Correlation between valvular interstitial cell morphology and phenotypes: A novel way to detect activation

Area of Science:

• Cardiovascular Biology
• Cellular Mechanobiology
• Tissue Engineering

Background:

• Valvular interstitial cells (VICs) are the primary cell type in heart valves, existing in quiescent fibroblastic and activated myofibroblastic states.
• VIC activation is observed during development, in diseased valves, and in vitro, often influenced by substrate stiffness and cell passage number.
• Understanding VIC activation is crucial for in vitro research and developing effective tissue-engineered heart valves.

Purpose of the Study:

• To characterize valvular interstitial cell (VIC) quiescence and activation across a range of substrate stiffness (1-21 kPa) and passage numbers.
• To develop and validate a cell morphology characterization system for identifying VIC activation states.
• To investigate the potential of using morphology as a non-destructive method for detecting VIC activation and inducing deactivation.

Main Methods:

• Valvular interstitial cells (VICs) were cultured on substrates with varying stiffness (1-21 kPa) and passage numbers.
• Cell morphologies were systematically categorized into four main types: tailed, spindle, rhomboid, and triangle.
• VIC activation was validated using markers such as α-smooth muscle actin (α-SMA), non-muscle myosin heavy chain B (SMemb), and transforming growth factor β (TGF-β).

Main Results:

• A distinct correlation was observed between substrate stiffness, passage number, and the distribution of VIC morphologies.
• The developed morphology characterization system accurately reflected VIC activation states, validated by established activation markers.
• Stiffness-induced deactivation of VICs was demonstrated, indicating the reversibility of the activation process.

Conclusions:

• VICs exhibit distinct morphologies corresponding to their activation states, which are influenced by substrate stiffness and passage number.
• A morphology-based system offers a potential non-destructive method for assessing VIC activation in vitro.
• The reversibility of VIC activation has significant implications for optimizing cell behavior in tissue engineering and in vitro studies.