Blood type and breed-associated differences in cell marker expression on equine bone marrow-derived mesenchymal stem cells including major histocompatibility complex class II antigen expression

The Myofibroblast Fate of Therapeutic Mesenchymal Stromal Cells: Regeneration, Repair, or Despair?

Mesenchymal stromal cells (MSCs) can be isolated from various tissues of healthy or patient donors to be retransplanted in cell therapies. Because the number of MSCs obtained from biopsies is typically too low for direct clinical application, MSC expansion in cell culture is required. However, ex vivo amplification often reduces the desired MSC regenerative potential and enhances undesired traits, such as activation into fibrogenic myofibroblasts. Transiently activated myofibroblasts restore tissue integrity after organ injury by producing and contracting extracellular matrix into scar tissue. In contrast, persistent myofibroblasts cause excessive scarring-called fibrosis-that destroys organ function. In this review, we focus on the relevance and molecular mechanisms of myofibroblast activation upon contact with stiff cell culture plastic or recipient scar tissue, such as hypertrophic scars of large skin burns. We discuss cell mechanoperception mechanisms such as integrins and stretch-activated channels, mechanotransduction through the contractile actin cytoskeleton, and conversion of mechanical signals into transcriptional programs via mechanosensitive co-transcription factors, such as YAP, TAZ, and MRTF. We further elaborate how prolonged mechanical stress can create persistent myofibroblast memory by direct mechanotransduction to the nucleus that can evoke lasting epigenetic modifications at the DNA level, such as histone methylation and acetylation. We conclude by projecting how cell culture mechanics can be modulated to generate MSCs, which epigenetically protected against myofibroblast activation and transport desired regeneration potential to the recipient tissue environment in clinical therapies.

Impact of different formulations of platelet lysate on proliferative and immune profile of equine mesenchymal stromal cells

Platelet lysate (PL) is investigated as a potential replacement for fetal bovine serum (FBS) in cell culture. However, there is limited research on its impact on the immune profile of equine mesenchymal stromal cells (eMSCs). This study aimed to evaluate the effects of different PL formulations on the proliferative capacity, multipotentiality, and immune profile of equine adipose tissue-derived MSCs (eAD-MSCs). In vitro growth kinetics and trilineage differentiation of eAD-MSCs (n = 7) were assessed under three culture conditions: medium-concentration PL (MPL), high-concentration PL (HPL), and FBS as a control. The immune profile was evaluated by studying the expression of immunogenic receptors such as MHC I, MHC II, and immunomodulatory molecules IL-6, IL-10, and TNF-α, determined by gene expression, surface marker expression, and cytokine quantification. Both PL formulations, pooled from 5 donors, exhibited 3.3 and 6.5-fold higher platelet counts than baseline plasma for MPL and HPL, respectively. Higher concentrations of TGF-β and PDGF were found in both PL formulations compared to baseline. Furthermore, MPL and HPL subcultures demonstrated proliferative, clonogenic, and multipotent capacities similar to FBS. The immune profile of PL-cultured cells exhibited gene expression levels related to immunogenicity and immunomodulation similar to the reference condition, and the surface antigen presence of MHC II was also similar. However, HPL media exhibited higher IL-6, IL-10, and TNF-α concentrations in the culture supernatant. In conclusion, both PL media contained higher concentrations of growth factors compared to FBS, supporting the in vitro culture of eAD-MSCs with proliferative, clonogenic, and multipotent capacity similar to the reference medium. Nonetheless, PL usage led to a variation in the immunomodulatory cytokine microenvironment, with higher concentrations of IL-6, IL-10, and TNF-α in HPL media compared to MPL and FBS.

Impact of platelet lysate on immunoregulatory characteristics of equine mesenchymal stromal cells

