No abstract

Whether the adventitia component of blood vessels directly participates in the regulation of vascular tone remains to be demonstrated. We have recently developed a human tissue-engineered blood vessel comprising the three tunicae of a native blood vessel using the self-assembly approach. To investigate the role of the adventitia in the modulation of vascular tone, this tissue-engineering method was used to produce three vascular constructs from cells explanted and proliferated from donor vessel tunicae 1) an adventitia + a media, or only 2) an adventitia, or 3) a media. The vasoconstriction responses of these 3 constructs to endothelin, the most potent vasopressor known up-to-date, as well as to nonselective and selective agonists and antagonists, were compared. The adventitia contracted to endothelin-1, -2, whereas the media and the media+adventitia contracted to all three endothelins. Endothelin-induced contraction of the adventitia was dependent on ET(A) receptors, whereas that of the media and the adventitia+media was ET(A) and ET(B) receptor-dependent. RT-PCR studies corroborated these results. SNP induced a dose-dependent relaxation of the three tissue constructs. We also demonstrated that the endothelin-converting enzyme, responsible for the formation of the active endothelin peptides, was present and functional in the adventitia. In conclusion, this is the first direct demonstration that the adventitia has the capacity to contract and relax in response to vasoactive factors. The present study suggests that the adventitia of a blood vessel could play a greater role than expected in the modulation of blood vessel tone.

We have developed a tissue-engineering approach for the production of a completely biological blood vessel from cultured human cells. In the present study, we took advantage of this tissue-engineering method to demonstrate that it can be used to reproduce the subtle differences in the expression of receptors present on the media of native human blood vessels. Indeed, a small percentage (3 of 18) of native human umbilical cord veins (HUCVs) responded to endothelin, the most powerful vasopressor agent known to date, via both endothelin A (ET(A)) and endothelin B (ET(B)) receptor activation. In contrast, most HUCVs tested responded to ET via ET(A) receptor activation only. Tissue-engineered vascular media (TEVM) were next reconstructed by using vascular smooth muscle cells (VSMCs) isolated and cultured from HUCVs expressing both ET(A) and ET(B) receptors to determine the functional integrity of our TEVM model. The reconstructed TEVM presents an endothelin response similar to that of respective HUCVs from which VSMCs were isolated. Reverse transcriptase polymerase chain reaction on TEVM reconstructed in vitro correlated these vasocontractile profiles by showing the presence of messenger RNA for both ET(A) and ET(B) receptors. Taken together with recently published results on TEVM expressing only ET(A) receptor, these results show that our reconstructed TEVM present a similar ET response profile as the blood vessel from which the VSMCs were isolated and cultured. These findings indicate that subtle differences, such as receptor expression, are preserved in the reconstructed tissue. Therefore, our TEVM offers a valuable human in vitro model with which to study the functionality of human blood vessels, such as their vasoactive response, or to perform pharmacologic studies.

Background-Cardiovascular diseases remain a major cause of death and disability in the Western world. Among the various approaches adopted to counteract the morbidity associated with these diseases, surgical procedures and cardiac and vascular xenotransplantations or allotransplantations are routinely performed. The suitable vascular graft would be as close as possible to the native and healthy vessel composed exclusively of human components provided by the patient and would adapt to the donor's hemodynamics. We have developed such a tissue-engineered human blood vessel reconstructed with human cells. Because endothelin is the most potent vasopressor known to date, we were interested in investigating the functionality of the endothelinergic system in our reconstructed human blood vessel. Methods and Results-Vasoconstriction studies were performed with nonselective and selective agonists and antagonists to demonstrate that ET A receptors were present and functional in tissue-engineered human vascular media constructed with the self-assembly method. Reverse-transcriptase polymerase chain reaction studies demonstrated that mRNA of the ET A but not the ET B receptor was present in these human tissue-engineered blood vessels. Furthermore, we demonstrated that the endothelin-converting enzyme, the main enzyme responsible for the formation of the biologically active endothelin peptides, was present and functional in these same bioengineered vascular media. Key Words: endothelin Ⅲ muscle contraction Ⅲ myocytes, smooth muscle C oronary artery disease is the most common cause of morbidity and mortality in Western countries. 1 Treatment options include drugs, balloon angioplasty, and CABG surgery. Most artery bypass graft surgery involves harvesting of the long saphenous vein or mammary artery. However, in about a third of patients, this surgery proves inadequate or unsuitable. 2 Surgeons have therefore turned to the use of prosthetic materials like polyethylene terephthalate (Dacron), polytetrafluoroethylene, expanded polytetrafluoroethylene, and polyurethane. [2][3][4][5][6][7][8] However, the results obtained with these prosthetic materials prove to be inferior to those obtained with autologous conduits, especially when the blood vessel diameter is Ͻ5 mm. The problems that can arise when these types of materials are used include increased risk of thrombosis and infection, limited durability, lack of compliance both of the graft and around the anastomosis, 9 and failure as a result of restenosis. These problems necessitate further interventions. 10 -12 One approach to the elaboration of a vascular prosthesis would be to construct one that would very closely resemble a natural healthy blood vessel in both composition and characteristics. This prosthesis would be composed of human cells only (devoid of exogenous synthetic material) and would have the capacity to contract and relax in response to vasoactive agents. We have recently developed a tissueengineering approach to produce a completely biological blood vessel from...