Improved Cell Yield Research Articles

B-086 High Precision T Cell Testing Using the T-SPOT Technology: Improved Cell Yields From Lower Volumes of Blood When the T-SPOT Technology is Used With the T-Cell Select Reagent Kit for Cell Isolation

Abstract Background T cells play a critical role in protecting humans from disease, and are a powerful diagnostic tool when used to measure immune responses to infection. However, the use of T cells in a clinical setting has been limited due to challenges associated with T cell testing methodologies. One of the key challenges has been the ability to scale up T cell testing to meet the needs of clinical laboratories. The T-SPOT technology is most widely known for the T-SPOT.TB test, an Interferon-Gamma Release Assay (IGRA) diagnostic test based on the detection of Mycobacterium tuberculosis-specific effector T cells using a single cell resolution platform (ELISPOT). The conventional method of running the T-SPOT.TB test was to use density gradient isolation on 6 mL of whole blood to isolate peripheral blood mononuclear cells (PBMCs) for high precision T cell testing. However, this testing was not accessible to some clinical laboratories due to the hands-on time associated with isolating PBMCs from whole-blood. The T-Cell Select reagent kit was developed to positively select mononuclear cells and enhance cell separation efficiency for the T-SPOT technology. The T-Cell Select reagent kit offers the opportunity to automate the T-SPOT technology which improves scalability and reliability, but it also means that an improved cell yield can be achieved from a lower volume of blood. This makes high precision T cell testing more accessible, whilst maintaining the high sensitivity and specificity of the T-SPOT technology. Methods PBMCs from 242 samples were isolated from 6 mL of whole blood, and were processed according to the T-SPOT.TB test package insert for density gradient isolation. Matched samples were used to isolate PBMCs from 3.5 mL of whole blood using magnetic bead-based positive selection according to the T-Cell Select reagent kit package insert. Results Cell yields were compared using matched samples for density gradient and the T-Cell Select reagent kit isolated cells. Cell count means were 6.6 vs 6.7 × 10^6 cell/mL for the T-Cell Select reagent kit and density gradient isolation methods, respectively. Of the 242 samples tested, two samples had insufficient yields to run the T-SPOT.TB test with the density gradient method, whilst the T-Cell Select reagent kit isolated sufficient numbers from all samples. Results of the T-SPOT.TB test had an overall agreement between the two methods of 97%, negative agreement 99% and positive agreement 94%. Conclusion When used with the T-SPOT technology, the T-Cell Select reagent kit provides an improved cell isolation methodology, requiring up to 50% lower blood volumes, and reducing the hands-on time associated with T cell testing. This makes T cell testing more accessible to labs, meaning that fewer blood samples need to be redrawn due to low cell numbers, providing an advantage in the immunosuppressed.

Large-scale two-photon calcium imaging in freely moving mice

SummaryWe developed a miniaturized two-photon microscope (MINI2P) for fast, high-resolution, multiplane calcium imaging of over 1,000 neurons at a time in freely moving mice. With a microscope weight below 3 g and a highly flexible connection cable, MINI2P allowed stable imaging with no impediment of behavior in a variety of assays compared to untethered, unimplanted animals. The improved cell yield was achieved through a optical system design featuring an enlarged field of view (FOV) and a microtunable lens with increased z-scanning range and speed that allows fast and stable imaging of multiple interleaved planes, as well as 3D functional imaging. Successive imaging across multiple, adjacent FOVs enabled recordings from more than 10,000 neurons in the same animal. Large-scale proof-of-principle data were obtained from cell populations in visual cortex, medial entorhinal cortex, and hippocampus, revealing spatial tuning of cells in all areas.

Effectively Improve the Astaxanthin Production by Combined Additives Regulating Different Metabolic Nodes in Phaffia rhodozyma.

