Study: Transplantation of genome-edited iPS cells delivers therapeutic molecules in vivo

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Induced pluripotent stem (iPS) cells have a great impact on medicine and biology, and they are likely to shift the paradigm in regenerative medicine.

Since 2014 when a sheet of retinal pigment epithelial cells derived from iPS cells was transplanted into patients with age-related macular degeneration, clinical trials have been conducted with various cell types derived from iPS cells.

According to a Tokyo Metropolitan Institute of Medical Science news release, while iPS cells derived from healthy individuals have been used so far, it is expected that transplantation therapy using iPS cells can be enhanced through genetic modification in the future.

According to the study,¹ researchers examined the possibility by utilizing a Fabry disease mouse model, as a proof of concept. 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,” the researchers said in the news release. “Because mNAGA maintains the original antigenicity of NAGA, this modified enzyme has no immunological cross-reactivity with GLA, while having the GLA enzymatic activity. In this study, we tested whether transplantation of iPS cells secreting mNAGA by genome editing could supply the GLA activity in vivo.”

The researchers generated iPS cells secreting mNAGA by TALEN-mediated knock-in to the AAVS1 site, a safe harbor locus.¹

Genome editing enables the expression and secretion of therapeutic molecules from induced pluripotent stem (iPS) cells. Furthermore, transplantation of these cells allows for the delivery of therapeutic molecules to organs and tissues in vivo. (Image courtesy of TMIMS)

“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,” the researchers said in the study. “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.”

The researchers then 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.¹

“We also quantified the amounts of Gb3 and Lyso-Gb3 in the liver, but there was no detectable reduction of the substrates,” they said in the study.

Moreover, the researchers noted that due to the limited amount of mNAGA secreted from the transplanted iPS cells, the GLA activity in the liver was not high enough to reduce Gb3 or Lyso-Gb3. However, in the future, it may be possible to enhance the amount of secreted mNAGA through genome editing.

“There is also the possibility to directly deliver mNAGA to organs and tissues that need the GLA activity. For example, transplantation of a cardiomyocyte sheet derived from iPS cells secreting mNAGA directly delivers mNAGA to the heart,” the researchers said. “Furthermore, while this study focused on Fabry disease, the same strategy can be applied to other diseases.”

According to researchers, the 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,” the researchers concluded.

Reference:

1. Ittetsu Nakaima, Takihiro Tsukimura, Yuichiro Mihaoka. In Vivo Delivery of Therapeutic Molecules by Transplantation of Genome-Edited Induced Pluripotent Stem Cells. Cell Transplantation. Published May 15, 2023. DOI: https://doi.org/10.1177/09636897231173734