Mechanosensitive Responses of Human Cardiac Fibroblasts within Engineered Connective Tissue: Implications for Cell Activation and Fibrosis Propagation

Cardiac fibrosis arises when quiescent cardiac fibroblasts (CF) transdifferentiate into myofibroblasts due to cardiac stress. Whether changes in the mechanical environment, as occurs in scarring, are as important as biochemical signals, or even a key factor in the propagation of fibrosis in the diseased heart is currently unknown. Furthermore, the lack of appropriate models for studying different cellular states and mechanisms hinder the identification and development of new anti-fibrotic drugs.

Developing a dual-engineered connective tissue (ECT) model to explore how mold geometry and stiffness affect human CF phenotype. Intended for mechanistic studies, disease modeling, and anti-fibrotic drug screening.

We examined human CFs’ mechanical response using ECT models with two flexible poles (low-stress) or one central rod (high-stress) cultured for 5 days, mimicking healthy and fibrotic myocardium respectively. High-stress ECT displayed scar-like features, with lower strain resistance and heart failure-resembling ECM gene signature. Low-stress models showed increasing tissue stiffness, but plateaued at lower levels than high-stress ECT, even with TGF-β1. Regardless of pole stiffness, TGF-β1 doubled ECT contraction. Ischemic cardiomyopathy (ICM) and non-ICM patient cell cultures revealed critical relationships between cell/tissue characteristics and biomechanical parameters. Prolonged low-stress cultures displayed a second phase of contraction and increased stiffness, indicating that a mechanical homeostasis cannot be reached in the non-uniform model. Elastic (Polyacrylamide) PAA beads showed higher stress in the pole area that correlated with elevated smooth muscle-actin expression compared to the arms’ region. Cell proliferation, as indicated by BrdU staining, was elevated in areas experiencing higher stress. In the pole region, proliferation increased over time, contrasting the steady levels observed in the arms. Notably, at the scar region (arm), cell proliferation reached its peak three days post-cryoinjury.

CF adapt to mechanical conditions, with high-stress areas driving remodelling. Paratensile signalling is a possible mechanism, while TGF-β1 could not replicate high mechanical stress effects, emphasizing mechanical environment's dominance. The ECT model helps discern CF phenotypes in healthy and diseased hearts, thereby supporting the identification of anti-fibrotic drugs.
(DGK-Stipendiaten Sitzung.)