Autophagy Regulates Age-Related Jawbone Loss via LepR⁺ Stromal Cells

Bone aging and decreased autophagic activity are related but poorly explored in the jawbone. This study aimed to characterize the aging jawbones and jawbone-derived stromal cells (JBSCs) and determine the role of autophagy in jawbone mass decline. We observed that the jawbones of older individuals and mice exhibited similar age-related bone loss. Furthermore, leptin receptor (LepR)-lineage cells served as the primary source for in vitro cultured and expanded JBSCs, referred to as LepR-Cre⁺/JBSCs. RNA-sequencing data from the jawbones and LepR-Cre⁺/JBSCs showed the upregulated expression of the phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) pathway during aging. Through single-cell transcriptomics, we identified a decrease in the proportion of osteogenic lineage cells and the activation of the PI3K/AKT pathway in LepR-lineage cells in aging bone tissues. Reduced basal autophagic activity, diminished autophagic flux, and decreased osteogenesis occurred in the jawbones and LepR-Cre⁺/JBSCs from older mice (O-mice; O-JBSCs). Pharmacologic and constitutive autophagy activation alleviated the impaired osteogenesis in O-JBSCs. In addition, the suppression of mTOR-induced autophagy improved the aging phenotype of O-JBSCs. The activation of autophagy in LepR-Cre+/JBSCs using chemical autophagic activators reduced the alveolar bone resorption in O-mice. Therefore, our study demonstrated that ATG molecules and pathways are crucial in jawbone aging, providing novel approaches to understanding age-related jawbone loss.