Mechanically Induced Collagen Fibre Synthesis

In vitro mechanical conditioning has been demonstrated to be of critical importance in the tissue engineering of cardiovascular substitutes, i.e. vascular grafts and heart valves. Therefore, after static culturing, cell seeded constructs are placed in a bioreactor and subjected to pulsatile loading conditions. The objective is to stimulate cell proliferation and differentiation as well as extra cellular matrix production. In particular for aortic heart valves, the leaflets have to carry substantial hemodynamic loads, in particular during the diastolic phase. Since collagen fibers are known to provide a substantial part of the structural integrity of cardiovascular substitutes, the production of sufficient amounts of appropriately aligned collagen fibers appears mandatory. The production and alignment of collagen fibers is known to be strain sensitive, which suggests that the strain distribution, i.e. deformation modes, inside the leaflets or a graft must be controlled carefully during in vitro conditioning. Furthermore, at implantation the heart valves or vascular grafts may not necessarily have to be morphologically identical to the native heart valves, they, however, should be sufficiently functional.