Histological and structural effects of biodegradable polydioxanone stents in the rabbit trachea

OBJECTIVES: The aim of this study was to evaluate the potential biologic effects caused by the successive placement of biodegradable polydioxanone (PDO) stents in the rabbit trachea. PDO stents could eventually induce a fibroproliferative reaction in the submucosa that could be beneficial in the treatment of malacia due to an increase in its consistency without impairing the tracheal lumen. METHODS: Sixteen adult NZ rabbits were distributed into 3 groups with different survival times according to the number of stents placed: 1 stent (14 weeks), 2 stents (28 weeks) and 3 stents (42 weeks). Stent insertion was performed endoscopically in the cervical trachea of the animal. Histopathological studies included Masson's trichrome staining for submucosal fibrosis and Safranin O to assess the structural integrity of cartilage. Potential inflammatory changes were analysed by means of immunohistochemistry determining the number of CD45-positive cells. RESULTS: Stent placement was successful in every case. Histological studies did not show a statistically significant increase in tracheal wall collagen area and cartilage structure was not modified in those rabbits with 1 or more PDO stents inserted compared to non-stented tracheal sections. Furthermore, no statistically significant changes in the number of CD45+ cells were observed in stented tracheal segments compared to normal tracheal tissues. CONCLUSIONS: According to our data, successive PDO stenting caused mild inflammatory changes in the tracheal wall and no increase in the collagen matrix, and the cartilaginous support was not modified during a long follow-up period (up to 42 weeks). These findings suggest that they may be safe and show good biocompatibility in the long term.