Mo1702 Wound Integrity and Collagen Expression in Experimental Crohn's Disease: Effect of Pegylated Murinized Rabbit Anti-Mouse TNF

Abstract

Wound dehiscence and anastomotic leaks are dreaded complications of ileal resection in patients with Crohn's disease (CD). Like patients with CD, rats with PGPS enterocolitis are at increased risk of wound infections and incisional hernias. We have previously shown that anti-TNF treatment affects mRNA levels of collagen and key cytokines at the laparotomy skin site in this model. Our aim was to study the effect of anti-TNF on wound integrity and ileal tissue during the early and late phases of experimental CD.Methods: Peptidoglycanpolysaccharide (PGPS) or human serum albumin (HSA, control) was injected into the bowel wall of Lewis rats at laparotomy. PGPS and HSA injected rats were given pegylated murinized rabbit anti-mouse TNF (aTNF) or vehicle SC 3 times a week beginning d1 post-op. Animals were sacrificed on d7, d14 and d21 (n=3 each time point). Incisions and ileal tissues were collected and quantitative real-time PCR for type I procollagen was performed. Histologic sections were stained with Masson's trichrome stain and image analysis was performed to measure the gap between the inner edges of the rectus muscles on transverse sectioning of the incisional tissues. Results: Ileal procollagen I mRNA was increased in PGPS/Veh and HSA/Veh as early as 7 days post laparotomy (fold increase over d0, 7d: PGPS/Veh 3.9 ± 0.1; HSA/Veh 1.9 ± 0.6). Procollagen mRNA in the incision was increased at all time points and there was no difference with aTNF treatment. Treatment with aTNF had little effect on procollagen mRNA in ileum at d7 and d14 in either the PGPS or HSA injected animals. Anti-TNF normalized procollagen mRNAs in ileum and incision by day 21 in the HSA rats; the PGPS/aTNF group had variable collagen expression. Image analysis revealed a small rectus gap in the HSA-injected rats at all time points independent of treatment with aTNF(d7 HSA/Veh v HSA/aTNF 4.40 mm ± 0.44 v 4.36 ± 0.20; d21 HSA/Veh v HSA/aTNF 5.07 mm ± 0.62 v 4.91 ± 0.28). The PGPS/Veh rats also had a small gap at all time points (d7: 4.69 mm ± 0.02; d14: 4.97 ± 0.56; d21: 4.58 ± 0.28). There was a trend toward increased rectus gap in the PGPS/aTNF group compared to other groups (7d: 1.40 fold; 14d 1.12 fold; 21d 1.23 fold; p=0.08). Conclusion: Changes in collagen expression in the ileum and skin occur earlier in the course of experimental Crohn's disease than previously thought. As in patients with CD, inflammation and fibrosis coexist throughout most of the course of the disease. Early changes in the skin and ileal collagen mRNA and protein occur that can affect wound repair and anastomotic integrity. In our model, anti-TNF therapy tended to increase the rectus gap while collagen mRNA decreased with therapy. This is consistent with TNF-independent factors that influence the overall repair process.