Vezhenkova I V, Mikhaĭlov V M
Tsitologiia. 2008;50(4):287-92.
Mdx mice cardiomyocytes are a perspective model to study survival of terminally differentiated cardiomyocytes and formation of cardiomyopathy under conditions of oxidative stress. It was previously observed that dynamical stress induced formation of low molecular DNA fragments. It is beyond question that DNA fragmentation develops because of formation of double strand DNA breaks (DNA DSB). To record appearance and disappearance of DNA DSB we used antibodies to phosphorylated histone H2Ax (histone gamma-H2Ax.). The presence of DNA DSB was estimated in 0.05% and 6.7% of cardiomyocytes in the myocardium form C57B1 and mdx mice without stress, respectively. The part of cardiomyocytes with DNA DSB increased in an hour after stress up to 1.0% and 41.7% in C57B1 and mdx mice, respectively. In 24 h after stress, the myocardium from mdx mice contained 5.2% of gamma-H2Ax-positive cardiomyocytes and no C57B1 myocardium was found with any amount of gamma-H2Ax-positive cells. The results presented show induction of DNA damage by dynamical stress and restoration of normal DNA structure in the cells of both strains in 24 h after stress. There was no mdx mice death after used dynamical stress. To estimate the real contribution of DNA repair to the survival of cardiomyocytes we have counted the cardiomyocyte loss. Morphometric analysis demonstrated that cell concentration in myocardium from mdx mice under normal conditions was less than that one in myocardium of C57B1/6. The cell loss varied between 20% for the base and 40% for the apex of mdx mice hearts. In 24 h after stress, the cell loss in the myocardium of mdx mice amounted to 2.5%. The difference between the number of cells with damaged DNA structure and the index of the real cell loss allows concluding that DNA repair makes a real contribution to the survival of mdx mice cardiomyocytes after dynamical stress.
mdx小鼠心肌细胞是研究终末分化心肌细胞存活以及氧化应激条件下心肌病形成的理想模型。此前观察到动态应激可诱导低分子DNA片段的形成。毫无疑问，DNA片段化是由于双链DNA断裂（DNA DSB）的形成所致。为了记录DNA DSB的出现和消失，我们使用了针对磷酸化组蛋白H2Ax（组蛋白γ-H2Ax）的抗体。在无应激的情况下，C57B1和mdx小鼠心肌中分别有0.05%和6.7%的心肌细胞存在DNA DSB。应激1小时后，C57B1和mdx小鼠中出现DNA DSB的心肌细胞比例分别增加到1.0%和41.7%。应激24小时后，mdx小鼠心肌中有5.2%的γ-H2Ax阳性心肌细胞，而C57B1小鼠心肌中未发现任何数量的γ-H2Ax阳性细胞。所示结果表明动态应激可诱导DNA损伤，且应激24小时后两种品系细胞中的正常DNA结构均可恢复。使用动态应激后mdx小鼠未死亡。为了评估DNA修复对心肌细胞存活的实际贡献，我们对心肌细胞损失进行了计数。形态计量分析表明，正常条件下mdx小鼠心肌中的细胞浓度低于C57B1/6小鼠心肌中的细胞浓度。mdx小鼠心脏基部的细胞损失为20%，心尖部为40%。应激24小时后，mdx小鼠心肌中的细胞损失达2.5%。DNA结构受损细胞数量与实际细胞损失指数之间的差异表明，DNA修复对动态应激后mdx小鼠心肌细胞的存活有实际贡献。
