Invited commentary

Abstract

In their well-written article, the authors [1Ota T. Sawa Y. Iwai S. et al.Fibronectin-hepatocyte growth factor enhances reendothelialization in tissue-engineered heart valve.Ann Thorac Surg. 2005; 80: 1794-1802Abstract Full Text Full Text PDF PubMed Scopus (44) Google Scholar] describe the in-vivo re-endothelialization of decellularized tissue in a dog-model. The re-population of the implanted tissue was improved by introducing fibronectin-hepatocyte growth factor into the scaffold. The lack of endothelialization of foreign surfaces in humans is surely one of the most important issues of all biomaterials with direct blood contact. Whereas several animals, dogs included, still possess the ability to cover various implants with endothelial cells, only a short distance is covered with a kind of neointima in primates, leaving the remaining surface in direct blood contact. Lining these surfaces with autologous endothelial cells would surely improve biocompatibility. It would be the most elegant way to let it be done by the recipient himself after implantation. So far so good, but there are several limitations to the presented work and still a lot of questions to be asked.The dog model is far from being an ideal model for endothelialization, because dogs re-endothelialize various surfaces including polytetrafluoroethylene. Therefore the results achieved in this model are not transferable to humans. Introducing a growth factor obviously improved re-population. Today, several growth factors, including those attracting endothelial progenitor cells are tested in the labs. However, a clinical application would be very difficult and expensive, because the manufacturer of such pre-coated prostheses has to guarantee for the factor, its origin and purity, and its freedom from side effects. The decellularization process also requires further research to define hemodynamic stability, durability, and immunogenicity of these prostheses.The presented article can not answer all these questions; it shows an original way to achieve endothelialization after implantation of biological valve prostheses. This is a completely different approach compared with the more “classical” way of tissue engineering (ie, seeding of different cell types onto a matrix, letting them grow to confluence, and implanting the complete construct). In-vivo re-endothelialization seems to be closer to the physiological ways to repair endothelial defects but its efficacy has to be proven in long-term animal experiments. However, the article shows that the field of tissue engineering still creates new ideas and concepts. In their well-written article, the authors [1Ota T. Sawa Y. Iwai S. et al.Fibronectin-hepatocyte growth factor enhances reendothelialization in tissue-engineered heart valve.Ann Thorac Surg. 2005; 80: 1794-1802Abstract Full Text Full Text PDF PubMed Scopus (44) Google Scholar] describe the in-vivo re-endothelialization of decellularized tissue in a dog-model. The re-population of the implanted tissue was improved by introducing fibronectin-hepatocyte growth factor into the scaffold. The lack of endothelialization of foreign surfaces in humans is surely one of the most important issues of all biomaterials with direct blood contact. Whereas several animals, dogs included, still possess the ability to cover various implants with endothelial cells, only a short distance is covered with a kind of neointima in primates, leaving the remaining surface in direct blood contact. Lining these surfaces with autologous endothelial cells would surely improve biocompatibility. It would be the most elegant way to let it be done by the recipient himself after implantation. So far so good, but there are several limitations to the presented work and still a lot of questions to be asked. The dog model is far from being an ideal model for endothelialization, because dogs re-endothelialize various surfaces including polytetrafluoroethylene. Therefore the results achieved in this model are not transferable to humans. Introducing a growth factor obviously improved re-population. Today, several growth factors, including those attracting endothelial progenitor cells are tested in the labs. However, a clinical application would be very difficult and expensive, because the manufacturer of such pre-coated prostheses has to guarantee for the factor, its origin and purity, and its freedom from side effects. The decellularization process also requires further research to define hemodynamic stability, durability, and immunogenicity of these prostheses. The presented article can not answer all these questions; it shows an original way to achieve endothelialization after implantation of biological valve prostheses. This is a completely different approach compared with the more “classical” way of tissue engineering (ie, seeding of different cell types onto a matrix, letting them grow to confluence, and implanting the complete construct). In-vivo re-endothelialization seems to be closer to the physiological ways to repair endothelial defects but its efficacy has to be proven in long-term animal experiments. However, the article shows that the field of tissue engineering still creates new ideas and concepts.