Astaxanthin is an important natural resource that is widely found in marine environments. Metabolic regulation is an effective method for improving astaxanthin production in Phaffia rhodozyma. Most studies have focused on single regulators, which have limited effects. In this study, 16 metabolic regulators were screened to improve astaxanthin production in high-yield and wild-type strains. Fluconazol and glutamic acid increased astaxanthin volumetric yield in MVP14 by 25.8 and 30.9%, respectively, while ethanol increased astaxanthin volumetric yield in DSM626, 29.3%. Furthermore, six additives that inhibit the competing pathways and promote the main pathway for astaxanthin synthesis were selected for combination treatment. We found that the optimal combination was penicillin, ethanol, triclosan, and fluconazol, which increased astaxanthin cell yield by 51%. Therefore, we suggest that simultaneously promoting the master pathways (mevalonate) and inhibiting competing pathways (fatty acid synthesis and ergosterol) is the best strategy to improve astaxanthin cell yield. Moreover, regulators of the biomass pathway should be avoided to improve cell yield. This study provides a technical basis for the utilisation of astaxanthin in P. rhodozyma.

Improved strategy for jet-in-air cell sorting with high purity, yield, viability, and genome stability.

Flow cytometric sorting is a vital tool in biological research and clinical diagnostics. Theoretically, a high‐speed jet‐in‐air sorter is a fluorescent‐activated cell sorting sorter that ideally processes cells with high purity, yield, and viability. However, high‐speed jet‐in‐air sorting is a complex process due to its inherent requirements for high fluidic stability and electronic and timing precision. Here, we report that an additional manual correction of drop delay leads to improved cell yield. Adding 2% FBS to the loading buffer had no significant effect on the fate of sorted cells in 4 h. However, the addition of a suitable concentration of FBS/BSA in the collecting buffer resulted in a notable increase in cell count and proliferation and a significant decrease in cell apoptosis for cell lines and primary cells. Moreover, the level of gene expression remained steady in the 5% FBS collecting buffer. In summary, here we demonstrate techniques that can be easily followed to refine sorted yields of healthy cells.

Abstract 1530: Anti-HER2 CAR monocytes demonstrate targeted anti-tumor activity and enable a single day cell manufacturing process

Abstract Recent advances in cell therapy have led to significant efficacy in hematologic malignancies, but solid tumors remain an intractable challenge. We have previously developed a CAR macrophage (CAR-M) adoptive cell therapy platform and demonstrated potent anti-tumor activity in pre-clinical models. CAR-M overcome several of the barriers to efficacy in the solid tumor setting - trafficking, immunosuppression, lymphocyte exclusion, and antigen heterogeneity. Currently, CAR-M are generated via ex vivo differentiation of peripheral blood monocytes into macrophages prior to genetic manipulation. In order to streamline the manufacturing process, improve cell yields, and potentially improve tumor infiltration, we sought to evaluate the feasibility of directly engineering CD14+ monocytes to express CAR. Using the chimeric adenoviral vector Ad5f35, we engineered primary human CAR-monocytes to target tumors overexpressing HER2. CAR expression and viability both exceeded 90%. Anti-HER2 CAR-monocytes produced pro-inflammatory cytokines in response to antigen, specifically phagocytosed HER2 overexpressing target cells, and eradicated HER2-overexpressing tumor cells in a time and dose-dependent manner. CAR-monocytes efficiently differentiated into CAR-expressing macrophages in response to various maturation factors and cytokines within 3-5 days. Adenoviral based gene modification resulted in the upregulation of several pro-inflammatory markers on CAR-monocytes and pre-conditioned these cells to differentiate into M1 macrophages in the absence of exogenous M1 polarization factors. The M1 phenotype was maintained when CAR-monocytes were challenged with immunosuppressive cytokines in vitro. These cells demonstrated potent effector function after differentiation into macrophages, regardless of exposure to GM-CSF, M-CSF, or immunosuppressive factors. Anti-HER2 CAR monocytes carried broadly expressed myeloid chemokine receptors and responded to a panel of chemotactic factors. In order to optimize the cell manufacturing process associated with CAR-M, we established a closed-system, ultra-rapid CAR monocyte process. This process enabled same day manufacturing of the final CAR monocyte cell product, significantly reducing the cost of goods associated with autologous cell therapy as well as “vein to vein” time. This study demonstrated the successful development of CAR-monocytes with direct anti-tumor activity and capacity to differentiate into M1 polarized CAR-M. In addition, we established an ultra-rapid same-day CAR monocyte manufacturing process. The CAR-monocyte platform represents an advance in the field of adoptive cell therapy. Citation Format: Linara Gabitova, Brett Menchel, Rashid Gabbasov, Stefano Pierini, Andrew Best, Kayleigh Ross, Yumi Ohtani, Daniel Blumenthal, Sascha Abramson, Thomas Condamine, Michael Klichinsky. Anti-HER2 CAR monocytes demonstrate targeted anti-tumor activity and enable a single day cell manufacturing process [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1530.

