Multiparameter flow cytometry for the characterisation of extracellular markers on human mesenchymal stem cells

Expansion of human mesenchymal stem/stromal cells on temporary liquid microcarriers

BACKGROUND

Traditional large-scale culture systems for human mesenchymal stem/stromal cells (hMSCs) use solid microcarriers as attachment substrates. Although the use of such substrates is advantageous because of the high surface-to-volume ratio, cell harvest from the same substrates is a challenge as it requires enzymatic treatment, often combined with agitation. Here, we investigated a two-phase system for expansion and non-enzymatic recovery of hMSCs. Perfluorocarbon droplets were dispersed in a protein-rich growth medium and were used as temporary liquid microcarriers for hMSC culture.

RESULTS

hMSCs successfully attached to these liquid microcarriers, exhibiting similar morphologies to those cultured on solid ones. Fold increases of 3.03 ± 0.98 (hMSC1) and 3.81 ± 0.29 (hMSC2) were achieved on day 9. However, the maximum expansion folds were recorded on day 4 (4.79 ± 0.47 (hMSC1) and 4.856 ± 0.7 (hMSC2)). This decrease was caused by cell aggregation upon reaching confluency due to the contraction of the interface between the two phases. Cell quality, as assessed by differentiation, cell surface marker expression and clonogenic ability, was retained post expansion on the liquid microcarriers. Cell harvesting was achieved non-enzymatically in two steps: first by inducing droplet coalescence and then aspirating the interface. Quality characteristics of hMSCs continued to be retained even after inducing droplet coalescence.

CONCLUSION

The prospect of a temporary microcarrier that can be used to expand cells and then 'disappear' for cell release without using proteolytic enzymes is a very exciting one. Here, we have demonstrated that hMSCs can attach and proliferate on these perfluorocarbon liquid microcarriers while, very importantly, retaining their quality.

Adipose tissue micrograft in a scaffold of plasma-gel combined with platelet-derived growth factors in dermal wrinkle regeneration

Background: The dermal aging process and the formation of deep wrinkles are a biological involution that also involves the regeneration system of cells immersed in the extracellular matrix and the papillary dermis. The progressive loss of niches of adult stem cells (MSCs) is more evident after the first third of life; it increases the phenotypic expression and the characteristics of the tissue senescence process. The purpose of this study was to clinically demonstrate that in viable micrograft there may be an improvement of deep wrinkles and surrounding tissues. Methods: This study involved 11 female patients who underwent the correction of deep dermal wrinkles through a suspension containing 0.8 mL of viable micrografts in a 5 mL plasma gel scaffold, obtained from the centrifugation of a 20 cc venous sample peripheral blood, gelled by heat in a dry steriliser and the buffy coat coming from the same venous sample, in order verify overtime the improvement of the interested anatomical area. Individual signs of wrinkles and the degree of correction obtained for each treatment and each area were objectively evaluated by using a 10-0 visual analog scale (VAS), Modified Vancouver scale and Berardesca's scale. Results: With this technique excellent results were obtained. In fact, wrinkles were improved, as well as surrounding tissues, even after 60 days, as shown by the Berardesca's, VAS and Modified Vancouver scales. Conclusion: This retrospective clinical evaluation allowed us to consider the excellent clinical results obtained with this method for the treatment of deep wrinkles and surrounding tissues, through a suspension of progenitors with MSCs derived from adipose tissue (ADSCa) in a not inflammatory plasma gel scaffold combined with buffy coat.

Pleiotropic effects of vitamin D3 on CD4+ T lymphocytes mediated by human periodontal ligament cells and inflammatory environment

Aims

Both, vitamin D₃ and human periodontal ligament cells (hPDLCs) possess immunosuppressive properties, but their combined effect on immune cells has never been investigated. Here, we analysed the impact of vitamin D₃ on the immunosuppressive properties of hPDLCs towards CD4⁺ T lymphocytes.

Material and Methods

Allogenic CD4⁺ T lymphocytes were activated by phytohemagglutinin either in monoculture or co‐culture with hPDLCs, in the presence or absence of IFN‐γ and 1,25(OH)₂D₃. After 5 days, CD4⁺ T‐lymphocyte proliferation, CD4⁺ CD25⁺ FoxP3⁺ regulatory T lymphocytes (T_regs) proportion and IL‐10, TGF‐β1 and IL‐17A production were analysed.

Results

In monoculture, 1,25(OH)₂D₃ suppressed CD4⁺ T‐lymphocyte proliferation, increased the percentage of CD4⁺ FoxP3⁺ CD25⁺ FoxP3⁺ T_regs and enhanced IL‐10 and TGF‐β1 production. In the presence of IFN‐γ treated hPDLCs, 1,25(OH)₂D₃ significantly increased CD4⁺ T‐lymphocyte proliferation and decreased the percentage of CD4⁺ CD25⁺ FoxP3⁺ T_regs. IL‐10 and IL‐17A expression was significantly diminished by 1,25(OH)₂D₃, whereas TGF‐β1 was slightly increased. The effects of 1,25(OH)₂D₃ in co‐culture were reversed by inhibition of indoleamine‐2,3‐dioxygenase‐1, prostaglandin‐endoperoxide synthase and programmed cell death 1 ligand 1. 1,25(OH)₂D₃ also suppressed the expression of these proteins in hPDLCs.

