Fail-Safe System against Potential Tumorigenicity after Transplantation of iPSC Derivatives.

Go Itakura,Jun Kohyama,Miki Ando,Morio Matsumoto,Rei Kashiwagi,Kota Kojima,Hiromitsu Nakauchi,Masahiro Ozaki,Hideyuki Okano,Tsuyoshi Iida,Kaori Yasutake,Soya Kawabata,Yuichiro Nishiyama,Masaya Nakamura,Akio Iwanami,Toshiki Ookubo,Narihito Nagoshi,Keiko Sugai,Hiroyuki Miyoshi

doi:10.1016/j.stemcr.2017.02.003

Abstract

SummaryHuman induced pluripotent stem cells (iPSCs) are promising in regenerative medicine. However, the risks of teratoma formation and the overgrowth of the transplanted cells continue to be major hurdles that must be overcome. Here, we examined the efficacy of the inducible caspase-9 (iCaspase9) gene as a fail-safe against undesired tumorigenic transformation of iPSC-derived somatic cells. We used a lentiviral vector to transduce iCaspase9 into two iPSC lines and assessed its efficacy in vitro and in vivo. In vitro, the iCaspase9 system induced apoptosis in approximately 95% of both iPSCs and iPSC-derived neural stem/progenitor cells (iPSC-NS/PCs). To determine in vivo function, we transplanted iPSC-NS/PCs into the injured spinal cord of NOD/SCID mice. All transplanted cells whose mass effect was hindering motor function recovery were ablated upon transduction of iCaspase9. Our results suggest that the iCaspase9 system may serve as an important countermeasure against post-transplantation adverse events in stem cell transplant therapies.

Highlights

The establishment of induced pluripotent stem cells, which exhibit pluripotent differentiation and self-renewal potential comparable with that of embryonic stem cells (ESCs), by reprogramming via the introduction of several genes into somatic cells has opened up new prospects for regeneration medicine, and a number of possible clinical applications are currently being studied (Okano and Yamanaka, 2014; Takahashi et al, 2007)
Integrated iC9 with chemical inducers of dimerization (CIDs) Reliably Induced Apoptosis in induced pluripotent stem cells (iPSCs), iPSC-NS/PCs, and Terminally Differentiated Derivatives We prepared a lentiviral vector with the iCaspase9 gene and the puromycin resistance gene as a selectable marker integrated under the EF-1a or UbC promoter (Figure 1A)
The iCaspase9 gene was transduced into two human iPSC (hiPSC) lines with potential tumorigenicity after iPSCNS/PCs transplantation in previous unpublished and published studies, TKDA3-4 and 253G1 (Nori et al, 2015)

Summary

Introduction

The establishment of induced pluripotent stem cells (iPSCs), which exhibit pluripotent differentiation and self-renewal potential comparable with that of embryonic stem cells (ESCs), by reprogramming via the introduction of several genes into somatic cells has opened up new prospects for regeneration medicine, and a number of possible clinical applications are currently being studied (Okano and Yamanaka, 2014; Takahashi et al, 2007). Our group has conducted studies involving the transplantation of cells that have been induced to differentiate into hiPSC-NS/PCs in immunodeficient animals to allow for the assessment of the cells prior to transplantation (Okano et al, 2013). Even if such attempts are successful, the risk of tumor formation in residual pluripotent stem cells below the threshold of detection cannot be completely eliminated. Posttransplantation safety measures, such as surgery and g-ray

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