Tissue growth associated transition of podoplanin-expressing stromal cells in the postnatal mouse femur

Abstract

AbstractSkeletal stem/progenitor cells are tissue-resident stem/progenitor cells involved in the formation of the skeletal tissue, bone marrow, and hematopoietic microenvironment. Podoplanin-expressing stromal cells (PDPN-SCs) are skeletal stem/progenitor cell-lineage stromal cells. In the adult mouse bone marrow, PDPN-SCs are present on the diaphyseal arterioles and promote megakaryo/erythropoiesis. However, the localized distribution of PDPN-SCs in neonatal and postnatal femurs remains unclear. In this study, we histologically examined the transition of PDPN-SCs during postnatal femoral growth. In the diaphyseal marrow, PDPN-SCs were present in the neonatal marrow space but disappeared with femoral growth. In the cortical bone, abundant PDPN-SCs existed in the primitive neonatal bone and transitioned to restricted localization in the periosteum and endosteum with tissue growth. In the metaphysis, PDPN-SCs resided in nascent trabecular bones. We also found a novel subset of PDPN-SCs that expressed osterix, suggesting that osterix-positive PDPN-SCs were involved in bone formation. Furthermore, in the diaphyseal arterioles, periarteriolar PDPN-SCs appeared sporadically between 1–2 weeks of age and populated to surround the arterioles. These histological observations can contribute to the understanding of how stromal cells, including PDPN-SCs, engage in postnatal bone and marrow formation.