Fig. 4: Type S vessels contribute to osteogenesis by secreting type I collagen.
From: Spatial heterogeneity of bone marrow endothelial cells unveils a distinct subtype in the epiphysis
a, A heatmap showing osteogenic factors based on the scRNA-seq data shown in Fig. 1. b, Quantitative PCR analysis of CD31+CD45− cells derived from femurs of P11 mice (n = 3, biologically independent experiments). c, Protocol for 4OHT injection in neonates. d–i, TEM of epiphyseal sections of P11 mice. Panels d, f and h are from control, and e, g and i are from Col1a1iΔEC mice. Panels f and g show the area of perivascular collagen fibres with dotted area of d and e. Panels h and i show high magnification views of the area indicated in d and e, respectively. The bands of collagen fibres around blood vessels (dotted area) are thin and sparse in Col1a1iΔEC mice (asterisks). j,k, Whole-mount Alizarin Red staining of femurs at P11 (j) and quantification (k) (control: n = 7; Col1a1iΔEC: n = 6, biologically independent experiments). Arrows indicate reduced mineralization in the epiphyses and the asterisk indicates intact ossification in the diaphyses and metaphyses of Col1a1iΔEC mice. l–p, Immunohistochemistry of femur sections at P11 stained with Runx2, Emcn and DAPI (l,m) or Osx, Emcn and DAPI (n,o). Panels l and n are from control, and m and o are from Col1a1iΔEC mice. Quantification of Osx+ cells (n = 4, biologically independent experiments) is shown in p. q, X-ray images of adult mice. Col1a1iΔEC mice show reduced X-ray intensity (asterisks) in the epiphysis. r–t, Mechanical strength of the femoral distal epiphysis or diaphysis measured by a compression test. Panel r shows the scheme of the test, and quantification of the maximum load of the epiphysis (s) and the metaphysis (t) is shown individually (control: n = 4; Col1a1iΔEC: n = 3, biologically independent experiments). The epiphysis has inferior biomechanical properties in Col1a1iΔEC mice. Scale bars, 1 mm (j and q); 200 μm (l–o); 10 μm (d–g); and 1 μm (h and i). *P < 0.05; data presented are the mean ± s.d. The comparisons between the averages of two groups were evaluated using the two-tailed Student’s t-test.
