TARGETING YAP1 AND CCN2 IN SCLERODERMA: A THERAPEUTIC APPROACH TO COMBAT FIBROSIS
Date
2024-09-16
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
ORCID
Type
Thesis
Degree Level
Doctoral
Abstract
Scleroderma, also known as systemic sclerosis, is a multisystemic connective tissue disorder characterized by vasculopathy and immune dysregulation, resulting in skin and internal organ fibrosis. The clinical manifestations and progression are quite heterogeneous, with life expectancy significantly influenced by the degree of lung and heart involvement. In developed countries, diseases involving fibrosis are estimated to account for about 45% of all deaths. Fibroblasts and myofibroblasts are the primary effector cells central to the development of fibrosis. In fibrotic tissue, the ECM becomes excessively stiff due to the accumulation of collagen and matrix components produced by fibroblasts. The elevated stiffness in ECM promotes increased adhesion of fibroblasts, leading to amplified mechanotransductive signalling that sustains the fibrotic phenotype. This self-perpetuating signalling loop drives fibrosis, therefore leading to increased tissue stiffness. Therefore, targeting this loop to mitigate fibrosis holds significant potential for creating effective therapeutic strategies. The mechanosensitive transcriptional co-activator, yes activated protein-1 (YAP1), and its downstream effector, CCN2, are activated in SSc fibroblasts and are found to be overexpressed in the skin and lungs of SSc patients. Given this, I tested the hypothesis that celastrol, which was recently identified as a YAP inhibitor and BLR200, a CCN3-based therapeutic peptide that reduces CCN2, might block experimental skin and lung fibrosis respectively and thus may represent a therapeutic option for SSc fibrosis. First, I used cell culture models and found that celastrol significantly hindered the TGF-induced profibrotic gene expression in dermal fibroblasts and disrupted the persistence of the fibrotic phenotype in SSc lesions. Second, In the bleomycin-induced skin fibrosis mouse model, celastrol mitigated the bleomycin-induced fibrotic changes and inhibited the nuclear translocation of YAP. Furthermore, through spatial transcriptomic analysis, bleomycin-induced gene expressions associated with reticular fibroblasts and the Hippo pathway were found to be sensitive to celastrol treatment. Finally, I used a bleomycin-induced lung fibrosis model to test the ability of BLR200 to inhibit and impair lung fibrosis. I found that BLR200 prevented alveolar thickening, collagen deposition and mRNA expression of profibrotic factors in the lung tissue. The results presented here suggest that modulating the microenvironment that impacts mechanotransduction may offer a promising therapeutic strategy for addressing scleroderma-associated skin and lung fibrosis.
Description
Keywords
Scleroderma, Fibrosis, Profibrotic factors, fibroblast, myofibroblast, matricellular proteins, YAP1, CCN2, bleomycin-induced fibrosis, Spatial transcriptomics
Citation
Degree
Doctor of Philosophy (Ph.D.)
Department
Dentistry
Program
Precision Oral and Systemic Health