Feature Article: The involvement of mitochondrial fission in maintenance of the stemness of bone marrow mesenchymal stem cells

Mitochondrial dynamics, a complicated cellular process consisting of mitochondrial fusion and fission, has been suggested to be involved in regulating the stemness of bone marrow mesenchymal stem cells (BMSCs). This study was undertaken to explore the relationship between mitochondrial dynamics and the maintenance of BMSCs' stemness. Rat BMSCs were treated with fibroblast growth factor 2 (FGF2) and epithelial growth factor (EGF) to induce differentiation. Mitochondrial dynamics was determined by mitochondrial length observed by confocal microscope and DLP1 (a protein promoting mitochondrial fission), OPA1 (a protein promoting mitochondrial fusion) expression revealed by Western blotting analysis. BMSCs' stemness was determined by flow cytometry and osteogenic/adipogenic differentiation ability. We found that in the process of BMSCs differentiation, mitochondrial length was increased, along with a decreased protein level of DLP1 and an increased protein level of OPA1 in the mitochondria, indicating a shift toward mitochondrial fusion in BMSCs during differentiation. Notably, when the mitochondrial fission was inhibited by Mdivi-1, the stemness marker, CD90, was deceased along with the reduction of DLP1 expression. Under the same condition, the potential of BMSCs to be induced into adipocytes or osteocytes was decreased. Correspondingly, when BMSCs were treated with tyrphostin A9, a reagent promoting mitochondrial fission by increasing DLP1, the stemness marker, CD54, was increased with an increased potential of BMSCs to be induced into adipocytes or osteocytes. Hence, our results demonstrated that mitochondrial fission contributed to the maintenance of BMSCs' stemness. Impact statement How to maintain the stemness of bone marrow mesenchymal stem cells (BMSCs) in cultures is a long-standing question. The present study found that mitochondrial dynamics affects the stemness of BMSCs in cultures and the retaining of mitochondrial fission enhances the stemness of BMSCs. This work thus provides a novel insight into strategic approaches to maintain the stemness of BMSCs in cultures in relation to the clinical application of bone-marrow stem cells.