Figure 1. Fetal surgery performed for repair of cleft lip allowed for scarless fusion. E16 mouse embryo with cleft upper lip (black arrowheads) was identified through the uterine wall, and exposed for fetal surgery (a). Bilateral clefts were identified, and the left cleft was repaired by suturing; the contralateral side was allowed to develop without repair as control. Sixty hrs following surgery (b), the repaired left cleft was fused (white arrowheads), and the control side remained clefted (black arrowheads). Newborn animal with repaired left cleft (white arrowheads) displayed smooth, scarless surface (d), as compared with control unoperated side (black arrowheads), and control animal that did not receive surgery (c). Serial cross-sections were obtained from the lower face region (e) for further histological and molecular analyses of cleft lip repair. Histological section of fetus with left cleft lip that was repaired and fused (g) showed continuity of epithelial and mesenchymal components (between open arrowheads), although an apparent decrease in the number of vibrissae follicles was observed as compared with the similar region in the unaffected fetus (f). The unoperated right cleft remained open (between black arrowheads). Higher magnification of the repaired region (h and box in g) showed no inflammation, fibrotic changes, or histological evidence of scarring. This region was filled with loose mesenchymal cells. Scale bars in (a) for (a-d) and in (f) and (g) are 1 mm. Scale bar in (h) is 100 µm.