Hydrodynamic Evaluation of a Bioreactor for Tissue Engineering Heart Valves

Abstract

The principal objective was to develop an autoclavable pulsatile bioreactor capable of subjecting discshaped 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.

Assessment of Parylene C Thin Films for Heart Valve Tissue Engineering

“…The VAD was attached to a stepper motor (Placepower UK Ltd). 18 Once assembled, the bioreactor was moved into an incubator at 37°C and 5% CO 2 attached to the VAD. Pressure gradient between the windkessel and the reservoir was set at 0-50 mmHg with the stepper motor set at 60 beats/min.…”

Cardiovascular Modeling

“…One major use of mock loops is to study cardiac assist devices, such as axial flow pumps (Camus et al 2007;Nakatani et al 1994), centrifugal pumps (Jahanmir et al 2009;Takami 2006) and counterpulsators (Bowles et al 1991;Kolyva et al 2010;Papaioannou et al 2004). They are also useful to study heart valves (Scharfscherdt et al 2009) in the aortic (Kuehnel et al 2005), mitral (Jimenez et al 2005) and pulmonary (Gohean et al 2006) positions, as well as being used as ''bioreactors'' for bioengineering tissue valves (Bowles et al 2010;Dumont et al 2002). Finally, mock loops are an extremely effective teaching tool (Pantalos et al 2010;Zannoli et al 2009).…”