PhD Student University of Houston Houston, Texas, United States
Introduction: Air pollution, an ever-increasing challenge in the developing world, poses a threat to individual and societal health due to deposition of particulate matter (PM) from industrial processes, smoke, and general pollution that, when inhaled, can permeate into the bloodstream and travel to the heart. PM has been identified as an independent risk factor for cardiovascular morbidities and mortalities, including an increased risk for cardiac fibrosis, myocardial infarction, and atherosclerosis1. Currently, there are limited tools that adequately mimic features of the heart and for disease studies. There remains a gap in knowledge surrounding pollution mediated mechanisms and pathways that contribute to cardiomyopathies. We seek to develop an in vitro model to investigate the role of air pollution in cardiovascular diseases. We will test specific genetic modifications and microenvironmental cues that trigger heart disease. We assert that this model can be used to improve our current understanding of the pollution-driven mechanisms associated with heart disease. Further the chip can be used as a testbed for drug candidates which can lead to improved clinical outlook.
Materials and
Methods: Cell culture: C57BL/6 neonatal mouse cardiomyocytes, endothelial cells, and fibroblasts will be seeded onto a mechanically tunable gelatin hydrogel creating 2D engineered microtissues. Cells will be exposed to varying levels of particulate matter for 1 week and then processed for PCR, mechanical analysis, and morphological assays. Gene studies: We will test whether the pollutants microenvironment induces gene expression profiles characteristic of pathological hypertrophy and heart failure in our in vitro system. Morphological studies: We will measure cell size and sarcomere orientation to assess whether particulate matter exposure induces structural remodeling in our system. Cells will be stained for Connexin 43, vimentin, desmin, and VE-Cadherin. Functional studies: We will use the muscular thin film assay to measure the effects of particulate matter in the engineered cardiac tissues. Film contraction will be captured on video and custom ImageJ and MatLab algorithms will be used to calculate stress generation. Stress generation between treated and control tissues will be compared. Mechanical assessment: Mechanical testing was conducted on hydrogels and cells using the Piuma Nanoindenter. Tissue will be probed with the nanoindenter to assess changes in the Young's modulus of treated engineered microtissues.
Results, Conclusions, and Discussions: Gene expression studies suggest that PM exposure leads to a proinflammatory and profibrotic gene expression profile with an upregulation in connective tissue growth factor and transforming growth factor beta (TGFβ). Our preliminary data show that PM exposure leads to an increase in ROS level in fibroblasts and cardiomyocytes. Elevated reactive oxygen species (ROS) levels are a feature of cardiovascular disease. Additionally, nanoindentation analysis suggests that PM exposure leads to an increase in the tissue modulus which can be indicative of fibrosis. Our preliminary data suggest that our model adequately captures features of mechanical and particulate matter induced cardiac remodeling. This heart-on-chip model is a suitable platform for investigating environmental factors on heart health.
Acknowledgements (Optional): This work was supported by the John S. Dunn Foundation and the Oak Ridge Associated Universities Ralph Powe Award.
