P2RY1/ALK3-Expressing Cells within the Adult Human Exocrine Pancreas Are BMP-7 Expandable and Exhibit Progenitor-like Characteristics.

Treatment of human pancreatic non-endocrine tissue with Bone Morphogenetic Protein 7 (BMP-7) leads to the formation of glucose-responsive β-like cells. Here, we show that BMP-7 acts on extrainsular cells expressing PDX1 and the BMP receptor activin-like kinase 3 (ALK3/BMPR1A). In vitro lineage tracing indicates that ALK3 cell populations are multipotent. PDX1/ALK3 cells are absent from islets but prominently represented in the major pancreatic ducts and pancreatic duct glands. We identified the purinergic receptor P2Y1 (P2RY1) as a surrogate surface marker for PDX1. Sorted P2RY1/ALK3 cells form BMP-7-expandable colonies characterized by NKX6.1 and PDX1 expression. Unlike the negative fraction controls, these colonies can be differentiated into multiple pancreatic lineages upon BMP-7 withdrawal. RNA-seq further corroborates the progenitor-like nature of P2RY1/ALK3 cells and their multilineage differentiation potential. Our studies confirm the existence of progenitor cells in the adult human pancreas and suggest a specific anatomical location within the ductal and glandular networks.