Flow-dependent re-endothelialization of tissue-engineered heart valves

Area of Science:

• Biomaterials Science
• Cardiovascular Engineering
• Tissue Engineering

Background:

• Heart valve tissue engineering aims to create functional, non-immunogenic constructs using autologous cells on decellularized extracellular matrix.
• Achieving a stable endothelial cell (EC) layer under physiological flow is crucial for construct success.

Purpose of the Study:

• To determine optimal culturing conditions for a stable EC layer on decellularized ovine pulmonary valves (PVs) under physiological flow.
• To investigate the impact of different flow rates and pulsation patterns on EC proliferation and viability.

Main Methods:

• Detergent-decellularized ovine PVs were reseeded with ovine venous ECs in bioreactors.
• Dynamic culture involved two groups: one with slow, incremental flow increase (0.1 L/min increments, max 0.5 L/min, 20 bpm) and another with rapid increase (0.7 L/min/day, max 2.0 L/min, 50 bpm).
• Valves were analyzed morphologically and for metabolic activity post-culture.

Main Results:

• Moderate pulsatile flow led to complete EC monolayer confluence on PV surfaces.
• High flow rates resulted in partial cell loss and complete cell detachment from cusps.
• Metabolic activity was significantly higher in valves cultured under moderate flow compared to high-flow or static conditions.

Conclusions:

• Gradual, moderate pulsatile flow promotes EC proliferation and stability on decellularized valve scaffolds.
• Abrupt increases to high flow cause significant endothelial damage and cell loss, potentially explaining in-vivo failures of static tissue-engineered valves.
• Optimized flow conditions are essential for developing functional tissue-engineered heart valves.