Protection Mechanism Of The Bone Marrow Mesenchymal Stem Cells On Photoreceptor Cells

Objective: To investigate the structural and functional change in the retinas of rats after intense light exposure; to study the protective effects of subretinal transplanted BMSCs on photoreceptors in light-damaged retina and explor the possible mechanisms.Methods:1. Rat model of light-damaged retina: Sprague-Dawley rats were exposed to 4k Lux cycle light in the self-designed mould. At the point of 3rd, 5th, 7 th, 9 th, 12 th day during light exposure, the rats’ eyes were removed after F-ERG testing. Histological changes in the retina were observed by HE staining. 2. Subretinal transplantation of GFP-BMSCs: Rats were randomly assigned to control group, light damaged group, DMEM-injected group and BMSCs-injected group. 3-5P GFP-BMSCs and DMEM were injected into the subretinal space of light-damaged rat model. At the point of 1st, 4th, 8th, 12 th week after transplantation, the rats’ eyes were removed after F-ERG testing. Structural changes of outer segment of photoreceptors among groups were observed by TEM; the ONL thickness were investigated by HE staining; immunofluorescence were conducted to observed the migration of transplanted cells and the residual Rho at 12 th week; Western blot were applied to detect the expression of GDNF and GS the groups at 1st、3rd day and 1st、2nd、4th、6th、8th、12th week after transplantation.Results:1. F-ERG test revealed the retinal function was impaired after light exposure(p<0.05), HE staining indicated that the ONL thickness became thiner(p<0.05), the functional and histological were consistently declined with the prolongation of light exposure time. However, during the light exposure, the thinning rates of ONL thickness were slower within 5 days and after 9 days.2. GFP-BMSCs subretinal transplantation was capable of delaying reduction of the ONL thickness(p<0.05). F-ERG test showed better retinal function in BMSCs-injected group(p<0.05) than in other two light exposure groups. The injury in outer segment of photoreceptors was relieved in BMSCs-injected group. Immunofluorescence demonstrated that a few of GFP-BMSCs migrated to the outer retina; residual Rho was significantly more in BMSCs-injected group than that in other two groups(p<0.05); After transplantation, Western blot revealed the expression of GS decreased to the lowest at the 3rd day and increased until the 2nd week in the two subretina-injected groups, nevertheless GS in the BMSCs-injected group was the highest throughout; the expression of GDNF was higher as well(p<0.05), but the peak value appeared at the 1st week.Conclusions: Subretinal transplantation of GFP-BMSCs exerted neuroprotective effect on photoreceptor in light damaged retina. The transplanted BMSCs secrete neurotrophic factors and promote host retinal cells secrete GDNF and other neuroprotective agents at the same time,which upregulate GS to enhance the ability of resisting excitotoxic trauma. Both direct and indirect ways might be the protection mechanisms.