GDNF and Parkinson disease: Given that the clinical translation of foetal-derived dopaminergic neuron regenerative therapies in Parkinson’s disease is limited by the extremely poor survival of cells post-transplantation and the consequent requirement of multiple foetal donors per transplant, if a single infusion of an injectable, non-toxic and GDNF-rich hydrogel can dramatically increase cell survival and efficacy, it can potentially reduce the number of foetal donors needed per striatal transplant.