Editors' ChoiceStem Cells

Stem cells in gels

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Science Translational Medicine  03 Jun 2015:
Vol. 7, Issue 290, pp. 290ec90
DOI: 10.1126/scitranslmed.aac5089

On 12 September 2014, a Japanese woman in her 70s became the first person to receive a transplant of human induced pluripotent stem cell (hiPSC)–derived retinal pigmented epithelium (RPE) cells. She likely will not be the last, as it seems plausible that the first major application of hiPSC-based therapies will be for macular diseases. Now that safety has been preliminarily established in one person, the next major barriers to cell replacement therapies—whether they involve cells of the eye, brain, heart, or pancreas—will be improving the survival and integration of donor cells. Ballios et al. developed an injectable hydrogel to help stem cells survive when implanted.

Macular degeneration is a major cause of visual impairment in older adults, typically arising from atrophy of the RPE and loss of photoreceptors. hiPSCs can be coaxed to form RPE cells and then transplanted into the retina to improve vision in recipient animals. However, efficacy may be limited by the relatively low survival of RPE cells after transplant. In an effort to improve survival of retinal stem cell–derived RPEs following transplantation, Ballios et al. placed the cells within an injectable hyaluronan and methylcellulose (HAMC) hydrogel. The hydrogel-encased cells demonstrated better distribution, survival, and integration within the eye than control cells delivered without hydrogel, and were sufficient to improve visual outcomes in blind mice. The authors suggest that the HAMC hydrogel enhanced survival of mature rods by inhibiting CD44-mediated apoptosis.

The HAMC hydrogel may have broad utility beyond the retina. The authors showed significant improvements in the motor deficits of stroke-injured mice treated with HAMC-injected neural stem cells, likely owing to improved survival of the transplanted cells. Moving forward, it will be exciting to test whether HAMC hydrogel is as efficacious in improving survival of hiPSC–derived donor cells, to help translate the many stem cell replacement therapies currently under development.

B. G. Ballios et al., A hyaluronan-based injectable hydrogel improves the survival and integration of stem cell progeny following transplantation. Stem Cell Rep. 10.1016/j.stemcr.2015.04.008 (2015). [Abstract]

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