Myo/Nog cells increase in areas of stress in a mouse model of retinitis pigmentosa

Abstract

Purpose : Myo/Nog cells are known to be neuroprotective and are found in areas of stress, including the retina. We hypothesize that Myo/Nog cells increase in a congenital murine model of retinitis pigmentosa (RP) in which photoreceptor cells progressively degenerate.

Methods : The RP C3H/HeJ and wild type C57Bl/6J strains were compared by Ocular Computer Topography (OCT), electroretinography (ERG) and immunofluorescence localization in tissue sections. OCT images were obtained weekly for the C57 and C3H strains between the ages P17 to P42. The images were analyzed to measure the different cell layers in the retina at fixed points. ERGs were performed weekly to assess retinal functionality. Histological data was obtained by enucleating the eyes, fixing in paraformaldehyde, cryosectioning and labeling with antibodies against Myo/Nog cells, and the TUNEL technique to detect apoptotic cells. The numbers of Myo/Nog and dead cells in tissue sections were recorded along the length of the retina.

Results : The results show a difference in retinal health of control C57 when compared with the congenital mutated C3H mice. OCT and histological analysis revealed that control mice maintained each cell layer of the retina from P17 to P42, whereas C3H mice lost a significant depth of their photoreceptor cell layer as early as P21. The ERG further supported the data as the C57 maintained normal and expected A and B waves of oscillatory potential, while the C3H quickly lost the integrity of the A and B waves. Myo/Nog cells increased in the retinas of the C3H strain compared to C57 mice. More Myo/Nog cells were found in the choroid neighboring the outer nuclear layer (ONL) (photoreceptor) layer of the retina where most of the cell death occurred.

Conclusions : Myo/Nog cells increase in number coincident with cell death, thinning of the ONL and loss of function in the retina. Further investigation would be needed to confirm that Myo/Nog cells specific to RP are neuroprotective.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.