Fig. 2. Col2⁺ lineage cells adopt LEC fate in the Achilles tendon of mice after tenotomy.

a–d Representative confocal images of ectopic bone sections stained with Sox9 (a, b) or Runx2 (c, d) (green) and DAPI (blue) in Col2^tomato (a, c) and FGFR3^f/f-Col2^tomato mice (b, d) at 8 weeks after Achilles tenotomy. n = 5 per group. Solid line boxes indicate HO lesion (higher magnification, middle). Dashed line boxes indicate the site of tdTomato-labeled cells (higher magnification, right). Scale bars, 100 μm (left); 20 μm (middle and right). e Representative H&E images of repaired Achilles tendon in wild-type (WT) mice (n = 7) at 8 weeks after surgery. Dashed line boxes indicate the site of newly formed blood vessels (higher magnification, right). Scale bars, 200 μm (left); 50 μm (right). f Representative confocal images of CD31 (green) and DAPI (blue) immunostained Achilles tendon sections in Col2^tomato (left) and FGFR3^f/f-Col2^tomato mice (right) at 8 weeks after surgery. n = 5 per group. Blood vessels (BV) are marked with dashed lines. Scale bars, 100 μm. g–i Representative confocal images of sections of repaired Achilles tendon (g), connective tissue near the Achilles tendon (h), and uninjured Achilles tendon (i) immunostained with LYVE1 (green) and DAPI (blue) in Col2^tomato mice at 8 weeks after surgery. n = 4–6 per group. Dashed line boxes indicate LYVE1⁺ tdTomato-labeled cells (higher magnification with split channels, right). Scale bars, 100 μm (left); 20 μm (right). j–l Representative confocal images of repaired Achilles tendon sections stained with LYVE1 (j), Prox1 (k) or PDPN (l) (white), and DAPI (blue) in Col2^mTmG mice at 4 weeks after tamoxifen injection. n = 4 per group. Dashed line boxes indicate the site of GFP-labeled cells (higher magnification with split channels, right). Scale bars, 100 μm (left); 20 μm (right). m, n Representative confocal images of uninjured Achilles tendon in Col2^tomato mice 1 day after tamoxifen induction (m) and repaired Achilles tendon with peritendineum and adjacent connective tissues in Col2^tomato mice at 8 weeks after surgery (n) immunostained with LYVE1 (green) and DAPI (blue). n = 4 per group. Dashed line boxes indicate the site of tdTomato-labeled cells (higher magnification, right). Bone tissue of calcaneus is marked with dashed lines. Scale bars, 100 μm (left); 20 μm (right). Yellow arrows indicate Col2-derived cells labeled by CD31 (f), LYVE1 (g–j), Prox1 (k), or PDPN (l). White dashed lines indicate outlines of the tendon (a–d, g, i–m).