Fig. 4

Larval zebrafish regenerated the caudal fin following amputation and extended projections.

(A) Time-lapse microscopy of caudal fin regeneration revealed the formation of epithelial projections by 24 hpw. Projections extending from the amputated plane are indicated with an arrow and arrowhead. (B, C) Morpholino knockdown of vimentin expression led to a significant reduction in the proportion of larvae forming projections at 24 hpw compared to control larvae (p=0.0348; n = 3 replicate percentages: for ctl MO 76 larvae total and for Vim MO 78 larvae total were scored over the three replicates, with 18 to 34 larvae per treatment per replicate; Ctl MO 95% CI = 66.13% to 88.54%; vim MO 95% CI = 7.56% to 65.78%). (D) Inhibition of early ROS signaling with DPI treatment also significantly reduced the proportion of larvae forming wound healing projections at 24 hpw (p=0.0129, n = 3 replicate percentages: for DMSO 72 larvae total and for DPI 66 larvae total were scored over the three replicates, with 11 to 26 larvae per treatment per replicate; DMSO 95% CI = 31.76% to 99.58%, DPI 95% CI = 8.79% to 41.87%). (E, F) Bright field microscopy of projections revealed the presence of fibrillar structures (box, black arrow). (G) Polarization microscopy was used to identify the fibers as organized structures, likely collagen, and by showing the cell membranes, confirmed that the fibers extended to the tip of the projections (white arrow). (H) The association of the fibers and overlying cells was further verified by combining SHG with phalloidin staining of actin. (I) 3D reconstruction surface rendering from time-lapse microscopy, collecting SHG and fluorescence signals in the Tg(krt4:egfp-caax) line, showed extending SHG fibers pushing the healing plane forward. Scale bars represent 100 µm in A and B,10 µm in E-H and 30 µm in I. *p<0.05, error bars are standard deviation.