Quality assessment of a serum and xenofree medium for the expansion of human GMP-grade mesenchymal stromal cells

Serum-free endothelial cell culture medium for vascular smooth muscle cells sheet formation

BACKGROUND

Cell sheet technology has been identified as a promising approach for the construction of tissue-engineered vascular grafts (TEVGs). However, concerns regarding immunogenicity and ethical issues, which are raised by the use of fetal bovine serum (FBS) in traditional culture systems, limit its potential for clinical translation. Serum-free medium (SFM) has emerged as a safer and more controllable alternative, but further validation is required to determine its effectiveness and superiority in generating high-quality cell sheets.

METHODS

This study systematically compared cell sheets generated under SFM and 10% FBS culture conditions in terms of structure, cellular phenotype, and functional properties. The expression levels of α-SMA and SM22, markers of vascular smooth muscle cells(VSMCs), were evaluated using immunofluorescence staining, qRT-PCR, and Western blot analysis to assess cellular phenotype. Histological staining and mechanical testing were employed to compare the morphology and mechanical properties of the cell sheets, while extracellular matrix (ECM) deposition and biochemical characteristics were also analyzed.

RESULTS

Under SFM conditions, cells exhibited significantly higher α-SMA and SM22 expression levels (qRT-PCR showed a 1.8-fold and 2-fold increase, respectively; ****p < 0.0001) with clearer cytoskeletal arrangement. Cell sheets formed in SFM displayed comparable area(ns, p > 0.05), thickness(**p < 0.01), and mechanical properties to those cultured in 10% FBS, while ECM deposition was significantly enhanced (collagen content increased by approximately 40%, **p < 0.01). Furthermore, histological analysis revealed that cell sheets generated under SFM conditions were more compact and uniform, exhibiting superior structural organization.

CONCLUSION

SFM facilitates the generation of cell sheets that exhibit structural and functional properties analogous to those cultured in FBS. Additionally, SFM promotes cellular phenotype transition and ECM deposition. Consequently, SFM provides a safer, more controllable, and clinically translatable solution for cell sheet construction.

Automated Manufacturing Processes and Platforms for Large-scale Production of Clinical-grade Mesenchymal Stem/ Stromal Cells

Mesenchymal stem/stromal cells (MSCs) hold immense potential for regenerative medicine due to their remarkable regenerative and immunomodulatory properties. However, their therapeutic application requires large-scale production under stringent regulatory standards and Good Manufacturing Practice (GMP) guidelines, presenting significant challenges. This review comprehensively evaluates automated manufacturing processes and platforms for the scalable production of clinical-grade MSCs. Various large-scale culture vessels, including multilayer flasks and bioreactors, are analyzed for their efficacy in MSCs expansion. Furthermore, automated MSCs production platforms, such as Quantum® Cell Expansion System, CliniMACS Prodigy®, NANT001/ XL, CellQualia™, Cocoon® Platform, and Xuri™ Cell Expansion System W25 are reviewed and compared as well. We also underscore the importance of optimizing culture media specifically emphasizing the shift from fetal bovine serum to humanized or serum-free alternatives to meet GMP standards. Moreover, advances in alternative cryopreservation methods and controlled-rate freezing systems, that offer promising improvements in MSCs preservation, are discussed as well. In conclusion, advancing automated manufacturing processes and platforms is essential for realizing the full potential of MSCs-based regenerative medicine and accomplishing the increasing demand for cell-based therapies. Collaborative initiatives involving industry, academia, and regulatory bodies are emphasized to accelerate the translation of MSCs-based therapies into clinical practice.

Comparative Analysis of Serum and Serum-Free Medium Cultured Mesenchymal Stromal Cells for Cartilage Repair

Mesenchymal stromal cells (MSCs) are promising candidates for cartilage repair therapy due to their self-renewal, chondrogenic, and immunomodulatory capacities. It is widely recognized that a shift from fetal bovine serum (FBS)-containing medium toward a fully chemically defined serum-free (SF) medium would be necessary for clinical applications of MSCs to eliminate issues such as xeno-contamination and batch-to-batch variation. However, there is a notable gap in the literature regarding the evaluation of the chondrogenic ability of SF-expanded MSCs (SF-MSCs). In this study, we compared the in vivo regeneration effect of FBS-MSCs and SF-MSCs in a rat osteochondral defect model and found poor cartilage repair outcomes for SF-MSCs. Consequently, a comparative analysis of FBS-MSCs and SF-MSCs expanded using two SF media, MesenCult™-ACF (ACF), and Custom StemPro™ MSC SFM XenoFree (XF) was conducted in vitro. Our results show that SF-expanded MSCs constitute variations in morphology, surface markers, senescence status, differentiation capacity, and senescence/apoptosis status. Highly proliferative MSCs supported by SF medium do not always correlate to their chondrogenic and cartilage repair ability. Prior determination of the SF medium's ability to support the chondrogenic ability of expanded MSCs is therefore crucial when choosing an SF medium to manufacture MSCs for clinical application in cartilage repair.

