Dr. Mar Guilarte, researcher of the Physiology and Pathophysiology of the Digestive tract group at Vall d'Hebron Research Institute (VHIR), has received the Extraordinary Doctoral Award from the Universitat Autònoma de Barcelona to study the function of mast cells and the role of stress in irritable bowel syndrome with diarrhoea predominance. She conducted her thesis under the direction of Dr. Javier Santos and Dr. Maria Vicario.The Irritable Bowel Syndrome (IBS), traditionally considered as a functional disease of the colon, is a highly prevalent disorder, with great impact on quality of life with few effective treatment options. Although there is still very little understanding of its aetiology, stress has been associated with the development and maintenance of the IBS.Its pathophysiological mechanisms are not known exactly, but recent scientific evidence questioned the conventional view of IBS as a functional disease, not organic. In particular, a common finding is the alteration of the intestinal barrier along with the presence of a microinflammation and immune activation in the mucosa, and more pronounced in patients with IBS subtype with predominant diarrhea (IBS-D). The mast cell qualifies as a candidate to modulate cell pathophysiology of IBS because at a intestinal level it is involved in the regulation of intestinal motility, visceral sensitivity and epithelial function.Today, there are no useful biomarkers for diagnosis, which is based on clinical diagnostic criteria and exclusion. Therefore, one of the priorities of the scientific community is to direct research towards the identification of biomarkers which facilitate the diagnosis of IBS.Dr. Guilarte analyzed in her thesis the mast cell function as a regulator of epithelial dysfunction caused by stress and its role in IBS-D. "Through two studies in patients with IBS-D and an experimental rat model, we demonstrated for the first time that at the jejunum of these patients there is an increase in the number and activation of mast cells," says the VHIR's researcher.Given that patients with IBS-D have higher levels of stress, she wanted to study what was the role of chronic stress in the intestinal changes observed in patients with IBS-D. To this end, she developed an experimental model of agglomeration stress in rats and found that stress causes activation and mast cell hyperplasia, which is accompanied by increased intestinal permeability, that is dependent of the mast cell.Finally, as to whether stress had a role in the epithelial dysfunction in patients with IBS-D and the role it had in the mast cell, she observed in vivo that changes in the secretion and intestinal epithelial permeability in the jejunum of patients with IBS-D after the administration of CRH (the stress hormone) were dependent on mast cell activation.Ultimately, the results of the thesis show that the at jejunum of patients with IBS-D there is not only a mast cell hyperplasia at mucosa, but also activation of these cells. Moreover, there is an increase in intestinal permeability, manifested especially after the activation of mast cells in response to acute stress. According to Dr. Guilarte, this extends the traditional concept that "irritable bowel syndrome is a bowel disease and shows that the sections closest to the intestine, with important nutritional and immunological, are also affected."