Disorganization Of Outer Segments Research Articles

Mesenchymal stem cells as a possible therapy in experimentally induced retinal damage in Albino rat: Histological study

ABSTRACTIntroduction: Retinal degeneration had been increased as a common cause of blindness nowadays. Stem cells could be apromising therapy for treating retinal degeneration.Aim of the work: To investigate the possible role of BMSCs on the damaged retina resulting from continuous fluorescentlight exposure.Materials and Methods: Twenty- five albino rats (80- 100) gm were used in this study. Of which, 5 rats were used forpreparation of the BMSCs. The other twenty adult rats were divided into three groups. Rats of the control group were kept in12 hrs light/ 12 hrs dark. Rats of group II (fluorescent light exposure group) were exposed to two 20W white fluorescent lamps60 cm length continuously for 2 weeks at an illumination of 500 Lux. Group II rats were examined 8 weeks after fluorescentlight exposure. Group III animals were injected once by PKH 26–labeled BMSCs into the vitreous cavity of the eye at the endof the second week of fluorescent light exposure and kept for 8 weeks. Retinal specimens were prepared for light (LM) andelectron microscopic (EM) examination. Morphometric and statistical study was performed.Results: Sections of group II showed thinning and disorganization of outer segments. There were spaces and disorganizationof the cells of the outer and inner nuclear layers. Most ganglion cells had vacuolated cytoplasm and some appeared with densenuclei. Most of retinal cells had distorted organelles. Immunohistochemical reaction revealed significant increase in GFAPimmune reaction. Statistical analysis revealed a significant decrease in the thickness of most retinal layers. Meanwhile, groupIII retinas showed restoration of most of the histological structure.Conclusion: BMSCs could ameliorate retinal degeneration resulted from continuous fluorescent light exposure.

Impaired cone function and cone degeneration resulting from CNGB3 deficiency: down-regulation of CNGA3 biosynthesis as a potential mechanism

The cone cyclic nucleotide-gated (CNG) channel is essential for central and color vision and visual acuity. This channel is composed of two structurally related subunits, CNGA3 and CNGB3; CNGA3 is the ion-conducting subunit, whereas CNGB3 is a modulatory subunit. Mutations in both subunits are associated with achromatopsia and progressive cone dystrophy, with mutations in CNGB3 alone accounting for 50% of all known cases of achromatopsia. However, the molecular mechanisms underlying cone diseases that result from CNGB3 deficiency are unknown. This study investigated the role of CNGB3 in cones, using CNGB3(-/-) mice. Cone dysfunction was apparent at the earliest time point examined (post-natal day 30) in CNGB3(-/-) mice. When compared with wild-type (WT) controls: photopic electroretingraphic (ERG) responses were decreased by approximately 75%, whereas scotopic ERG responses were unchanged; visual acuity was decreased by approximately 20%, whereas contrast sensitivity was unchanged; cone density was reduced by approximately 40%; photoreceptor apoptosis was detected; and outer segment disorganization was observed in some cones. Notably, CNGA3 protein and mRNA levels were significantly decreased in CNGB3(-/-) mice; in contrast, mRNA levels of S-opsin, Gnat2 and Pde6c were unchanged, relative to WT mice. Hence, we show that loss of CNGB3 reduces biosynthesis of CNGA3 and impairs cone CNG channel function. We suggest that down-regulation of CNGA3 contributes to the pathogenic mechanism by which CNGB3 mutations lead to human cone disease.