Retinal apoptosis of laser-induced retinal injury in mice after bone marrow mesenchymal stem cells transplantation

Abstract

Objective To observe the retinal apoptosis of laser-induced retinal injury in mice after bone marrow mesenchymal stem cells transplantation.Methods Green fluorescent protein (GFP) labeled MSCs from C57BL/6 mice were cultured in vitro.A total of 135 C57BL/6 mice were divided into three groups including normal control group (15 mice),injured control group (60 mice) and MSCs treatment group (60 mice).Laser retinal injuries were induced by laser photocoagulation.One day after photocoagulation,0.2 ml cell suspension,which contained 1 × 106 GFP-MSCs,were injected into the mice in treatment group via tail vein,and the mice in injured control group were given equal volume of phosphate buffer solution.Animal were execute on three,seven,14 and 21 days following laser damage.Hematoxylin and eosin (HE) staining was performed to assess the changes of injured retinas.The diameters of laser spots and areas with total loss of cells in outer nuclear layer (ONL) were analyzed by image processing software.The apoptosis of retinal cells was examined by terminal-deoxynucleoitidyl transferase mediated nick end labeling (TUNEL) staining.The migration of GFP-MSCs into the retina was observed by fluorescence microscope.Results HE staining showed that the retinal structures were integrated in normal control group.Retinal damages were observed both in injured control group and MSCs treatment group,but milder in the latter.Though the average diameter of area with total loss of cells in ONL of MSCs treatment group was less than the injured control group (t =5.769,P ＜ 0.05),the diameters of laser spots show no difference (t=0.964,P＞0.05) on day three.Both the average diameter of laser spots (t=5.180,5.417,2.381) and area with total loss of cells in ONL (t=3.530,3.224,3.162) were less in the MSCs treatment group on day seven,14 and 21 (P＜0.05).TUNEL staining shows that the apoptosis were decreased after MSCs transplantation on day three,seven,14 and 21 (t=11.142,7.479,6.678,3.953,P＜0.05).No apoptosis was observed in normal control group.Very few GFP-MSCs were observed in the retina at all time-points.They were only seen in the subretinal and choroidal neovascularization occasionally on day seven and 14.Conclusion MSCs transplantation can effectively limit the range of retinal laser damage and inhibit cell apoptosis. Key words: Mesenchymal stem cell transplantation; Retina/pathophysiology; Apoptosis