Hydrodynamic Evaluation of a Bioreactor for Tissue Engineering Heart Valves

The principal objective was to develop an autoclavable pulsatile bioreactor capable of subjecting disc-shaped or trileaflet valve tissue constructs to prescribed, reproducible hydrodynamic profiles. The pump actuator consisted of: a computer-controlled stepper motor and a lead-screw attached to the piston of a water filled cylinder which was connected to the outer chamber of a pulsatile sac ventricular assist device with tilting disc valves. Reciprocation of the piston caused circulation of tissue culture medium in a bioreactor comprising a vented low-pressure reservoir and a sealed windkessel (air spring) and flow resistor to simulate arterial compliance and systemic vascular resistance, respectively. Disc-shaped tissue constructs could be interposed between the windkessel and the reservoir to allow them to be subjected to controllable pressure waveforms. Alternatively, the outflow valve of the pulsatile pump could be replaced with a valve-like tissue construct. Evaluation of the hydrodynamic capabilities of the system showed that for both the disc-shaped and the valve constructs a wide range of stable hydrodynamic profiles could be specified and attained, free of pressure transients and valve closure-associated pressure oscillations. Pressure rise within the windkessel was primarily determined by pump driving parameters whereas the time constant of the decay of pressure was determined by the product of windkessel compliance (C) and outflow resistance (R) of the windkessel. In conclusion, the novel bioreactor has a number of characteristics which may be valuable for the development of tissue engineered heart valves. © 2010 Biomedical Engineering Society.