Fig. 3: CD26⁺ TSPCs are primitive stem cells.

a Fluorescence activated cell sorting (FACS) of Sca1⁺ CD26⁺ TSPCs and Sca1⁺Sema5a⁺ progenitors. b Proliferation assay of CD26⁺ TSPCs and Sema5a⁺ progenitors. n = 3 biological replicates. Scale bar: 100 μm. c CCK8 assay of CD26+ TSPCs and Sema5a+ progenitors. n = 3 biological replicates. Two-tailed unpaired Student’s t test, t = 7.321, df=4. d Alizarin red, alcian blue and oil red O staining of CD26⁺ TSPCs and Sema5a⁺ progenitors under osteogenesis, chondrogenesis or adipogenesis. Scale bar: 100 μm. e Quantification of CD26⁺ TSPCs and Sema5a⁺ progenitors under osteogenesis, chondrogenesis or adipogenesis. n = 3 biological replicates. Two-tailed unpaired t test. Osteogenesis: t = 8.675, df=3.868; chondrogenesis: 0.881, df=2.625; adipogenesis: t = 9.796, df= 3.080. f Sort-purified CD26⁺ TSPCs and Sema5a⁺ progenitors from adult mice were analyzed before cultured (day 0). 14 days after cultivation, sorted cells were analyzed for the expression of CD26 and Sema5a. n = 3 biological replicates. g Scheme for the generation of CD26-CreER^T2-hDTR; H11-mZsGmtdT mice. h Top: Scheme for the TMX induction, with the tdTomato (tdT) marking CD26⁺ TSPCs and chased up to 3 months. Bottom: Immunofluorescent images of tdTomato and Sema5a. Scale bar: 100 μm. i quantification of tdT⁺ Sema5a⁺ cells. n = 3 biological replicates. Two-tailed unpaired Student’s t test, t = 7.352, df=4. j, k Flow cytometry analysis of stem cell and tenocyte markers in CD26⁺ TSPCs. n = 3 biological replicates. l Flow cytometry analysis of Tppp3 in CD26⁺ TSPCs, Apoe⁺ and Sema5a⁺ progenitors. n = 3 biological replicates. m Immunofluorescent images of Tppp3 in CD26⁺ TSPCs and Sema5a⁺ progenitors. Scale bar: 100 μm. n Quantification of Tppp3⁺ cell rate in each cluster. n = 3 biological replicates. Two-tailed unpaired Student’s t test, t = 0.351, df=4. Data shown are mean ± SEM. Source data are provided as a Source Data file.