Abstract
Metabolic programming of bone marrow stromal cells (BMSCs) could influence the function of progenitor osteoblasts or adipocytes and hence determine skeletal phenotypes. Adipocytes predominantly utilize oxidative phosphorylation, whereas osteoblasts use glycolysis to meet ATP demand. Here, we compared progenitor differentiation from the marrow of two inbred mouse strains, C3H/HeJ (C3H) and C57BL6J (B6). These strains differ in both skeletal mass and bone marrow adiposity. We hypothesized that genetic regulation of metabolic programs controls skeletal stem cell fate. Our experiments identified Bcl-2-like protein 13 (Bcl2l13), a mitochondrial mitophagy receptor, as being critical for adipogenic differentiation. We also found that Bcl2l13 is differentially expressed in the two mouse strains, with C3H adipocyte progenitor differentiation being accompanied by a >2-fold increase in Bcl2l13 levels relative to B6 marrow adipocytes. Bcl2l13 expression also increased during adipogenic differentiation in mouse ear mesenchymal stem cells (eMSCs) and the murine preadipocyte cell line 3T3-L1. The higher Bcl2l13 expression correlated with increased mitochondrial fusion and biogenesis. Importantly, Bcl2l13 knockdown significantly impaired adipocyte differentiation in both 3T3-L1 cells and eMSCs. Mechanistically, Bcl2l13 knockdown reprogrammed cells to rely more on glycolysis to meet ATP demand in the face of impaired oxidative phosphorylation. Bcl2l13 knockdown in eMSCs increased mitophagy. Moreover, Bcl2l13 prevented apoptosis during adipogenesis. Our findings indicate that the mitochondrial receptor Bcl2l13 promotes adipogenesis by increasing oxidative phosphorylation, suppressing apoptosis, and providing mitochondrial quality control through mitophagy. We conclude that genetic programming of metabolism may be important for lineage determination and cell function within the bone marrow.