Impaired Barrier Integrity of the Skeletal Muscle Vascular Endothelium Drives Progression of Cancer Cachexia

Cancer patients experience cachexia, which is characterized by extensive skeletal muscle wasting that worsens the quality of life and increases mortality. Currently, there are no approved treatments that can effectively counteract cancer cachexia. Vascular endothelial cells (ECs) are essential for maintaining tissue perfusion, nutrient supply, and preventing inappropriate transmigration of immune cells into the tissue. However, little is known about the role of the muscle vasculature in cancer cachexia. We hypothesized that endothelial dysfunction in the skeletal muscle mediates cancer cachexia. Using transgenic pancreatic ductal adenocarcinoma (PDAC) mice and a tissue clearing and high-resolution 3D-tissue imaging approach, we found that the loss of skeletal muscle vascular density precedes the loss of muscle mass. Importantly, we show that cancer cachexia patients exhibit significantly decreased muscle vascular density and severe muscle atrophy when compared to non-cancer patients. Unbiased single cell transcriptomic analyses of the muscle endothelium unveiled a unique EC population present in cachexia muscles. Increased circulating Activin-A suppresses the expression of the transcriptional co-activator PGC1alpha in the muscle endothelium, thus disrupting junctional integrity in the vasculature and increasing vascular leakage. Conversely, restoration of endothelial-specific PGC1alpha prevented the decreased vascular density and muscle loss observed in tumor-bearing mice. Our study suggests that EC-PGC1alpha is essential for maintaining the integrity of the skeletal muscle vascular barrier and that restoring muscle endothelial function could be a valuable therapeutic approach to prevent or reverse cancer cachexia.