Fetal airway wound repair: a new frontier.

Purpose: Fetal dermal repair is regenerative and scarless until middle to late gestation, when there is a transition to fibrotic repair. Fetal skeletal muscle and tendon undergo repair with fibrosis similar to the process in adults. This study addresses whether fetal mucosal healing is regenerative and scarless.

Methods: Anesthetized pregnant rabbits underwent laparotomy and controlled hysterotomy at 21 to 23 days' gestation (term is 31 days). A midline thyrotomy was made, followed by cricoidotomy and circumferential cauterization of the subglottic mucosa. A similar insult was applied to weanlings. The data were collected in 2 groups. One group was followed to term and killed at 4 weeks. A second group was killed after 6 days (30 days' gestation). The weanlings were killed at similar points. The larynges were harvested and processed for histological and morphometric analysis.

Results: Three litters were followed to term. Of these, 1 was not recovered; in the other two, 7 of 8 manipulated fetuses were found and 3 of 8 were viable. The fourth litter was harvested after 6 days; all 4 injured fetuses were recovered and viable. All animals in the fetal injury groups healed with complete regeneration of the airway mucosa. In contrast, weanlings injured post partum had mucosal inflammation, necrosis, and ulceration; squamous metaplasia and basal cell hyperplasia were also found. There were fibrosis, granulation tissue, and inflammation in the lamina propria; chondritis, cartilaginous necrosis, chondrolysis, and perichondritis were also found.

Conclusions: Fetal airway mucosal healing is regenerative and, thus, scarless. This study provides further support for the thesis that skin and mucosa respond to injury similarly in both the developmental and postpartum stages, and that subglottic stenosis is reasonably thought of as the "hyperplastic scar" of the airway. These results have potential therapeutic applications for mucosal wound management.