Lineage tracing of alpha-to-beta cell transition after injection of Wnt pathway-stimulated human multipotent stromal cell-secreted proteins

Diabetes is projected to affect >600 million people by 2045. Although life-saving insulin therapy can manage hyperglycemia, exogenous insulin is not a cure for diabetes, and life-expectancy for those affected is reduced by 10-15 years. Regenerative therapies aimed at replenishing functional beta cell mass have gained interest. However, the cellular mechanisms that mediate islet regeneration remain unclear. We have shown that human bone marrow-derived multipotent stromal cells (MSC), licenced by WNT-pathway activation using CHIR99021 (CHIR), secrete factors (CHIR CdM) that promote beta-cell recovery in streptozotocin (STZ)-treated immunodeficient NOD/SCID mice. Here, we investigated whether this regeneration involved alpha-to-beta cell conversion, using a Glucagon-iCre;Rosa26-TdTomato (GcgXTdT) lineage-tracing model. Following hyperglycemia induction with STZ and intrapancreatic injection of CHIR CdM, TdTomato+/insulin+ cells were transiently increased within 4 days of injection, indicating alpha cell plasticity and acquisition of insulin expression. CHIR CdM injection also increased the abundance and proliferation of insulin+ cells at day 28. Additionally, CHIR CdM injection altered infiltrating pancreatic immune cell composition, including increased CD4+ and CD68+ cells. Together, these findings demonstrate that intrapancreatic administration of a single injection of CHIR CdM initiates a regenerative response characterized by alpha-to-beta cell plasticity, insulin+ cell-proliferation, and immune remodeling in immune competent GcgxTdT mice. While additional regenerative stimuli may be required for beta cell maturation to restore glycemic control, understanding the mechanisms by which pancreatic beta cell regeneration is initiated in the presence of immune cells may help inform therapies for the treatment of diabetes.