Mitochondrial dysfunction affects osteogenic differentiation potential of bone marrow mesenchymal stem cells
Gu Chao1, 2, Chen Weikai1, 2, Liu Tao1, Yang Huilin1, 2, He Fan1, 2
1Department of Orthopedics, First Affiliated Hospital of Soochow University, Suzhou 215006, Jiangsu Province, China; 2Institute of Orthopedics, Soochow University, Suzhou 215007, Jiangsu Province, China
Abstract: BACKGROUND: The occurrence of osteoporosis is closely related to the damage of cellular antioxidant system, and mitochondria is the main part of cellular energy metabolism and oxidative stress. The effect of mitochondrial injury on the osteogenic differentiation of bone marrow mesenchymal stem cells and its specific mechanism remain to be explored.
OBJECTIVE: To investigate the effect of high level of oxidative stress on mitochondrial function and antioxidant capacity, and the effect of mitochondrial injury on the osteogenic differentiation potential of bone marrow mesenchymal stem cells.
METHODS: The rat model of osteoporosis was established by ovariectomy. Bone marrow mesenchymal stem cells were isolated from femurs of female rats in ovariectomized group and sham operation group. Reactive oxygen species detection kits and MitoSOX Red fluorescent probe were used to detect reactive oxygen species levels in bone marrow mesenchymal stem cells and mitochondria. Subsequently, JC-1 fluorescent probe was used to detect the mitochondrial membrane potential level of the two kinds of stem cells. ATP production was measured by the ATP detection kit. The changes of mitochondrial function were analyzed in both groups. qPCR and western blot assay were used to detect the mRNA and protein expression of key genes of respiratory chain and antioxidant enzyme superoxide dismutase 2 in two kinds of stem cells. Finally, the two groups of stem cells were subjected to osteogenic induction for 14 days. Alizarin red staining and qPCR were utilized to determine osteogenic related gene expression.
RESULTS AND CONCLUSION: (1) There was high oxidative stress level in rat bone marrow mesenchymal stem cells of the ovariectomized group, and the superoxide in the mitochondria also maintained a high level. (2) The mitochondrial membrane potential and ATP content of rat bone marrow mesenchymal stem cells were decreased significantly, and the mitochondrial function was impaired in the ovariectomized group. (3) In the ovariectomized group, the respiratory chain was damaged and the expression of antioxidant enzyme superoxide dismutase 2 was decreased in rat bone marrow mesenchymal stem cells. (4) The osteogenic differentiation potential of rat bone marrow mesenchymal stem cells was decreased in the ovariectomized group. (5) These findings confirm that the level of oxidative stress in bone marrow mesenchymal stem cells from osteoporosis is increased, and the mitochondrial function is impaired, which ultimately leads to the decrease of osteogenic differentiation potential of stem cells.
Key words: osteoporosis, bone marrow mesenchymal stem cells, oxidative stress, mitochondrial damage, osteogenic differentiation, superoxide dismutase 2