Adventitia contribution to vascular contraction: hints provided by tissue-engineered substitutes.

It is well accepted that the adventitia is much more than a simple elastic membrane which surrounds the media. However, the extent of its contribution to vascular physiology, as well as the mechanisms involved, remains to be clearly established and characterised. Investigation into these topics is hampered by a few technical challenges, like the paucity of available healthy human vascular samples and the variability such samples can display. Another challenge is the isolation and preparation of intact adventitia without contaminating cells from the media. For those reasons, although other models have proved useful to address these questions, data from tissue-engineered vascular substitutes can also provide quite valuable answers. Results from such substitutes indicate that a reconstructed adventitial layer can respond to classic vasoactive agents such as endothelin and sodium nitroprusside.