The mechanical memory of lung myofibroblasts

Area of Science:

• Cell Biology
• Biophysics
• Pulmonary Medicine

Background:

• Fibroblasts transform into myofibroblasts on stiff substrates mimicking fibrotic tissue.
• Assessing cellular responses to stiffness typically occurs over short durations, limiting understanding of myofibroblast persistence in fibrosis.

Purpose of the Study:

• To investigate the long-term effects of substrate stiffness on lung fibroblast fibrotic behavior.
• To determine if mechanical priming can induce persistent myofibroblast activity.

Main Methods:

• Lung fibroblasts were cultured and passaged on silicone substrates of varying stiffness.
• Fibrotic activity was assessed by measuring myofibroblast proliferation, contractility, alpha-smooth muscle actin expression, extracellular matrix deposition, and active TGF-beta1.
• Cells were mechanically primed on stiff or soft substrates for 3 weeks before returning to soft or stiff conditions.

Main Results:

• Myofibroblast activity increased with substrate stiffness.
• Priming fibroblasts on stiff substrates for 3 weeks resulted in sustained myofibroblast activity even after transfer to soft substrates.
• Primed cells exhibited higher fibrotic activity than continuously cultured soft cells and were comparable to continuously stiff-cultured cells.
• Priming on soft substrates offered partial protection against subsequent activation on stiff substrates.

Conclusions:

• Mechanical cues from the cellular environment can permanently induce fibrotic behavior in lung fibroblasts.
• This 'priming' phenomenon has significant implications for the development and persistence of fibrotic lung diseases, including idiopathic pulmonary fibrosis.