Ann Thorac Surg 2006;81:56
© 2006 The Society of Thoracic Surgeons
Original article: Cardiovascular
Invited commentary
Kirsten Schlaudraff, MD
Clinic for Cardiovascular Surgery, University Hospital, Rue du Bugnon 47, Lausanne, CH 1011 Switzerland
(Email: kirsten.schlaudraff{at}gmx.ch).
The fact that none of the heart valve prostheses that are currently available are ideally suited for any clinical situation is well known. Looking for new materials more recently chemically-altered polyurethane (PU) has been used in artificial heart valve design, whereas the new concept of tissue-engineering has enhanced the prospects toward an ideal cardiac valve replacement. PU scaffolds are already used as vascular biomaterials due to their mechanical properties and good hemocompatibility [1]. Several studies with vascular grafts demonstrate that these are encapsulated by the surrounding tissues to form an intima, decreasing the surface thrombogenicity. Lots of research groups have investigated polyurethanes as well for the application in heart valves [2], but reported problems with calcification and thrombosis. So the discussion of the intrinsic property of polyurethane, which may be unfavorable for endothelial cell growth, leads to the necessity of a modification of its property toward improving cytocompatibilty.
Stachelek and associates [3] have already published a newly designed polyurethane heart valve that was constructed by covalent attachment of cholesterol to polyurethane (PU-Chol) and was meant to create a high-affinity surface for the attachment and adhesion of endothelial cells. The present study [4] now evaluates cytological aspects (ie, the possible use of the PU-Chol-heart valve prostheses for pulmonary cusp replacement and their biocompatibility due to the seeding of autologous blood outgrowth endothelial cells [BOECs] in vitro and in sheep). It demonstrates the possibility of seeding BOECs onto PU cholesterol leaflets and shows significantly higher adhesion rates under shear stress conditions on PU-Chol than on PU surfaces. Altogether it was also possible to obtain constant endothelial cell layers on the PU-Chol valve leaflets.
However, some questions and ideas remain. Methodologically we miss some results here of the long-term implants (ie, 150 days and more) and their grade of calcification. In simulating aortic shear stress it would have also been nice to implant some valves in the aortic positions and not only in the pulmonary position in vivo. In addition, there is no explanation why unseeded PU-Chol valves showed less cell adherence after 30-day PU valves, because we know that the PU-Chol heart valves should have a greater affinity for cell membranes and for endothelial cell seeding due to the more lipophilic and hydrophobic surface.
In summary, this is a nice study about PU-Chol as a possible new and cellular seedable material for heart valves. However, further large studies including detailed long-term follow-up and comparisons with seeding of other biological heart valves are required to assess the superiority of one material in comparison with another.
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- Seal BL, Otero TC, Panitch A, Mater. Sci Eng R 2001;34:147.
- Nistal F, Garcia-Martinez V, Arbe E, Fernandez D, Mazzora F, Gallo I. In vivo experimental assessment of polytetrafluoroethylene trileaflet heart valve prosthesis J Thorac Cardiovasc Surg 1990;99:1074-1081.[Abstract]
- Stachelek SJ, Alferiev I, Choi H, et al. Cholesterol-derivatized polyurethanecharacterization and endothelial cell adhesion. J Biomed Mater Res A 2005;72:200-212.[Medline]
- Stachelek SJ, Alferiev I, Connolly JM, et al. Cholesterol-modified polyurethane valve cusps demonstrate blood outgrowth endothelial cell adhesion post-seeding in vitro and in vivo Ann Thorac Surg 2006;81:47-56.[Abstract/Free Full Text]
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