Background The ability to measure the expression of pro-inflammatory cytokines from intestinal biopsies in patients with Crohn’s disease in an accurate and reproducible way is critical for proof-of-concept and mechanism-of-action trials; however, the number of biopsies from a segment of the ileum or colon required to yield reproducible results has not been rigorously evaluated. We examined intestinal biopsies from patients with Crohn’s disease to validate methods for detecting changes in inflammatory gene expression. Methods To evaluate the reproducibility of gene expression measurements, intestinal biopsies were obtained from designated segmentsfrom6 healthy controls, 6 patients with active Crohn’s disease, and 6 patients with inactive Crohn’s disease. Disease activity was based on the simple endoscopic score for Crohn’s disease (SES-CD). Expression of 7 pro-inflammatory genes was measured from each biopsy using quantitative PCR. Using a linear mixed effects model, the power to detect transcriptional changes corresponding to active and inactive Crohn’s disease was calculated. Results Total SES-CD score corresponds with expression of most inflammatory biomarkers. For most genes, 2 – 5biopsies are needed to reduce sampling error to <25% for most genes. To measure changes in mRNA expression corresponding to active versus inactive Crohn’s disease, one to two intestinal biopsies from 3 patients before and after treatment are needed to yield power of at least 80%. Conclusion Measuring pro-inflammatory gene expression from mucosal biopsies from patients with Crohn’s disease is practicable and provides objective biomarkers that can be utilized in proof-of-concept and mechanism-of-action trials to assess response to therapy.

No abstract

Summary Background Accurate and reproducible measurement of expression of pro-inflammatory cytokines in colonic biopsies from patients with ulcerative colitis (UC) is essential for proof-of-concept and mechanism-of-action studies. Few studies have rigorously established the number of biopsies required for accurate and reproducible biomarker measurements. Aim To validate methods for measuring changes in gene expression in colonic biopsy samples. Methods Twelve colonic biopsies were obtained from each of 6 healthy controls, 6 patients with inactive UC, and 7 patients with active UC. Mayo endoscopic scores were used as a clinical reference standard. Quantitative PCR was used to assess mRNA expression of eight known inflammatory genes. The power to detect a reduction in gene expression in active versus inactive UC was calculated using a linear mixed effect model. Results mRNA analysis of colonic biopsies is a sensitive and feasible approach for measuring inflammatory gene expression in colonic biopsies. Inflammatory biomarkers correlate with Mayo endoscopic subscores for each colonic region. For most genes, 3 rectal biopsies from 2–4 patients are required to detect changes in gene expression corresponding to active versus inactive UC to achieve a power of 80% with an alpha of 0.05. Conclusions Our data suggest that systematic measurement of inflammatory biomarkers at the mRNA level can be a valuable tool for hypothesis testing and assessment of clinical activity and response to therapy in ulcerative colitis.

No abstract