Viral Delivery of GDNF Promotes Functional Integration of Human Stem Cell Grafts in Parkinson’s Disease

Abstract

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 Parkinson's 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.

Pluripotent Stem Cell Therapies for Parkinson Disease: Present Challenges and Future Opportunities

“…Interestingly, the Pitx3 finding was recently confirmed in an independent study using human ESC genetic reporter lines for PITX3 and for LMX1A (de Luzy et al, 2019). While PITX3 + mDA neuron showed very poor survival, LMX1A + cells at the floor-plate precursor stage showed efficient engraftment, albeit the resulting grafts (similar to Corin + grafts) were far from representing pure mDA neuron grafts (Gantner et al, 2020).…”

“…The application of hPSC derivatives in human patients has progressed slowly due to potential risks associated with the use of pluripotent stem cells, where a few contaminating hPSCs could proliferate and develop into a teratoma or into early stage neuroepithelial tumors (Brederlau et al, 2006;Sonntag et al, 2007;Elkabetz et al, 2008). Furthermore, the transplantation of heterogenous neuronal population may entail the risk of side effects such as graft-induced dyskinesia (Dorsey et al, 2018) which have been attributed to the presence of serotonergic neurons in fetal grafts, as documented in grafted human PD patients by histological analysis and by functional studies (Gantner et al, 2020) 502+/−11 5-HT+HNA+ cells (Gantner et al, 2020) Representative studies are presented across different research groups that are working toward translating dopamine neuron cell therapy in PD. Comparison of key in vitro and in vivo parameters are presented based on the data taken from the published reports.…”

“…The resulting floor-plate derived mDA cells showed the biochemical and electrophysiological properties of mDA neurons in vitro and resulted in more robust survival and function in vivo while reducing the risk of neural overgrowth or teratoma formation ( Kriks et al, 2011 ; Table 1 ). Since those initial studies, several groups have developed independent mDA neuron differentiation paradigms ( Kirkeby et al, 2012 , 2017 ; Sundberg et al, 2013 ; Doi et al, 2014 ; Hallett et al, 2014 ; Steinbeck et al, 2015 ; Chen et al, 2016 ; Niclis et al, 2017 ; Gantner et al, 2020 ; Song et al, 2020 ) but all of those are based on the specification of mDA neurons via a floor-plate intermediate ( Figure 1 ).…”

“…Several studies have been proposed to enhance fetal or PSC-derived mDA neuron grafts such as by promoting their survival or function. Examples include treatment with pifithrin-alpha, increase of polysialic acid levels ( Chou et al, 2011 ; Battista et al, 2014 ), or delivery of neurotrophic factors such as glial cell line-derived neurotrophic factor (GDNF) which may provide benefits to facilitate graft integration and functional recovery ( Rosenblad et al, 1996 ; Redmond et al, 2009 ; Gantner et al, 2020 ).…”

Gene and Cell-Based Therapies for Parkinson's Disease: Where Are We?

“…Time will tell which if any of the current and future candidate GT treatments emerges as useful and practical therapy and so ends up dominating the therapeutic arena for PD. It is also possible that GTs could be used synergistically with cell therapies [ 144 ].…”