Abstract Body: Introduction: Micronanoplastics (MNPs) have been detected in carotid artery plaques in humans and are associated with cardiovascular events. Mechanisms by which MNPs influence atherosclerosis remain obscure. Vascular smooth muscle cells (VSMCs) have been shown to switch from contractile to dedifferentiated phenotype after physiologic insults, thereby inciting atherosclerotic lesions by proliferation and osteogenic behavior. MNPs have been shown to disrupt cellular physiology in endothelial and neuronal cells but their effects on VSMCs specifically remain poorly understood.
Hypothesis: We hypothesize that MNPs contribute to atherosclerotic disease by inducing VSMC dedifferentiation and phenotype switching.
Methods: Primary Human Aortic VSMCs were incubated for 7 days with commercial polystyrene (PS) nanospheres (200 nm) or natural ocean-derived nanoplastics (ODNP, <20 µm) created from ocean plastic garbage by cryomilling and UV-photoaging, yielding a mix of 49% polyethylene, 37% polypropylene, 8% polyurethane and 6% other polymers. Vehicle-exposed cells serve as control. Confocal fluorescent microscopy evaluated nanoparticle entry into cells. Relative expression of contractile markers ACTA2 and SM22α as well as dedifferentiation markers OPN and PCNA were measured by RT-qPCR and normalized to GAPDH.
Results: Cell viability, morphology and confluence did not differ between groups. Both PS and ODNP groups observed nanoparticle entry into cells by confocal microscopy. Total RNA extracted from cells and quantified using Qubit fluorometer showed RNA concentrations ranging from 291 ng/μL to 508 ng/μL. Relative expression of contractile markers ACTA2 and SM22α were modestly downregulated in the PS-exposed cells (0.91 and 0.83-fold) and ODNP-exposed cells (0.82-fold and 0.80-fold) compared to control. Relative expression of dedifferentiation markers OPN and PCNA in the PS-exposed cells were 0.91-fold and 0.98-fold, respectively. In ODNP-exposed cells, OPN and PCNA were 0.95 and 1.15-fold changed from control, respectively.
Conclusion: These results suggest that both polystyrene and mixed-polymer MNPs may play a role in VSMC dedifferentiation, suggesting modest downregulation of contractile markers but without change in dedifferentiation markers tested. Future studies will investigate whether dedifferentiation occurs at other timepoints and if other common markers of phenotype switching are changed in cells incubated with MNPs.