Decellularization
does not Eliminate Thrombogenicity and Inflammatory Stimulation in Tissue-Engineered
Porcine Heart Valves
Marie-Theres Kasimir1, Erwin Rieder2,
Gernot Seebacher1, Anneliese Nigisch1, Barbara Dekan1, Ernst Wolner1,
Guenter Weigel1, Paul Simon1
Departments of 1Cardiothoracic Surgery
and 2Surgery, Medical University of Vienna, Vienna, Austria |
Background and aim of the study: In tissue engineering
of heart valves using decellularized xenogenic valves, it has been suggested
that cell elimination would result in a biologically inert matrix. The
aim of this in-vitro investigation was to evaluate different decellularization
methods in regard to the completeness of cell removal, inflammatory response,
and thrombocyte activation.
Methods: Decellularized porcine Synergraft® valves were compared with
porcine pulmonary conduits decellularized with Triton X-100, sodium deoxycholate,
Igepal CA-630® and ribonuclease. Completeness of decellularization
was evaluated with staining for nuclei and a-Gal epitope. Decellularized
heart valves with and without seeding with endothelial cells (ECs) were
incubated with human platelet-rich plasma and stained for CD41 and PAC-1
to evaluate thrombocyte activation. Samples were processed for laser scanning
microscopy (LSM) and scanning electron microscopy (SEM). Migration of human
monocytic cells towards extracted valve proteins was tested.
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Results: In contrast to the Synergraft, complete cell
removal and elimination of the a-gal epitope was achieved with the new
decellularization method. Numerous adherent and activated platelets were
found on the decellularized matrix. This was inhibited by seeding with
ECs. Even in completely cell-free valve tissue extracellular matrix proteins
attracted human monocytic cells as in early inflammation, depending on
whether porcine or human tissue was used.
Conclusion: Important differences were found in the decellularization efficacy
of treatment methods. However, even complete elimination of cells and their
remnants did not result in a biologically inert matrix. The decellularized
porcine heart valve matrix has the potential to attract inflammatory cells
and to induce platelet activation. These findings suggest that it will
be important to control the different inflammation-stimulating factors
if porcine tissues are to be used successfully in tissue engineering.
The Journal of Heart Valve Disease 2006;15:278-286. |