Fibrinogen-Depleted Equine Platelet Lysate Affects the Characteristics and Functionality of Mesenchymal Stem Cells

Culture and Immunomodulation of Equine Muscle-Derived Mesenchymal Stromal Cells: A Comparative Study of Innovative 2D versus 3D Models Using Equine Platelet Lysate

Muscle-derived mesenchymal stromal cells (mdMSCs) hold great promise in regenerative medicine due to their immunomodulatory properties, multipotent differentiation capacity and ease of collection. However, traditional in vitro expansion methods use fetal bovine serum (FBS) and have numerous limitations including ethical concerns, batch-to-batch variability, immunogenicity, xenogenic contamination and regulatory compliance issues. This study investigates the use of 10% equine platelet lysate (ePL) obtained by plasmapheresis as a substitute for FBS in the culture of mdMSCs in innovative 2D and 3D models. Using muscle microbiopsies as the primary cell source in both models showed promising results. Initial investigations indicated that small variations in heparin concentration in 2D cultures strongly influenced medium coagulation with an optimal proliferation observed at final heparin concentrations of 1.44 IU/mL. The two novel models investigated showed that expansion of mdMSCs is achievable. At the end of expansion, the 3D model revealed a higher total number of cells harvested (64.60 ± 5.32 million) compared to the 2D culture (57.20 ± 7.66 million). Trilineage differentiation assays confirmed the multipotency (osteoblasts, chondroblasts and adipocytes) of the mdMSCs generated in both models with no significant difference observed. Immunophenotyping confirmed the expression of the mesenchymal stem cell (MSC) markers CD-90 and CD-44, with low expression of CD-45 and MHCII markers for mdMSCs derived from the two models. The generated mdMSCs also had great immunomodulatory properties. Specific immunological extraction followed by enzymatic detection (SIEFED) analysis demonstrated that mdMSCs from both models inhibited myeloperoxidase (MPO) activity in a strong dose-dependent manner. Moreover, they were also able to reduce reactive oxygen species (ROS) activity, with mdMSCs from the 3D model showing significantly higher dose-dependent inhibition compared to the 2D model. These results highlighted for the first time the feasibility and efficacy of using 10% ePL for mdMSC expansion in novel 2D and 3D approaches and also that mdMSCs have strong immunomodulatory properties that can be exploited to advance the field of regenerative medicine and cell therapy instead of using FBS with all its drawbacks.

The dark side of foetal bovine serum in extracellular vesicle studies

Extracellular vesicles (EVs) have been shown to be involved in cell-cell communication and to take part in both physiological and pathological processes. Thanks to their exclusive cargo, which includes proteins, lipids, and nucleic acids from the originating cells, they are gaining interest as potential biomarkers of disease. In recent years, their appealing features have been fascinating researchers from all over the world, thus increasing the number of in vitro studies focused on EV release, content, and biological activities. Cultured cell lines are the most-used source of EVs; however, the EVs released in cell cultures are influenced by the cell culture conditions, such as the use of foetal bovine serum (FBS). FBS is the most common supplement for cell culture media, but it is also a source of contaminants, such as exogenous bovine EVs, RNA, and protein aggregates, that can contaminate the cell-derived EVs and influence their cargo composition. The presence of FBS contaminants in cell-derived EV samples is a well-known issue that limits the clinical applications of EVs, thus increasing the need for standardization. In this review, we will discuss the pros and cons of using FBS in cell cultures as a source of EVs, as well as the protocols used to remove contaminants from FBS.

A Review of Fetal Bovine Serum in the Culture of Mesenchymal Stromal Cells and Potential Alternatives for Veterinary Medicine

Fetal bovine serum (FBS) remains widely used as a supplement in cell culture media used in the isolation and expansion of mesenchymal stromal cells (MSC) despite longstanding practical, clinical, and ethical concerns over its use. As a result, research on alternative culture media supplement solutions that conserve crucial MSC characteristics has become increasingly relevant. Species-specific supplements and serum-free media such as platelet lysate or chemically defined media have been assessed for their effect in MSC cultures regarding proliferation, differentiation, and immunomodulatory capacity. While none of the alternatives offer a complete solution in replacing traditional FBS supplemented media for culturing MSCs for all species, short-term or transitional use of FBS-free media can perform equally well and could address some of the concerns over the use of FBS.

Preparation Technique Affects Recipient Immune Targeting of Autologous Mesenchymal Stem Cells

Fetal bovine serum (FBS) is used for MSC preparation in pre-clinical animal models and veterinary applications, recently in US clinical trials, and for MSC products with current foreign market authorizations. The effect of anti-bovine titers, which are common in animals and humans, has not been investigated. In the equine model, where anti-bovine titers are universally high due to routine vaccination, we evaluated the recipient immune response to autologous MSCs prepared with and without FBS. Preparation of MSCs with FBS resulted in post injection inflammation and antibody mediated cytotoxicity of MSCs when compared to MSCs prepared without FBS. Importantly, synovial MSC concentrations were reduced and LPS induced pain was higher, when FBS was used to prepare MSCs, demonstrating reduced efficacy of FBS prepared MSCs. Fetal bovine serum should no longer be utilized for MSC preparation in pre-clinical study, clinical study, or veterinary applications. The use of FBS in previously reported studies, and in MSC therapeutics with current foreign market authorization, should be considered when interpreting results.

