Abstract
Purpose: :
Rd1 mouse is a murine model for retinitis pigmentosa. Light exposure is one of the known factors that promotes the photoreceptor degeneration in this mouse. Total retinal detachment (TRD) blockes the physiological interaction between the photoreceptors and the retinal pigment epithelial cells that provide the 11–cis retinal , a molecule essential for the phototransduction, to the overlying photoreceptors. We hypothesized that TRD, which presumably reduces the phototransduction, may ultimately prevent the photoreceptor degeneration possibly by mimicing a reduced light exposure.
Methods: :
We created an artificial TRD in postnatal 6 day (PN6) rd1 mice by penetrating the globe around the equator using a 33 gauge needle. The control eyes with no retinal deatchment (NRD) underwent similar procedure except that the penetration took place 0.5 mm posterior to the corneal limbus. BrdU was administrated intraperitoneally from PN 9 to PN 12 to label the proliferating retinal progenitor cells. After TRD or NRD was confirmed with microscope, the eyes were enucleated at PN 30, cryosectioned, and stained for immunohistochemical analyses. We used anti–rhodoposin antibody and anti–BrdU antibody as the primary antibodies, and DAPI was used for staining nuclei. Images were obtained from midperipheral portion of the superior or the inferior retina for counting photoreceptors positive for DAPI or rhodopsin and peripheral retina and ciliary body for the BrdU–positive cells.
Results: :
The total numbers of the DAPI–positive nuclei in the outer nuclear layer (ONL) which represents the sum of rod and cone photoreceptors were 1.34–fold larger (P<0.0001) in the eyes with TRD (141.8±14.2; n=4) than those of the eyes with NRD (105.4±7.5; n=10). Interestingly, much larger degree of rod photoreceptors (rhodopsin–positive cells) preservation of 1.94–fold (P<0.001) was observed in the eyes with TRD (13.8±2.9) compared to those with NRD (7.1±1.8). The numbers of BrdU–positive cells in the peripheral retina or the non–pigmented epithelium of the ciliary body that presumably contains the retinal progenitor cells were not significantly different between the eyes with TRD (9.2±5.5) and those with NRD (14.9±7.7).
Conclusions: :
TRD preserved the rod photoreceptors by 1.94–fold and the cone–plus–rod photoreceptors by 1.34–fold in rd1 mouse. This rescue effect of the photoreceptors may not be due to the increased retinal regeneration by BrdU–positive retinal progenitor cells. While TRD is one of the main causes of blindness in humans, it has a resucue potential for the mice with severe photoreceptor degeneration.
Keywords: retinal degenerations: cell biology • retinal detachment • immunohistochemistry