Exercise promotes the functional integration of human stem cell-derived neural grafts in a rodent model of Parkinson’s disease

Human pluripotent stem cell (hPSC)-derived dopamine neurons can functionally integrate and reverse motor symptoms in Parkinson's disease models, motivating current clinical trials. However, dopamine neuron proportions remain low and their plasticity inferior to fetal tissue grafts. Evidence shows exercise can enhance neuron survival and plasticity, warranting investigation for hPSC-derived neural grafts. We show voluntary exercise (wheel running) significantly increases graft plasticity, accelerating motor recovery in animals receiving ectopic, but not homotopic, placed grafts, suggestive of threshold requirements. Plasticity was accompanied by increased phosphorylated extracellular signal-regulated kinase (ERK+) cells in the graft (and host), reflective of mitogen-activated protein kinase (MAPK)-ERK signaling, a downstream target of glial cell-derived neurotrophic factor (GDNF) and brain-derived neurotrophic factor (BDNF), proteins that were also elevated. Verifying improved graft integration was the increase in cFos+ postsynaptic striatal neurons. These findings have direct implications for the adoption of physical therapy-based approaches to enhance neural transplantation outcomes in future Parkinson's disease clinical trials.