Unit:
Faculty of MedicineLibrary of the School of Health Sciences
Author:
Paraskevopoulou Varvara
Dissertation committee:
Μαρία Ρουµπελάκη, Επίκουρος Καθηγήτρια, Ιατρική Σχολή, ΕΚΠΑ
Απόστολος Κλινάκης, Ερευνητής Α ́, Ίδρυμα Ιατροβιολογικών Ερευνών Ακαδημίας Αθηνών-ΙΙΒΕΑΑ
Λασκαρώ Ζαγοραίου, Ερευνήτρια Γ΄, ΙΙΒΕΑΑ
Αριστείδης Ηλιόπουλος, Καθηγητής, Ιατρική Σχολή Αθηνών, ΕΚΠΑ
Μαρία Γαζούλη, Αναπληρώτρια Καθηγήτρια, Ιατρική Σχολή Αθηνών, ΕΚΠΑ
Αθανάσιος Κοτσίνας, Επίκουρος Καθηγητής, Ιατρική Σχολή Αθηνών, ΕΚΠΑ
Θεόδωρος Ράµπιας, Ερευνητής Γ΄, ΙΙΒΕΑΑ
Original Title:
Μελέτη του ρόλου των βλαστοκυττάρων στην αναγέννηση και την καρκινογένεση του ουροθηλίου στο ποντίκι
Translated title:
Study of the role of stem cells in the regeneration and carcinogenesis of the mouse urothelium
Summary:
The urothelium is a transitional epithelium that lines the urinary tract extending from the renal pelvis to the proximal urethra. It serves as a barrier preventing ions, solutes, water and pathogens from crossing into the bloodstream. It consists of three cell types, namely basal, intermediate, and superficial/ umbrella cells, which are arranged in relatively distinct cell layers. Normally, quiescent, it regenerates immediately upon acute injury, but the regeneration process has not been clarified. Although some reports indicate the existence of progenitor cells in the tissue, their identity and precise topology, as well as their role in tissue regeneration or carcinogenesis still remains elusive. Our results suggest that a minor subpopulation of basal cells characterized by the expression of keratin 14 represents stem cells of the tissue, able for both self renewal and production of all cell types of the urothelium, including the most differentiated cell types, during both natural and injury-induced regeneration. Moreover, these cells represent cells of origin of urothelial cancer, as indicated by employing an in vivo chemical carcinogenesis model.
Recently published data from our laboratory support that the Notch signaling pathway, which mediates cell-cell communication regulating cellular processes and cell fate decisions in various tissues, acts as a tumor suppressor in the mouse urinary bladder, while mutations in Notch pathway components have been identified in human bladder cancer as well. However, the data presented herein highlight a major role for Notch in controlling epithelial integrity and bladder function in mice. We indicate that the genetic inactivation of Notch in mice leads to downregulation of cell-cell and cell-ECM interaction components including proteins previously implicated in interstitial cystitis/bladder pain syndrome (IC/BPS), structural defects and mucosal sloughing, inflammation and leaky urine-blood barrier. Molecular profiling of ailing mouse bladders showed similarities with IC/BPS patient tissue, which also presented low Notch pathway activity as indicated by reduced expression of canonical Notch targets. Urothelial integrity is reconstituted upon exogenous re-activation of the Notch pathway implying a direct involvement of Notch. Despite damage and inflammation, urothelial cells fail to proliferate, uncovering a possible role for integrin α4 in urothelial homeostasis. Overall, our data support a broad role for Notch in bladder homeostasis involving urothelial cell crosstalk with the microenvironment.
Genetic and epigenetic alterations are key features of urothelial cancer. Histone modifying enzymes are affected in the majority of the cases of human bladder cancers, with alterations in both lysine demethylases (KDM6A/UTX) and methyltransferases (KMT2C/MLL3). A recent report suggests that Mll3 abrogation leads to ureter cancer in mice, a phenotype reminiscent of what observed upon inactivation of Notch signaling in mouse models as well. Lineage tracing experiments described in this thesis showed that Kdm6a ablation accelerates the development of squamous cell carcinoma in the mouse bladder, under chemical induced carcinogenesis conditions. In support of this, it drives the formation of tumors with a higher proliferation rate in mouse xenograft experiments. Deletion of Kmt2c in urothelial cells leads to the development of hyperplasia in vivo, under normal tissue homeostasis conditions. Finally, in vitro clonogenic assays indicated a significantly higher clonogenic potential for primary urothelial cells lacking above genes, confirming the tumor suppressor role of these epigenetic agents in the mouse urothelium.
Main subject category:
Health Sciences
Keywords:
Urothelium, Bladder, Keratin 14, Stem cells, Carcinogenesis, Bladder cancer, Progenitors, Integrity, Integrins, Extracellular matrix, Microenvironment, Notch signaling pathway
Number of references:
129
