Table 1 . Advantages and disadvantages of stem cell types used in Parkinson’s disease (11, 26, 30, 31) .

Type of stem cell	Advantages	Disadvantages
Embryonic stem cell (ESCs)	(a) Highly proliferative/pluripotent (b) Able to form all three germ layer (c) Generate dopaminergic neurons (d) Transplantation survival/some degree of functional recovery	(a) Risk of tumor formation (b) Ethical issues (c) Genomic instability
Induced pluripotent stem cells (iPSCs)	(a) Unlimited PD patient-specific cells/autologous transplantation (b) Transplantation survival/some degree of functional recovery (c) Minimized immune reactions and ethical issues	(a) Risk of tumor formation (b) In autologous transplantation risk of susceptibility to the original pathology of the patient
Mesenchymal stem cells (MSCs)	(a) Improve motor performance in mice (b) No reported adverse effects in humans (c) A realistic cell source for regenerative medicine (d) Easily accessible from different tissues	(a) Modest clinical improvement in humans
Fetal brain neural stem cells (fNSCs)	(a) Lower risk of tumor formation and immune rejection in comparison with ESCs (b) Ability to differentiate into neurons, astrocytes, oligodendrocytes, and dopamine neurons	(a) Limited differentiation in vivo (b) Partial effect in PD-like symptoms (C) Risk of GIDs (d) Ethical issues (e) Histocompatibility concerns (f) limited supply