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Tsz Kin Ng, Jasmine Sum Yee Yung, Sun On Chan, Chi Chiu Wang, Herman S. Cheung, Andrew V. Schally, Chi Pui Pang; GHRH/IGF-1 pathway in retinal progenitor cell differentiation. Invest. Ophthalmol. Vis. Sci. 2017;58(8):1055.
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© ARVO (1962-2015); The Authors (2016-present)
Precise retinal cell maturation requires specific signaling pathway to guide retinal progenitor cell differentiation. We previously demonstrated that growth hormone-releasing hormone (GHRH) is expressed in retina and participated in retinal disease development. This study aimed to delineate the biological role of GHRH as well as its downstream signaling factor, insulin-like growth factor-1 (IGF-1), in retinal development and retinal progenitor cell differentiation.
Retinal GHRH receptor expression was determined by the immunofluorescence analysis on embryonic day (E) 14 to post-natal day (PN) 6 retinas of Sprague-Dawley rats. Retinal progenitor cells from E18 and PN1 rat retinas were isolated, purified and cultured in DMEM/F-12 medium with N2 supplement, basic fibroblast growth factor and epidermal growth factor on the non-adherent culture dishes for 3 days, followed by the treatment of retinal differentiation medium (DMEM/F-12 medium with B27 supplement) with or without the addition of GHRH or IGF-1. Retinal cell specification was evaluated by immunofluorescence analysis of specific retinal cell markers (Brn3b for retinal ganglion cells (RGCs), Rhodopsin for photoreceptors and S100 for Müller glia).
The expression of GHRH receptor was not observed in E14 retina until E18 in the retinal progenitor cell and RGC layer, which was indicated by the immunofluorescence signal of retinal progenitor marker Pax6. GHRH receptor signal persisted to E21 and PN6, and confined in the RGC layer, suggesting its involvement in RGC specification. Increased Brn3b-expressing cells were found in retinal progenitor cell differentiation treatment with GHRH by 3 folds for E18 and 5 folds for PN1 (p < 0.001). In contrast, IGF-1 enhanced the occurrence of rhodopsin-expressing cells of E18 retinal progenitor cell differentiation by 10 folds (p < 0.001).
GHRH receptor expresses in retinal progenitor cell and RGC layer during retinal development. GHRH promotes the specification of retinal progenitor cells towards retinal ganglion cell lineage, whereas IGF-1 is more prone to the photoreceptor specification.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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