Autologous bone marrow-derived rat mesenchymal stem cells promote PDX-1 and insulin expression in the islets, alter T cell cytokine pattern and preserve regulatory T cells in the periphery and induce sustained normoglycemia

Cell-based therapies offer considerable promise for prevention or cure of diabetes. We explored the potential of autologous, self-renewing, mesenchymal stem cells (MSC) as a clinically-applicable approach to promote glucose homeostasis. In vitro-expanded syngeneic bone marrow-derived MSC were administered following or prior to diabetes induction into a rat model of streptozotocin-induced beta cell injury. MSC were CD45^-/CD44⁺/CD54⁺/CD90⁺/CD10 6⁺. MSC spontaneously secreted IL-6, HGF, TGF-β1 and expressed high levels of SDF-1 and low levels of VEGF, IL-1β and PGE₂, but no EGF, insulin or glucagon. MSC homed to the pancreas and this therapy allowed for enhanced insulin secretion and sustained normoglycemia. Interestingly, immunohistochemistry demonstrated that, the islets from MSC-treated rats expressed high levels of PDX-1 and that these cells were also positive for insulin staining. In addition, peripheral T cells from MSC-treated rats exhibited a shift toward IL-10/IL-13 production and higher frequencies of CD4⁺/CD8⁺ Foxp3⁺ T cells compared to the PBS-treated rats. These data suggest that the bioactive factors secreted by MSC establish a tissue microenvironment that supports beta cell activation/survival in the pancreas. In addition, because of anti-inflammatory and immunoregulatory effects of MSC on T cells, this work can lead to clinical trial of autologous MSC to prevent/cure type-1 diabetes.