Morphological changes and cellular proliferation in mouse colon during fetal and postnatal development

Abstract

To document regional structural and cellular proliferation changes in the developing mouse colon, tissues from fetal, suckling, and weanling mice were analyzed by light microscopy (LM), transmission electron microscopy (TEM), scanning electron microscopy (SEM), [3H]-thymidine incorporation studies, and radioautography. The proximal and distal colon were studied independently at all ages. At 17-18 days of gestation, the mouse proximal colonic mucosa was projected into high and low longitudinal folds disposed in a V-shaped pattern. From birth up to 9 days, the mucosal folds observed by SEM can easily be misinterpreted as being a succession of high and low villus-like structures at LM level. TEM study confirmed the presence of highly specialized absorptive cells in the upper halves of the mucosal folds during this period. No recognizable crypts were noted at birth. Instead, LM and radioautography showed the presence of cell aggregates developing at the base of the epithelium at all levels of the mucosal folds. These cell aggregates evolved into rudimentary crypts giving fully differentiated crypts by day 16 with radiolabeled cells located in the midcrypt portion. As opposed to the proximal segment, a flat mucosa interspersed with well defined short crypts at birth was observed in the distal colon. During the following days, crypts further developed and by 16 days, the radiolabeled epithelial cells were still exclusively located at the base of the crypt. TEM observations illustrated that specialized cells as those found in the proximal segment did not differentiate in this segment.(ABSTRACT TRUNCATED AT 250 WORDS)

Short-Chain Fatty Acids Induce Colonic Mucosal Injury in Rats with Various Postnatal Ages

“…There are significant normal structural and functional changes in the intestinal tract during the first few weeks of life, especially at the time of weaning (22)(23)(24). Some factors that are important in maintaining the intestinal mucosal barrier function also develop postnatally (25,26).…”

CCAAT/Enhancer binding protein isoforms expression in the colon of neonatal mice

“…These aggregates give rise 6 days after birth to rudimentary crypts which are fully developed by day 16, at the start of weaning (Menard et al, 1994). At birth, differentiated non-proliferating cells are more numerous than proliferating cells.…”

“…Cellular aggregates begin to form between post-natal days 2 and 4 and become well developed crypts by day 16 (Menard et al, 1994). To determine the precise localization and pattern of expression of C/EBP isoforms during post-natal colon development, we performed immunocytochemical studies on frozen sections of colon from 4-and 21-day-old mice.…”

“…Before birth, proximal colon consists of mucosal folds (Colony and Conforti, 1993;Menard et al, 1994). At birth, proliferating cells are scattered along the surface epithelium of the mucosal folds.…”

“…At birth, proliferating cells are scattered along the surface epithelium of the mucosal folds. Between post-natal days 2 and 4, cell aggregates are 0 1995 WILEY-LISS, INC. formed and develop into glandular crypts by day 16 (Menard et al, 1994). Since the colonic epithelium lacks villi, the surface epithelium surrounding the colonic crypts represents the small intestinal villus homolog (Schmidt et al, 1985).…”