Table 1.

Key cell types participating in regulation of HSCs activity in BM niches.

Cells	Markers	Function	Main Molecules
Mesenchymal stem cells	CD73+, CD90+, CD105+, CD14−, CD19−, CD34−, CD45−, HLA−DR−, Terl119−, CD31−, CD51+, PDGFRa+, Sca1−	Support and regulation of HSC quiescence, proliferation, differentiation HSC mobilization	CXCL12, SCF, angiopoietin-1, VCAM-1, osteopontin
Endothelial cells	CD45−, CD31+, CD144+, Terl119−	Support of HSC proliferation and expansion Hematopoietic regeneration after irradiation	CXCL12, SCF, Notch ligands, E-selectin, Del-1, pleiotrophin
Osteoblasts	CD45−, Terl19−, CD31−, CD51+, PDGFRa−, Sca1−	Support of HSC quiescence	Osteopontin, N-cadherin, TPO, angiopoietin-1
Megakaryocytes	CD41+, CXCR4, Mpl	Support of HSC quiescence HSC expansion after irradiation	CXCL4, TGF-β, thrombopoietin, FGF1
Macrophages	CD68+, CD169+	HSC retention in niche Support of HSC quiescence	VCAM-1, DARC, TGF-β
Adipocytes	ADIPOQ, FABP4, Leptin	Support of HSC survival, proliferation and differentiation Hematopoietic regeneration after irradiation	MCP-1, CXCL12, SCF, IL-8, LIF, CSF3, adiponectin, leptin
Treg lymphocytes	FOXP3	Protection of HSC from immune attack Support of HSC quiescence	IL-10, CDC39, adenosine
Sympathetic nerve fibers	Tyrosine hydroxylase	HSCs mobilization	Noradrenaline
Parasympathetic nerve fibers	Choline acetyltransferase	HSC retention in niche, homing	Acetylcholine