Conclusion

Effects of vitamin D₃ on CD4⁺ T lymphocyte are modified by hPDLCs depending on the microenvironment.

Identifying the optimum source of mesenchymal stem cells for use in knee surgery

Single sitting procedures where the mononuclear cell fraction is extracted from bone marrow and implanted directly into cartilage and bone defects are becoming more popular as novel treatments for cartilage defects which have, until now had few treatment options. This is on the basis that the mesenchymal stem cells (MSCs) contained within will repair the damaged tissue. This study sought to determine if the femur and tibia could provide equivalent amounts of mesenchymal stem cells, with equivalent viability and proliferative capacity, to that obtained from the gold standard of the pelvis in order to potentially reduce the morbidity associated with these procedures. Bone marrow was extracted from the pelvis, femur, and tibia of human subjects. The mononuclear cell fraction was extracted and cultured in the laboratory. Mesenchymal stem cell populations were assessed using a colony forming unit count. Viability was assessed using a PrestoBlue viability assay. Population doubling number was calculated between the end of passage 0 and passage three to determine the proliferative abilities of the different populations. Finally, the cell surface phenotype of the cells was determined by flow cytometry. The results showed that the pelvis was superior to the femur and tibia in terms of the number of stem cells isolated. There was no statistically significant difference in the phenotype of the cells isolated from different locations. This work shows that when undertaking single sitting procedures, the pelvis remains the optimum source for obtaining MSCs, despite the morbidity associated with bone marrow collection from the pelvis. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1868-1875, 2017.

Process development of human multipotent stromal cell microcarrier culture using an automated high-throughput microbioreactor

Microbioreactors play a critical role in process development as they reduce reagent requirements and can facilitate high-throughput screening of process parameters and culture conditions. Here, we have demonstrated and explained in detail, for the first time, the amenability of the automated ambr15 cell culture microbioreactor system for the development of scalable adherent human mesenchymal multipotent stromal/stem cell (hMSC) microcarrier culture processes. This was achieved by first improving suspension and mixing of the microcarriers and then improving cell attachment thereby reducing the initial growth lag phase. The latter was achieved by using only 50% of the final working volume of medium for the first 24 h and using an intermittent agitation strategy. These changes resulted in >150% increase in viable cell density after 24 h compared to the original process (no agitation for 24 h and 100% working volume). Using the same methodology as in the ambr15, similar improvements were obtained with larger scale spinner flask studies. Finally, this improved bioprocess methodology based on a serum-based medium was applied to a serum-free process in the ambr15, resulting in >250% increase in yield compared to the serum-based process. At both scales, the agitation used during culture was the minimum required for microcarrier suspension, N_JS . The use of the ambr15, with its improved control compared to the spinner flask, reduced the coefficient of variation on viable cell density in the serum containing medium from 7.65% to 4.08%, and the switch to serum free further reduced these to 1.06-0.54%, respectively. The combination of both serum-free and automated processing improved the reproducibility more than 10-fold compared to the serum-based, manual spinner flask process. The findings of this study demonstrate that the ambr15 microbioreactor is an effective tool for bioprocess development of hMSC microcarrier cultures and that a combination of serum-free medium, control, and automation improves both process yield and consistency. Biotechnol. Bioeng. 2017;114: 2253-2266. © 2017 Wiley Periodicals, Inc.

Expansion of bone marrow-derived human mesenchymal stem/stromal cells (hMSCs) using a two-phase liquid/liquid system

BACKGROUND

Human mesenchymal stem/stromal cells (hMSCs) are at the forefront of regenerative medicine applications due to their relatively easy isolation and availability in adults, potential to differentiate and to secrete a range of trophic factors that could determine specialised tissue regeneration. To date, hMSCs have been successfully cultured in vitro on substrates such as polystyrene dishes (TCPS) or microcarriers. However, hMSC sub-cultivation and harvest typically employs proteolytic enzymes that act by cleaving important cell membrane proteins resulting in long-term cell damage. In a process where the cells themselves are the product, a non-enzymatic and non-damaging harvesting approach is desirable.

RESULTS

An alternative system for hMSC expansion and subsequent non-enzymatic harvest was investigated here. A liquid/liquid two-phase system was proposed, comprising a selected perfluorocarbon (FC40) and growth medium (DMEM). The cells exhibited similar cell morphologies compared with TCPS. Moreover, they retained their identity and differentiation potential post-expansion and post-harvest. Further, no significant difference was found when culturing hMSCs in the culture systems prepared with either fresh or recycled FC40 perfluorocarbon.

