Application of vascular endothelial cells in stem cell medicine

Table 1 Summary of roles of vascular endothelial cells as checkpoint for immunological patrolling

Role of VECs	Molecule type	Suggested mechanisms	Ref
Express pattern recognition receptors	TLRs (TLR1-TLR10)	Contribute to early stages of the immune response against various microbial agents	Sturtzel et al[15]
	NLRs	Sense intracellular microbial invaders and danger molecules produced under stress	Fleissner et al[58]
	RLRs	Involved in antiviral immune response and contribute to chronic inflammatory disease	Asdonk et al[59]
	AIM2-like receptors	Form an inflammasome with the ligand and ASC to activate caspase-1	Hornung et al[60]
	C-type lectin receptors	Regulate signal cascades in response to distinct pathogen- or self-derived components	Kim et al[61]
Express proangiogenic molecules	FGFs	Anneal adherens junctions and promote VEC migration	Potente et al[13]
	NEU1	Restrains VEC migration	Cross et al[62]
	VEGF	Induces VEC phenotype changes and regulates proliferation and migration of VECs	Potente et al[13]
	IL-8	Induces VEC proliferation	Sturtzel et al[15]
Express adhesion molecules	P-selectin	Recruits leukocytes	Sturtzel et al[15]
	E-selectin	Attaches monocytes	Sturtzel et al[15]
	ICAM-1; VCAM-1	Function as VEC activation markers	Sturtzel et al[15]
Express MHC	MHC I	Leads to recruitment of antigen-specific; naïve CD8+ T cells	Mai et al[63]
	MHC II	Presents endothelial antigens to immune cells	Mai et al[63]
Express immune checkpoints	PD-L1/2	Inhibits T cell activation	Rodig et al[64]
	ENO-1	A major glycolytic enzyme, over-expressed in various cancer tissues	Zheng et al[65]
Express pro-inflammatory cytokines	IL-10, IL-6, and IL-8	Function as a complementary mechanism for the detrimental effects of viruses on atherosclerosis	Asdonk et al[59]

TLRs: Toll-like receptors; NLRs: Nucleotide-binding oligomerization-domain (NOD)-like receptors; RLRs: Retinoic acid inducible gene-I (RIG-I) like receptors; AIM2: Absent in melanoma 2; NEU1: Epidermal growth factor like domain 7; IL: Interleukin; ICAM: Intercellular adhesion molecule; VCAM: Vascular cell-adhesion molecule; MHC: Major histocompatibility complex; PD-L1/2: Programmed death-ligand 1/2; ENO-1: Enolase 1; FGFs: Fibroblast growth factors; VEC: Vascular endothelial cell; VEGF: Vascular endothelial growth factor.