Investigating the cause of cardiovascular dysfunction in chronic kidney disease: capillary rarefaction and inflammation may contribute to detrimental cardiovascular outcomes.

Myocardial ischemia-reperfusion (IR) injury is a major cause of morbidity and mortality in patients with chronic kidney disease (CKD). The most frequently used and representative experimental model is the rat dietary adenine-induced CKD, which leads to CKD-associated CVD. However, the continued intake of adenine is a potential confounding factor. This study investigated cardiovascular dysfunction following brief adenine exposure, CKD development and return to a normal diet. Male Wistar rats received a 0.3% adenine diet for 10 weeks and normal chow for an additional 8 weeks. Kidney function was assessed by urinalysis and histology. Heart function was assessed by echocardiography. Sensitivity to myocardial IR injury was assessed using the isolated perfused rat heart (Langendorff) model. The inflammation profile of rats with CKD was assessed via cytokine ELISA, tissue histology and RNA sequencing. Induction of CKD was confirmed by a significant increase in plasma creatinine and albuminuria. Histology revealed extensive glomerular and tubular damage. Diastolic dysfunction, measured by the reduction of the E/A ratio, was apparent in rats with CKD even following a normal diet. Hearts from rats with CKD had significantly larger infarcts after IR injury. The CKD rats also had statistically higher levels of markers of inflammation including myeloperoxidase, KIM-1 and interleukin-33. RNA sequencing revealed several changes including an increase in inflammatory signaling pathways. In addition, we noted that CKD induced significant cardiac capillary rarefaction. We have established a modified model of adenine-induced CKD, which leads to cardiovascular dysfunction in the absence of adenine. Our observations of capillary rarefaction and inflammation suggest that these may contribute to detrimental cardiovascular outcomes.