The issue of heterogeneity of MSC-based advanced therapy medicinal products-a review

Mesenchymal stromal stem cells (MSCs) possess a remarkable potential for numerous clinical applications due to their unique properties including self-renewal, immunomodulation, paracrine actions and multilineage differentiation. However, the translation of MSC-based Advanced Therapy Medicinal Products (ATMPs) into the clinic has frequently met with inconsistent outcomes. One of the suspected reasons for this issue is the inherent and extensive variability that exists among such ATMPs, which makes the interpretation of their clinical efficacy difficult to assess, as well as to compare the results of various studies. This variability stems from numerous reasons including differences in tissue sources, donor attributes, variances in manufacturing protocols, as well as modes of administration. MSCs can be isolated from various tissues including bone marrow, umbilical cord, adipose tissue and others, each with its unique phenotypic and functional characteristics. While MSCs from different sources do share common features, they also exhibit distinct gene expression profiles and functional properites. Donor-specific factors such as age, sex, body mass index, and underlying health conditions can influence MSC phenotype, morphology, differentiation potential and function. Moreover, variations in preparation of MSC products introduces additional heterogeneity as a result of cell culture media composition, presence or absence of added growth factors, use of different serum supplements and culturing techniques. Once MSC products are formulated, storage protocols play a pivotal role in its efficacy. Factors that affect cell viability include cell concentration, delivery solution and importantly, post-thawing protocols where applicable. Ensuing, differences in administration protocols can critically affect the distribution and functionallity of administered cells. As MSC-based therapies continue to advance through numerous clinical trials, implication of strategies to reduce product heterogeneity is imperative. Central to addressing these challenges is the need for precise prediction of clinical responses, which require well-defined MSC populations and harmonized assessment of their specific functions. By addressing these issues by meaningful approaches, such as, e.g., MSC pooling, the field can overcome barriers to advance towards more consistent and effective MSC-based therapies.

The influence of xeno-free culture conditions on the angiogenic and adipogenic differentiation properties of adipose tissue-derived stem cells

Introduction

Before performing cell therapy clinical trials, it is important to understand how cells are influenced by different growth conditions and to find optimal xeno-free medium formulations. In this study we have investigated the properties of adipose tissue-derived stem cells (ASCs) cultured under xeno-free conditions.

Methods

Human lipoaspirate samples were digested to yield the stromal vascular fraction cells which were then seeded in i) Minimum Essential Medium-α (MEM-α) supplemented with 10 % (v/v) fetal bovine serum (FBS), ii) MEM-α supplemented with 2 % (v/v) human platelet lysate (PLT) or iii) PRIME-XV MSC expansion XSFM xeno-free, serum free medium (XV). Flow cytometry for ASCs markers CD73, CD90 and CD105 together with the putative pericyte marker CD146 was performed. Growth rates were monitored over multiple passages and adipogenic differentiation performed at early and expanded passage culture. Growth factor gene expression was analyzed and an in vitro angiogenesis assay performed.

Results

Cells in FBS and PLT grew at similar rates whereas the cells cultured in XV medium proliferated significantly faster up to 60 days in culture. All cultures were >98 % positive for CD73, CD90 and CD105, whereas CD146 expression was significantly higher in XV cells. Adipogenic differentiation was most pronounced in cells which had been cultured in XV medium whilst cells grown in PLT were inferior compared with cells from the FBS cultures. IGF1 gene expression was highest in cells cultured in PLT whilst cells grown in XV medium showed 10-fold lower expression compared with FBS cells. In contrast, HGF gene expression was 90-fold greater in cells cultured in XV medium compared with those cultured in FBS. Conditioned medium from XV cultured cells showed the most angiogenic activity, inducing the greatest endothelial cell network formation and maturation.

Conclusion

Culture under different conditions alters the ASCs characteristics. Since cells cultured in XV medium showed the best adipogenic and angiogenic profile this might be a preferred medium formulation for preparing cells required for reconstructive surgical applications such as cell-assisted fat grafting.

