P017 C86/CD16 macrophages accumulate in the mucosa of B3 patients and could mediate EMT in Crohn’s disease

Abstract

Abstract Background Macrophages contribute to fibrosis through the release of different mediators and the pattern of secretion may vary according to their phenotype. Methods The aim of the present study is to analyse the pattern of expression of macrophages, of EMT-related genes and cytokines in surgical resections from Crohn’s disease (CD, n = 43) patients which were categorised according to Montreal classification (B2 or B3); unaffected mucosa of patients with ileocecal cancer was used as control (n = 20). mRNA was isolated from intestinal samples and the expression of macrophage, EMT markers and cytokines were analysed by RT-PCR. PBMCS were isolated from healthy donors and treated during 5 days with secretomes, from control, B2 or B3 surgical resections; the mRNA expression of macrophage markers was determined by RT-PCR. U937 cells were differentiated to macrophages and then treated with IFNγ (20 ng/ml) for 4 days, the mRNA expression of macrophages markers were determined by RT-PCR. Results are expressed as mean ± SEM (n ≥ 5). Statistical analysis was performed by ANOVA + Newman–Keuls or t-test. Correlations between data were analysed using Pearson’s correlation coefficient (*p < 0.05). Results The expression of CD16 and CD86 was significantly higher in intestinal samples from B3 CD patients (7.2 ± 1.1 and 7.7 ± 1.3, respectively) than in controls (1.4 ± 0.2 and 2.5 ± 0.4, respectively) or B2 CD patients (4.8 ± 0.9 and 4.5 ± 0.6, respectively). The mRNA expression of CD16 and CD86 were significantly higher in PBMCS treated with B3-secretomes than in those treated with B2- or control secretomes. The expression of CD16 and CD86 significantly correlated with FSP1 (r = 0.74, p = 0.002* and r = 0.66, p = 0.003*, respectively), VIMENTIN (r = 0.60, p = 0.02* and r = 0.82, p = 0.001*, respectively), SNAIL1 (r = 0.61, p < 0.01* r = 0.52, p = 0.04*, respectively), IL4 (r = 0.63, p = 0.01* and r = 0.60, p = 0.02*, respectively) and IFNγ (r = 0.56, p = 0.001* and r = 0.58, p = 0.01*, respectively) in intestinal tissue from the fistulising CD group. U937 cells treated with IFNγ increased significantly the mRNA expression of CD16 (1.94 ± 0.24* vs. vehicle) and CD86 (1.60 ± 0.17* vs. vehicle). Conclusion A macrophage phenotype expressing CD86/CD16 may act as a source of EMT mediators in intestinal tissue from CD patients with a penetrating (B3) behaviour. IFNγ could be responsible for the increase in the number of CD86/CD16 macrophages in the B3 behaviour.