Multipotent mesenchymal stromal cells (MSC) play an increasing role in the treatment of immune-mediated diseases and inflammatory processes. They regulate immune cells via cell-cell contacts and by secreting various anti-inflammatory molecules but are in turn influenced by many factors such as cytokines. For MSC culture, platelet lysate (PL), which contains a variety of cytokines, is a promising alternative to fetal bovine serum (FBS). We aimed to analyze if PL with its cytokines improves MSC immunoregulatory characteristics, with the perspective that PL could be useful for priming the MSC prior to therapeutic application. MSC, activated peripheral blood mononuclear cells (PBMC) and indirect co-cultures of both were cultivated in media supplemented with either PL, FBS, FBS+INF-γ or FBS+IL-10. After incubation, cytokine concentrations were measured in supernatants and control media. MSC were analyzed regarding their expression of immunoregulatory genes and PBMC regarding their proliferation and percentage of FoxP3+ cells. Cytokines, particularly IFN-γ and IL-10, remained at high levels in PL control medium without cells but decreased in cytokine-supplemented control FBS media without cells during incubation. PBMC released IFN-γ and IL-10 in various culture conditions. MSC alone only released IFN-γ and overall, cytokine levels in media were lowest when MSC were cultured alone. Stimulation of MSC either by PBMC or by PL resulted in an altered expression of immunoregulatory genes. In co-culture with PBMC, the MSC gene expression of COX2, TNFAIP6, IDO1, CXCR4 and MHC2 was upregulated and VCAM1 was downregulated. In the presence of PL, COX2, TNFAIP6, VCAM1, CXCR4 and HIF1A were upregulated. Functionally, while no consistent changes were found regarding the percentage of FoxP3+ cells, MSC decreased PBMC proliferation in all media, with the strongest effect in FBS media supplemented with IL-10 or IFN-γ. This study provides further evidence that PL supports MSC functionality, including their immunoregulatory mechanisms. The results justify to investigate functional effects of MSC cultured in PL-supplemented medium on different types of immune cells in more detail.

Trends of regenerative tissue engineering for oral and maxillofacial reconstruction in veterinary medicine

Oral and maxillofacial (OMF) defects are not limited to humans and are often encountered in other species. Reconstructing significant tissue defects requires an excellent strategy for efficient and cost-effective treatment. In this regard, tissue engineering comprising stem cells, scaffolds, and signaling molecules is emerging as an innovative approach to treating OMF defects in veterinary patients. This review presents a comprehensive overview of OMF defects and tissue engineering principles to establish proper treatment and achieve both hard and soft tissue regeneration in veterinary practice. Moreover, bench-to-bedside future opportunities and challenges of tissue engineering usage are also addressed in this literature review.

Bioprocess development for cord blood mesenchymal stromal cells on microcarriers in Vertical-Wheel bioreactors

Equine mesenchymal stromal cells (MSCs) have been found to be beneficial for the treatment of many ailments, including orthopedic injuries, due to their superior differentiation potential and immunomodulating properties. Cell therapies require large cell numbers, which are not efficiently generated using conventional static expansion methods. Expansion of equine cord blood-derived MSCs (eCB-MSCs) in bioreactors, using microcarriers as an attachment surface, has the potential to generate large numbers of cells with increased reproducibility and homogeneity compared with static T-flask expansion. This study investigated the development of an expansion process using Vertical-Wheel (VW) bioreactors, a single-use bioreactor technology that incorporates a wheel instead of an impeller. Initially, microcarriers were screened at small scale to assess eCB-MSC attachment and growth and then in bioreactors to assess cell expansion and harvesting. The effect of different donors, serial passaging, and batch versus fed batch were all examined in 0.1 L VW bioreactors. The use of VW bioreactors with an appropriate microcarrier was shown to be able to produce cell densities of up to 1E6 cells/mL, while maintaining cell phenotype and functionality, thus demonstrating great potential for the use of these bioreactors to produce large cell numbers for cell therapies.

Transcriptome changes during osteogenesis of porcine mesenchymal stem cells derived from different types of synovial membranes and genetic background

Synovial membrane mesenchymal stem cells (SMSCs) often serve as in vitro model for bone disease, but the molecular mechanisms driving osteogenesis in SMSCs from different donor cells of various sources and breeds remain unclear. In this study, porcine SMSCs isolated from adipose synovium (FP) and fibrous synovium (FS) of Angeln Saddleback (AS) and German Landrace (DL) were used to discover the signaling network change after osteogenic induction. During osteogenic differentiation, mineral deposition was first observed at day 14 and further increased until day 21. Transcriptional changes between day 1 and day 21 were enriched in several signaling pathways, including Wnt, PI3K-Akt, and TGF-beta pathway. Certain pathways related to osteogenesis, including osteoblast differentiation, regulation of bone mineralization, and BMP signaling pathway, were enriched at late time points, as confirmed by the osteogenic markers ALPL, COL1A1, and NANOG. A fraction of differentially expressed genes (DEGs) were found between FP and FS, while DEGs between AS and DL increased during the differentiation phase until day 7 and then decreased from day 14 to day 21. These genes are involved in several important signaling pathways, including TGF-beta, Wnt, and lipid-related signaling pathways, suggesting that SMSCs from these two breeds have different osteogenic capabilities.

