Amniotic fluid induces rapid epithelialization in the experimentally ruptured fetal mouse palate - implications for fetal wound healing

Abstract

Cleft of the secondary palate is one of the most common congenital birth defects in humans. The primary cause of cleft palate formation is a failure of fusion of bilateral palatal shelves, but rupture of the once fused palate has also been suggested to take place in utero. The possibility of post-fusion rupture of the palate in humans has hardly been accepted, mainly because in all the cleft palate cases, the cleft palatal edge is always covered with intact epithelium. To verify whether the intrauterine environment of the fetus plays roles in wound healing when the once fused palate is torn apart, we artificially tore apart fetal mouse palates after fusion and cultivated them in culture medium with or without mouse or human amniotic fluid. We thereby found that the wounded palatal edge became completely covered with flattened epithelium after 36 hours in culture with amniotic fluid, but not in culture without amniotic fluid. Using histological and scanning electron microscopic analyses of the healing process, it was revealed that the epithelium covering the wound was almost exclusively derived from the adjacent nasal epithelium, but not from the oral epithelium. Such actions of amniotic fluid on the fetal wound were never simulated by exogenous epidermal growth factor (EGF), albumin, or both. In addition, the rapid epithelialization induced by amniotic fluid was not prevented by either PD168393 (an inhibitor of the EGF receptor-specific tyrosine kinase) or SB431542 (a specific inhibitor of TGFbeta receptor type I/ALK5). The present study provides new insights into the unique biological actions of amniotic fluid in the repair of injured fetal palate.

Human amniotic fluid stimulates the proliferation of human fetal and adult skin fibroblasts: The roles of bFGF and PDGF and of the ERK and Akt signaling pathways

“…The presence of more than one growth factor is evident from the effect of heat‐ and acid‐treatment, which showed the presence of both stable and labile active molecules in this mixture. This is in agreement with previous studies indicating that the effects of AF on wound healing are due to the presence of many factors rather than a single component 16 …”

“…This is in agreement with previous studies indicating that the effects of AF on wound healing are due to the presence of many factors rather than a single component. 16 Previous studies have shown the presence of various known growth factors in AF, such as bFGF, PDGF, TGF-b, EGF, or IGF-I. [22][23][24][25] In our effort to clarify which of the above factors is responsible for the mitogenic action of AF we have used inhibitors against their transmembrane receptors, and our data showed that the factors mainly responsible for this stimulatory action are PDGF and most importantly bFGF.…”

“…AF is a major factor in the fetal environment and several lines of evidence indicate that, in combination with the specific properties of the fetal tissues, it may be involved in fetal wound healing. 16 However, the underlying mechanisms are not yet adequately understood. Previously, a number of laboratories have investigated the effect of AF on cell proliferation, a crucial step in the wound healing process.…”

“…For example, human fetal skin transplanted subcutaneously into nude mice repairs without scarring, while when grafted cutaneously it heals in an adult‐like manner 14 . On the other hand, AF, an essential parameter of fetal environment, seems to influence the wound repair process 15,16 . However, its effect is subjected to species variability.…”

“…14 On the other hand, AF, an essential parameter of fetal environment, seems to influence the wound repair process. 15,16 However, its effect is subjected to species variability. For example, sheep AF stimulates contraction, a major parameter of wound repair, in contrast to rabbit AF.…”