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S. Chien Wong, Mei Cheng, Wendy Dailey, Joseph Vercellone, Charlotte Massoll, Kenneth P. Mitton, Kimberly A. Drenser; In Vivo Time-Lapse Retinal Ganglion Cell Imaging in Retinal Ischemia and the effect of Norrin. Invest. Ophthalmol. Vis. Sci. 2012;53(14):4651.
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© ARVO (1962-2015); The Authors (2016-present)
The murine oxygen induced retinopathy (OIR) model has been widely used to study vascular health and development under ischemic conditions. Corresponding data on neuroretinal development is limited.The purpose of this study was two-fold: (1) to assess neuroretinal development and survival, specifically retinal ganglion cells (RGC), in a murine model of OIR using in vivo time-lapse imaging, (2) to test Norrin, a neurotropic protein, as a possible RGC therapeutic rescue agent.
Transgenic mice (B6.Cg-Tg(Thy1-YFP)16Jrs/J) that express yellow fluorescent protein (YFP) in a subset of their RGC were divided into 2 groups: group A in room-air only (n = 14), and group B exposed to 75% oxygen from postnatal (P) day 7 to P12 (n = 7). In group B, upon return to room air at P12, intravitreal injection of Norrin (20ng, 100ng or 200ng in 1μl) or Phosphate Buffered Saline (PBS) (1μl) was administered to the right and left eyes respectively. In vivo time-lapse imaging of YFP-RGCs and retinal vessels within a 50 degree area of the posterior retina was performed with a retinal imaging microscope (Micron III) at P17, P21, P28 and P42. The number and features of the YFP-RGCs were evaluated.
Mean number of fluorescent RGCs in room-air controls were 9, 14, 17 and 17 at P17, P21, P28 and P42, respectively. In the OIR PBS control group, mean number of cells were 8, 5, 8 and 10 respectively. The difference was significant at P21 (p=0.05), P28 (p<0.05) and across all time points (p=0.002). In the Norrin treated eyes, overall YFP-RGC cell numbers were higher compared to contralateral PBS control eyes. Mean increase were 54.2%, 27.7% and 16.7% with 20ng (n = 5), 100ng (n = 3) and 200ng (n = 2) of Norrin, respectively.
Our study demonstrates the feasibility of performing in vivo time-lapse imaging and assessment of retinal ganglion cells in transgenic YFP mice with oxygen induced retinopathy. Compared to room-air controls, OIR mice have reduced ganglion cell numbers across all time points. Norrin may have a dose dependent role in improving retinal ganglion cell health.
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