P050 Effect of biological treatments (anti-TNFs) in the creeping fat of Crohn’s disease patients

Abstract

Background Crohn’s disease (CD) is characterized by persistent inflammation and ulcerations at the small or large bowel, provoking chronic low-grade systemic inflammation. Adipose tissue (AT) is believed to play an active role in the pathogenesis of CD, as the expansion of mesenteric fat attached to the inflamed segments of the intestine, also known as “creeping fat,” is a hallmark of the disease that seems to be directly related to disease activity. We demonstrated that adipose-stem cells (ASC) isolated from the creeping fat of CD patients showed a proinflammatory phenotype and increased the proliferation, migration, and phagocytic capacities of these cells. Taking into account the widely described effects of TNFalpha on the biology and functionality of adipocytes, we believe that biological therapies based on anti-TNF agents modify the inflammatory status of creeping fat. In this context, the effect of anti-TNF treatment on mesenteric fat is poorly studied, and the results are divergent. Methods Creeping fat biopsies were obtained from active CD patients that underwent surgery for symptomatic complications: 10 patients were on anti-TNF therapy (at least 6-months prior to surgery) and 10 patients never received any biological therapy. The groups were comparable in age, sex, and body mass index. We isolated from AT biopsies: AT explants, ASC, and adipose tissue macrophages (ATM). Adipose tissue was fixed in 10% phosphate-buffered formalin and embedded in paraffin for histological studies. The proliferation of ASC was performed using the CellTraceTM Violet Cell proliferation kit using flow cytometry and the cell migration of ASC was analyzed using a Tranwell system (8 mmpore polycarbonate membrane). Results Histological studies revealed that AT of patients treated with anti-TNF therapy recovered adipocytes morphology and showed lower infiltration of immune cells. Interestingly, we found a significant decrease in the gene expression of pro-inflammatory cytokines (IL1B, IL6, TNFA) in the creeping fat of CD patients treated with anti-TNF (Figure 1A). Furthermore, ATMs isolated from patients treated with anti-TNF showed a significant decrease in the gene expression of antigen-presenting markers (CD74, CIITa, HLA-DPB and HLA-DM) (Figure 1B). To note, ASC isolated from patients with anti-TNF therapy has significantly decreased their proliferation and migration capacities as well as the pro-inflammatory gene expression. Moreover, the anti-inflammatory gene expression and secretion were significantly increased in these cells (Figure 1C). Conclusion Anti-TNF therapies impact on the creeping fat of CD patients improving the phenotype of this tissue and this may cause a beneficial effect on CD.

Creeping fat formation and interaction with intestinal disease in Crohn's disease

“… 15 , 16 Interestingly, anti‐TNF treatment notably decreased the infiltration of immune cells and the gene expression of antigen‐presenting markers of adipose tissue macrophages, as well as the gene expression of pro‐inflammatory cytokine (IL1β, IL‐6, TNF‐α). 52 T‐cell subpopulations differed between CrF and the corresponding mucosa. Comparing fat and mucosa, the total percentage of Th1, Th17 and Treg populations were significantly higher within CrF than in the mucosa in ileal CD patients.…”

“…Notably, it contains higher amount of M2 than M1 cells in CrF, in contrast to the lamina propria where M1 are more common 15,16 . Interestingly, anti‐TNF treatment notably decreased the infiltration of immune cells and the gene expression of antigen‐presenting markers of adipose tissue macrophages, as well as the gene expression of pro‐inflammatory cytokine (IL1β, IL‐6, TNF‐α) 52 . T‐cell subpopulations differed between CrF and the corresponding mucosa.…”