Coordinated interactions between endothelial cells and macrophages in the islet microenvironment promote ß cell regeneration.

Endogenous ß cell regeneration could alleviate diabetes, but proliferative stimuli within the islet microenvironment are incompletely understood. We previously found that ß cell recovery following hypervascularization-induced ß cell loss involves interactions with endothelial cells (ECs) and macrophages (MΦs). Here we show that proliferative ECs modulate MΦ infiltration and phenotype during ß cell loss, and recruited MΦs are essential for ß cell recovery. Furthermore, VEGFR2 inactivation in quiescent ECs accelerates islet vascular regression during ß cell recovery and leads to increased ß cell proliferation without changes in MΦ phenotype or number. Transcriptome analysis of ß cells, ECs, and MΦs reveals that ß cell proliferation coincides with elevated expression of extracellular matrix remodeling molecules and growth factors likely driving activation of proliferative signaling pathways in ß cells. Collectively, these findings suggest a new ß cell regeneration paradigm whereby coordinated interactions between intra-islet MΦs, ECs, and extracellular matrix mediate ß cell self-renewal.