Human stem cells harboring a suicide gene improve the safety and standardisation of neural transplants in Parkinsonian rats

Despite advancements in human pluripotent stem cells (hPSCs) differentiation protocols to generate appropriate neuronal progenitors suitable for transplantation in Parkinson's disease, resultant grafts contain low proportions of dopamine neurons. Added to this is the tumorigenic risk associated with the potential presence of incompletely patterned, proliferative cells within grafts. Here, we utilised a hPSC line carrying a FailSafe(TM) suicide gene (thymidine kinase linked to cyclinD1) to selectively ablate proliferative cells in order to improve safety and purity of neural transplantation in a Parkinsonian model. The engineered FailSafe(TM) hPSCs demonstrated robust ventral midbrain specification in vitro, capable of forming neural grafts upon transplantation. Activation of the suicide gene within weeks after transplantation, by ganciclovir administration, resulted in significantly smaller grafts without affecting the total yield of dopamine neurons, their capacity to innervate the host brain or reverse motor deficits at six months in a rat Parkinsonian model. Within ganciclovir-treated grafts, other neuronal, glial and non-neural populations (including proliferative cells), were significantly reduced-cell types that may pose adverse or unknown influences on graft and host function. These findings demonstrate the capacity of a suicide gene-based system to improve both the standardisation and safety of hPSC-derived grafts in a rat model of Parkinsonism. Stem cell grafts present a risk of tissue overgrowth/tumors. Here, the authors utilise a human pluripotent stem cell line carrying a FailSafe suicide gene to not only ablate proliferative cells, but through timely gene activation, improve the purity of neural grafts in Parkinsonian rats.

Automated summary

This study used a human pluripotent stem cell line carrying a FailSafe suicide gene to selectively ablate proliferative cells in a Parkinsonian model, resulting in improved safety and purity of neural grafts. Activation of the suicide gene post-transplantation led to smaller grafts without affecting dopamine neuron yield, innervation capacity, or motor deficits reversal, demonstrating the potential of a suicide gene-based system to enhance the standardization and safety of stem cell-derived grafts.