VIRAL DELIVERY OF GDNF PROMOTES FUNCTIONAL INTEGRATION OF HUMAN STEM CELL GRAFTS IN PARKINSONS DISEASE
The derivation of neurotransmitter and region-specific neuronal populations from human pluripotent stem cells (PSC) provides impetus for advancing cell therapies into the clinic. At the forefront is our ability to generate ventral midbrain (VM) dopaminergic (DA) progenitors, suitable for transplantation in Parkinsons disease (PD). Pre-clinical studies, however, have highlighted the low proportion of DA neurons within these grafts and their inferior plasticity by comparison to human fetal donor transplants. Here we sought to examine whether modification of the host environment, through viral delivery of a developmentally critical molecule, glial cell line-derived neurotrophic factor (GDNF), could improve graft survival, integration and function in Parkinsonian rodents. Utilising LMX1A- and PITX3-GFP hPSC reporter lines, we tracked the response of DA progenitors implanted into either a GDNF-rich environment, or in a second group, after a 3-week delay in onset of exposure. We found that early exposure of the graft to GDNF promoted survival of DA and non-DA cells, leading to enhanced motor recovery in PD rats. Delayed overexpression of intrastriatal GDNF also promoted motor recovery in transplanted rats, through alternate selective mechanisms including enhanced A9/A10 specification, increased DA graft plasticity, greater activation of striatal neurons and elevated DA metabolism. Lastly, transcriptional profiling of the grafts highlighted novel genes underpinning these changes. Collectively these results demonstrate the potential of targeted neurotrophic gene therapy strategies to improve human PSC graft outcomes.