Islet regeneration protein Reg3g promotes macrophage clearance of β cell-derived dysfunctional mitochondria-rich...

Under metabolic stress in type 2 diabetes mellitus (T2DM), β cells accumulate damaged mitochondria, and proinflammatory macrophages infiltrate pancreatic islets. In several tissues, mitochondrial transfer between macrophages and parenchymal cells has been shown to alleviate inflammation and sustain cellular function reponse to stress. However, whether a similar process occurs between pancreatic β cells and macrophages remains unclear. Here, we identified a form of intercellular communication mediated by damaged mitochondrial-rich extracellular vesicles (mEVs) from β cells to macrophages within the inflammatory islets, promoted by Reg3g. Using time-lapse confocal microscopy, flow cytometry and split-GFP mitochondrial fusion assays, we demonstrated that stressed β cells release damaged mitochondria via mEVs, which were internalized by macrophages through a heparan sulfate (HS)-dependent mechanism and subsequently degraded through mitophagy. Under metabolic stress, β cells increased mEVs release, but macrophage uptake was impaired due to reduced HS biosynthesis. The protein Reg3g restored this process by binding macrophage exostosin-like glycosyltransferase 3 (EXTL3) receptors, promoting HS synthesis. Mechanically, increased HS enhanced mEVs uptake and strengthened the heparan sulfate proteoglycan (HSPG)-NF-κB interaction, sequestering NF-κB in the cytoplasm and suppressing purinergic receptor P2X7 (P2RX7) expression. P2RX7 downregulation subsequently promoted metabolic remodeling and an anti-inflammatory shift in macrophages. Collectively, our study identifies a Reg3g-orchestrated transcellular mitophagy pathway, wherein macrophages clear mEVs from β cells, promoting islet homeostasis. Targeting this axis may offer new therapeutic strategies for T2DM.