A critical appraisal of humanized alternatives to fetal bovine serum for clinical applications of umbilical cord derived mesenchymal stromal cells

OBJECTIVE

The study is aimed to verify the possibility of using humanized alternatives to fetal bovine serum (FBS) such as umbilical cord blood plasma (CBP) and AB⁺ plasma to support the long-term growth of mesenchymal stromal cells (MSCs) derived from the umbilical cord. We hypothesized that umbilical CBP would be a potential substitute to FBS, especially for small scale autologous clinical transplantations.

METHODS

The MSCs were cultured for six consecutive passages to evaluate xeno-free media's ability to support long-term growth. Cell proliferation rates, colony-forming-unit (CFU) efficiency and population doublings of expanded MSCs, were investigated. Ex vivo expanded MSCs were further characterized using flow cytometry and quantitative PCR. The impact of cryopreservation and composition of cryomedium on phenotype, viability of MSC was also assessed.

RESULTS

Our results on cell proliferation, colony-forming unit efficiency suggested that the expansion of the cells was successfully carried out in media supplemented with humanized alternatives. MSCs showed lower CFU counts in FBS (~ 25) than humanized alternatives (~ 35). The gene expression analysis revealed that transcripts showed significant differential expression by two to three folds in the FBS group compared with MSCs grown in medium with humanized alternatives (p < 0.05). In addition, MSCs grown in a medium with FBS had more osteogenic activity, a signature of unwanted differentiation. The majority of ex vivo expanded MSCs at early and late passages expressed CD44⁺, CD73⁺, CD105⁺, CD90⁺, and CD166⁺ in all the experimental groups tested (~ 90%). In contrast to the other MSC surface markers, expression levels of STRO-1⁺ (~ 21-10%) and TNAP⁺ (~ 29-11%) decreased with the increase in passage number for MSCs cultured in a FBS-supplemented medium (p < 0.05).

CONCLUSION

Our results established that CBP supported culture of umbilical cord tissue-derived MSCs and is a safer Xeno free replacement to FBS. The use of CBP also enables the storage of umbilical cord tissue derived MSCs in patient-specific conditions to minimize adverse events if cells are delivered directly to the patient.

[Standardized management of platelet derivatives for tissue regeneration research and applications]

Objective

To summary the standardized management in research and applications of platelet derivatives for tissue regeneration.

Methods

The related literature about bottlenecks and standardized management of platelet derivatives in recent years was reviewed and analyzed.

Results

Although the platelet derivatives are increasingly used to accelerate the regenerative processes of injured joint, skin, nerve, ligament/tendon, and alveolar bone, etc., the large variation in preparation methods, diverse nomenclature, incomplete reporting system, and lack of quantitative and standardized management of the preparation process have caused uncertainty and incomparability of research and application results. In recent years, there has been a trend towards standardized research and management of platelet derivatives.

Conclusion

The implementation of standardized research and quality management will contribute to promote the research and application of platelet derivatives in the field of tissue regeneration.

Scalable Production of Equine Platelet Lysate for Multipotent Mesenchymal Stromal Cell Culture

Translation of multipotent mesenchymal stromal cell (MSC)-based therapies is advancing in human and veterinary medicine. One critical issue is the in vitro culture of MSC before clinical use. Using fetal bovine serum (FBS) as supplement to the basal medium is still the gold standard for cultivation of many cell types including equine MSC. Alternatives are being explored, with substantial success using platelet lysate-supplemented media for human MSC. However, progress lags behind in the veterinary field. The aim of this study was to establish a scalable protocol for equine platelet lysate (ePL) production and to test the ePL in equine MSC culture. Whole blood was harvested into blood collection bags from 20 healthy horses. After checking sample materials for pathogen contamination, samples from 19 animals were included. Platelet concentrates were prepared using a buffy coat method. Platelets, platelet-derived growth factor BB, and transforming growth factor β1 concentrations were increased in the concentrates compared with whole blood or serum (p < 0.05), while white blood cells were reduced (p < 0.05). The concentrates were lysed using freeze/thaw cycles, which eliminated the cells while growth factor concentrations were maintained. Donor age negatively correlated with platelet and growth factor concentrations after processing (p < 0.05). Finally, all lysates were pooled and the ePL was evaluated as culture medium supplement in comparison with FBS, using adipose-derived MSC from four unrelated donor horses. MSC proliferated well in 10% FBS as well as in 10% ePL. However, using 5 or 2.5% ePL entailed highly inconsistent proliferation or loss of proliferation, with significant differences in generation times and confluencies (p < 0.05). MSC expressed the surface antigens CD90, CD44, and CD29, but CD73 and CD105 detection was low in all culture media. Adipogenic and osteogenic differentiation led to similar results in MSC from different culture media. The buffy coat method is useful to produce equine platelet concentrate with increased platelet and reduced white blood cell content in large scales. The ePL obtained supports MSC expansion similar as FBS when used at the same concentration (10%). Further investigations into equine MSC functionality in culture with ePL should follow.