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X Zhao, AV Das, I Ahmad; Noggin Enhances Neural Conversion of Adult Corneal Limbal Stem Cells by Antagonizing BMP Signaling . Invest. Ophthalmol. Vis. Sci. 2002;43(13):1626.
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Purpose: Noggin belongs to a class of polypeptides that play an important role during neural induction. It functions by antagonizing bone morphogenetic proteins (BMPs), members of the TGFß superfamily of molecules. We have shown that adult corneal limbal stem cells, which like neural stem cells are ectodermally derived, can give rise to multipotential neural progenitors. We want to know if inhibition of BMPs by Noggin can enhance the neural conversion of adult corneal limbal stem cells. Methods: Adult rat limbal corneas were dissociated and cultured in the medium containing EGF (20ng/ml), FGF2 (10ng/ml), supplemented with either BMP4 (20ng/ml) or Noggin (200ng/ml). The control included limbal dissociates cultured in EGF+FGF2. After 5 days in culture, floating spheres of cells were collected for RT-PCR analysis or transferred to gelatin/poly-D-lysin coated glass cover slips for immunocytochemical analysis of neural progenitor and pan neural markers. Results: Limbal dissociates cultured in the presence of BMP4 generated fewer clonal spheres than those in the control and Noggin groups. The proportion of nestin positive cells in clonal spheres in the control group and those exposed to BMP4 was 9% and 5%, respectively. In contrast, nestin positive cells constituted 21% of Noggin-exposed cells in the clonal spheres. While neural differentiation can be readily detected by the expression of MAP2 in the control and Noggin groups, immunoreactivity or transcripts corresponding to MAP2 were undetectable in BMP4-exposed spheres. Conclusion: Our results suggest that BMP signaling may play a critical role in the neural conversion of adult corneal limbal stem cells. Supported by NEI, Nebraska Research Initiative and Foundation Fighting Bliness.
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