Cardiac lymphatic vessel (LyV) remodeling as a contributor to heart failure has not been extensively evaluated in metabolic syndrome (MetS). Our studies have shown structural changes in cardiac LyV in MetS that contribute to the development of edema and lead to myocardial fibrosis. Tissue macrophages may affect LyV via secretion of various substances, including noncoding RNAs. The aim of the study was to evaluate the influence of macrophages modified by miR-31-5p, a molecule that regulates fibrosis and lymphangiogenesis, on lymphatic endothelial cells (LECs) in vitro. The experiments were carried out on the RAW 264.7 macrophage cell line and primary dermal lymphatic endothelial cells. RAW 264.7 macrophages were transfected with miR-31-5p and supernatant from this culture was used for LEC stimulation. mRNA expression levels for genes associated with lymphangiogenesis and fibrosis were measured with qRT-PCR. Selected results were confirmed with ELISA or Western blotting. miR-31-5p-modified RAW 264.7 macrophages secreted increased amounts of VEGF-C and TGF-β and a decreased amount of IGF-1. The supernatant from miR-31-5p-modified RAW 264.7 downregulated the mRNA expression for genes regulating endothelial-to-mesenchymal transition (EndoMT) and fibrosis in LECs. Our results suggest that macrophages under the influence of miR-31-5p show the potential to inhibit LEC-dependent fibrosis. However, more studies are needed to confirm this effect in vivo.

Cardiac lymphatic vessels (LyVs) are suggested to be important players in cardiovascular disease-associated myocardial remodeling. However, there is a gap in the knowledge of whether LyV remodeling is an integral component of cardiac remodeling, especially in obesity associated with other comorbidities, including increased levels of circulating angiotensin II (Ang II). We studied the structural alterations in the myocardium and LyVs in Ang II-treated db/db mice compared with db/db mice and Ang II-treated wild-type mice with histopathological imaging methods, confocal microscopy, ultrastructural morphology, and morphometric analysis. We demonstrated that Ang II-treated db/db mice exhibited significantly increased fibrosis, cardiomyocyte hypertrophy, and local edema compared with untreated db/db mice; however, the cardiomyocyte hypertrophy was similar to that in Ang II-treated control mice. The decreased density of the LyVs and their wall shape alterations, with disorganized anchoring filaments, widened junctional gaps, decreased numbers of cytoplasmic vesicles indicative of a leaky phenotype, and increased basement membrane (BM) thickness, were observed in Ang II-treated db/db mice compared with Ang II-treated controls. Our findings revealed a structural basis for intensive LyV remodeling in association with cardiac remodeling in obesity.

Background/Objectives: Metabolic syndrome (MetS) conditions lead to structural and functional alterations in cardiomyocytes, microvasculature, and extracellular matrix (ECM), leading to myocardial fibrosis and impaired diastolic function. Cardiac lymphatic vessels (LVs) are increasingly recognized as key regulators of myocardial homeostasis, yet their response to MetS remains poorly understood. Therefore, we aimed to investigate transcriptional changes in cardiac lymphatic endothelial cells (LECs) in db/db mice, a well-established model of MetS. Methods: Using flow cytometry-sorted LECs and RT-PCR, we analyzed mRNA expression of genes involved in lymphangiogenesis, metabolism, mechanotransduction, immune cell trafficking, and ECM interactions. Results: Our findings show the transcriptional plasticity of cardiac LECs in response to MetS. Conclusions: Although our study is limited by the lack of protein-level validation and functional assays, our approach provides a broader interpretative framework and identifies potential directions for future research, including functional studies and pathway-specific investigations of the identified genes to assess their impact on lymphatic flow and cardiac function. Understanding LEC responses to metabolic stress may uncover novel therapeutic targets for heart failure associated with MetS.