Chronology of the effect of massive small bowel resection and hepatocyte growth factor (HGF) on intestinal adaptation.

Background: We previously demonstrated that hepatocyte growth factor (HGF) increases mucosal protein and DNA content at single time points during intestinal adaptation in rats. This study evaluates mucosal changes after massive small bowel resection (MSBR) and with the addition of IV HGF measured over the timeframe of intestinal adaptation.

Methods: Sixty adult female Sprague-Dawley rats were divided into three groups and underwent massive small bowel resection (MSBR), MSBR+HGF (intravenous 150 mg/kg/d), or sham operation (control). Five animals per group were sacrificed at 7, 14, 21, and 28 d. Ileal mucosa was harvested and DNA and protein extracted. DNA content (ug/mg mucosa) was measured at 260 nm and protein content (ug/mg mucosa) was measured using the Bradford assay. MIB-5 immunohistochemical staining was done to confirm that the increased DNA content was due to proliferation. Statistical analysis was by ANOVA with post-hoc Tukey's HSD test.

Results: At 7 and 14 d, protein concentration was increased following HGF administration in comparison to MSBR alone and in control rats (P<0.05 and P<0.03, respectively). Mucosal DNA content in the MSBR-HGF rats was significantly increased over MSBR and control groups at 21 and 28 d (P<0.02 and P<0.004, respectively). MIB-5 immunohistochemical staining correlated with mucosal DNA content at 21 and 28 d (P<0.0005 and P<0.002, respectively).

Conclusions: The mucosal response to MSBR for the period 7-14 d after surgery demonstrates that protein content is increased due to an emphasis on hypertrophy, whereas at 21-28 d hyperplasia is the primary change as demonstrated by the increase in DNA content. This response was enhanced by HGF. This is the first demonstration correlating the bimodal gene response during intestinal adaptation to the bimodal mucosal response. Also, this is the first demonstration of a biphasic response by the mucosa to HGF during intestinal adaptation.