Effects of Oral Cavity Stem Cell Sources and Serum-Free Cell Culture on Hydrogel Encapsulation of Mesenchymal Stem Cells for Bone Regeneration: An In Vitro Investigation

INTRODUCTION

To develop a stem cell delivery model and improve the safety of stem cell transplantation for bone regeneration, this study aimed to determine the effects of stem cell sources, serum-free cell culture, and hydrogel cell encapsulation on the growth and osteogenic differentiation of mesenchymal stem cells (MSCs) from the oral cavity.

METHODS

The study groups were categorized according to stem cell sources into buccal fat pad adipose (hBFP-ADSCs) (Groups 1, 4, and 7), periodontal ligament (hPDLSCs) (Groups 2, 5, and 8), and dental pulp-derived stem cells (hDPSCs) (Groups 3, 6, and 9). MSCs from each source were isolated and expanded in three types of sera: fetal bovine serum (FBS) (Groups 1-3), human serum (HS) (Groups 4-6), and synthetic serum (SS) (StemPro™ MSC SFM) (Groups 7-9) for monolayer (m) and hydrogel cell encapsulation cultures (e). Following this, the morphology, expression of MSC cell surface antigens, growth, and osteogenic differentiation potential of the MSCs, and the expression of adhesion molecules were analyzed and compared.

RESULTS

SS decreased variations in the morphology and expression levels of cell surface antigens of MSCs from three cell sources (Groups 7m-9m). The levels of osteoblastic differentiation of the hPDLSCs and hBFP-ADSCs were increased in SS (Groups 8m and 7m) and the cell encapsulation model (Groups 1e, 4e, 7e-9e), but the promoting effects of SS were decreased in a cell encapsulation model (Groups 7e-9e). The expression levels of the alpha v beta 3 (ITG-αVβ3) and beta 1 (ITG-β1) integrins in the encapsulated cells in FBS (Group 1e) were higher than those in the SS (Group 7e).

CONCLUSIONS

Human PDLSCs and BFP-ADSCs were the optimum stem cell source for stem cell encapsulation by using nanohydroxyapatite-calcium carbonate microcapsule-chitosan/collagen hydrogel in serum-free conditions.

Challenges of Cell Counting in Cell Therapy Products

Cell counting is a common and fundamental cell measurement technique that plays a crucial role in the development and quality control of cell therapy products. However, accurate and reliable cell counting can be challenging owing to the complexity of cell preparations, diverse counting purposes, and various counting methods. This review summarizes the challenges encountered in cell counting for cell therapy products and provides strategies to improve the cell counting accuracy, thereby guiding the counting process and ensuring the quality of cell therapy products.

Expansion and characterization of human limbus-derived stromal/mesenchymal stem cells in xeno-free medium for therapeutic applications

BACKGROUND

Mesenchymal stem cells (MSCs) have been proven to prevent and clear corneal scarring and limbal stem cell deficiency. However, using animal-derived serum in a culture medium raises the ethical and regulatory bar. This study aims to expand and characterize human limbus-derived stromal/mesenchymal stem cells (hLMSCs) for the first time in vitro in the xeno-free medium.

METHODS

Limbal tissue was obtained from therapeutic grade corneoscleral rims and subjected to explant culture till tertiary passage in media with and without serum (STEM MACS XF; SM), to obtain pure hLMSCs. Population doubling time, cell proliferation, expression of phenotypic markers, tri-lineage differentiation, colony-forming potential and gene expression analysis were carried out to assess the retention of phenotypic and genotypic characteristics of hLMSCs.

RESULTS

The serum-free medium supported the growth of hLMSCs, retaining similar morphology but a significantly lower doubling time of 23 h (*p < 0.01) compared to the control medium. FACS analysis demonstrated ≥ 90% hLMSCs were positive for CD90⁺, CD73⁺, CD105⁺, and ≤ 6% were positive for CD45^-, CD34^- and HLA-DR^-. Immunofluorescence analysis confirmed similar expression of Pax6⁺, COL IV⁺, ABCG2⁺, ABCB5⁺, VIM⁺, CD90⁺, CD105⁺, CD73⁺, HLA-DR^- and CD45^-, αSMA^- in both the media. Tri-lineage differentiation potential and gene expression of hLMSCs were retained similarly to that of the control medium.

CONCLUSION

The findings of this study demonstrate successful isolation, characterization and culture optimization of hLMSCs for the first time in vitro in a serum-free environment. This will help in the future pre-clinical and clinical applications of MSCs in translational research.