Recombinant Activated Protein C (rhAPC) Affects Lipopolysaccharide-Induced Mechanical Compliance Changes and Beat Frequency of mESC-Derived Cardiomyocyte Monolayers

BACKGROUND: Septic cardiomyopathy increases mortality by 70% to 90% and results in mechanical dysfunction of cells. METHODS: Here, we created a LPS-induced in-vitro sepsis model with mouse embryonic stem cell-derived cardiomyocytes (mESC-CM) using the CellDrum technology which simultaneously measures mechanical compliance and beat frequency of mESCs. Visualization of reactive oxygen species (ROS), actin stress fibers, and mRNA quantification of endothelial protein C receptor (EPCR) and protease-activated receptor 1 (PAR1) before/after LPS incubation were used for method validation. Since activated protein C (APC) has cardioprotective effects, samples were treated with human recombinant APC (rhAPC) with/-out LPS predamage to demonstrate the application in therapeutic studies. RESULTS: Twelve hours LPS treatment (5 μg/mL) increased ROS and decreased actin stress fiber density and significantly downregulated EPCR and PAR1 compared to control samples (0.26, 0.39-fold respectively). rhAPC application (5 μg/mL, 12 h) decreased ROS and recovered actin density, EPCR, and PAR1 levels were significantly upregulated compared to LPS predamaged samples (4.79, 3.49-fold respectively). The beat frequencies were significantly decreased after 6- (86%) and 12 h (73%) of LPS application. Mechanical compliance of monolayers significantly increased in a time-dependent manner, up to eight times upon 12-h LPS incubation compared to controls. rhAPC incubation increased the beat frequency by 127% (6h-LPS) and 123% (12h-LPS) and decreased mechanical compliance by 68% (12h-LPS) compared to LPS predamaged samples. CONCLUSION: LPS-induced contraction dysfunction and the reversal effects of rhAPC were successfully assessed by the mechanical properties of mESC-CMs. The CellDrum technology proved a decent tool to simulate sepsis in-vitro.