Cell therapy using genome-edited iPS cells could be a new treatment for Fabry disease
Fabry disease is caused by the genetical deficiency of α-Galactosidase A (GLA), leading to the accumulation of its substrates such as globotriaosylceramide (Gb3) and globotriaosylsphingosine (Lyso-Gb3). We previously developed an engineered enzyme, modified α-N-acetylgalactosaminidase (mNAGA), to cure Fabry disease by altering the substrate specificity of NAGA, which is a paralog of GLA, into that of GLA. Because mNAGA maintains the original antigenicity of NAGA, this modified enzyme has no immunological cross-reactivity with GLA, while having the GLA enzymatic activity.
First, we generated iPS cells secreting mNAGA by TALEN-mediated knock-in to the AAVS1 site, a safe harbor locus. In addition, to exclude the possible immunogenic reactions caused by the endogenous GLA of iPS cells in patients, we disrupted the GLA gene by CRISPR-Cas9. When the Fabry model cardiomyocytes and fibroblasts with no GLA activity were co-cultured with mNAGA-secreting iPS cells, the GLA activity was restored by mNAGA-expressing cells in vitro.
Next, we transplanted the iPS cells secreting mNAGA into the testes of Fabry disease model mice. After 7 or 8 weeks, the GLA activity in the liver was significantly improved, although no recovery of the activity was observed in the heart, kidney, or blood plasma. We also quantified the amounts of Gb3 and Lyso-Gb3 in the liver, but there was no detectable reduction of the substrates.
This study demonstrated the potential of cell therapy using genome-edited iPS cells secreting therapeutic molecules. These genome-edited iPS cells could serve as not only a resource for cell transplantation but also a drug delivery system.
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