Table 1.

Advantages and disadvantages of the different cellular approaches for transplantation in Parkinson's disease (PD)

	Fetal VM progenitors	ES cells	iPS cells	Induced neurons
Advantages	Grafts can survive, integrate, re‐innervate the striatum and release dopamine Promote functional recovery in pre‐clinical PD models Proven efficacious in some patients	Unlimited availability of the cell product Have the potential to form authentic DA progenitors that survive well, integrate, re‐innervate the striatum, release dopamine and mature after transplantation Promote functional recovery in pre‐clinical PD models Production can be standardized and cells cryopreserved and stored GMP manufacturing protocols already established	Easy access of the cell source Unlimited availability of the cell product Have the potential to form authentic DA progenitors that survive well, integrate, re‐innervate the striatum, release dopamine and mature after transplantation Promote functional recovery in pre‐clinical PD models Production can be standardized and cells cryopreserved and stored Possibility of autografting or to use banks for haplotype matching	Easy access of the cell source Lower tumorogenic potential due to avoidance of pluripotent stage Fast and efficient generation that makes the cells suitable to adapt for autologous grafting
Disadvantages	Very limited availability of the tissue Variable results from clinical trials Allografting that requires immunosuppression Ethical issues The graft may contain unwanted cell types	Risk of tumor formation after grafting if not properly differentiated Allografting that requires immunosuppression Ethical issues The graft may contain unwanted cell types Cells could migrate outside of the striatum Risk of long‐term genetic instability	Risk of tumor formation after grafting if not properly differentiated High costs Additional risks associated with the reprogramming process Variability in the cell products in the context of autologous grafting The graft may contain unwanted cell types Cells could migrate outside of the striatum Risk of long‐term genetic instability	Current lack of study showing the long‐term survival, integration, re‐innervation of the striatum and the release of dopamine Current lack of study showing a functional recovery in pre‐clinical PD models High variability in cell product and thus more challenging to standardize The graft may contain unwanted cell types Risk of long‐term genetic instability