Biomimetic Approach to Cardiac Tissue Engineering: Oxygen Carriers and Channeled Scaffolds

Abstract

We report that the functional assembly of engineered cardiac muscle can be enhanced by oxygen supply provided by mechanisms resembling those in normal vascularized tissues. To mimic the capillary network, cardiomyocytes and fibroblasts isolated from the neonatal rat hearts were cultured on a highly porous elastomer with a parallel array of channels that were perfused with culture medium. To mimic oxygen supply by hemoglobin, culture medium was supplemented with a perfluorocarbon (PFC) emulsion; constructs perfused with unsupplemented culture medium served as controls. In PFC-supplemented medium, the decrease in the partial pressure of oxygen in the aqueous phase was only 50% of that in control medium (28 mmHg vs. 45 mmHg between the construct inlet and outlet at a flow rate of 0.1 mL/min). Consistently, constructs cultivated in the presence of PFC contained higher amounts of DNA and cardiac markers (troponin I, connexin-43) and had significantly better contractile properties as compared to control constructs. In both groups, electron microscopy revealed open channels and the presence of cells at the channel surfaces as well as within constructs. Improved properties of cardiac constructs could be correlated with the enhanced supply of oxygen to the cells, by a combined use of channeled scaffolds and PFC.

Endothelial cells guided by immobilized gradients of vascular endothelial growth factor on porous collagen scaffolds

“…In addition, this system has also been used to achieve a more uniform cell-seeding density within the construct [33]. Further enhancement in the oxygen delivery was achieved by supplementing the culture medium with an oxygen carrier [34,35]. Both the perfusion and the oxygen carrier improved the viability and enabled the formation of compact layers of viable cells around the channels.…”

Cardiac tissue engineering using perfusion bioreactor systems

“…1f)and perfused with culture medium 15 . To mimic oxygen supply by hemoglobin, culture medium was supplemented by 5.4% vol/vol perfluorocarbon (PFC) emulsion (Oxygent, kindly donated by Alliance Pharmaceuticals), constructs perfused with unsupplemented culture medium served as controls.…”

“…PFC droplets were assumed to be small with uniform oxygen concentration (C p ) near equilibrium with the oxygen concentration in the aqueous phase (C a ), such that the total oxygen concentration in the emulsion, C tot , is: (14) where ø is the fraction of PFC droplets. If the partition coefficient is defined as K = C p /C a , then equation (14) can be expressed as: (15) The governing equation for oxygen transfer in the channel lumen of the constructs perfused with PFC-supplemented medium is then: (16) where D eff is the effective diffusion coefficient of oxygen in the culture medium supplemented with PFC.…”

“…1, panels a-c). To overcome oxygen diffusional limitations during tissue culture, we employed perfusion bioreactors with interstitial medium flow (using porous collagen sponge scaffolds 14 ) or flow through the channel array (using channeled poly(glycerol sebacate) (PGS) scaffolds 15 ). We provide here a complete protocol for the assembly and operation of the perfusion system for engineering thick and compact cardiac tissue constructs.…”

Hydrogels for cardiac tissue engineering

“…56,57 For example, fluorinated compounds 58 or peroxides have been incorporated into scaffolds to enable the controlled release of oxygen. 51,59 Such 3D biomimetic materials can be fabricated in the form of thin polymer films, 60 electrospun fibers, 61 porous scaffolds 62 and hydrogels. 63,64 The use of oxygen-releasing materials is particularly useful for providing sufficient amount of oxygen, especially during the early stages of in vitro cultures and in vivo implants.…”