Fig. 3: TGFβ1 secreted by MKs promotes the osteogenic lineage commitment of LepR⁺ SSCs.

a Left: representative micro-CT images of longitudinal section femurs, cross-sectional view of the distal femurs and reconstructed trabecular structure of the region of interest from TGFβ1^MKΔ/Δ mice and their littermate controls (TGFβ1^fl/fl mice). Right: quantitative micro-CT analysis of the TB fraction (BV/TV, Tb.N, Tb.Th, Tb.Sp and Ct.Th) in TGFβ1^MKΔ/Δ mice and their littermate controls (TGFβ1^fl/fl mice) (n = 6 mice per group). b LepR⁺ SSCs were induced in osteogenic differentiation medium with or without MKs or (pretreated TGFβ type I receptor inhibitor SB431542) from wild-type (WT) mice after 14 days. Representative alkaline phosphatase staining images (left) and quantification of the activity of alkaline phosphatase was calculated (right) (n = 6 per group). c LepR⁺ SSCs were induced in osteogenic differentiation medium with or without MKs or (pretreated TGFβ type I receptor inhibitor SB431542) from WT mice after 21 days. Representative alizarin red staining images (left) and quantification of matrix mineralization was calculated (right) (n = 6 per group). d LepR⁺ SSCs were induced in adipogenic differentiation medium with or without MKs or (pretreated TGFβ type I receptor inhibitor SB431542) from WT mice after 21 days. Representative Oil O staining images (left) and the quantification of area was calculated (right) (n = 6 per group). e qPCR analysis of the expression of Osterix, Runx2, Adipoq and PPARγ in LepR⁺ SSCs with or without MKs or (pretreated TGFβ type I receptor inhibitor SB431542) from WT mice after 7 days (n = 3 per group). f LepR⁺ SSCs were induced in osteogenic differentiation medium with or without MKs from the BM of TGFβ1^MKΔ/Δ and TGFβ1^fl/fl mice after 14 days. Representative alkaline phosphatase staining images and quantification of the activity of alkaline phosphatase was calculated (n = 6 per group). g LepR⁺ SSCs were induced in osteogenic differentiation medium with or without MKs from the BM of TGFβ1^MKΔ/Δ and TGFβ1^fl/fl mice after 21 days. Representative alizarin red staining images and quantification of matrix mineralization was calculated (n = 6 per group). Data on graphs are shown as mean ± SD. One-way ANOVA was used to analyze the data in a–e and an unpaired two-tailed t-test was used to analyze the data in f and g. *P < 0.05, **P < 0.01 and ***P < 0.001. For all panels in this figure, data are representative of three independent experiments.