Studies on cellular and molecular mechanisms that drive normal and regenerative processes in the liver and pathological processes in Dupuytren’s contracture

Abstract

Maks on imetaja suurim siseorgan, mis omab unikaalset taastumisvõimet, kuid pidev krooniline maksakahjustus põhjustab tema regeneratsioonivõime vähenemist, fibroosse armkoe tekkimist ja maksa funktsioonide kadumist. Sageli on lõppstaadiumis oleva kroonilise maksahaiguse ainsaks ravivõimaluseks maksasiirdamine. Leidmaks maksasiirdamisele alternatiivseid ravimeetodeid, on oluline uurida maksa regeneratsiooni ja haiguslike protsessidega seotud molekulaarseid ja rakulisi mehhanisme. Käesolevas töös uurisime, kuidas maksa aeglaselt jagunevad rakud panustavad koe taastamisse, millised rakuvälise maatriksi muudatused leiavad aset vastusena maksakahjustusele ja kuidas need võiksid mõjutada rakkude käitumist. Samuti uurisime, kas signaalirajad, mis on olulised maksafibroosis, omavad rolli ka teist tüüpi fibrootilises haiguses ja lõpuks viisime läbi suuremahulise kemikaalide skriinimise, leidmaks AKT1-PDPK1 interaktsiooni inhibiitorit, mis vähendaks kasvajate-ja fibroosiseoselise AKT1 aktivatsiooni. Töö tulemusena leidsime, et maksa aeglaselt jagunevad rakud on unipotentsed sapijuharakud, mis aktiveeruvad ainult kroonilise kahjustuse korral. Samuti selgus, et maksa rakuvälise maatriksi muutused sõltuvad kahjustuse tüübist ning erinevad maatriksi komponendid omavad hepatotsüütide ja sapijuharakkude proliferatsioonile erinevat mõju. Uurides fibrootilisi protsesse Dupuytren´i kontraktuuri koes, avastasime, et haige koe erinevad komponendid sünteesivad erinevaid fibroosi ja proliferatsiooni soodustavaid molekule, moodustades haiguse arenguks sobiliku keskonna. Töö viimases osas kirjeldasime AKT1-PDPK1 interaktsiooni inhibiitori, väikesemolekulaarse ühendi NSC156529, identifitseerimise protsessi. NSC156529 vähendas AKT valgu ja tema sihtmärkvalkude aktiivsust ning pidurdas rakkude kasvu in vitro ja tuumori kasvu in vivo. Seega on NSC156529 sobiv alusmolekul uudsete ravimite väljatöötamiseks selliste haiguste nagu kasvajad ning fibroos vastu, mille puhul AKT signaaliraja aktiivsus on kõrgenenud.The liver is the largest mammalian visceral organ with a remarkable regenerative capacity. However, in case of persistent chronic liver injury, this regenerative potential declines, the parenchyma becomes fibrotic, and finally, the liver is not able to exert its biological functions anymore. Since liver transplantation is often the only treatment option for end-stage chronic liver diseases, development of alternative therapies has become increasingly important. In order to generate new treatments, it is necessary to understand the cellular and molecular mechanisms that control liver regeneration and disease progression. The first objective of this thesis was to determine the role of slowly-cycling liver cells in liver regeneration. Secondly, we studied the changes in extracellular matrix (ECM) that occur in response to different liver injuries, and the effect of these alterations on the regenerative properties of liver cells. We also studied, how the signaling pathways that are associated with liver fibrosis, are involved in another type of fibrotic disease–Dupuytren’s contracture (DC). And finally we conducted a large-scale chemical screening to find inhibitors for AKT1-PDPK1interaction that would suppress AKT pathway, which is aberrantly activated in many cancers and fibrotic diseases. We discovered that slowly-cycling liver cells are unipotent biliary cells which are activated and take part in liver regeneration only in response to chronic liver injury. The changes in ECM appear to be dependent on the type of injury, and the hepatocytes and cholangiocytes have different proliferative activity on different matrix components. When studying fibrotic processes in DC we found that different compartments in DC tissue synthesize distinct fibrosis-and proliferation-inducing molecules, which synergize in forming a supportive microinvironment for disease progression. In the last part of this work we described the identification process of NSC156529–the novel inhibitor of AKT1-PDPK1 interaction. NSC156529 is a small molecule compound that inhibited AKT pathway and restricted cell growth in vitro and tumor growth in vivo. We proposed that NSC156529 is a new strong candidate for the development of novel anti-tumor therapeutics.