The importance of luminal factors in neomucosal growth

Growing neomucosa on patched intestinal defects has been investigated as a method of expanding the intestinal absorptive area. The purpose of this study was to determine the effect of luminal factors on the rate of growth and function of neomucosa in rabbit ileum. A 2 × 5-cm distal ileal defect was patched with adjacent colon serosa in 10 New Zealand white male rabbits. A similar defect was patched in a bypassed ileal segment in an additional 10 rabbits. Five animals in each group were sacrificed at 4 and 8 weeks for determination of the gross and microscopic growth of neomucosa, glucose uptake, and disaccharidase activity. In addition, tritiated thymidine uptake was measured in neomucosa and incontinuity ileum at the 4-week sacrifice. Grossly, the patched defects were covered in nearly all animals by 4 weeks and coverage was complete at 8 weeks. Microscopically, the mucosa was less well developed in the bypassed group with a mean villous height significantly less than the incontinuity group (139.9 ± 13.9 μm vs 212.33 ± 30.3 μm, P < 0.0005). In vitro uptake of [³H]thymidine was significantly higher in neomucosa in bypassed segments when compared with neomucosa in incontinuity segments (692.5 ± 347.8 vs 278.0 ± 134.8, P < .05, expressed as percentage of normal incontinuity ileum). Glucose uptake was similar in both groups but disaccharidase activity was significantly less in the bypassed group. The increased uptake of [³H]thymidine in neomucosa in the bypassed segment may reflect the histologic immaturity of this tissue with a greater proportion of DNA synthesizing cells. Morphologically and functionally, the intestinal neomucosa appears better developed in incontinuity segments compared to bypassed segments. Thus, the growth of neomucosa appears to be influenced by luminal contents.