Establishment of a in vivo tissue-engineered heart valve model without cardiopulmonary bypass in sheep

Objective:To explore a simple and economical method for establishing an in vivo animal model of tissue-engineered heart valve(TEHV) in sheep. Methods: Nine adult sheep, weighing 20-30 kg, were implanted with decellularized porcine valvular conduits in thoracic descending aorta without cardiopulmonary bypass. The native aortic valves were cut by self-made scissors to induce valve regurgitation. Arterial pressure of the sheep was monitored and recorded during the operation and the function of implanted conduits was evaluated by MRI. The animals were sacrificed 6 months later and pathological changes, thickness of conduit's wall, and lumenal diameter were observed by optical microscopy and scanning electron microscopy. Results: After native aortic valve was split, arterial systolic pressure increased and arterial diastolic pressure decreased. Pulse pressure increased in the proximal part of the implanted valve; the implanted valve pressure gradient was obviously increased during diastolic period. MRI showed that the implanted valve had excellent performance 2 months after operation and echocardiogram showed that the native aortic valve had moderate to severe regurgitation. There was no enlargement, thrombosis, valvular adhension, thickening, stenosis, and regurgitation in the implanted valvular conduits 6 months after operation. The aortic wall thickness and lumenal diameter had no significant change but obvious stiffness and calcification were found. Ultrastructure observation and pathological examination showed that the conduits and the valve leaflets were re-endothelialized with sparse inflammatory infiltration. Conclusion: Implanting decellularized porcine valvular conduits in thoracic descending aorta without cardiopulmonary bypass is a convenient and economical way for establishing an animal model of TEHV.Besides, this method is mini-invasive, more reliable and with high post-operation survival rate. -