Cell Proliferation in Developing Human Jejunum

Abstract

Cell proliferation of the developing human jejunum was investigated by radioautography using organ culture. The sites of [³H]-thymidine uptake were localized in the epithelium, the mesenchyme and the muscularis externa of fetal human small intestinal explants from 8 to 18 weeks of gestation. Proliferating cells were abundant and scattered throughout the stratified epithelium before the appearance of villi. Many nuclei in the mesenchyme and the muscular layer were labeled. With the villi formation and the simplification of the epithelium, there was a confinement of the proliferating zone in the intervillus areas and developing crypts. The quantitation of proliferating cells showed a labeling index at its highest value between 8 and 10 weeks of gestation decreasing gradually up to 18 weeks of gestation at the epithelial and mesenchymal level. In the muscularis externa, the labeling remained more or less constant between 11 and 18 weeks of gestation. The organ culture of intestinal explants for 5 days did not modify epithelial cell proliferation. The present investigation provides for the first time basic quantitative data regarding cell proliferation in the developing human jejunum.

Cell Proliferation during Morphogenesis of the Human Colon

“…As long as the epithelium is stratified, the proliferative pool is large based on the presence of labeled nuclei throughout the thickness of the epithelium. The highest epithelial labeling indices are found during this period, a situation identi cal to that reported for human fetal small intestine [2], With the formation of villi, the proliferative pool focuses more and more in the intervillus regions, and by 14-15 weeks the labeled epithelial nuclei are exclusively located in the developing crypts. The quanti tative determinations of [3H]-thymidine up take into total DNA parallel the develop mental profile of the labeling indices estab lished on autoradiographs, thereby provid ing further support for the decrease of the total cell proliferation.…”

“…Cellular kinetic data are well established throughout the development of the rodent small intestine [11], but are very limited for the colon [5,8], No data are available con cerning the proliferative compartments nor the DNA synthesis in the developing human colon. In our continuing effort to further our understanding of the cellular proliferation during human fetal gastrointestinal tract de velopment [2,3], the present study was un dertaken (1) to identify proliferating cells by autoradiographic localization of [3H]-thymidine uptake, (2) to establish the labeling in dices of the different layers of the colonic wall, and (3) to quantitate DNA synthesis between 8 and 18 weeks of gestation.…”

Insulin Modulates Cellular Proliferation in Developing Human Jejunum and Colon

“…The labeling indices were determined to establish whether insulin (3 mU/ml) affected the proliferation at the epithelial cell levels (table 1). The incorporation of the radioactive precursor occured mainly in the epithelium and to a lesser degree in the mesenchyme and muscular layers, as expected [23,24]. The labeling index was significantly higher in insulin-treated explants (p !…”

“…All results were expressed as disintegrations per minute per microgram of DNA. Selected tissues were fixed and embedded in Epon as previously described [23,24]. The sections (1 Ìm) were mounted on glass slides and stained with aldehyde fuchsin.…”

Presence and characteristics of epidermal growth factor receptors in human fetal small intestine and colon

“…Moreover, have recently demonstrated the presence of immunoreactive EGF in intestinal Paneth cells of the 20-week-old fetus. Paneth cells normally appear at approximately 11-12 weeks gestation [20]. If these Paneth cells are indeed able to synthesize an active form of EGF, then the appearance of endogenous sources of this growth factor coincides well with the high number of EGF receptors of both gut tissues at this early age.…”