Figure 4. Scx-Cre mediated Adamtsl2 inactivation in tendon results in altered tendon morphology and non-autonomous bone shortening.

(A, B) Fluorescence imaging of the ankle from newborn Adamtsl2-Scx mice shows green fluorescence in tendons indicating specific Scx-Cre recombinase activity (A, arrows indicating Achilles tendon) compared to red fluorescence in mG/mT mice without Scx-Cre (B, arrows). Scale bars in A and B are 1 mm. Images shown are representative of n=2 littermates. (C, D) Longitudinal section through distal tibia (T) showing Scx-Cre activity in Achilles tendon tissue (AT, green), but neither gastrocnemius muscle (GM), tibial bone (red) (C) nor the calcaneal insertion (C) of the Achilles tendon showed Scx-Cre activity. (D). Scale bars in C and D represent 100 μm. (E) Gross view of Achilles tendon shows altered dimensions from the dorsal (left-hand panels) or lateral aspects (right-hand panels). Images shown are representative of n=8-10 from n=4-5 littermates. Scale bars in E are 1 mm. (F) Adamtsl2-deficient Achilles tendons are significantly shorter and tended to be wider (n=8-10). Relative reduction in length is indicated in %. (G) Alizarin red-Alcian blue stained tibiae showing normal morphology. Scale bars represent 1 mm. (H) Bone length measurements of forelimb and hind limb long bones and metatarsals demonstrates bone shortening in Adamtsl2-Scx limbs (n=8-10). Relative reduction in length is indicated in %. P-values were calculated with 2-sided Student t-test. * p<0.05; ** p<0.01, n.s. not significant. The box indicates the 25^th-75^th percentile, the line indicates mean value and whiskers indicate standard deviation.