Hierarchical organization and regulation of the hematopoietic stem cell osteoblastic niche.

Hematopoietic stem cells (HSCs) are characterized with long-term self-renewal and multi-lineage differentiation. HSCs preferentially reside in osteoblastic niche that is hierarchically organized so as to exactly regulate HSCs properties and maintain organism hematopoietic homeostasis. Hematopoietic stem cell-mesenchymal stem cell pairings share stem cell niches in adult bone marrow under immune-humoral-neural regulation. Here, we review the hierarchical HSC osteoblastic niche in terms of its localization, composition, function, and multi-layer regulation systems.