Evaluation of the antifibrotic potential of Serelaxin in two experimental models of cardiac fibrogenesis
by Tim Pascal Wilhelmi
Date of Examination:2023-09-21
Date of issue:2023-08-28
Advisor:Prof. Dr. Elisabeth Zeisberg
Referee:Prof. Dr. Elisabeth Zeisberg
Referee:Prof. Dr. Susanne Lutz
Persistent Address:
http://dx.doi.org/10.53846/goediss-10076
Files in this item
Name:Dissertation_Wilhelmi_Tim_Gutachter_SUB_Inhalt.pdf
Size:16.6Mb
Format:PDF
The following license files are associated with this item:
Abstract
English
This study is based on the finding that Relaxin was identified in Rln1 gene knockout mice as a naturally occurring regulator of collagen turnover in the heart (Du et al. 2003). Additionally, in a model of spontaneously hypertensive rats, Relaxin was able to prevent the fibrogenesis of multiple organs (Lekgabe et al. 2005). However, these studies could not provide any insight into the pathomechanisms or molecular pathways involved. Since an anti- TGFβ/SMAD3-mediated preventive effect of Relaxin on the activation of fibroblasts was revealed, this suggested an inhibitory influence of Serelaxin on equally SMAD3-mediated profibrotic mechanisms and EndMT (Sassoli et al. 2013). Clinical trials on the administration of Serelaxin in patients suffering from acute HF showed a significant improvement in dyspnea and reduction of early worsening of HF but could not significantly affect systolic parameters such as cardiac output and thereby reinforced the suspicion of a possible influence of Serelaxin on wall tension and cardiac fibrosis (Metra et al. 2019). Consequently, the aim of this work was to evaluate and assess the precise influence of Serelaxin on the development of cardiac fibrosis. For this purpose, we quantified the dosedependent, anti-fibrotic effect on interstitial and perivascular fibrosis. As per literature, we hypothesized that Serelaxin could influence EndMT. To examine this hypothesis and to evaluate possible regulatory effects of Serelaxin, EndMT was induced both in vivo and in vitro. Further, we investigated receptor subtypes through which Serelaxin may potentially mediate its effects in the heart and in endothelial cells. The focus was on the cellular distribution of the receptors and their regulation. However, the most central question was how Serelaxin mediates a possible anti-fibrotic effect. To elucidate on how signaling pathways play a role, and on mechanisms the recombinant form of Relaxin steers for, extensive downstream experiments were performed. By carrying out this broad-based study, detailed and novel knowledge about the impact of Serelaxin on the diseased heart could be gained: The anti-fibrotic effect of Serelaxin was demonstrated in two independent pressure overload mouse models, AAC and ATII infusion, and was even more pronounced in perivascular than in interstitial fibrotic lesions. The antifibrotic effect was associated with lower mortality in mice, but not with an improvement in cardiac performance, which is in line with clinical studies. Furthermore, Serelaxin developed its anti-fibrotic impact at least partially due to an inhibition of EndMT. This influence on EndMT was led through activation of Notch signaling, which was mediated via RXFP1. Finally, this study was able to show for the first time that Serelaxin can prevent histone modifications of the Rxfp1 promoter by blocking the TGFβ/SMAD2/3 signaling pathway. As a result, the expression of initially low-expressed Rxfp1 was upregulated in the sense of a positive feedback loop, whereby the effect of Serelaxin can in principle be potentiated.
Keywords: cardiac fibrosis; Serelaxin; EndMT; histone modification; Notch
