Biomedical Engineering Reference
In-Depth Information
Fig. 17
Macroscopical appearance of tissue-engineered blood vessel grafts prior to im-
plantation and 1, 3, 6, 12 and 24 weeks after implantation [262] (reprinted by permission
of Elsevier)
tained significantly less elastin. The lack of mature, cross-linked elastic fiber
formation has been identified as a major limitation of current tissue engin-
eering approaches in the high-pressure circulation [262].
Cardiovascular Patches
Patch materials for augmentation of the pulmonary artery or the right ven-
tricular outflow tract necessary in congenital cardiac defect surgeries have
been made of highly porous P4HB films. In contrast to nonseeded P3HB-
based cardiovascular patches (see Sect. 3.4), P4HB patches were seeded with
autologous vascular cells prior to implantation into the pulmonary artery
in sheep. Postoperative echocardiography of the seeded patches demon-
strated a smooth surface without dilatation or stenosis. Histologically, for-
mation of organized and functional tissue could be demonstrated 24 weeks
after implantation. Despite an ingrowth of tissue from the surrounding na-
tive pulmonary artery onto the unseeded control patch, it showed a slight
bulging, potentially indicating a beginning dilatation, after 20 weeks [42]. No
aneurysm formation was reported from a similar study using unseeded P3HB
patches [145]. Thus, to prevent aneurysm formation, cellular preseeding of
biodegradable patches might be necessary, depending on the degradation
time of the scaffold and the ability to provide mechanical strength for a suffi-
cient period of time [42].
Tubular scaffolds made from PGA/P4HB composites have also been con-
sidered as vascular conduits to repair congenital cardiac defects such as
surgical reconstruction of the right ventricle to pulmonary artery conti-
