Primary murine cardiac endothelial cells exhibit Lcn2 up-regulation under uremic conditions.

Cardiovascular diseases, including uremic cardiomyopathy, remain the leading cause of mortality in patients with chronic kidney disease (CKD). Myocardial capillary rarefaction and microvascular dysfunction were proposed as potential mechanisms of uremic cardiomyopathy, but the understanding was hampered by the lack of in vitro models and primary myocardial endothelial cells (ECs). Methods & Results: We developed an in vitro model for studying uremic endothelial dysfunction using primary murine cardiac endothelial cells (pmCECs). We describe the isolation and culture protocol for pmCECs in parallel to the isolation of primary cardiomyocytes . We validated the cell lineage of pmCECs using flow cytometry (CD146⁺, CD31⁺) and isolating cells from transgenic mice with EC-specific reporter (Cdh5-Cre::tdTomato). pmCEC exhibited similar endothelial responses as Human umbilical vein endothelial cells (HUVECs) to hypoxia, including Hif1-α upregulation and enhanced angiogenesis. Exposure to hemodialysate from CKD patients significantly impaired pmCEC proliferation and angiogenic capacity. Bulk RNA sequencing revealed enrichment of oxidative stress pathways, including the up-regulation of lipocalin-2, a key component of these pathways. Increased lipocalin-2 expression in myocardial ECs was confirmed in vivo in Col4a3⁻/⁻ mice, a model of progressive CKD. In the Alport mice, lipocalin-2 correlated with diastolic dysfunction, reduced ejection fraction, and increased cardiac injury markers (pro-ANP, BNP). Conclusion: Primary murine cardiac ECs represent a useful in vitro model, facilitating studies of uremic cardiomyopathy and identification of potential molecular mediators, such as endothelial-derived lipocalin-2.