Fig. 6
From: Molecular and cellular mechanisms of aging in hematopoietic stem cells and their niches
HSC niche regeneration. Type-H ECs in arteriolar niches are stimulated by Dll4-Notch signaling to produce angiocrine factors. Such factors stimulate angiogenesis and osteogenesis to generate endosteal/arteriolar niches during early development and maintain these niches into adulthood. In response to irradiation or chemically induced BM damage, HSCs produce angiopoietin I/VEGF and ECs express Jag2. Such factors collaboratively induce the regeneration of sinusoid niches by stimulating the production of angiocrine factors by type-H ECs. In old mouse BM, the endosteal/arteriolar niches are significantly restricted while the sinusoid niches show minimal changes