CONCLUSIONS

These findings make the FC40/DMEM system an attractive alternative for traditional cell culture substrates due to their ease of cell recovery and recyclability, the latter impacting on overall process costs. © 2017 The Authors. Journal of Chemical Technology & Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

The effect of Me2SO overexposure during cryopreservation on HOS TE85 and hMSC viability, growth and quality

With the cell therapy industry continuing to grow, the ability to preserve clinical grade cells, including mesenchymal stem cells (MSCs), whilst retaining cell viability and function remains critical for the generation of off-the-shelf therapies. Cryopreservation of MSCs, using slow freezing, is an established process at lab scale. However, the cytotoxicity of cryoprotectants, like Me₂SO, raises questions about the impact of prolonged cell exposure to cryoprotectant at temperatures >0 °C during processing of large cell batches for allogenic therapies prior to rapid cooling in a controlled rate freezer or in the clinic prior to administration. Here we show that exposure of human bone marrow derived MSCs to Me₂SO for ≥1 h before freezing, or after thawing, degrades membrane integrity, short-term cell attachment efficiency and alters cell immunophenotype. After 2 h's exposure to Me₂SO at 37 °C post-thaw, membrane integrity dropped to ∼70% and only ∼50% of cells retained the ability to adhere to tissue culture plastic. Furthermore, only 70% of the recovered MSCs retained an immunophenotype consistent with the ISCT minimal criteria after exposure. We also saw a similar loss of membrane integrity and attachment efficiency after exposing osteoblast (HOS TE85) cells to Me₂SO before, and after, cryopreservation. Overall, these results show that freezing medium exposure is a critical determinant of product quality as process scale increases. Defining and reporting cell sensitivity to freezing medium exposure, both before and after cryopreservation, enables a fair judgement of how scalable a particular cryopreservation process can be, and consequently whether the therapy has commercial feasibility.

Serum-free process development: improving the yield and consistency of human mesenchymal stromal cell production

BACKGROUND AIMS

The cost-effective production of human mesenchymal stromal cells (hMSCs) for off-the-shelf and patient specific therapies will require an increasing focus on improving product yield and driving manufacturing consistency.

METHODS

Bone marrow-derived hMSCs (BM-hMSCs) from two donors were expanded for 36 days in monolayer with medium supplemented with either fetal bovine serum (FBS) or PRIME-XV serum-free medium (SFM). Cells were assessed throughout culture for proliferation, mean cell diameter, colony-forming potential, osteogenic potential, gene expression and metabolites.

RESULTS

Expansion of BM-hMSCs in PRIME-XV SFM resulted in a significantly higher growth rate (P < 0.001) and increased consistency between donors compared with FBS-based culture. FBS-based culture showed an inter-batch production range of 0.9 and 5 days per dose compared with 0.5 and 0.6 days in SFM for each BM-hMSC donor line. The consistency between donors was also improved by the use of PRIME-XV SFM, with a production range of 0.9 days compared with 19.4 days in FBS-based culture. Mean cell diameter has also been demonstrated as a process metric for BM-hMSC growth rate and senescence through a correlation (R(2) = 0.8705) across all conditions. PRIME-XV SFM has also shown increased consistency in BM-hMSC characteristics such as per cell metabolite utilization, in vitro colony-forming potential and osteogenic potential despite the higher number of population doublings.

CONCLUSIONS

We have increased the yield and consistency of BM-hMSC expansion between donors, demonstrating a level of control over the product, which has the potential to increase the cost-effectiveness and reduce the risk in these manufacturing processes.

Expansion, harvest and cryopreservation of human mesenchymal stem cells in a serum-free microcarrier process

Human mesenchymal stem cell (hMSC) therapies are currently progressing through clinical development, driving the need for consistent, and cost effective manufacturing processes to meet the lot‐sizes required for commercial production. The use of animal‐derived serum is common in hMSC culture but has many drawbacks such as limited supply, lot‐to‐lot variability, increased regulatory burden, possibility of pathogen transmission, and reduced scope for process optimization. These constraints may impact the development of a consistent large‐scale process and therefore must be addressed. The aim of this work was therefore to run a pilot study in the systematic development of serum‐free hMSC manufacturing process. Human bone‐marrow derived hMSCs were expanded on fibronectin‐coated, non‐porous plastic microcarriers in 100 mL stirred spinner flasks at a density of 3 × 10⁵ cells.mL⁻¹ in serum‐free medium. The hMSCs were successfully harvested by our recently‐developed technique using animal‐free enzymatic cell detachment accompanied by agitation followed by filtration to separate the hMSCs from microcarriers, with a post‐harvest viability of 99.63 ± 0.03%. The hMSCs were found to be in accordance with the ISCT characterization criteria and maintained hMSC outgrowth and colony‐forming potential. The hMSCs were held in suspension post‐harvest to simulate a typical pooling time for a scaled expansion process and cryopreserved in a serum‐free vehicle solution using a controlled‐rate freezing process. Post‐thaw viability was 75.8 ± 1.4% with a similar 3 h attachment efficiency also observed, indicating successful hMSC recovery, and attachment. This approach therefore demonstrates that once an hMSC line and appropriate medium have been selected for production, multiple unit operations can be integrated to generate an animal component‐free hMSC production process from expansion through to cryopreservation. Biotechnol. Bioeng. 2015;112: 1696–1707. © 2015 The Authors. Biotechnology and Bioengineering Published by Wiley Periodicals, Inc.