Thèse Comprendre le Rôle de l'Hypoxie dans la Fibrose Cutanée H/F

Doctorat.Gouv.Fr

Ce projet vise à étudier le rôle des HIF dans les fibroblastes cutanés, ainsi que leur implication dans la synthèse, la maturation et le dépôt du collagène. La sclérose systémique sera utilisée comme modèle de maladie, car elle est caractérisée par une hypoxie et une fibrose cutanée et pulmonaire. Le projet vise à élucider les multiples mécanismes par lesquels l'hypoxie contribue au dépôt de collagène dans des contextes fibrotiques physiologiques et pathologiques. Un des objectifs du projet de recherche sera de comprendre le rôle de l'hypoxie sur la maturation protéolytique du collagène par la protéine morphogénétique osseuse 1 (BMP-1). Les résultats permettront d'améliorer significativement notre compréhension de l'équilibre entre fibrogenèse saine et fibrose pathologique et pourraient ouvrir des perspectives translationnelles directes pour les patients atteints de maladies fibrotiques.

Ce projet combinera recherche fondamentale, utilisant des techniques de biochimie et de biologie cellulaire, avec une recherche translationnelle impliquant des modèles murins précliniques et des échantillons cliniques. L'équipe d'encadrement est experte en signalisation de l'hypoxie et en assemblage du collagène et travaillera en étroite collaboration avec une équipe basée à Paris, spécialiste de la compréhension moléculaire de la sclérose systémique et de sa prise en charge clinique.

Pré-requis : une solide connaissance en biologie moléculaire et cellulaire (niveau master)
Fibrogenesis is an essential and dynamic process of extracellular matrix (ECM) remodelling at the core of tissue formation and repair. It is characterised by the synthesis and breakdown of extracellular fibrous proteins, mainly collagens. Prolonged tissue insults cause deregulation of this physiological process and result in aberrant accumulation of ECM proteins, a phenomenon called fibrosis. Fibrosis is a common pathological feature in chronic diseases, including cardiovascular diseases, chronic kidney disease, idiopathic pulmonary fibrosis, skin wounds, or metabolic disorders affecting the liver. It affects millions of people worldwide, representing a serious clinical challenge with limited treatment options. To alleviate the burden of fibrosis and foster the development of novel antifibrotic therapies, a comprehensive understanding of the fibrotic molecular mechanisms is crucially needed. Regardless of the clinical context, fibrosis is commonly characterised by an excessive deposition of collagen, particularly type I collagen, which leads to tissue stiffening and impaired function. Such excessive collagen deposition is due to an abnormal balance between its production, secretion, maturation and degradation. The fine-tuning of this equilibrium needs to be understood to better control the aberrant fibrotic process. Whilst the key roles of inflammation and Transforming Growth Factor beta (TGF-) dependent signalling in fibrosis development have been extensively studied, the impact of the local decrease of oxygen concentrations (hypoxia), a common feature of fibrosis, is less well understood. Additionally, how these microenvironmental factors influence each other is not known. Hence, our first objective will be to depict the impact of hypoxia and its crosstalk with TGF- on fibrogenesis, using cell culture of primary skin fibroblasts from healthy donors.
One fibrotic disease, where hypoxia is central from the very early stages, is Systemic Sclerosis (SSc). SSc is an auto-immune disease of unknown aetiology, characterised by widespread vascular injury and progressive fibrosis of the skin and internal organs. Alteration of the vascular architecture and density, and impaired angiogenesis generate chronic hypoxia within the fibrotic tissues of SSc patients. Although SSc is an orphan disease, the total cost of SSc is estimated to account for up to €3.1 billion per year across Europe. It causes a significant loss of quality of life for the patients and an increased mortality. Further understanding the molecular and cellular roles of hypoxia signalling in this disease context will open new avenues for SSc therapeutic strategies and will likely be translatable beyond, to many fibrotic pathological contexts, since hypoxia is a common feature of these diseases. The cellular effects of hypoxia are mainly mediated by the Hypoxia Inducible Factors (HIF-1 and HIF-2) with a global net effect described as profibrotic. Our second objective will be to determine how the HIF and TGF- signalling pathways are modified in the pathological context.
HIF-dependent transcriptional mechanisms increase collagen levels and some of the collagen-modifying enzymes (e.g. collagen hydroxylases and oxidases). We will here explore if HIFs impact another major effector in collagen maturation: the Bone Morphogenetic Protein 1 (BMP-1). BMP-1 is a pleiotropic metalloprotease affecting collagen deposition and fibrosis through multiple entry points, including the direct control of (i) collagen fibrillogenesis, (ii) collagen cross-linking and tissue stiffness, and (iii) TGF- activation. The latter activity can further induce collagen and BMP-1 expression through a positive feedback loop, leading to an amplification of the fibrotic process. Our third objective is directly translational, and will evaluate the most promising HIF and BMP-1 inhibitors in preclinical models of SSc. Cell culture, proteomics, fluorescence and electron microscopy, cell biology (western-blot, qPCR, gene silencing),