Fig. 2

Wound closure mediated by purse-string contraction. a) High-resolution ultrasound imaging of a 24 h wound confirmed that the marginal skin was drawing closed over the musculature and nervous tissue constituting the core of the arm (S, suckers; arrowhead, wound). b Equally, scanning EM showed tissue puckering at the wound margin, which was incomplete ventrally (arrowheads). Higher magnification analysis revealed: 1) that each tissue fold consisted of two, three or more cell widths c; 2) that the wave-like advancing epithelial margin (wound-edge epithelium, WE) is at least two cell heights c; and 3) a belt-like structure that may constitute a contractile cable, could be observed between some of the cells d). e At 24 h, basal wound edge epithelial cells (WE) displayed continued adhesion to their neighbours, lamella on the leading edge, and cell adhesions to the underlying wound matrix (arrows), suggestive of collective cell migration. WB, wound bed. Scale bars: b, 500 μm; c, 100 μm; d, 10 μm; e, 50 μm