Cardiovascular Tissue Engineering: A New Laminar Flow Chamber for In Vitro Improvement of Mechanical Tissue Properties

Abstract

A new in vitro flow system was developed to investigate the impact of laminar flow on extracellular matrix formation and tissue development. The dynamic in vitro system was designed to provide a cross flow arrangement of main flow induced by a dialysis roller pump (500 ml/min), and nutrition flow by a perfusion pump (3 ml/hr). Poly-L-lysine precoated polyglycolic acid (PGA) scaffolds (3.14 cm2) were seeded with myofibroblasts of human aortic origin (3.0 x 10(6) cells/ mesh) and incubated for 14 days under static conditions. The tissue was exposed to shear stress over a time period of 14 days (n = 4). The control group was seeded under static conditions (n = 4). To obtain a CO2 independent medium, 25 mM HEPES and 1 mM bicarbonate buffer was supplemented to modified MEM without bicarbonate. Gas samples were collected from the medium, and hydroxyproline assay was performed as a marker of collagen production. The newly developed flow system maintained stable cell culture conditions, with the hydroxyproline concentration significantly higher in group F (p< 0.05). These preliminary experiences with a new in vitro tissue culture system demonstrate the feasibility of using flow induced mechanical stress to enhance extracellular matrix formation.

In Vitro Comparison of Novel Polyurethane Aortic Valves and Homografts After Seeding and Conditioning

“…33 To provoke the establishment of an ECM by the seeded cells of a tissue engineering construct, an appropriate stimulus is necessary. in cardiovascular tissue engineering, Jockenhoevel et al 34 and other research groups showed that flow-depending mechanical stress induces ECM formation. 35 in line with these results, the establishment of an ECM and the habituation of the cells were observed during the 5-day conditioning periods, demonstrated by positive staining against collagen iV and fibronectin.…”

A Novel Flex-Stretch-Flow Bioreactor for the Study of Engineered Heart Valve Tissue Mechanobiology

“…The pleiotropic actions of mechanical stimulation can both accelerate the de novo synthesis of collagen, 6,13,16 as well as guide its structural organization. 3,4 For example, while DNA and collagen concentrations can approach native-like values over 4 weeks static culture with basic fibroblast growth factor (bFGF), 9 it is only with 3-4 weeks mechanical stimulation that layer stratification begins, 6,11 and not until several months in vivo that a trilayered morphology reminiscent of a native semilunar valve develops.…”

“…However, to systematically quantify how individual modes of mechanical stimulation contribute to the tissue formation and maturation process for specific cell/ scaffold combinations, a different bioreactor approach involving multiple specimens and decoupled stimuli is necessary. Toward this goal, we and others have designed bioreactors for investigating the independent effects of cyclic flexure, 5,6 tension, 16 and flow (i.e., fluid shear stress) 13 on TEHV tissue formation in vitro.…”

Autologous Human Tissue-Engineered Heart Valves

“…7 Also, flow was reported to be beneficial for tissue formation. 6 The effect of conditioning found in this study most likely represents a combination of the effects of flexure and tension as flow was kept to a minimum. Tissue distribution was more homogeneous when using conditioning, potentially caused by enhanced nutrient supply and removal of metabolic waste products.…”