Patogeneza fibroze pri kronični vnetni črevesni bolezni

Jerala, Miha (author), Zidar, Nina (mentor), Hauptman, Nina (comentor)

V doktorskem delu smo raziskali, kateri geni in celice so vključeni v patogenezo fibroze pri kronični vnetni črevesni bolezni (KVČB). Fibroza je pogost zaplet KVČB, predvsem v Crohnovi bolezni (CB), za katero je značilna izrazita fibroza in transmuralno vnetje, ter v mnogo manjši meri pri ulceroznem kolitisu (UK), kjer je fibroza blaga in je vnetje omejeno le na notranje plasti. Z bioinformatsko analizo smo poiskali gene, ki imajo spremenjeno izražanje v fibrozi v različnih organih, ter jih potrdili na vzorcih KVČB. Na vzorcih KVČB smo analizirali izražanje izbranih mRNA in miRNA ločeno v zunanji (subserozni) in notranji (submukozni) plasti črevesne stene. Opravili smo imunohistokemično barvanje na označevalce miofibroblastov in pericitov ter proteinov trombospondin 2 (THBS2) in matriksni Gla protein (MGP). S programom za digitalno patološko analizo smo primerjali morfometrične lastnosti vlaken kolagena v submukozi in subserozi črevesne stene v KVČB. Naši rezultati so pokazali, da so spremembe v izražanju genov, ki so skupne različnim organom, prisotne tudi pri fibrozi v KVČB. Periciti, predhodniki aktiviranih miofibroblastov, so prisotni tudi v črevesni steni, podobno kot v drugih organih, vendar pa se njihova gostota ne razlikuje med subserozo in submukozo. Namesto razlike v gostoti pa smo ugotovili razliko v značilnostih fibroblastov v submukozi in subserozi. Prvi smo dokazali, da sta v črevesni steni med subserozo in submukozo prisotni dve različni populaciji fibroblastov, ki se razlikujeta v izražanju THBS2, MGP in gladkomišičnega aktina (GMA), ter postavili hipotezo, da je za izrazito fibrozo v CB odgovorna aktivacija subseroznih fibroblastov kot posledica transmuralnega vnetja. Digitalna patološka analiza je dodatno potrdila razlike med subserozo in submukozo, ko je pokazala razlike v kvaliteti vlaken kolagena. Prav tako smo naredili primerjavo submukoze in subseroze v CB s fibrostenozo in CB z vnetno stenozo s panelom miRNA, ki je pokazala, da je večina razlik med obema skupinama prisotnih v subserozni plasti, kar prav tako podpira pomen subseroznih fibroblastov v nastanku fibroze.

• Language: Slovenian
• Keywords: kronična vnetna črevesna bolezen, fibroza, miofibroblasti, izražanje genov, subseroza
• Work type: Doctoral dissertation
• Organization: MF - Faculty of Medicine
• Year: 2025
• PID: 20.500.12556/RUL-167637
• Publication date in RUL: 05.03.2025

Secondary language

• Language: English
• Title: Pathogenesis of fibrosis in inflammatory bowel disease

Abstract

In this doctoral work we researched which genes and cells have a role in the pathogenesis of fibrosis in inflammatory bowel diseases (IBD). Fibrosis is a common complication of IBD, especially in Crohn`s disease (CD), which is characterized by prominent fibrosis and transmural inflammation and to a much lesser extent in ulcerative colitis (UC), in which fibrosis is mild and inflammation is limited to the inner layers. We used bioinformatics analysis to identify genes with differential expression in fibrosis of various organs, which we validated on samples of IBD. We analyzed the expression of select mRNA and miRNA in samples of IBD, separately in the outer (subserosal) and inner (submucosal) layers. We performed immunohistochemical staining of markers of activated myofibroblasts and pericytes as well as the protein thrombospondin 2 (THBS2) and matrix Gla protein (MGP). Using a program for digital pathological analysis, we compared the morphometric properties of collagen fibers in submucosa and subserosa of the bowel wall in IBD. Our results show that changes in gene expression that are common to different organs are also present in fibrosis in IBD. Pericytes, the predecessors of activated myofibroblasts are present in the bowel wall, similarly to other organs, but there are no differences in their density between subserosa and submucosa. Instead of a difference in their density, we discovered a difference in the properties of subserosal and submucosal fibroblasts. We were the first to show that the submucosa and subserosa of the bowel wall contain distinct populations of fibroblasts, which differ in the expression of THBS2, MGP and smooth muscle actin and formulated the hypothesis that the prominent fibrosis in CD is a consequence of subserosal fibroblast activation caused by transmural inflammation. Digital pathology analysis additionally confirmed differences between subserosa and submucosa by revealing differences in the quality of collagen fibers. We also performed a comparison of submucosa and subserosa in CD with fibrostenosis and CD with inflammatory stenosis with a panel of miRNA, which showed that most of the differences are present between the subserosal layers, which also supports the importance of subserosal fibroblasts in the formation of fibrosis.

• Keywords: inflammatory bowel disease, fibrosis, myofibroblasts, gene expression, subserosa