NUOVE ACQUISIZIONI SUI MECCANISMI DELLE MALATTIE INFIAMMATORIE INTESTINALI E IDENTIFICAZIONE DI NUOVI TARGET TERAPEUTICI

The intestinal microflora is known to be implicated in the etiopathogenesis of inflammatory bowel disease (IBD). Numerous microbial populations, mostly bacterial, that interact to form a community of considerable biomass, biodiversity and stability, inhabit the large bowels of humans. The intestinal microflora digests complex polymers derived from the host's food and from the host's secretions; fermentation of the molecules resulting from the hydrolysis of polysaccharides and proteins produces short chain fatty acids, gases, phenols, indols, and amines as major products. The fermentation products and the incalculable antigenic load associated with the bacterial cells, affect the development and maintenance of mucosal immune system and physiological processes. Microbial colonisation of the gastrointestinal tract is known to affect the composition of gut-associated lymphoid tissue (GALT); indeed, immediately after exposure to luminal microorganisms, the number of intraepithelial lymphocytes expands greatly, germinal centres with immunoglobulin-producing cells arise rapidly in follicles and in the lamina propria, and concentrations of immunoglobulins increase substantially in serum. Epidemiological and clinical studies indicate that the increased incidence of autoimmune and inflammatory diseases in developed countries is associated with reduced microbial exposure and alteration of microbial communities in the gastrointestinal tract. One attractive hypothesis is that IBD may be a result of dysbiosis in the intestinal microbial community that promotes the overgrowth of bacteria that aberrantly stimulate the intestinal immune system. Many reports have shown that the microbial populations in the intestine of IBD patients are different from those of healthy individuals, suggesting that a change in the gut microbiota composition could have a key role not only in IBD, but also in the development of systemic immune disease, as allergic diseases. The microbiota affects the host immune system through multiple factors, which include microbial components and their metabolites. Constitutive signalling induced by the microbiota keeps the intestinal mucosa in a state of physiological inflammation, with continuous production of tissue repair factors, antimicrobial proteins, and immunoglobulin a (IgA) that, together, maintain intestinal barrier integrity and provide beneficial functions to the microbiota. Without constitutive innate signalling, intestinal barrier injury and bacterial translocation may occur. Probably, continuous challenge of the mucosal immune system by bacterial antigens as a result of abnormal epithelial permeability may drive the chronic immune inflammation observed in IBD. This Unit will analyze the intestinal mucosa-associated bacteria at genera, species and strain level in the intestinal biopsies from IBD patients with different disease activity grades and phases. The characterization of gut microbiota will be done preliminary by conventional culture techniques, which will allow us to detect the main viable bacterial genera in the intestinal bioptic specimens analyzed, and molecular methods, such as Real Time PCR, for a more detailed analysis of the gastrointestinal microbiota. Subsequently, bacteria will be identified at species and strain level by sequencing 16S rDNA using Pyrosequencing.