Allo-Recognition of Equine Bone Marrow-Derived Mesenchymal Stem Cells is Dependent on Major Histocompatibility Complex Haplotype
Presented by: Aileen Rowland
Authors: Aileen L. Rowland(1), Donald Miller (2), Doug F. Antczak(2), Gwen J. Levine (3), Ashlee E. Watts(1)
Affiliations: (1) Department of Large Animal Clinical Sciences, Texas A&M University, College Station, TX, USA (2) Baker Institute for Animal Health, Cornell University, Ithaca, NY, USA (3) Department of Veterinary Pathobiology, Texas A&M University, College Station, TX, USA
Introduction: Long considered non-immunogenic and immuno-modulatory, allo-MSCs are used and often preferred for their reduced cost, off-the-shelf availability, better characterized cell quality, and ease of FDA approval of cell lines as compared to autologous preparations and there are numerous veterinary reports on allogeneic MSC use. Subsequently, there are numerous veterinary reports on clinical use of allogeneic MSCs. However, we have previously shown allo-recognition causes an increased adverse response to repeated allogeneic MSC administration in the horse.
Hypothesis / Objectives: Our current objective was to determine if allo-recognition is due to MHC mismatch. We hypothesized that injection of allogeneic MHC haplotype mis-matched MSCs would result in immune recognition with MSC destruction, donor specific antibody production and adverse clinical reaction compared to MHC haplotype matched MSCs and autologous MSCs.
Materials and Methods: We performed repeated intra-articular injections (day 0 and day 29) with MHC matched allogeneic MSCs (n=12), MHC mismatched allogeneic MSCs (n=12) and autologous MSCs (n = 6). On days 0 and 29, the left metacarpophalangeal joint was injected with 10 million MSCs, and the contralateral joint injected with autologous serum as a control. We then assessed the clinical response via lameness and limb edema on day 1, 7, 30 and 36. Blood was drawn weekly for 112 days and assessed for antibody development. On day 30, 8 drops of synovial fluid was collected for colony-forming-unit (CFU) analysis.
Results: There was no significant difference in lameness between groups at any time point. There was significantly more limb edema in the mismatched group on day 30 (p=<0.0001) compared to the matched or autologous groups. There was greater antibody development in the mismatched group compared to the matched group with significantly higher cell death in the mismatched group from day 28 to 63 (Figure 1). On day 30, colonies were present in all samples collected from the matched and auto group (5/5 and 6/6), and no colonies were present in the mismatched group (0/3).
Conclusions: We found mildly worsened inflammation (edema, but not lameness), development of donor specific antibody and reduced synovial MSC concentration in horses injected with MHC mismatched MSCs as compared to MHC matched and autologous MSCs. This provides evidence for immune recognition and destruction of allogeneic MSCs. Although MSCs are not always able to overcome the non-crossmatched allogeneic immune response, the minimal local reaction may be due to the immunomodulatory properties of MSCs minimizing clinical adverse response. Until a universal donor or a method to minimize MHCI expression are identified, allogeneic MHC mismatched MSCs are not a suitable alternative to autologous use.
Acknowledgements, Funding, and Conflicts of Interest: Funding provided by Link Endowment for Equine Research at Texas A&M University, the Dennis and Linda Clark Endowment for Equine Orthopedic Research from the Department of Large Animal Sciences at Texas A&M University, and the Formula Animal Health Fund. There are no conflicts of interest.