Table 1.

Stem cell sources and their potential for the treatment of retinal and optic nerve diseases.

Stem Cell Source	Main Advantages and Disadvantages	Cell Type	Potential Applications
	Retinal Progenitor Cells
Fetal stem cells	Simple accessibility, safety and effectiveness Shortage of sufficient donor cells Limited proliferative capacity Restricted ability to differentiate into specific types of cells Relatively low risk of immune rejection and tumorigenesis	Retinal progenitor cells (RPCs)	Paracrine neuroprotection Exogenous cell replacement
		Cortical progenitor cells (CPCs)	Paracrine neuroprotection
	Pluripotent Stem Cells
Human embryonic stem cells	Ability to differentiate into photoreceptors under certain circumstances, but presenting difficulties in obtaining a specific targeted cell type Shortage of sufficient donor cells Limited proliferative capacity Restricted ability to differentiate into specific targeted cells Potential of tumor formation Requires immunosuppressive treatment increasing risks and burden Ethical concerns	Human embryonic stem cell derived retinal pigment epitheliums (hESC-RPE)	Exogenous cell replacement Non-cell-based therapy screening
Adult induced pluripotent stem cells	Able to provide large number of cells for treatments Low risk of immune reaction (autologous) Ameliorate the ethical issues of hESCs Low differentiation efficiency Relatively high risk of gene mutation	Adult induced pluripotent stem cells (iPSC)	Exogenous cell replacement Disease modeling Non-cell-based therapy screening
	Multipotent Stem Cells
Mesenchymal stem cells	Able to provide large number of cells for treatments ADRCs obtained in less invasive procedures and higher immunomodulatory capacity than BMSCs Anti-inflammatory immunosuppressive antiangiogenic and antiapoptotic or neuroprotective effects Ability to differentiate into damaged cells Low rate of cell migration and differentiation Reported to differentiate into photoreceptors and retinal pigment epithelial (RPE) cells	Bone marrow-derived stem cells (BMSCs)	Paracrine neuroprotection
		Adipose-derived stem cells (ADRCs)	Paracrine neuroprotection
	Higher antiapoptotic effect Strong rescue effect on retinal function Potential RPE cell differentiation capacity	Human umbilical multipotent stem cells retrieved from donor umbilical cords (hUTSCs)	Paracrine neuroprotection
Other sources		Ciliary epithelium-derived stem cells (CESCs)	Exogenous cell replacement Endogenous cell replacement?
		Cells extracted from the adult human RPE, obtained from eye banks and activated in vitro into a stem cell state (RPESCs)	Exogenous cell replacement Endogenous cell replacement?
		Reprogrammed endogenous Müller glia into RGCs (hMSCs)	Exogenous cell replacement Endogenous cell replacement?