Facile bead-to-bead cell-transfer method for serial subculture and large-scale expansion of human mesenchymal stem cells in bioreactors.

The conventional planar culture of adherent cells is inefficient for large‐scale manufacturing of cell and gene therapy products. We developed a facile and efficient bead‐to‐bead cell‐transfer method for serial subculture and large‐scale expansion of human mesenchymal stem cells (hMSCs) with microcarriers in bioreactors. We first compared culture medium with and without nucleosides and found the former maintained the expression of surface markers of hMSCs during their prolonged culture and enabled faster cell proliferation. Subsequently, we developed our bead‐to‐bead cell transfer method to subculture hMSCs and found that intermittent agitation after adding fresh microcarriers to cell‐populated microcarriers could promote spontaneous cell migration to fresh microcarriers, reduce microcarrier aggregation, and improve cell yield. This method enabled serial subculture of hMSCs in spinner flasks from passage 4 to passage 9 without using proteolytic enzymes, which showed faster cell proliferation than the serial planar cultures undergoing multiple enzyme treatment. Finally, we used the medium containing nucleosides and our bead‐to‐bead cell transfer method for cell culture scale‐up from 4‐ to 50‐L cultures in single‐use bioreactors. We achieved a 242‐fold increase in the number of cells to 1.45 × 1010 after 27‐day culture and found that the cells harvested from the bioreactors maintained proliferation ability, expression of their surface markers, tri‐lineage differentiation potential and immunomodulatory property. This study shows the promotive effect of nucleosides on hMSC expansion and the potential of using our bead‐to‐bead transfer method for larger‐scale manufacturing of hMSCs for cell therapy.

Experimental design of a culture approach for corneal endothelial cells of New Zealand white rabbit

The harvesting of corneal endothelial cells (CEC) has received special attention due to its potential as a therapy for corneal blindness. The main challenges are related to the culture media formulation, cellular density at the primary isolation, and the number of passages in which CEC can retain their functional characteristics. To alternate different media formulations to harvest CEC has an impact on the cellular yield and morphology. Therefore, we analyzed four different sequences of growth factor-supplemented Stimulatory (S) and non-supplemented Quiescent (Q) media, upon passages to find the optimal S-Q culture sequence. We assessed cell yield, morphology, procollagen I production, Na+/K+-ATPase function, and the expression of ZO-1 and Na+/K+-ATPase. Our results show SQSQ and SQQQ sequences with a balance between an improved cell yield and hexagonal morphology rate. CEC cultured in the SQQQ sequence produced procollagen I, showed Na+/K+-ATPase function, and expression of ZO-1 and Na+/K+-ATPase. Our study sets a culture approach to guarantee CEC expansion, as well as functionality for their potential use in tissue engineering and in vivo analyses. Thus, the alternation of S and Q media improves CEC culture. SQQQ sequence demonstrated CEC proliferation and lower the cost implied in SQSQ sequences. We discarded the use of pituitary extract and ROCK inhibitors as essential for CEC proliferation.

Fluorescence-Activated Cell Sorting Is More Potent to Fish Intervertebral Disk Progenitor Cells Than Magnetic and Beads-Based Methods.

