Biomedicine: Visionary stem-cell therapies.

Abstract

Stem-cell engineering has allowed successful cornea transplantations in rabbits and the regeneration of transparent lens tissue in children, demonstrating the therapeutic potential of this approach. See Article p.323 & Letter p.376 The only current treatment for cataracts, the leading cause of blindness, is to extract the damaged lens surgically and implant an artificial intraocular lens. The technique has its limitations, so there is great interest in the possibility of a regenerative medicine approach. Two papers published in this issue of Nature report advances that could bring that prospect a little closer. Kang Zhang and colleagues isolate mammalian lens epithelial stem/progenitor cells and show that Pax6 and Bmi1 are required for their renewal. They have also developed a removal procedure for cataract-affected tissue that preserves these cells, and achieved lens regeneration in rabbits, macaques and in human infants with cataracts. In the second paper, Kohji Nishida and colleagues describe a protocol for in vitro generation of a self-formed ectodermal autonomous multi-zone (SEAM) from human induced pluripotent stem cells. The SEAM includes distinct cell lineages from the ocular surface ectoderm, lens, neuro-retina, and retinal pigment epithelium. Previous experiments had focused mainly on obtaining one cell type. These authors show that cells from the SEAM can be expanded to form a functional corneal epithelium when transplanted to an animal model of blindness.