Insights into Endothelial Progenitor Cells: Origin, Classification, Potentials, and Prospects

Table 1

Differences between eEPCs and lEPCs.

	Early EPCs	Late EPCs
Synonyms	CACs [82]	OECs [83, 91] or ECFCs [84]
Cell population [81, 91]	Heterogeneous	Homogenous
Cell morphology [81]	Spindle-shaped cells	Cobblestone-like cells
Appearance in culture	<1 week [5, 81]	2–4 weeks [81]
Lifespan [81]	3-4 weeks	≈12 weeks
Morphogenic potential [81]	Low	High
Angiogenic potential [81]	Good	Good
Tube formation in vitro [5, 92, 134]
Tube formation by EPCs alone	Absent	Present
Tube formation by EPCs with HUVECs	Absent	Present
Tube formation in vivo [92]	Absent	Present
Neovascularization in vivo [82, 92, 93, 134]	Indirect paracrine fashion	Directly providing ECs; hence can be referred to as “true EPCs”
Surface expression
CD34 [88, 134]	+	+
CD45 [81, 88, 134]	+	−
CD14	+ and − [91, 93]/+ [92]	−
CD133	− [88] and + [89, 136]	− [88, 89, 136]
CD31 (PECAM 1) [81, 134, 137]	−/+	++
VEGFR-2 [81, 92, 93, 134, 137]	−/+	++
VE cadherin [81, 93, 134]	−/+	++
vWf [81]	−/+	+
Phenotype [90]	Monocytic	Endothelial
AcLDL uptake [5]	+	++
Lectin binding [5]	+	++
NO production [5]	+	++

+: present; ++: strongly present; −: absent; and −/+: limited/weak/focal.