Abstract
Purpose: :
We have observed that stem cells/progenitors in limbal epithelium (LE) possess neural potential that is displayed upon neutralization of BMP signaling in vitro (Zhao et al., 2002, Dev. Biol.250: 317-331). Neural progenitors derived from limbal stem cells/progenitors can generate neurons with functional properties and given suitable culture conditions can differentiate into retinal neurons (Zhao et al. 2008, Stem cells. 26: 939-949). Here, we examined the remarkable plasticity of limbal stem cells/progenitors further and demonstrate their reprogramming into cells with pluripotent properties.
Methods: :
Cells isolated from the basal LE were cultured in the presence of Noggin and EGF to generate spheres. LE Sphere were co-cultured with ES cells and examined for the generation embryoid bodies and the expression of iPS cell genes. The induced LE iPS cells were transplanted in SCID mice to examine their potential to form teratoma and exposed to different culture conditions to evaluate their ability to differentiate into cells of all three embryonic lineages.
Results: :
We observed that Noggin-exposed LE cells formed embryoid bodies seemingly indistinguishable from those generated by ES cells. We observed a temporal induction of iPS genes including Nanog and Oct4 in co-culture conditions. These cells were able to activate reporter genes driven by Nanog promoter in the presence of ES cell conditioned medium (CM). The LE iPS cells when transplanted in SCID mice formed teratoma, containing tissues of all three lineages. The induced cells when cultured in previously defined conditions differentiated into cardiomyocytes, hepatocytes and neurons.
Conclusions: :
Our results demonstrate the reprogramming of somatic stem cells/progenitors to pluripotency by the microenvironment, and as such raises the possibility of iPS cell therapy without the intervention of genetic engineering.
Keywords: plasticity • cell-cell communication • differentiation