The Proteomic Signature of Intestinal Acute Rejection in the Mouse

Intestinal acute rejection (AR) lacks a reliable non-invasive biomarker and AR surveillance is conducted through frequent endoscopic biopsies. Although citrulline and calprotectin have been suggested as AR biomarkers, these have limited clinical value. Using a mouse model of intestinal transplantation (ITx), we performed a proteome-wide analysis and investigated rejection-related proteome changes that may eventually be used as biomarkers. ITx was performed in allogenic (Balb/C to C57Bl) and syngeneic (C57Bl) combinations. Graft samples were obtained three and six days after transplantation (n = 4/time point) and quantitative proteomic analysis with iTRAQ-labeling and mass spectrometry of whole tissue homogenates was performed. Histology showed moderate AR in all allografts post-transplantation at day six. Nine hundred and thirty-eight proteins with at least three unique peptides were identified in the intestinal grafts. Eighty-six proteins varying by >20% between time points and/or groups had an alteration pattern unique to the rejecting allografts: thirty-seven proteins and enzymes (including S100-A8 and IDO-1) were significantly upregulated whereas forty-nine (among other chromogranin, ornithine aminotransferase, and arginase) were downregulated. Numerous proteins showed altered expression during intestinal AR, several of which were previously identified to be involved in acute rejection, although our results also identified previously unreported proteome changes. The metabolites and downstream metabolic pathways of some of these proteins and enzymes may become potential biomarkers for intestinal AR.

Utility of colon allograft biopsies in surveillance of patients with small intestinal transplantation – A systematic study of 129 biopsies

Introduction/Objective A segment of right colon is sometimes included with small intestinal allografts to preserve the ileocecal valve and maintain water reabsorption. We correlated pathological findings of colon allograft biopsies obtained during surveillance colonoscopies with clinical, endoscopic, and microbiologic findings. Methods/Case Report All colon allograft biopsies from surveillance colonoscopies over a 3-year period were reviewed for crypt apoptotic activity, cryptitis, lamina propria inflammation, ulceration, and crypt architectural distortion. Clinical and endoscopic findings, and positive cultures a week before and after the biopsies were recorded. Results (if a Case Study enter NA) There were 129 colon biopsies from 29 patients; 98 were histologically normal, whereas 28 showed rare apoptoses (n=14), focal cryptitis (n=8), increased intraepithelial lymphocytes (n=2), moderate acute rejection (n=1), and crypt architectural distortion (n=2). Of these 29 patients, 8 had abnormal endoscopic findings, 21 were normal. Out of 8 patients with abnormal endoscopic exams, 50% had normal histology on biopsy. Twenty-one biopsies were associated with positive cultures in the blood (n=5), urine (n=16) or wound, peritoneal, stool (n=6); 3 had abnormal endoscopies, and 4, abnormal histology. One patient with C.difficle toxin had normal endoscopy and focal cryptitis, whereas another with CMV DNA in blood showed endoscopically congested mucosa and rare apoptoses on biopsy. Of 12 biopsies (7 patients) with abnormal endoscopic findings, (erythema, congestion, ulceration), 4 biopsies had no pathologic findings, 8 had rare apoptosis, and one each had focal cryptitis and chronic colitis. Paired small intestinal biopsies were present with 59 biopsies; 10 showed rare apoptosis and 2, focal cryptitis. Of 70 without paired small intestinal biopsies, there were 5 with rare apoptotic bodies, 5 with focal cryptitis, and 2 with crypt architectural distortion. Conclusion The correlation of histologic, endoscopic, and microbiologic findings in colonic allograft surveillance biopsies is inconsistent. Colon allograft biopsies have limited utility in the follow-up of patients, particularly in absence of paired small intestinal biopsies.