Biodegradable self-expanding poly-L/D-lactic acid vascular stent: a pilot study in canine and porcine iliac arteries.

Purpose: To report results of an in vivo pilot study to evaluate the biocompatibility and delivery system of a new biodegradable vascular stent and validate the study design.

Methods: Two self-expanding intravascular stents, a biodegradable poly-D/L-lactic acid (PLA) and a medical stainless steel stent (Wallstent) were implanted in the common iliac arteries of 2 postpuberal female pigs and 3 laboratory-bred beagle dogs. Specimens were harvested after 45 days in the dogs and 32 days in the pigs for histomorphometry of the stented iliac artery segments. Preliminary measurements were made to assess the reliability of the quantitative histomorphometric measurements before final measurements.

Results: Histomorphometry analyses showed that mean luminal diameter and area were decreased in the PLA stent group (1.97+/-0.48 mm and 14+/-6.4 mm2, respectively) compared to the control stent group (4.28+/-0.83 mm and 61+/-19 mm2, respectively). The intimal thickness was higher in the PLA stent group (0.65+/-0.07 mm) than in the control group (0.44+/-0.21 mm). The mean injury score was 0.19+/-0.12 in the PLA stent group and 0.78+/-0.39 in the controls. In the PLA stent group, the mean inflammation score was 1.46+/-0.78 compared to 0.58+/-0.40 in the control group. There were no differences observed between the animal models.

Conclusions: The PLA stent showed increased neointimal formation and reduced patency during early follow-up. Mechanical properties of the new biodegradable vascular stents are still inadequate, and the stent and the delivery device require modifications. The study methods were assessed as reliable and reproducible.