CD34 + cell–derived fibroblast-macrophage cross-talk drives limb ischemia recovery through the OSM-ANGPTL signaling axis

CD34 + cells improve the perfusion and function of ischemic limbs in humans and mice. However, there is no direct evidence of the differentiation potential and functional role of these cells in the ischemic muscle microenvironment. Here, we combined the single-cell RNA sequencing and genetic lineage tracing technology, then provided exact single-cell atlases of normal and ischemic limb tissues in human and mouse, and consequently found that bone marrow (BM)–derived macrophages with antigen-presenting function migrated to the ischemic site, while resident macrophages underwent apoptosis. The macrophage oncostatin M (OSM) regulatory pathway was specifically turned on by ischemia. Simultaneously, BM CD34 + -derived proregenerative fibroblasts were recruited to the ischemia niche, where they received macrophage-released OSM and promoted angiopoietin-like protein–associated angiogenesis. These findings provided mechanisms on the cellular events and cell-cell communications during tissue ischemia and regeneration and provided evidence that CD34 + cells serve as fibroblast progenitors promoting tissue regeneration.