Mechanical loading reveals cell type-specific responses and role of PHGDH in endothelial cell growth
Skeletal muscles and blood vessels are continuously exposed to mechanical forces, particularly during exercise. We subjected human endothelial and skeletal muscle cells to cyclic mechanical stretch to mimic exercise and investigated acute molecular responses. Mechanical loading elicited both shared and cell type-specific alterations in transcriptomic and metabolomic profiles, several of which mirrored changes observed in vivo following exercise. Both cell types released acetate in response to mechanical loading, at least partly via reactive oxygen species -dependent mechanism. Interestingly, transcriptomic changes occurred in opposite directions in endothelial and muscle cells. For example, genes associated with the electron transport chain were repressed in endothelial cells but upregulated in skeletal muscle cells. In endothelial cells mechanical loading remodelled intercellular junctions, promoted a transcriptomic shift indicative of increased barrier integrity and attenuated proliferation. Metabolic changes were more pronounced in endothelial cells, which exhibited increased serine biosynthesis from glucose, as demonstrated by 13C-(U)-glucose tracing. Targeting phosphoglycerate dehydrogenase (PHGDH), a key enzyme in the serine synthesis pathway, underscored the role of serine biosynthesis in endothelial cell anabolism. These findings suggest that mechanical loading recapitulates several exercise-induced effects in endothelial and muscle cells, and highlights a potential link between mechanical stimuli, serine synthesis, and endothelial cell quiescence.