Isolation and cultivation as well as in situ identification of MSCs from equine dental pulp and periodontal ligament

Introduction

The lifelong eruption places a great demand on the dental pulp and periodontal ligament (PDL) of horse teeth. Cells within the pulp and PDL seem to play a key role during this remodeling.

Methods

In this study, we isolated and cultivated MSCs (medicinal signaling cells) from dental pulp, PDL and retrobulbar fat of four horses. Subsequently, we analyzed them by flow cytometry and immunohistochemistry to determine and compare their characteristics. In addition, we localized these cells within the tissue structure via immunohistochemistry of histological sections. For these analyses, several surface markers were applied.

Results

The described method illustrates a feasible approach to isolate and cultivate MSCs from equine dental pulp and PDL. In the flow cytometry a vast majority of cultivated cells were positive for CD90 and CD40 and negative for CD11a/18, CD45, CD105 and MHCII suggesting that these cells feature characteristics of MSCs. Immunohistochemistry of histological pulp and PDL sections showed the localization of CD90 positive cells especially in the perivascular region and the subodontoblastic layer.

Discussion

Our findings indicate that the isolation and cultivation of MSCs from equine dental pulp and PDL is feasible although an elaborate and complicated harvesting protocol is required. MSCs isolated from dental pulp and PDL are regarded as candidates for new therapeutical approaches in equine dental medicine like regeneration of periodontal lesions, enhancement of periodontal re-attachment after dental replantation and stimulation of pulp-obliteration and apexification in combination with endodontic therapies.

The immunomodulation-immunogenicity balance of equine Mesenchymal Stem Cells (MSCs) is differentially affected by the immune cell response depending on inflammatory licensing and major histocompatibility complex (MHC) compatibility

The immunomodulatory properties of equine mesenchymal stem cells (MSCs) are important for their therapeutic potential and for their facilitating role in their escape from immune recognition, which may also be influenced by donor-recipient major histocompatibility complex (MHC) matching/mismatching and MHC expression level. Factors such as inflammation can modify the balance between regulatory and immunogenic profiles of equine MSCs, but little is known about how the exposure to the immune system can affect these properties in equine MSCs. In this study, we analyzed the gene expression and secretion of molecules related to the immunomodulation and immunogenicity of equine MSCs, either non-manipulated (MSC-naive) or stimulated by pro-inflammatory cytokines (MSC-primed), before and after their exposure to autologous or allogeneic MHC-matched/-mismatched lymphocytes, either activated or resting. Cytokine priming induced the immunomodulatory profile of MSCs at the baseline (MSCs cultured alone), and the exposure to activated lymphocytes further increased the expression of interleukin 6 (IL6), cyclooxygenase 2, and inducible nitric oxide synthase, and IL6 secretion. Activated lymphocytes were also able to upregulate the regulatory profile of MSC-naive to levels comparable to cytokine priming. On the contrary, resting lymphocytes did not upregulate the immunomodulatory profile of equine MSCs, but interestingly, MSC-primed exposed to MHC-mismatched lymphocytes showed the highest expression and secretion of these mediators, which may be potentially linked to the activation of lymphocytes upon recognition of foreign MHC molecules. Cytokine priming alone did not upregulate the immunogenic genes, but MSC-primed exposed to activated or resting lymphocytes increased their MHC-I and MHC-II expression, regardless of the MHC-compatibility. The upregulation of immunogenic markers including CD40 in the MHC-mismatched co-culture might have activated lymphocytes, which, at the same time, could have promoted the immune regulatory profile aforementioned. In conclusion, activated lymphocytes are able to induce the equine MSC regulatory profile, and their effects seem to be additive to the priming action. Importantly, our results suggest that the lymphocyte response against MHC-mismatched MSC-primed would promote further activation of their immunomodulatory ability, which eventually might help them evade this reaction. Further studies are needed to clarify how these findings might have clinical implications in vivo, which will help developing safer and more effective therapies.

Immune response to allogeneic equine mesenchymal stromal cells

BACKGROUND

Mesenchymal stromal cells (MSCs) are believed to be hypoimmunogeneic with potential use for allogeneic administration.

METHODS

Bone marrow was harvested from Connemara (n = 1), Standardbred (n = 6), and Thoroughbred (n = 3) horses. MSCs were grouped by their level of expression of major histocompatibility factor II (MHC II). MSCs were then sub-grouped by those MSCs derived from universal blood donor horses. MSCs were isolated and cultured using media containing fetal bovine serum until adequate numbers were acquired. The MSCs were cultured in xenogen-free media for 48 h prior to use and during all assays. Autologous and allogeneic MSCs were then directly co-cultured with responder leukocytes from the Connemara horse in varying concentrations of MSCs to leukocytes (1:1, 1:10, and 1:100). MSCs were also cultured with complement present and heat-inactivated complement to determine whether complement alone would decrease MSC viability. MSCs underwent haplotyping of their equine leukocyte antigen (ELA) to determine whether the MHC factors were matched or mismatched between the donor MSCs and the responder leukocytes.

