Objectives: Alternative heart valve prostheses are warranted to overcome numerous limitations
of implants currently used in pediatric patients. In order to determine the fate of
decellularized aortic conduit transplants beyond histological measures, including
detailed functional evaluation, we created a growing rodent model as described below.
Methods: Young Wistar rats (70–80g) were anesthetized and underwent median laparotomy for
exposition of the abdominal aorta. After administration of heparin and aortic clamping,
a U-shaped aortic conduit was sutured to the infrarenal aorta in an end-to-side manner.
Intermittent reperfusion was used to keep limb ischemia times below 30 minutes. Following
release of blood flow via the conduit, the native aorta between the two anastomoses
was ligated to improve perfusion of the graft. According to the small size of the
animals, functional assessment could be performed not only by doppler sonography after
explantation, but also via high resolution rodent MRI. Histology, immunohistochemistry
and graft plastination followed after 8 weeks.
Results: Eighty percent of the operated rats (n=10) recovered without adverse effects. Conforming
with clinical observations, postoperative MRI on day 5 and doppler sonography after
8 weeks revealed unimpaired perfusion of both, the conduit and the distal aorta. Explanted
prostheses were luminally completely covered by neoendothelium, whereat local hyperplasia
of α-smooth muscle actin (+) cells occurred. Moreover, a mild microcalcification of
the tunica media of the decellularized scaffolds was shown. Staining against inflammatory
cell markers (CD3 & CD68) was negative at 8 weeks.
Conclusions: Our downsized variant of aortic conduit transplantation enables an overall characterization
with detailed analysis of graft maturation along with an evaluation of growth potential
of tissue engineered and native grafts in a growing organism. Furthermore, with the
advent of novel contrast agents specific for inflammatory cells (such as emulsified
perfluorocarbons), MRI measurements may elucidate early immune response against the
implants.
