to promote ATP production, elevated glucose metabolic flux through PPP to promote biosynthesis for better cell expansion. These findings may provide the basis for ex vivo CIK cell expansion process optimization.

Bioactive poly(ε-caprolactone) microspheres with tunable open pores as microcarriers for tissue regeneration

Microparticles with porous structure can be applied as microcarriers for both cell culture and tissue regeneration. While well-controlled pore structure represents a critical challenge to be achieved. In the present study, in order to develop microcarriers for cell culture, a series of poly(ε-caprolactone) microspheres were fabricated with varied macroporous structures. Poly(ε-caprolactone) microspheres were prepared via the integration of the emulsion/solvent evaporation and particle leaching mechanisms. Particularly, by adjusting poly(ε-caprolactone) concentration and the ratio between the porogen paraffin and poly(ε-caprolactone), the microspheres with the pore size of 25.6-84.0 μm and the porosity of 57.4-75.5% were obtained. Further, the microspheres were subjected to alkaline hydrolysis, followed by surface coating with hydroxyapatite. These porous poly(ε-caprolactone) microspheres with surface modification well supported the adhesion and growth of human fibroblasts. Together, bioactive poly(ε-caprolactone) microspheres with controlled pore structure are potential to be applied in cell culture and tissue regeneration.

Comparative study of mesenchymal stem cells from rat bone marrow and adipose tissue

Several therapeutic products based on mesenchymal stem cells (MSCs) have been translated into clinical applications. MSCs should undergo in vitro culture before a sufficient quantity can be achieved. Hence, both expansion kinetics and the biological characteristics of derived cells from primary culture are pertinent to their applications. In the present study, MSCs were isolated from rat bone marrow and adipose tissue (designated as bMSCs and aMSCs, respectively) and cells were comparatively analyzed regarding cell morphology, proliferation, colony formation, differentiation potential, and immunophenotype following the long-term subculture. No apparent differences could be noticed concerning the morphology between bMSCs and aMSCs. The long-term subculture made both types of cells smaller, weakened their colony-forming ability, and stimulated the proliferation rate. However, bMSCs demonstrated better proliferation and colony-forming ability than aMSCs. No significant difference was observed about the expression of some immunophenotypes (i.e. CD29+/CD90+/CD34-/CD45-) regardless of cell types or population doublings. Notably, bMSCs, but not aMSCs, maintained the differentiation potential well after the long-term subculture. The present study demonstrates that MSCs derived from different tissues can be well expanded for the long term, although cells display gradually declined self-renewal and differentiation potentials to different extents depending on the tissue origins.

Fabrication and in vitro evaluation of a packed-bed bioreactor based on an optimum two-stage culture strategy

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 × 10⁶ cells/mL, respectively. Under this optimum perfusion condition, hiHeps showed good proliferation ability, high viability, homogeneous distribution, high metabolism activities and efficient albumin secretion as well as high liver-specific genes expression. Therefore, the two-stage culture strategy based on operating parameters optimization provides a new method for the development of PB bioreactors.

Dynamic suspension culture improves ex vivo expansion of cytokine-induced killer cells by upregulating cell activation and glucose consumption rate

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 Y_Lac/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.

The effect of gap junction-mediated transfer of miR-200b on osteogenesis and angiogenesis in a co-culture of MSCs and HUVECs

For successful engineering of pre-vascularized bone tissue in vitro, 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 ZEB2, ETS1, KDR and GATA2 Additionally, TGF-β was found to trigger the transfer of miR-200b to HUVECs. Upon adding the TGF-β inhibitor SB431542 or TGF-β-neutralizing antibody, the formation of capillary-like structures in co-culture could be partially rescued. These findings may be fundamental to the development of a cell-based bone regeneration strategy.