Differentiation and maturation of cultured fetal rat jejunum

Abstract

To determine whether differentiation and maturation of mammalian intestinal mucosa require influences available only in vivo or whether they can occur in vitro, fetal rat jejunum was cultured in chemically defined medium using organ culture methodology. Segments of jejunum from 18-day fetal rats were cultured in modified Liebowitz L-15 medium in room air at 37°C. Segments harvested after 24, 48, and 72 hr of culture were examined by light and electron microscopy. Uncultured jejunum from 18-day fetuses had either no or very few rudimentary villi and was lined largely by undifferentiated stratified epithelium. Goblet cells were not seen. In contrast, villi were present in the majority of 24-hr cultures, and simple columnar rather than stratified epithelium predominated. After 48 and 72 hr, villi were present in over 90% of cultured jejunal segments and stratified epithelium had disappeared. Goblet cells were seen in jejunal segments cultured 48 hr or longer in 47 of 74 fetuses. Electron microscopy further documented progressive differentiation of the epithelium during culture. Microvilli increased in number and height, a terminal web developed in the apical cytoplasm and the number of apical vesicles, mitochondria and formed elements of endoplasmic reticulum increased in absorptive cells. Jejunal lactase and alkaline phosphatase activity increased nine- and sevenfold, respectively, during 72 hr of culture, while the activity of the mitochondrial enzyme, ornithine carbamoyl transferase, increased fourfold. These observations indicate that jejunum from 18-day fetal rats can be cultured in vitro for at least 72 hr in chemically defined medium and that, during culture, maturation of the jejunal mucosa takes place with the appearance of villi, conversion of stratified to columnar epithelium and differentiation of individual epithelial cells.