Editors' ChoiceTissue Engineering

Heart Valve Job

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Science Translational Medicine  11 Nov 2009:
Vol. 1, Issue 6, pp. 6ec20
DOI: 10.1126/scitranslmed.3000559

The heart is an efficient pump, but when its valves are leaky or too stiff it tries to beat harder and causes shortness of breath, weakness, or palpitations. Diseased valves can develop with age or result from bacterial colonization. They are often replaced with artificial substitutes, which last a long time, but require the patient to be on blood thinners to prevent blood from clotting on the valve surfaces. Replacement valves from animals or humans don’t encourage blood clots but they do wear out. Tissue engineers and cardiovascular scientists have now teamed up to make a more natural tissue-based valve that may be able to renew itself and last longer. After removing associated cells, the investigators impregnated bovine pericardium—the fibrous membrane that surrounds the heart—with proteins that participate in embryogenesis and encourage stem cell and progenitor engraftment. With two of these proteins (stromal-derived cell factor-1α and fibronectin) incorporated into the porous mesh of the bovine tissue, the authors fabricated a replacement heart valve and implanted it into sheep. Cells recruited from the sheep’s circulation took up residence in the implant and produced new extracellular matrix and endothelium. Cell numbers were similar to those of normal valves. Unlike previous valves made by this group, there were few contractile cells in the reconstituted tissue, which can distort and impair the implanted valve, and the immune reaction was minimal. These recellularized, implanted valves functioned well for 5 months in the sheep. Because heart valves made with biological materials that are coated with cell-attracting proteins can potentially continue to recruit cells from the circulation, they may be able to survive and function longer than their uncoated predecessors.

G. De Visscher et al., The remodeling of cardiovascular bioprostheses under influence of stem cell homing signal pathways. Biomaterials 22 September 2009 (10.1016/j.biomaterials.2009.09.016) [Abstract]

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