Morphological changes of cell proliferation and apoptosis in rat jejunal mucosa at different ages

AIM: To study the changes of cell proliferation and apoptosis in rat jejunal epithelium at different ages. METHODS: Cell proliferation and apoptosis of the jejunal mucosal and glandulous epithelia from birth to postnatal 12(th) month were observed using immunocytochemistry (ICC), and TUNEL method. The height of villus, the thickness of muscle layer and the number of goblet cells in jejunal mucosal and glandulous epithelia were measured by BeiHang analytic software and analyzed by STAT. RESULTS: (1) Proliferating cell nuclear antigen (PCNA) positive cells of jejunal glandulous recess were found and increased in number from birth to the postnatal 3(rd) month. The number of PCNA positive cells peaked in the postnatal 3(rd) month, and decreased from then on. (2) The number of apoptotic cells also peaked in the postnatal 3(rd) month, showing a similar trend to that of the PCNA positive cells. (3) The height of jejunal villus increased after birth, peaked in the postnatal 3(rd) month and decreased from then on. The jejunal muscle layer became thicker in the postnatal 3(rd) week and the postnatal 12(th) month. The number of goblet cells of the jejunal mucosal and glandulous epithelia had a linear correlation with age. CONCLUSION: (1) PCNA positive cells are distributed in the jejunal glandulous recess. (2) Apoptotic cell number peaks in the postnatal 3(rd) month, indicating that cell proliferation and apoptosis are developed with the formation of digestive metabolism as rat grows to maturity. (3) The thickness of jejunal muscle layer increases to a maximum in the postnatal 3(rd) week, which may be related to the change in diet from milk to solid food. (4) The number of goblet cells increases rapidly in the postnatal 3(rd) week, probably due to ingestion of solid food.