Transforming Growth Factor-β2 Downregulates Major Histocompatibility Complex (MHC) I and MHC II Surface Expression on Equine Bone Marrow-Derived Mesenchymal Stem Cells Without Altering Other Phenotypic Cell Surface Markers

Abstract

Allogeneic mesenchymal stem cells (MSCs) are a promising cell source for treating musculoskeletal injuries in horses. Effective and safe allogeneic therapy may be hindered, however, by recipient immune recognition and rejection of major histocompatibility complex (MHC)-mismatched MSCs. Development of strategies to prevent immune rejection of MHC-mismatched MSCs in vivo is necessary to enhance cell survival and potentially increase the efficacy and safety of allogeneic MSC therapy. The purposes of this study were to evaluate if transforming growth factor-β2 (TGF-β2) downregulated MHC expression on equine MSCs and to determine if TGF-β2 treatment altered the phenotype of MSCs. Equine bone marrow-derived MSCs from 12 horses were treated with 1, 5, or 10 ng/ml TGF-β2 from initial isolation until MHC expression analysis. TGF-β2-treated MSCs had reduced MHC I and MHC II surface expression compared to untreated controls. TGF-β2 treatment also partially blocked IFN-γ-induced upregulation of MHC I and MHC II. Constitutive and IFN-γ-induced MHC I and MHC II expression on equine MSCs was dynamic and highly variable, and the effect of TGF-β2 was significantly dependent on the donor animal and baseline MHC expression. TGF-β2 treatment did not appear to change morphology, surface marker expression, MSC viability, or secretion of TGF-β1, but did significantly increase the number of cells obtained from culture. These results indicate that TGF-β2 treatment has promise for regulating MHC expression on MSCs to facilitate allogeneic therapy, but further work is needed to maintain MHC stability when exposed to an inflammatory stimulus.

Tenogenically Induced Allogeneic Peripheral Blood Mesenchymal Stem Cells in Allogeneic Platelet-Rich Plasma: 2-Year Follow-up after Tendon or Ligament Treatment in Horses

“…This could explain the low immunogenicity and the absence of observable adverse events in the horses that were injected in this study. Finally, Berglund et al described the downregulation of MHC I and MHC II on equine BM-derived MSCs without alteration of other phenotypic cell surface markers when culturing the cells in specific media, suggesting that media selection could be an interesting option to guaranty the safe use of allogeneic MSCs ( 42 ). Nevertheless, more robust in vivo studies are required to detail the precise immunologic effect of allogeneic cell treatment in the horse.…”

The Potential of Mesenchymal Stem Cells to Treat Systemic Inflammation in Horses

“…Exposing equine bone marrow derived MSCs to TGF-β2 has been shown to downregulate MHC-I and MHC-II surface expression when compared to controls. It also partially blocked the IFN-γ induced upregulation of MHC (44). Exposing donor MSCs to TGF-β2 prior to allogeneic use may decrease the potential for immune reaction, however individual variation was noted.…”

“…Exposing donor MSCs to TGF-β2 prior to allogeneic use may decrease the potential for immune reaction, however individual variation was noted. The effect of TGF-β2 was dependent on the baseline expression of MHC and donor animals (44). Further in vitro evidence suggests that cytokine priming has a negative impact on the MSCs viability and differentiation when compared to MSCs primed in an inflammatory synovial fluid (45).…”

Adipose-derived stem cell therapy shows promising results for secondary lymphedema

“…ADSCs produce immunomodulatory cytokines including TGF-β that block IFN-γ-induced MHC expression[ 51 ]. The downregulation of MHC can avoid immune surveillance, producing immune-privileged cells ADSCs[ 52 ]. Complications relating to immune rejection are therefore sparse.…”