Low back pain related to intervertebral disk (IVD) degeneration has a major socioeconomic impact on our aging society. Therefore, stem cell therapy to activate self-repair of the IVD remains an exciting treatment strategy. In this respect, tissue-specific progenitors may play a crucial role in IVD regeneration, as these cells are perfectly adapted to this niche. Such a rare progenitor cell population residing in the nucleus pulposus (NP) (NP progenitor cells [NPPCs]) was found positive for the angiopoietin-1 receptor (Tie2+), and was demonstrated to possess self-renewal capacity and in vitro multipotency. Here, we compared three sorting protocols; that is, fluorescence-activated cell sorting (FACS), magnetic-activated cell sorting (MACS), and a mesh-based label-free cell sorting system (pluriSelect), with respect to cell yield, potential to form colonies (colony-forming units), and in vitro functional differentiation assays for tripotency. The aim of this study was to demonstrate the efficiency of three widespread cell sorting methods for picking rare cells (<5%) and how these isolated cells then behave in downstream functional differentiation in adipogenesis, osteogenesis, and chondrogenesis. The cell yields among the isolation methods differed widely, with FACS presenting the highest yield (5.0% ± 4.0%), followed by MACS (1.6% ± 2.9%) and pluriSelect (1.1% ± 1.0%). The number of colonies formed was not significantly different between Tie2+ and Tie2- NPPCs. Only FACS was able to separate into two functionally different populations that showed trilineage multipotency, while MACS and pluriSelect failed to maintain a clear separation between Tie2+ and Tie2- populations in differentiation assays. To conclude, the isolation of NPPCs was possible with all three sorting methods, while FACS was the preferred technique for separation of functional Tie2+ cells. Impact Statement Tissue-specific progenitor cells such as nucleus pulposus progenitor cells of the IVD could become an ultimate cell source for tissue engineering strategies as these cells are presumably best adapted to the tissue's microenvironment. Fluorescence-activated cell sorting seemed to outcompete magnetic-activated cell sorting and pluriSelect concerning selecting a rare cell population from IVD tissue as could be demonstrated by improved cell yield and functional differentiation assays.

GMP-compliant sorting of dendritic cells for CCR7 expression improves therapeutic efficacy in cancer by enhancing lymph node migration and antigen-specific T cell activation

Background & Aim Dendritic cells (DCs) are a potentially powerful cell therapy due to their ability to induce T cell activation to defined antigens; however, this potential has not yet been realised in clinical trials. Monocyte-derived DCs (moDCs) are most commonly used in cancer therapy, although the rare blood DC subsets have also been explored. Crucially, cell function requires the chemokine receptor CCR7, which guides DCs from the site of antigen uptake to the lymph nodes. CCR7 expression, and therefore migration, is variable after isolation of DCs from blood or ex vivo culture, and may account for the limited efficacy seen in clinical trials. We hypothesised that selection of CCR7+ DCs by sorting would to improve cell function and therapeutic use of DCs. Methods, Results & Conclusion We have previously shown that murine CCR7+ bone marrow DCs (BMDCs) can be sorted using a novel chemokine-based system and show enhanced lymph node migration. This CCL19-fluorophore construct was shown to also detect expression of CCR7 on human DCs, and significantly enrich CCR7+ cells to high purity and viability (>90%) using magnetic bead and fluorescence-based sorting methods. Both murine and human CCR7+ DCs were more mature than CCR7- DCs by expression of CD80 and CD86 and production of T cell chemoattractants such as CCL17 and CCL22. In vitro, CCR7+ DCs were also most effective in stimulating antigen-specific T cells, especially memory T cells producing IFNγ, TNFα and IL-2. In vivo, sorted murine CCR7+ BMDCs, but not unsorted DCs, were sufficient to reduce subcutaneous and metastatic tumour growth in the B16F10.ova mouse model. Increased migration of injected DCs to lymph nodes led to an elevated overall number of tumour-specific T cells in CCR7+ DC-receiving mice, but this was not seen in those receiving unsorted DCs. In agreement with in vitro data, CCR7+ DCs increased production of mature tumour-specific T cells, particularly with the desirable memory (CD62L+CD44+) phenotype, suggesting their potency in a human therapeutic context. As production of this chemokine construct is possible at GMP grade, this protocol is amenable to GMP translation using the MACSQuant Tyto cell sorter. Purity and viability of CCR7+ DCs remained consistently high between the original and GMP-ised protocols, with an improved cell yield versus bead sorting. Overall, this novel sorting process is compliant with current GMP manufacture and creates a realistic DC product with enhanced function and potential therapeutic benefit.

