Fig. 4: Tendon and epimysial-like ECM formed in the absence of muscle.

A–F” Decellularized E12.5-E14.5 WT and Pax3^Cre/Cre forelimbs were rich in WGA⁺ fibers at the insertion of the long triceps into the ulna (U; arrowheads; A’–F’) and origin of the long triceps at the scapula (S; arrowhead; A”–F”). However, the fiber bundles were less dense in Pax3^Cre/Cre compared to WT forelimbs. G, H For the long triceps of both E13.5 WT and Pax3^Cre/Cre embryos (dotted outline), WGA⁺ fibers formed epimysial-like structures. I, J In Pax3^Cre/Cre forelimbs, laminin (LAM⁺) blood vessels (magenta) were still present (arrowheads). Magnification 20×, z-projection: z = 230 µm (G, H), 138 µm (I), and 181 µm (J), scale bars = 1 mm (A–F), 100 µm (G–J). Representative images from N = 3 independent biological replicates.