Summary
An approach in tissue engineering of heart valves is the use of decellularized xenogeneic
matrices to avoid immune response after implantation. The decellularization process
must preserve the structural components of the extracellular matrix to provide a biomechanically
stable scaffold. However, it is known that in vascular lesions platelet adhesion to
extracellular matrix components occurs and platelet activation is induced. In the
present study we examined the effects of a decellularized porcine heart valve matrix
on thrombocyte activation and the influence of re-endothelialisation in vitro. Porcine
pulmonary conduits were decellularized using Triton X-100, Na-deoxycholate and Igepal
CA-630® followed by a ribonuclease digestion. Cryostat sections of decellularized
heart valves with and without seeding with human umbilical vein endothelial cells
(HUVEC) were incubated with platelet rich plasma. Samples were either stained with
fluorescent antibodies for CD41 and PAC-1 (recognizing the activated fibrinogen receptor)
or fixed with glutaraldehyde. Thereafter, the samples were processed for laser scanning
microscopy (LSM) or scanning electron microscopy (SEM). Examination by LSM showed
numerous platelets with co-localized staining for CD41 and PAC-1 on the nonseeded
decellularized heart valve matrix whereas after seeding with endothelial cells no
platelet activation was detected. SEM revealed platelet adhesion and aggregate formation
only on the surface of the non-seeded or partially denuded matrix specimens. We show
in this study that the decellularized porcine matrix acts as a platelet-activating
surface. Seeding with endothelial cells effectively abolishes the platelet adhesion
and activation and therefore is necessary to eliminate thrombogenicity in tissue engineered
heart valves.
Keywords
Biotechnology - tissue engineering - heart valves - decellularized - porcine matrix
- thrombogenicity