RESULTS

All allogeneic MSCs were found to be ELA mismatched with the responder leukocytes. MHC II-low and universal blood donor MSCs caused no peripheral blood mononuclear cell (PBMC) proliferation, no increase in B cells, and no activation of CD8 lymphocytes. Universal blood donor MSCs stimulated a significant increase in the number of T regulatory cells. Neutrophil interaction with MSCs showed that universal blood donor and MHC II-high allogeneic MSCs at the 6 h time point in co-culture caused greater neutrophil activation than the other co-culture groups. Complement-mediated cytotoxicity did not consistently cause MSC death in cultures with active complement as compared to those with inactivated complement. Gene expression assays revealed that the universal blood donor group and the MHC II-low MSCs were more metabolically active both in the anabolic and catabolic gene categories when cultured with allogeneic lymphocytes as compared to the other co-cultures. These upregulated genes included CD59, FGF-2, HGF, IDO, IL-10, IL-RA, IL-2, SOX2, TGF-β1, ADAMSTS-4, ADAMSTS-5, CCL2, CXCLB/IL-8, IFNγ, IL-1β, and TNFα.

CONCLUSIONS

MHC II-low MSCs are the most appropriate type of allogeneic MSC to prevent activation of the innate and cell-mediated component of the adaptive immune systems and have increased gene expression as compared to other allogeneic MSCs.

Therapeutic Use of Mesenchymal Stromal Cells: The Need for Inclusive Characterization Guidelines to Accommodate All Tissue Sources and Species

Following their discovery over 50 years ago, mesenchymal stromal cells (MSCs) have become one of the most studied cellular therapeutic products by both academia and industry due to their regenerative potential and immunomodulatory properties. The promise of MSCs as a therapeutic modality has been demonstrated by preclinical data yet has not translated to consistent, successful clinical trial results in humans. Despite the disparities across the field, MSC shareholders are unified under one common goal-to use MSCs as a therapeutic modality to improve the quality of life for those suffering from a malady in which the standard of care is suboptimal or no longer effective. Currently, there is no Food and Drug Administration (FDA)-approved MSC therapy on the market in the United States although several MSC products have been granted regulatory approval in other countries. In this review, we intend to identify hurdles that are impeding therapeutic progress and discuss strategies that may aid in accomplishing this universal goal of widespread therapeutic use.

Interactions Between Allogeneic Mesenchymal Stromal Cells and the Recipient Immune System: A Comparative Review With Relevance to Equine Outcomes

Despite significant immunosuppressive activity, allogeneic mesenchymal stromal cells (MSCs) carry an inherent risk of immune rejection when transferred into a recipient. In naïve recipients, this immune response is initially driven by the innate immune system, an immediate reaction to the foreign cells, and later, the adaptive immune system, a delayed response that causes cell death due to recognition of specific alloantigens by host cells and antibodies. This review describes the actions of MSCs to both suppress and activate the different arms of the immune system. We then review the survival and effectiveness of the currently used allogeneic MSC treatments.

A Small-Sized Population of Human Umbilical Cord Blood-Derived Mesenchymal Stem Cells Shows High Stemness Properties and Therapeutic Benefit

Mesenchymal stem cells (MSCs) represent a promising means to promote tissue regeneration. However, the heterogeneity of MSCs impedes their use for regenerative medicine. Further investigation of this phenotype is required to develop cell therapies with improved clinical efficacy. Here, a small-sized population of human umbilical cord blood-derived MSCs (UCB-MSCs) was isolated using a filter and centrifuge system to analyze its stem cell characteristics. Consequently, this population showed higher cell growth and lower senescence. Additionally, it exhibited diverse stem cell properties including differentiation, stemness, and adhesion, as compared to those of the population before isolation. Using cell surface protein array or sorting analysis, both EGFR and CD49f were identified as markers associated with the small-sized population. Accordingly, suppression of these surface proteins abolished the superior characteristics of this population. Moreover, compared to that with large or nonisolated populations, the small-sized population showed greater therapeutic efficacy by promoting the engraftment potential of infused cells and reducing lung damage in an emphysema mouse model. Therefore, the isolation of this small-sized population of UCB-MSCs could be a simple and effective way to enhance the efficacy of cell therapy.