Fig. 1. Activin promotes collagen deposition and maturation in healing skin wounds.

a Representative photomicrographs of Herovici-stained sections of 5-, 7-, 10-, and 14-day wounds from WT and Act mice. Yellow dotted line represents extent of hyperproliferative wound epidermis; red dotted line represents extent of open wound; green dotted line represents area of granulation tissue. b Left: Number of closed (fully re-epithelialized) or open wounds. n = 10 for WT, n = 9 for Act mice. Right: Granulation tissue area. n = 7 for WT, n = 8 for Act mice. c Quantification of young, mature, and total collagen density in skin wounds. n = 7, 11, 12, 11 for WT, n = 6, 11, 10, 8 for Act mice, for 5-, 7-, 10-, or 14-day wounds, respectively. ^&P < 0.10, *P < 0.05, ^#P < 0.05 (total collagen) for Act vs WT at each time point. d Length of granulation tissue/scar tissue in 10- and 21-day wounds. n = 12 for WT, n = 9 for Act mice (10d), and n = 11 for WT, n = 10 for Act mice (21d). e Representative photomicrographs of Picrosirius Red-stained sections from 5-day wounds with insets for corresponding areas in wound edge (i, ii) and wound center (iii, iv). f Quantification of collagen fiber types at the wound edges relative to total collagen (left) and in the wound centers relative to GT area (right). n = 4 for both genotypes. ^&P < 0.10, *P < 0.05, ^#P < 0.05 (total collagen) for Act vs WT. Graphs show mean ± SEM and P values; two-sided Chi-square test (b left), two-tailed Student's t-test (b right, c, d, f); see Supplementary Fig. 1a, b for all individual comparisons and P values in c and f. All n numbers indicate biological replicates. Gray triangles represent wound margins (WM); HE hyperproliferative epithelium, HF hair follicle, D dermis, Es eschar, GT granulation tissue. Scale bars: 500 µm. Source data are provided as a Source Data file (Fig. 1).