Mesenchymal Stem Cell Therapy Prolongs Corneal Allograft Survival in Rats

Abstract

Purpose: : To investigate the role of syngeneic and allogeneic mesenchymal stem cells (MSCs) to prolong rat corneal allograft survival.

Methods: : Syngeneic (syn) and allogeneic (allo) MSCs were isolated from bone marrow of Lewis (LEW) and Dark Agouti (DA) rats, respectively. 1 day before allograft transplantation, recipient (LEW) rats received 1x10⁶ syn-MSCs intravenously. A second injection of syn-MSCs (same dose) was given 7 days after transplantation. In contrast, 7 days prior to allograft transplantation, recipient (LEW) rats received 1x10⁶ allo-MSCs intravenously with a second injection of allo-MSCs (same dose) on the day of transplantation. A fully allogeneic rat cornea transplant model (DA to LEW) was used for in vivo studies. Graft survival and neovascularization was monitored and histology was used to analyze lymphocyte infiltration in the cornea. Moreover, flow cytometry was used to analyze the effects of MSCs on T cells and/or dendritic cells (DCs) following in vitro co-culture assays, and also, to analyze allo-antigen primed T cells and/or DCs following re-stimulation with allo-antigen ex vivo.

Results: : In vivo untreated allogeneic control grafts were uniformly rejected (MST 16.5±4.8d, n=20) and, while syn-MSC treated allograft recipients showed some evidence of attenuation of rejection (MST 20.5±7d, n=11), no clear pattern of either graft survival or graft rejection emerged following this treatment. In contrast, corneal allograft rejection was significantly delayed in a high percentage of allo-MSC treated allograft recipients (88%) (MST >30d, n=7, 17d, n=1). Histological analysis showed reduced cell infiltration in allo-MSC treated recipient corneas compared to untreated allogeneic control corneas. Furthermore, in an in vitro recall response assay following re-stimulation of lymphocytes and OX62+ DCs from allo-MSC injected LEW rats with allo-antigen, significantly fewer numbers of CD4+CD134+ T cells and MHCII+CD86+ DCs were present compared to syn-MSC treated LEW rats.

Conclusions: : Systemic administration of allo-MSCs shows remarkable prolongation of allograft survival with almost 90% of allograft recipients accepting grafts for ≥ 30 days. This can be in part explained by the presence of reduced numbers of activated T cells and/or DCs following allo-MSC treatment.

Keywords: cornea: basic science • immunomodulation/immunoregulation • transplantation