Summary

An approach in tissue engineering of heart valves is the use ofdecellularized xenogeneic matrices to avoid immune responseafter implantation.The decellularization process must preservethe structural components of the extracellular matrix toprovide a biomechanically stable scaffold. However, it is knownthat in vascular lesions platelet adhesion to extracellular matrixcomponents occurs and platelet activation is induced. In thepresent study we examined the effects of a decellularized porcineheart valve matrix on thrombocyte activation and the influenceof re-endothelialisation in vitro. Porcine pulmonary conduitswere decellularized using Triton X-100, Na-deoxycholateand Igepal CA-630 ® followed by a ribonuclease digestion.Cryostat sections of decellularized heart valves with and withoutseeding with human umbilical vein endothelial cells(HUVEC) were incubated with platelet rich plasma. Samples were either stained with fluorescent antibodies for CD41 andPAC-1 (recognizing the activated fibrinogen receptor) or fixedwith glutaraldehyde.Thereafter, the samples were processed forlaser scanning microscopy (LSM) or scanning electron microscopy(SEM). Examination by LSM showed numerous plateletswith co-localized staining for CD41 and PAC-1 on the nonseededdecellularized heart valve matrix whereas after seedingwith endothelial cells no platelet activation was detected. SEMrevealed platelet adhesion and aggregate formation only on thesurface of the non-seeded or partially denuded matrix specimens.We show in this study that the decellularized porcine matrixacts as a platelet-activating surface. Seeding with endothelialcells effectively abolishes the platelet adhesion and activationand therefore is necessary to eliminate thrombogenicity in tissueengineered heart valves.