P0693THE MATRIX PROTEIN THROMBOSPONDIN-1 CONTRIBUTES TO THE DEVELOPMENT OF CARDIOVASCULAR PATHOLOGY IN CHRONIC KIDNEY DISEASE
Authors: Rogers Natasha , Julovi Sohel , Ghimire Kedar , Minhas Nikita 
Published: June 2020

Abstract

Background and Aims
Patients with chronic kidney disease (CKD) are at significantly greater risk of cardiovascular disease (CVD), which remains the leading cause of hospitalisation and mortality. Cardiovascular complications are 20-30 times more likely to occur in these patients than progression to end-stage kidney disease. Traditional cardiovascular risk factors are prevalent in patients with CKD, but clinical trials targeting standard cardiovascular risks have failed to improve outcomes in patients with CKD. This has led to the investigation of non-traditional pathways that drive the development of the CVD in CKD. The matrix protein thrombospondin-1 (TSP1), and its receptor CD47, regulates cell responses and we recently identified their role in acute kidney injury. We now investigate this pathway in vascular changes in CKD.

Method
Human plasma TSP1 was collected from n=120 patients attending outpatient clinics and measured by ELISA. Age matched male C57BL/6 (WT) and TSP1KO mice (on a C57BL/6 background) were used to develop a model of CKD employing a 5/6 nephrectomy technique (5/6Nx). Blood pressure and weight were checked weekly, and echocardiography analysed cardiac function at baseline. After 12 weeks, we performed echocardiography and biomolecular phenotyping on tissues. Human cardiomyocytes were used to assess the effect of TSP1 and the uremic toxin indoxyl sulfate on cell proliferation and senescence.

Results
Linear regression analysis demonstrate that plasma TSP1 correlated inversely with eGFR (r2=-0.556, p&lt;0.001). WT mice undergoing 5/6Nx developed renal interstitial fibrosis, hypertension, and left ventricular (LV) hypertrophy after 12 weeks. Echocardiography confirmed LV thickness with a concurrent reduction in LV ejection fraction compared to baseline. Histologic examination of WT myocardium revealed interstitial and perivascular fibrosis, and increased myocardial TSP1 expression. These findings were mitigated in TSP1KO mice who had preserved LV function, reduced LV hypertrophy and reduced cardiac fibrosis despite equivalent changes in renal mass and blood pressure. mRNA levels of cardiac-based TNF-α, IL-6, collagen-1, fibronectin and α-smooth muscle actin were increased in WT 5/6Nx mice compared to sham-operated controls, and transcript expression was robustly reduced in TSP1KO mice.
In vitro, the addition of uremic toxin (indoxyl sulfate) to cardiomyocytes robustly upregulated expression of TSP1, and this was dependent upon activation of the aryl hydrocarbon receptor. TSP1 significantly down-regulated cardiomyocte proliferation and increased β-galactosidase activity. Pre-incubation with a blocking antibody reversed the proliferative and senescent effects of indoxyl sulfate and TSP1.

Conclusion
Our findings show that TSP1 is elevated in CKD and may drive the cardiovascular manifestations of uremia. TSP1KO mice were protected from disease, suggestion this protein has a crucial role in the development of CVD. Manipulation of TSP1 signaling is an attractive target to potentially reduce the excessive burden of CVD seen in the CKD population.