Redirecting valvular myofibroblasts into dormant fibroblasts through light-mediated reduction in substrate modulus

Area of Science:

• Biomaterials Science
• Cell Biology
• Tissue Engineering

Background:

• Fibroblasts maintain extracellular matrix (ECM) homeostasis and repair.
• Activated myofibroblasts contribute to fibrosis; understanding their deactivation is crucial for normal tissue repair.
• Substrate stiffness influences fibroblast behavior, but dynamic microenvironmental changes are less understood.

Purpose of the Study:

• To investigate the deactivation of valvular myofibroblasts in response to dynamic substrate softening.
• To determine if reducing substrate modulus can reverse the myofibroblast phenotype.
• To explore the reversibility of the quiescent fibroblast state.

Main Methods:

• Utilized a light-responsive hydrogel system to dynamically alter substrate stiffness.
• Reduced substrate Young's modulus from ~32 kPa (diseased) to ~7 kPa (healthy).
• Monitored valvular myofibroblast deactivation, proliferation, and gene expression (α-SMA, CTGF, vimentin).

Main Results:

• Substrate softening led to myofibroblast deactivation, characterized by reduced α-smooth muscle actin (α-SMA) stress fibers and proliferation.
• Myofibroblast gene signatures (α-SMA, CTGF) were significantly downregulated to fibroblast levels within 6 hours.
• Deactivated fibroblasts remained quiescent but could be re-activated by growth factors and TGF-β1 to re-express fibrogenic genes.

Conclusions:

• Lowering substrate modulus effectively downregulates the valvular myofibroblast phenotype, promoting a quiescent fibroblast population.
• Dynamic control of substrate stiffness can redirect cell fate, offering therapeutic potential.
• These findings inform the design of biomaterials with physiologically relevant stiffness for in vitro cell fate manipulation.