Table 2. Classification of Stem Cells with Their Most Important Characteristics.

stem cell type	characteristics	ref
MSCs	• self-renewal ability	(36, 40−43)
	• multipotent
	• ease of access
	• efficient in vitro expansion
	• free of ethical concerns
	• nonsignificant immune responses
	• variable therapeutic results depending on the source and the donor
ESCs	• pluripotent	(42, 44−48)
	• ethical concerns
	• possible tumor formation during the differentiation
	• possible immune rejection after transplantation
	• possible cell heterogeneity
iPSCs	• pluripotent	(41, 42, 47−50)
	• free of ethical concerns
	• possible tumor formation during the differentiation
	• possible immune rejection after transplantation
	• possible cell heterogeneity
NSCs	• multipotent	(42, 47, 50−52)
	• efficient in vitro expansion
	• secretion of neurotrophic factors
	• less potential of forming tumors compared with ESCs
Schwann cells	• production of growth factors, cell adhesion molecules, and extracellular matrix proteins	(41, 47)
	• myelinating function
	• support of axonal regeneration
	• efficacy and safety