Effects of intermittent T-cell cluster disaggregation on proliferative capacity and checkpoint marker expression

Background/aim: T-cell immunotherapies are rapidly gaining grounds in clinical success. Presently, there is first-to-market knowledge on the translation of research scale methods to clinical and commercial scales. Improved understanding can lead to more consistent and efficient production, scaling, and eventual potency. T-cell checkpoint markers, proliferation, and T-cell cluster size and disaggregation are one set of parameters that have yet to be explored.Methods: We herein activated T-cells and assessed various mechanical dissociation frequencies in relation to expression of checkpoint markers (measured by flow cytometry).Results: We herein find increased T-cell proliferation capacity with increased dissociation frequency. We also find that with increased cluster size and duration, lower proliferation, and increased expression of checkpoint markers.Conclusions: These findings reveal new translation findings with respect to T-cell handling and production and suggest that T-cell disaggregation may be important to improved cell yields and phenotype.

Optimization of single-cell plate sorting for high throughput sequencing applications

Single cell sequencing has recently been applied to many immunological studies. Flow cytometric index sorting isolates cells for single cell sequencing with protein level data linked to sequences. However, successful sequencing of index sorted samples requires careful optimization of several sort parameters, including nozzle size, flow rate, threshold rate, and yield calculations. In this study, considerations and optimization data for each of these variables are presented. Our analysis focused on index sorting, but the findings can be applied to any plate sorting protocol. Minimization of flow rates and use of the 70 μm nozzle improved cell yields. Improvements in total read counts after sequencing were obtained by decreasing the threshold rate, or the number of cells processed per second. In addition, this technique provided linked protein and gene expression analysis of the cytokine interferon (IFN)γ, demonstrating that on a single cell basis IFNγ+ cells tend to express IFNG mRNA, and IFNγ– cells do not. Through rigorous optimization and quality control, we have identified parameters important to plate sorting and recommend the use of the 70 μm nozzle and low flow and threshold rates for analysis of rare populations of human lymphocytes.

An Effect of Culture Media on Epithelial Differentiation Markers in Breast Cancer Cell Lines MCF7, MDA-MB-436 and SkBr3.

Background and objectives: Cell culture is one of the mainstays in the research of breast cancer biology, although the extent to which this approach allows to preserve the original characteristics of originating tumor and implications of cell culture findings to real life situations have been widely debated in the literature. The aim of this study was to determine the role of three cell culture media on transcriptional expression of breast cancer markers in three breast cancer reference cell lines (MCF7, SkBr3 and MDA-MB-436). Materials and methods: Cell lines were conditioned in three studied media (all containing 5% fetal bovine serum (FBS) + hormones/growth factors; different composition of basal media) for four passages. Population growth was characterized by cumulative population doubling levels, average generation time, cell yield and viability at the fourth passage. Transcriptional expression of breast cancer differentiation markers and regulatory transcriptional programs was measured by qPCR. Results: Differences in the composition of growth media significantly influenced the growth of studied cell lines and the expression of mammary lineage governing transcriptional programs and luminal/basal markers. Effects of media on transcriptional expression were more pronounced in luminal cell lines (MCF7, SkBr3), than in the basal cell line (MDA-MB-436). Changes in growth media in terms of supplementation and basal medium delayed growth of cells, but improved cell yields. Conclusions: The expression of breast cancer cell differentiation phenotypic markers depends on the composition of cell growth medium, therefore cell culture as a tool in phenotypic studies should be used considering this effect. The findings of such studies should always be interpreted with caution. The formulation of cell growth media has greater effect on the expression of phenotypic markers in luminal, rather than basal cell lines. Media containing mitogens and higher vitamin content improved efficacy of cell culture in terms of cell yields, although greatly increased growth times.

