Crohn's disease (CD), a chronic relapsing intestinal disorder, causes severe morbidity and poor quality of life. It belongs to the inflammatory bowel disease (IBD). While previously considered rare in children, IBD has emerged as a global disease in developed and developing nations. Epidemiological data from western countries indicate that 25% of all cases are diagnosed in childhood, with an incidence 10-12 new cases/100.000/year in a range age from 0 to 18 years.
There is a widely agreed view, supported by experimental studies, that an abnormal interplay between environment, genetic, intestinal immunity and gut microbiota (GM) plays a role in mechanisms of CD. The observed increase in the disease incidence in rapidly industrialized countries has highlighted that CD may have a strong environmental component.
Recently, experimental data have shown that western diet (characterized by overconsumption of refined sugars, saturated fats, animal proteins and low intake of plant-based fibers) damages the epithelial barrier and negatively impacts the composition and functionality of GM, with indirect effects on immunological homeostasis of the gut. This has suggested that dietary factors have a plausible role in triggering CD mechanisms.
Interestingly, specific diet programs, such as exclusive enteral nutrition (EEN) with a polymeric formula, and partial enteral nutrition (PEN) including polymeric formulae with an oral diet excluding specific foods, have been shown to play a therapeutic role in inducing and maintaining remission of CD, respectively. However, despite these clinical evidences, the exact mechanism of action of nutritional intervention in CD is uncertain.
Thus, we aim at investigating in children with CD, treated with PEN for maintaining remission, the impact of this strategy on molecular profile of gut microbiota and on fecal metabolome, the latter providing a functional readout of microbial activity. Intestinal Immunological scenario will also be studied.
This study has clinical and scientific implications, opening new horizons in the knowledge of the mechanisms underlying pediatric Crohn's disease (CD) as well as in the therapeutic strategies of the disease. Firstly, this project will compare two different strategies for maintaining remission in children with CD, i.e. a pharmacologic approach involving scheduled biologics (and/or immunomodulators) versus partial enteral nutrition (PEN) consisting of a polymeric oral formula (covering roughly 50% of the caloric requirement) in addition to a structured oral diet excluding foods known to damage intestinal epithelial barrier, alter the gut microbiota profile and function as well as intestinal immunity.
CD is a severe chronic and relapsing disorder carrying a high rate of morbidity and low quality of life. It requires an intense program of scheduled controls through day hospital or long-lasting admissions at referral centers for pediatric gastroenterology. It is widely agreed that CD, is the result of an abnormal interaction between intestinal (and systemic) immunological activity, gut microbiota, environment and genetics. The latter is related to genes that control the innate and the adaptive gut immunity, the integrity of the epithelial barrier and he interaction between gut epithelium and commensal microbes.
One innovative aspect of this project is the characterization of variables playing a critical role in the disease mechanisms. These variables will be related each other trying to make a link between them and the disease phenotype. Moreover, they will be related to the therapeutic outcome, aiming at searching for their potential role as predictor of therapeutic response and disease course. Noticeably, the project is also advanced since it aims at examining the impact of therapy on the pathogenetic mechanisms of the disease, that will be investigated in the patients included into the study.
The methodology of the study is also based on advanced tools. Specific platform for shotgun next generation sequencing (NGS) metagenomics will allow much deeper characterization of the microbiome complexity, allowing identification of a larger number of species for each sample, as compared to 16S rDNA amplicon sequencing. This will provide a better quantitative picture of the microbial communities, even allowing determination of species of low abundance as well as previously unknown species.
We will also investigate the functional aspects of gut microbiota through metabolomics on fecal samples. This will allow to: define the metabolic profile; identify and quantify classes and compounds of interest; characterize small molecules produced by intestinal microbes; and define the biochemical pathways of metabolites. We suggest that metabolomics, together with the high-throughput DNA sequencing techniques, may help to establish connections between gut microbiota and altered metabolites both at the intestinal and systemic levels, thus highlighting the role of gut microbial metabolites on the host.
The project also includes the investigation of intestinal immunity (another key player in the pathogenetic mechanisms of CD). We will use a real-time reverse-transcription quantitative polymerase chain reaction array to analyze messenger RNA (mRNA) expression patterns in intestinal mucosa samples. Expression of genes that mediate different types of immune response will be studied (Th1, Th2, Th17).
Characteristically, in this study, the clinical management is highly related to the investigation of the mechanisms of the disease; moreover, improving knowledge on mechanistic patients¿ profiles and how the therapy impact on the latter is in line with the recent concept of precision medicine that will influence treatment of CD in the next years.
Investigating the pathogenetic mechanism of CD may have clinical implications since it open new therapeutic perspectives in terms of targeted therapy. The treatment of CD has been revolutionized by the introduction of the concept of mucosal healing (MH) and deep remission (CD) as the main outcomes to be achieved in the management of CD. Both variables have been convincingly related to long-lasting steroid-free remission with marked decrease of hospitalization and surgery rates. There is a common view that biologics and nutritional therapy (as exclusive enteral nutrition [EEN] given through a polymeric formula) are capable to promote clinical remission and MH, and they are considered the two principal strategies to induce remission in active pediatric CD.
However, the main clinical challenge for pediatric gastroenterologists taking care of CD is the management of the disease remission due to the highly relapsing nature of the disease. We will also try to determine the value of PEN in maintaining remission, a strategy that might change the future therapeutic approach of pediatric CD, decreasing cost and the risk of adverse drug events, so dealing with a very original and innovative topic