UC San Diego

Mechanosensation is the process by which cells sense and remodel to the biophysical properties of their external environments. While the phenomena of converting mechanical stimuli into signals governing behavior and responses is shared across all organisms, the mechanisms governing mechanosensation remain underexplained. As we seek to better understand the factors driving cardiovascular disease, the leading cause of death worldwide, understanding how to model the microenvironment to perturb specific cellular mechanisms is key. This dissertation aims to define how engineering microenvironments can generate more physiological-relevant cell models and reveals how disease-like microenvironments drive pathological remodeling in the presence of disease-associated variants.

In the quest to better model and understand heart disease, much attention has been paid to the differentiation and maturation of human pluripotent stem cells (hPSCs) for therapeutic goals. In chapter one, we examine how physical cues from biomaterials can recapitulate aspects of native environments and drive hPSC-derived cardiomyocyte maturation. We describe the progress in the field of biomaterials, as defined matrices and electrically stimulating niches serve as biophysical stimuli to promote mature and robust cardiomyocyte cell populations.

Modern sequencing technology has enabled the inclusion of large numbers of rare or private variants in cardiac disease panels. Among these, variants in vinculin, a key protein in force-bearing costamere complexes, predispose carriers to stress induced cardiomyopathy. However, lack of functional validation explaining how these variants impact cardiomyocyte remodeling to environmental stressors hinders patient risk stratification and assignation of variant pathogencity. By exposing patient-derived hiPSC-CMs to physiologically relevant microenvironment stiffnesses, we defined the functional defects arising from maladaptive mechanosensitive remodeling. We describe the mechanisms by which VCL haploinsufficiency impairs mechanosensitive responses, hindering force-mediated costamere protein recruitment and resulting in contractile and sarcomere defects. These effects were ameliorated by ligating integrin receptors, showing the deleterious effects of VCL haploinsufficiency under microenvironment stressors is a result of disrupted mechanosensation.

In addition to the discoveries made within these studies, the mechanisms described here have broad applicability for understanding disease mechanisms and potential therapeutic targets. By defining the pathways through which microenvironment sensing can be stimulated or blocked, treatments targeting mechanosensitive pathways may be further investigated.