Single-cell RNA sequencing reveals classical monocytes are the major precursors of rat osteoclasts

To dissect which subset of bone marrow monocyte is the major precursor of osteoclast,3-month-old rat bone marrow was obtained for single-cell RNA sequencing.A total of 6091 cells were acquired for detailed analysis,with a median number of 1206 genes detected per cell and 17,959 genes detected in total.A total of 19 cell clusters were recognized,with the main lineages identified as B cells,Granulocytes,Monocytes,T cells,Erythrocytes and Macrophages.Monocytes were further divided into classical monocytes and non-classical monocytes.Compared with non-classical monocytes,classical monocytes highly expressed osteoclast differentiation related genes Mitf,Spi1,Fos and Csf1r.Additionally,biological processes of classical monocytes were related to osteoclast differentiation.qPCR revealed differentially expressed genes of classical monocytes played a role in osteoclast differentiation.In conclusion,classical monocytes were identified as the main precursors of osteoclasts in rats,and may contribute to osteoclast differentiation by regulating S100a4,S100a6,S100a10,Fn1,Vcan and Bcl2a1.The results of this study contribute to the understanding of the origin of osteoclasts and may provide potential biomarkers for early diagnosis of bone metabolic diseases,as well as molecular and cellular targets for clinical intervention in bone metabolic diseases.