Single cell protein production of Chlorella sp. using food processing waste as a cultivation medium

The aim of this study was to investigate the effect of various food processing wastes on the production of single cell protein by Chlorella sp. Three various food processing wastes i.e. tofu waste, tempeh waste and cheese whey waste were used as cultivation medium for Chlorella sp. growth. Sea water was used as a control of cultivation medium. The addition of waste into cultivation medium was 10%, 20%, 30%, 40%, and 50%. The result showed that the highest yield of cell mass and protein content was found in 50% tofu waste cultivation medium was 47.8 × 106 cell/ml with protein content was 52.24%. The 50% tofu waste medium showed improved cell yield as nearly as 30% than tempeh waste medium. The yield of biomass and protein content when 30% tempeh waste was used as cultivation medium was 37.1 × 106 cell/ml and 52%, respectively. Thus, food processing waste especially tofu waste would be a promising candidate for cultivation medium for single cell production from Chlorella sp. Moreover, the utilization of waste can reduce environmental pollution and increase protein supply for food supplement or animal feed.

Proteomes of Lactobacillus delbrueckii subsp. bulgaricus LBB.B5 Incubated in Milk at Optimal and Low Temperatures.

We identified the proteins synthesized by Lactobacillus delbrueckii subsp. bulgaricus strain LBB.B5 in laboratory culture medium (MRS) at 37°C and milk at 37 and 4°C. Cell-associated proteins were measured by gel-free, shotgun proteomics using high-performance liquid chromatography coupled with tandem mass spectrophotometry. A total of 635 proteins were recovered from all cultures, among which 72 proteins were milk associated (unique or significantly more abundant in milk). LBB.B5 responded to milk by increasing the production of proteins required for purine biosynthesis, carbohydrate metabolism (LacZ and ManM), energy metabolism (TpiA, PgK, Eno, SdhA, and GapN), amino acid synthesis (MetE, CysK, LBU0412, and AspC) and transport (GlnM and GlnP), and stress response (Trx, MsrA, MecA, and SmpB). The requirement for purines was confirmed by the significantly improved cell yields of L.delbrueckii subsp. bulgaricus when incubated in milk supplemented with adenine and guanine. The L.delbrueckii subsp. bulgaricus-expressed proteome in milk changed upon incubation at 4°C for 5days and included increased levels of 17 proteins, several of which confer functions in stress tolerance (AddB, UvrC, RecA, and DnaJ). However, even with the activation of stress responses in either milk or MRS, L.delbrueckii subsp. bulgaricus did not survive passage through the murine digestive tract. These findings inform efforts to understand how L.delbrueckii subsp. bulgaricus is adapted to the dairy environment and its implications for its health-benefiting properties in the human digestive tract. IMPORTANCELactobacillus delbrueckii subsp. bulgaricus has a long history of use in yogurt production. Although commonly cocultured with Streptococcus salivarius subsp. thermophilus in milk, fundamental knowledge of the adaptive responses of L.delbrueckii subsp. bulgaricus to the dairy environment and the consequences of those responses on the use of L.delbrueckii subsp. bulgaricus as a probiotic remain to be elucidated. In this study, we identified proteins of L.delbrueckii subsp. bulgaricus LBB.B5 that are synthesized in higher quantities in milk at growth-conducive and non-growth-conductive (refrigeration) temperatures compared to laboratory culture medium and further examined whether those L.delbrueckii subsp. bulgaricus cultures were affected differently in their capacity to survive transit through the murine digestive tract. This work provides novel insight into how a major, food-adapted microbe responds to its primary habitat. Such knowledge can be applied to improve starter culture and yogurt production and to elucidate matrix effects on probiotic performance.

Long-term in vitro cultivation of Histomonas meleagridis coincides with the dominance of a very distinct phenotype of the parasite exhibiting increased tenacity and improved cell yields.

