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

Abstract

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 FailSafeTM 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 FailSafeTM 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.

Extracellular Matrix Biomimetic Hydrogels, Encapsulated with Stromal Cell-Derived Factor 1, Improve the Composition of Foetal Tissue Grafts in a Rodent Model of Parkinson’s Disease

“…Recent studies have highlighted the importance of SDF1 in DA development [20][21][22], and the DA differentiation of pluripotent stem cells [16][17][18][19]. Added to this, we previously demonstrated that the co-transplantation of meningeal cells, together with VM fetal grafts, significantly increased the proportion of A9 DA neurons within VM grafts-an effect that was speculated to be modulated via SDF1-CXCR4 signalling [22].…”

“…More recently, a series of studies have provided new insight into the role of the chemokine Stromal cell-Derived Factor-1, SDF1 (also known as CXCL12), and the meninges in midbrain DA development to suggest that this protein may also improve graft outcomes. Several studies demonstrated that the co-culture of embryonic stem cells on stromal cell feeder layers, or meningeal cells, promoted neural induction and induced DA differentiation via secreted factors termed stromal derived inducing activity (SDIA) [16][17][18][19]. Genome expression analysis revealed that SDF1 was one of the secreted factors [19].…”

Translating musculoskeletal bioengineering into tissue regeneration therapies

“…Additionally, long-term safety of hiPSC therapies requires the elimination of their tumorigenic potential by ensuring use of non-integrating reprogramming factors, uniform and robust differentiation protocols, and identification and removal of pluripotent or immature, proliferating cells (99). Specifically, generation of hiPSC lines with drug-inducible suicide genes can be utilized to partially or fully eradicate transplanted cells in cases of adverse outcomes in vivo (100).…”

mRNA-mediated delivery of gene editing tools to human primary muscle stem cells

“… 6 , 7 However, iPSC-derived muscle cells do not yet meet quality and safety criteria for transplantation into patients. Overall, allogeneic transplantation requires immunosuppression or cloaking of transplantable cells, 8 , 9 adding another level of uncertainty, and it has not yet been shown for iPSC-derived muscle cells. In addition, MuSCs are irreplaceable in muscle regeneration; 10 , 11 thus, a long-term therapeutic effect of a stem cell therapy would require that the transplanted cells can reconstitute the MuSC compartment.…”