Engineered PD‐L1‐Expressing Platelets Reverse New‐Onset Type 1 Diabetes

Abstract The pathogenesis of Type 1 diabetes (T1D) arises from the destruction of insulin‐producing β‐cells by islet‐specific autoreactive T cells. Inhibition of islet‐specific autoreactive T cells to rescue β‐cells is a promising approach to treat new‐onset T1D. The immune checkpoint signal axis programmed death‐1/programmed death‐ligand 1 (PD‐1/PD‐L1) can effectively regulate the activity of T cells and prevent autoimmune attack. Here, megakaryocyte progenitor cells are genetically engineered to overexpress PD‐L1 to produce immunosuppressive platelets. The PD‐L1‐overexpressing platelets (designated PD‐L1 platelets) accumulate in the inflamed pancreas and may suppress the activity of pancreas autoreactive T cells in newly hyperglycemic non‐obese diabetic (NOD) mice, protecting the insulin‐producing β‐cells from destruction. Moreover, PD‐L1 platelet treatment also increases the percentage of the regulatory T cells (Tregs) and maintains immune tolerance in the pancreas. It is demonstrated that the rescue of β‐cells by PD‐L1 platelets can effectively maintain normoglycemia and reverse diabetes in newly hyperglycemic NOD mice.