TGF-b2 DOWNREGULATES CONSTITUTIVE AND IFN-g-INDUCED MHC SURFACE EXPRESSION ON EQUINE BONE MARROW-DERIVED MESENCHYMAL STEM CELLS
Alix Berglund, North Carolina State University
Alix K. Berglund1, Alexandra B. Grobman2, Matthew B. Fisher3, Lauren V. Schnabel1.
1. College of Veterinary Medicine, North Carolina State University.
2. College of Agriculture and Life Sciences, North Carolina State University
3. Joint Department of Biomedical Engineering, University of North Carolina – Chapel Hill and North Carolina State University
Allogeneic mesenchymal stem cell (MSC) therapy for musculoskeletal diseases is currently hindered by recipient immune recognition of mismatched-major histocompatibility complex (MHC) molecules expressed on donor MSCs. Our hypothesis was that culturing equine MSCs with TGF-β2 would decrease constitutive MHC I and MHC II expression and block IFN-γ- induced MHC expression without affecting the viability or immunomodulatory properties of the cells. Bone marrow was aspirated from the sternum of twelve healthy horses and MSCs wer isolated via Ficoll gradient centrifugation. MSCs were cultured with TGF-β2 before MHC I and MHC II surface expression was analyzed via fluorescent activated cell sorting (FACS). Cell yield and viability were measured at each passage. To determine if TGF-β2 blocked IFN-γ-induced MHC expression, untreated and TGF-β2-treated MSCs were stimulated with 1 ng/ml IFN-γ for up to 72 hours before FACS analysis. TGF-β2 treatment significantly reduced MHC I and MHC II surface expression on unstimulated MSCs and partially blocked IFN-γ-induced MHC I and MHC II surface expression. IFN-γ induced MHC expression varied significantly between individual MSC donors, however. TGF-β2 treatment also improved cell yield at each passage and there was no significant difference between the viability of untreated and treated MSCs. TGF-β2 treatment did not significantly change the secretion of TGF-β1 from unstimulated or stimulated MSCs. These results demonstrate that TGF-β2 treatment has significant promise for reducing recipient immune recognition of MHC-mismatched molecules on allogeneic MSCs. Further work is needed to stabilize MHC expression in inflammatory conditions on MSCs and determine the immunogenicity of TGF-β2-treated MSCs