Résumé
Abstract
Background and Aims
The heart and kidneys are vital organs that influence each other's function. Dysfunction in one inevitably leads to dysfunction in the other and is known as cardiorenal syndrome (CRS). CRS type 4 is defined by chronic kidney disease (CKD) causing impaired cardiac function, primarily through diastolic dysfunction and structural remodelling, including fibrosis and hypertrophy. This is accompanied by metabolic alterations, characterized by disrupted energy substrate utilization and a metabolic shift towards glycolysis instead of beta-oxidation. The progression of CRS IV occurs dynamically and gradually thus identifying key changes could prove beneficial for treatment and prediction of outcome for the patients. The present study assessed heart remodelling and function after 12 and 24 weeks of chronic kidney disease in rats undergoing subtotal nephrectomy (respectively SNx12 and SNx24).
Method
At 12 weeks, male Sprague Dawley rats underwent 5/6 nephrectomy (SNx) or Sham operation and were sacrificed after 12 or 24 weeks. Serum creatinine was measured with the epoc® Blood Analysis System. Before sacrifice, a carotid artery catheter was inserted to measure systolic arterial pressure (SAP). Left ventricular function was assessed by echocardiography (VisualSonics/Fujifilm) under isoflurane anaesthesia. Fibrosis (Sirius Red staining) in both kidney and heart, and cardiomyocyte size (H&E staining) were quantified. Vevolab 3.1.0 software was used to evaluate left ventricle posterior wall thickness during systole (LVPW_S), diastolic dysfunction by measurement of isovolumic relaxation time (IVRT), early diastolic strain rate (E/SRE) and Doppler mitral inflow velocities of the peak early (E) ‘/ Tissue doppler parameter e′ (E/e’). To further assess molecular alterations in the left ventricle, proteomics analysis was performed using LC-MS/MS method (n = 5 animals from each of Sham and SNx groups). Samples were prepared according to FASP protocol. Gene Set Variation Analysis (GSVA) was conducted using pathway terms from the Molecular Signatures Database and results were analysed using the limma method. Statistical analysis and GSVA was performed using GraphPad Prism 8 and R Studio, two-way ANOVA, non-parametric tests, with log transformation when applicable.
Results
Plasma creatinine levels were increased in both SNx12 and SNx24 animals (Table 1). Fibrosis in the kidney increased between SNx12 and SNx24 versus their corresponding Sham (Table 1). SNx24 rats exhibited increased heart fibrosis, cardiomyocyte size, and SAP in comparison to the respective Sham (Table 1). Cardiac remodelling between SNx12 and SNx24 was observed through the increase in the left ventricle wall thickness (Fig. 1A). In SNx24 diastolic dysfunction was observed through measurement of E/SRE, IVRT and E/e’ (Fig. 1B, Table 1). To better understand the molecular changes that correspond to pronounced hypertrophy and diastolic dysfunction, LC-MS/MS analysis was performed with a focus on the group SNx24. A heatmap was generated to illustrate top 20 up- and top 20 down-regulated proteins of SNx24 versus Sham 24 (Fig. 1C). When compared to Sham24, GSVA results indicated that SNX24 samples were associated with disrupted mitochondrial processes, downregulation of fatty acid oxidation, but also with overactivation of extracellular pathways including infiltration of immune cells, wound healing and cell-ECM interactions (Fig. 1D).
Conclusion
These results indicate that the SNx model captures key events in CRS development, cardiac remodelling and dysfunction, and suggest that the observed mitochondrial changes play a supportive role in these processes. This preclinical model also provides an opportunity to evaluate novel anti-fibrotic treatments and assess their impact on mitochondrial function, paving the way for potential therapeutic advancements.