Introduction Human induced pluripotent stem cells (hIPSCs) represent a unique opportunity for regenerative medicine since they offer the prospect of generating unlimited quantities of cells for autologous transplantation as a novel treatment for a broad range of disorders. We have previously developed disease specific human hepatocyte-like cells by reprogramming dermal fibroblasts taken from individuals with PiZ α1-antitrypsin deficiency. The resulting cells recapitulated the protein misfolding and intracellular polymer formation that characterise this disease (Rashid et al, J Clin Invest 2010;120:3127–36). However, use of iPS cells in treatment of individuals with PiZ α1-antitrypsin deficiency would also require correction of the underlying genetic abnormality in a manner fully compatible with clinical applications. The methods currently available, such as homologous recombination, lack the necessary efficiency and also leave residual sequences in the targeted genome.
Aim (1). To correct the genetic mutation responsible for PiZ α1-antitrypsin deficiency in human IPS cells in a clinically relevant way. (2). To investigate the potential of using corrected hIPS derived liver cells for cell based therapy by studying their in vivo function.
Method The genetic defect responsible for PiZ α1-antitrypsin deficiency (Glu342Lys) was targeted using a combination of engineered Zinc finger nucleases and a piggyBac vector in patient specific hiPSCs. Corrected cells were differentiated to hepatocytes using a previously optimised chemically defined in vitro platform. Assessment of phenotypic correction was then made in vitro as well as in vivo.
Results We demonstrate here for the first time an efficient gene editing technique capable of restoring normal structure, function and secretion of α1-antitrypsin in subsequently derived liver cells without leaving residual exogenous sequences in the targeted hiPSC genome. Moreover injection of corrected hiPS derived liver cells into a mouse model of liver injury confirmed their potential for functional capacity in vivo. Importantly none of the transplanted mice showed evidence of tumour formation.
Conclusion Our results provide proof of principle for the potential of combining hiPSCs with gene therapy to generate cells for autologous cell based treatment of α1-antitrypsin deficiency in humans.
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