Fig. 1

Schematics of skeletal stem cells and progenitors in mouse long bone. At fetal stage, limb bud mesenchymal cells express Prx1 and osteochondral progenitors are Sox9⁺. When fetal growth plate forms, Col2, Nes-GFP, and Osx mark progenitors at perichondrium. Neonatal long bone harbors various types of SSCs and progenitors, including Sox9⁺/Col2⁺/Acan⁺/Col10⁺ cells at growth plate, Gli1⁺/Osx⁺ cells at primary spongiosa, Ctsk⁺ cells at periosteum and Ranvier’s groove. Postnatal long bone is occupied with long-term SSCs and progenitors, including Grem1⁺/FoxA2⁺/PTHrP⁺/Sox9⁺/Col2⁺/Acan⁺/Col10⁺ cells at epiphysis and growth plate cartilage, Gli1⁺/Osx⁺ cells at primary spongiosa, PDGFRβ⁺/PαS⁺/Nes-GFP⁺/LepR⁺/Cxcl12⁺ cells in bone marrow, and αSMA⁺Mx1⁺/Ctsk⁺ cells at periosteum. Adult bone marrow is highly complex and contains endosteal, perisinusoidal, and periarteriolar niches, which harbor tissue-resident SSCs and progenitors essential for hematopoietic lineages