Structure and Functions of Blood Vessels and Vascular Niches in Bone

Table 1

Genetic studies illustrating functions of endothelial factors in bone are summarised below.

Factors	Modification	Functions	Reference(s)
Cxcr4	EC-specific deletion (induced)	Increased vascular permeability HSPC egress	[35]
Cxcl12	EC-specific deletion (constitutive)	Decreased HSC frequency	[69, 70]
Dll1	EC-specific deletion (induced)	Monocyte development	[90]
Dll4	EC-specific deletion (induced)	Regulates type H vessels; Coupling of angiogenesis and osteogenesis haematopoiesis	[10, 34]
Fbw7	EC-specific deletion (induced)	Reactivating type H vessels in aged bones induce arterioles formation increase PDGFRb+, alpha-SMA+ mesenchymal cells increase HSC frequency	[10, 29, 34]
Fgfr1/2	EC-specific deletion (induced)	Impaired vascular integrity reduced HSPCs and MSPCs	[35]
Gp130	EC-specific deletion (constitutive)	Hypocellular marrow, marrow dysfunction, and splenomegaly	[78]
Hif1a; Vhl	EC-specific deletion (induced)	Regulates type H vessels; Coupling of angiogenesis and osteogenesis	[8]
Pdgfb	EC-specific overexpression (induced)	Increased PDGFRb+, alpha-SMA+ mesenchymal cells	[34]
Pecam1	Global deletion	No substantial change in blood vessels	[29]
Scf	EC-specific deletion (constitutive)	Decreased HSC frequency	[81]
Sele	Global deletion	Promotes HSC quiescence and resistant to irradiation	[80]