Intestinal adaptation and enterocyte apoptosis following small bowel resection is p53 independent

Adaptation following small bowel resection (SBR) signals enterocyte prolife ration and apoptosis. Because p53-induced p21(waf1/cip1) may be important f or apoptosis in many cells, we hypothesized that these genes are required f or increased enterocyte apoptosis during adaptation. Male C57BL/6 (wild-typ e) or p53-null mice underwent 50% proximal SBR or sham operation (bowel tra nsection-reanastomosis). Adaptation (DNA-protein content, villus height-cry pt depth, enterocyte proliferation), appearance of apoptotic bodies, and p5 3 and p21(waf1/cip1) protein expression were measured in the ileum after 5 days. Adaptation was equivalent after SBR in both wild-type and p53-null mi ce as monitored by significantly increased ileal DNA-protein content, villu s height, and enterocyte proliferation. The number of crypt apoptotic bodie s increased significantly after SBR evenly in both wild-type and p53-null m ice. In the p53-null mice, SBR substantially induced the expression of p21( waf1/cip1) protein in villus enterocytes. The p53-independent induction of p21(waf1/cip1) may account for the similar intestinal response to SBR betwe en wild-type and p53-null mice. Intestinal adaptation and increased enteroc yte apoptosis following intestinal resection occur via a p53-independent me chanism.