Investigation on the Molecular and Biomechanical Interactions of Pentagalloyl Glucose on Mouse C2C12 Myoblast Cells

Abdominal aortic aneurysms (AAA) are one of the leading causes of death in adults over 65 years of age. AAA is characterized by thinning and weakening of the aortic wall due to its dilation, often exceeding 50% of the abdominal aorta's normal, healthy size. When the wall stretches and subsequently weakens, the extracellular matrix (ECM) also undergoes elastic degradation. Currently, the standard of care for AAA patients involves surgical intervention and there are no proven pharmacological treatment options. Pentagalloyl glucose (PGG) is a naturally occurring elastin-stabilizing polyphenolic compound that has increased antioxidant, anti-cancer, anti-viral, anti-microbial, and anti-inflammatory properties. It has been studied in various applications, including vascular health, with promising results. With its known limitations if administered systemically, the encapsulation of PGG within poly(lactide-co-glycolide) (PLGA) nanoparticles (NPs) would allow for enhanced drug-delivery mechanisms. To this end, the goals of this research were two-fold: (i) to assess the molecular interactions of PGG, directly administrated or encapsulated within PLGA NPs (PLGA(PGG) NPs), in C2C12 mouse myoblast cells; and (ii) to study the biomechanical properties of enzyme-stressed and unstressed C2C12 mouse myoblast cells before and after PGG and PLGA(PGG) NPs treatments. Collagenase and elastase enzyme treatment was administered to mimic a pathway of degenerative effects seen in the pathogenesis of human AAA. PGG and NPs were added to enzyme treated cells in either a suppressive or preventative scenario. Biomolecular interactions were analyzed using a composite of cell viability assays, a reactive oxygen species (ROS) assay, fluorescence confocal microscopy, and an enzyme linked immunosorbent assay (ELISA) for MMP-2 concentration. Biomechanical properties were tested using C2C12 cells subjected to enzyme degradation and PGG either directly administered or encapsulated in NPs, with force-displacement data collected with atomic force microscopy. The results suggested that PGG or PLGA(PGG) NPs caused minor to no cytotoxic effects on the C2C12 cells and they had a restorative effect on the cells if administered after ECM degradation by collagenase and elastase. ROS production was not influenced by the addition of PGG or PLGA(PGG) NPs. A quantitative comparison of Young's Moduli showed a significant increase in the modulus of the PGG and NP treated cells compared to the enzyme treated negative control. We conclude that the addition of PGG or PGG-laden PLGA NPs is not damaging to C2C12 cells and has a restorative effect on the cells' biomechanical properties after enzymatic ECM degradation. This work provides preliminary support for the use of PGG as part of a potential therapeutic treatment for AAA.