The majority of research on Histomonas meleagridis was performed in the first half of the last century, especially those on morphological aspects. In the present study identical monoxenic settings for cultures of the same H. meleagridis clonal strain in its virulent low passage and attenuated high passage form enabled a comparative analysis of parasite characteristics. For the first time, it could be shown that long-term in vitro cultivation led to a severe shift in cell morphology, with the occurrence of a very distinct phenotype expressing a flagellated and highly amoebic cell morphology. Furthermore, the attenuated parasites showed better growth rates and a higher tenacity when confronted with adverse conditions. During these experiments up to 100% of the parasites, both virulent and attenuated, assumed a completely rounded morphology elucidated by electron microscopy. The findings indicate that such previously reported cyst-like stages are a defence strategy of H. meleagridis, independent of the passage level in vitro and pathogenicity in vivo. In conclusion, long-term in vitro passaging of H. meleagridis led not only to an attenuation of the parasite, as previously demonstrated, but also to a shift in the parasite's phenotype regarding morphology, growth behaviour and a higher level of tenacity.

Nutrient Regulation by Continuous Feeding for Large-scale Expansion of Mammalian Cells in Spheroids.

In this demonstration, spheroids formed from the β-TC6 insulinoma cell line were cultured as a model of manufacturing a mammalian islet cell product to demonstrate how regulating nutrient levels can improve cell yields. In previous studies, bioreactors facilitated increased culture volumes over static cultures, but no increase in cell yields were observed. Limitations in key nutrients such as glucose, which were consumed between batch feedings, can lead to limitations in cell expansion. Large fluctuations in glucose levels were observed, despite the increase in glucose concentrations in the media. The use of continuous feeding systems eliminated fluctuations in glucose levels, and improved cell growth rates when compared with batch fed static and SSB culture methods. Additional increases in growth rates were observed by adjusting the feed rate based on calculated nutrient consumption, which allowed the maintenance of physiological glucose over three weeks in culture. This method can also be adapted for other cell types.

A simplified approach for efficient isolation of functional microglial cells: Application for modeling neuroinflammatory responses in vitro.

Purified microglial cells in culture are frequently used to model brain inflammatory responses but obtaining large yields of these cells on a routine basis can be quite challenging. Here, we demonstrate that it is possible to achieve high-yield isolation of pure microglial (MAC-1(+) /Fcrls(+) /Ccr2(-) ) cells from postnatal brain tissue through a simple culture procedure that mainly relies on the adhesion preference of these cells to the polycation polyethyleneimine (PEI) in serum-supplemented DMEM medium. Accordingly, other synthetic or biological substrates failed to mimic PEI effects under the same culture conditions. Replacement of DMEM by DMEM/F12 nutrient mixture did not permit microglial cell isolation on PEI coating, indicating that PEI effects were context-dependent. Remarkably, the lack of culture feeding during progression of microglial cell isolation strongly improved cell yield, suggesting that nutritional deprivation was required to optimize this process. When generated in large culture flasks coated with PEI, cultures of microglial cells were easily recovered by trypsin proteolysis to produce subcultures for functional studies. These cultures responded to lipopolysaccharide (LPS, 1-10 ng/ml) treatment by secreting pro-inflammatory cytokines such as TNF-α, IL-6, IL-1β and by generating nitric oxide and reactive oxygen species. Most interestingly, this response was curtailed by appropriate reference drugs. Microglial cells were also strongly responsive to the mitogenic cytokine GM-CSF, which confirms that the functional repertoire of these cells was well preserved. Because of its high yield and simplicity, we believe that the present method will prove to be especially convenient for mechanistic studies or screening assays. GLIA 2016;64:1912-1924.

