Introduction: Each organ is vascularized by specialized endothelial cells (ECs) with defined structural, angiocrine, and functional attributes. The two pancreatic compartments, the endocrine islets and the exocrine acini and ducts, perform distinct functions and thus likely require customized EC support. We hypothesize that islet-specific ECs (ISECs) have specialized molecular signatures, that alterations in these signatures contribute to the pathogenesis of diabetes, and that engineered ISECs can better support durable engraftment of transplanted islets.

Methods: We developed strategies to obtain large numbers of viable ISECs, acinar specific ECs (ASECs), and stromal cells from three human pancreas donors. Single cell RNA-sequencing and comparison with the vascular signatures of other organs enabled us to uncover the unique transcriptomic signatures of ISECs, ASECs, and corresponding perivascular cells. Candidate ISEC-transcription factors were subsequently transduced into generic endothelium, studied in microfluidic devices, and transplanted into diabetic mice.  

Results: ISECs are characterized by expression of distinct combinations of structural genes COL13A1, PLVAP, UNC5B, ESM1, and LAMA4, instructive angiocrine factors THBS1, BMP2, and Dll4, metabolic modulators PASK, CD36, and FABP5, and immune trafficking gatekeepers CXCR4, CXCR7, CD320, and SELE. ISECs manifest signaling pathways VEGF-A:VEGFR2, NOTCH1,4:DLL4, CXCL12:CXCR4/CXCR7, BMP2,4:TGFb, and INS:INSR, which regulate glucose sensing, lipid metabolism, and inflammatory functions of endocrine cells. Interactome analyses of diabetic patients indicated significant disruption of Notch, TGFb, CXCR4, PASK, LIF, and VEGF-A cross-talk among pancreatic vascular and stromal cells. Notably, we identified NKX2-3 as a novel transcription factor that specifies ISECs. Lentiviral transduction of NKX2-3 into human umbilical vein ECs generated “induced ISECs” (iISECs) displaying the transcriptomic signature of native ISECs. We validated disease-related differential expression of NKX2-3 by immunostaining of human pancreas showing rich NKX2-3+ ECs in non-diabetic islets but not diabetic islets. Unlike generic ECs, iISECs self-assembled into perfusable capillary networks within microfluidic devices. Transplantation of islets vascularized by iISECs augments islet engraftment, and iISECs, most likely by supplying angiocrine factors, bolster the differentiation of pluripotent stem cell derived beta cells into a more mature population.

Conclusions: NKX2-3 represents a previously unrecognized organotypic transcription factor that choreographs tubulogenic functions of ISECs, providing a specialized vascular niche for islets. Our data sets forth the transformative concept that organotypic vascular heterogeneity is dictated by the induction of distinct transcription factors, whose loss contributes to disease and whose restoration holds promise for the improvement of islet engraftment.