Development of epithelia in the ectopic transplant of the fetal rat epiglottis

Embryonic in situ development is strictly regulated within the specific microenvironment of developing tissues. However, for regenerative medicine purposes (supplementation of damaged tissues/organs), transplantation to ectopic sites has been considered. To investigate developmental potential of fetal epiglottic epithelia at an ectopic site, fetal epiglottis was transplanted under the kidney capsule and its development compared to fetal and adult epiglottis. Seventeen-day-old Fischer rat epiglottides were microsurgically isolated under a dissecting microscope and transplanted under the kidney capsule of adult males. After 14 days, classic histology and immunohistochemical detection of the Proliferating Cell Nuclear Antigen (PCNA) were done in isolated and accordingly fixed transplants. The 17-day-old fetal epiglottis and adult epiglottis were processed in the same way. The 17-day-old fetal epiglottides were covered with immature epithelium expressing PCNA in almost all cells. Adult epiglottis was covered with two types of epithelia (stratified squamous epithelium and ciliated pseudostratified epithelium). In the stratified squamous epithelium PCNA was abundantly expressed in the basal cell layer and absent from more superficial and more differentiated cells. Transplants survived well during the experimental period. On their surface ciliated pseudostratified epithelium could be easily recognized, but squamous epithelium was almost absent. PCNA was expressed in basal cells of the ciliated pseudostratified epithelium and was absent from the more differentiated superficial cells. It seems that at this ectopic site further differentiation of the epiglottic epithelia can proceed but differentiation of squamous epithelium seems not to be favored. It seems that this ectopic site is optimal for further differentiation of the epiglottic epithelium towards ciliated pseudostratified epithelium.