Adiponectin expressing skeletal stem/progenitor cells in the bone and bone marrow homeostasis

The bone marrow stroma supports hematopoiesis while replenishing osteoblasts and adipocytes. These functions rely on different stromal cell populations identified by lineage tracing, phenotypic markers and single-cell transcriptomic analysis. A marrow stromal cell subset expressing Adiponectin (Adipoq⁺) has been reported by different studies in mice. However, while there is a general agreement on the kinetics of Adipoq⁺ stromal cells during mouse growth, their ability to generate bone marrow adipocytes and to support the bone vasculature, contrasting results have been reported on their osteogenic activity. In this work, we review available data on Adipoq⁺ stromal cells, with special focus on the experimental evidence demonstrating their osteoprogenitor function and the potential reasons for the divergence observed among different studies. Furthermore, we discuss the potential overlap of Adipoq⁺ cells with other cell populations in the context of the widely recognized adipogenic bias that characterizes many marrow stromal stem cell populations.