Production of Good Manufacturing Practice Grade Equine Adiposederived Mesenchymal Stem Cells for Therapeutic Use

Mesenchymal stem cells (MSC) are currently being evaluated in equine clinical studies for their potential to treat various disorders and injuries. Studies have shown that both autologous and allogeneic stem cells appear to be safe. However, an efficient cell expansion method that is reliable and cost-effective is warranted to provide off-the-shelf clinical grade stem cells. Our study aimed to determine optimum culture conditions for efficient large-scale stem cell expansion. We produced cGMP standard equine adipose derived mesenchymal stem cells on a large scale. Five different medium combinations—Dulbecco’s modified Eagle’s medium-knockout (DMEM-KO), alpha modified minimum essential medium (α-MEM), 50:50 DMEM-KO/α-MEM, 75:25 DMEM-KO/α-MEM and 25:75 DMEM-KO/α- MEM—at seeding densities of 1000, 2000, 3000, 4000 and 5000 cells/cm2, were used to determine the optimum culture conditions for large-scale production. Growth kinetics, immunophenotypes, karyotypes, morphology, trilineage differentiation, T-cell proliferation, virus positivity, pre-clinical toxicity and expression of pluripotency markers were analysed. Among the medium combinations and seeding densities tested, 25:75 DMEM-KO/α-MEM at a seeding density of 5000 cells/cm2 was found to be optimum for large-scale expansion. This medium combination gave a significantly higher cell yield than the other medium combinations, while preserving their stem cell characteristics and differentiation potential. The results indicated that the adoption of an appropriate culture system significantly improved cell yield, thus enabling the production of sufficient cells for therapeutic application in a cost-effective manner. The results also showed that the method of large-scale expansion requires minimal manipulation of cells, and it could be expanded ex vivo within two passages while retaining the characteristics of true stem cells.

Modelling Improvements in Cell Yield of Banked Umbilical Cord Blood and the Impact on Availability of Donor Units for Transplantation into Adults

Umbilical cord blood (UCB) is used increasingly in allogeneic transplantation. The size of units remains limiting, especially for adult recipients. Whether modest improvements in the yield of cells surviving storage and thawing allow more patients to proceed to transplant was examined. The impact of improved cell yield on the number of available UCB units was simulated using 21 consecutive anonymous searches. The number of suitable UCB units was calculated based on hypothetical recipient weight of 50 kg, 70 kg, and 90 kg and was repeated for a 10%, 20%, and 30% increase in the fraction of cells surviving storage. Increasing the percentage of cells that survive storage by 30% lowered the threshold of cells needed to achieve similar engraftment rates and increased numbers of UCB units available for patients weighing 50 (P = 0.011), 70 (P = 0.014), and 90 kg (P = 0.003), controlling for differences in HLA compatibility. Moreover, if recipients were 90 kg, 12 out of 21 patients had access to at least one UCB unit that met standard criteria, which increased to 19 out of 21 patients (P = 0.035) when the fraction of cells surviving storage and thawing increased by 30%. Modest increases in the yield of cells in banked UCB units can significantly increase donor options for adult patients undergoing HSCT.

Improving cell yield and lactic acid production of Lactococcus lactis ssp. cremoris by a novel submerged membrane fermentation process

This work investigates the application of compact submerged hollow fibre membrane fermenters to boost the yield and performance of Lactococcus lactis ssp. cremoris fed with whey-based medium. The membrane allowed the removal of inhibitor-rich medium and simultaneous replacement with nutrient-rich medium by a novel media-backwash method. The simple submerged membrane system operated with sustained flux in the range of 10–65 L m−2 h−1 using only backwash to control fouling. It was found that replacement of fermented medium using submerged hollow fibre membranes more than doubled the lactic acid production and cell growth. Further testing with boosted lactose concentration of the backwash medium, improved cell yield (by 2.4 times) and yielded higher concentrations of lactic acid. The activity of the membrane treated cultures was higher than the control, even after 30 h of continuous fermentation. During the stationary phase of growth, membrane assisted fermentation continued to produce lactic acid, indicating that productivity became tied to the rate of nutrient addition and lactic acid removal. Simple compact submerged membrane bioreactors are a viable technology to enhance active cell and metabolic by-product yields, but careful control of nutrient replacement and metabolite removal are required to ensure the most optimal growth conditions.