Intra-bone marrow diversity of endothelial cells and its impact on hematopoietic stem cell development and maintenance.

In addition to supplying oxygen and nutrients, blood vessels secrete paracrine molecules known as angiocrine factors to promote tissue homeostasis and repair. The bone marrow (BM) vasculature in long bones has differing properties between the diaphysis, metaphysis, and epiphysis in terms of its morphology, plasticity, perivascular cellular components, and angiocrine profiles. Blood vessel formation is linked with bone formation through paracrine interactions between endothelial cells (ECs) and osteolineage cells, so-called angiogenic-osteogenic coupling. ECs also play essential roles in the maintenance of hematopoietic stem cells (HSCs) by forming vascular niches together with perivascular stromal cells. Recent studies highlighted the heterogeneity of vascular niches at different bone regions, suggesting that HSCs are regulated by locally distinct mechanisms. Here, we provided an overview of the BM vasculature and discussed how the heterogeneous vasculature contributes to bone formation and HSC maintenance.