WOUND SIZE AND GESTATIONAL-AGE MODULATE SCAR FORMATION IN FETAL WOUNDREPAIR

The early-gestation fetus heals incisional skin wounds rapidly and sca rlessly. The morphology with which the fetus heals excisional skin wou nds remains unclear. To characterize excisional fetal wound repair, an d to determine whether there is a developmentally regulated wound-size threshold beyond which fetal skin heals with scar, the authors create d excisional wounds in fetal lambs of varying gestational age. Time-ma ted pregnant ewes carrying 22 fetuses at 60 to 90 days' gestation (ter m, 145 days) underwent laparotomy and hysterotomy. An incisional wound and four circular, punch biopsy wounds of 2, 4, 6, and 10 mm in diame ter were placed on the back of each fetal lamb and marked with India i nk. The wounds were harvested at 14 days' postwounding and examined gr ossly and microscopically after serial sectioning and histological sta ining. Morphological features of all wounds were graded. By 14 days' p ostwounding all fetal wounds had healed completely. For lambs at each gestational age, increasing wound size was strongly associated with an increase in the frequency of scar. Also, as gestational age increased from 60 to 90 days' gestation the frequency of scarless repair decrea sed. By understanding the cellular and molecular processes that mediat e scar formation with increasing wound size and advancing gestational age, the authors hope to gain further insight into the mechanisms of s carless fetal wound repair. Copyright (C) 1997 by W.B. Saunders Compan y.