Long-term intubation, tracheostomy, neck or inhalational trauma are common causes for subglottic and tracheal stenosis. Current surgical techniques may not correct the condition in all cases, resulting in restenosis and sometimes requiring a permanent tracheostomy. Tracheal stents can be used to address stenosis, but they have a number of potential shortcomings such as such as risk of acute airway obstruction, migration and poor biocompatibility. We have developed a novel drug-eluting stent concept to effectively eliminate such shortcomings. We hypothesize that a mometasone-eluting highly biocompatible multiphasic and spatially graded polycaprolactone-collagen (PCL-Col) stent that can treat tracheal stenosis effectively. Collagen phase at the lumen of the stent will facilitate full mucosalization whereas the macroporous PCL phase will biodegrade and release a steroid into the tracheal tissue to prevent re-stenosis.
In Aim 1, the design of the self-deploying tracheal stent will be optimized. Geometric and compositional parameters of stent design will be varied to attain a stent, which expands and securely stays within the trachea after deployment to provide adequate tracheal wall support. Biomechanical tests will measure the strength of anchorage to avoid migration following stent expansion.
Aim 2 will focus on optimizing the anti-inflammatory and epithelialization capacity of the stent: mometasone content will be systematically varied to study their anti-inflammatory effects using macrophage and airway epithelial cell cultures. High performance liquid chromatography will be used to quantify the release profile of mometasone over time.
Aim 3 will focus on in vivo testing of the bioabsorbable, drug eluting stent: The effectiveness of stents will be tested in a rabbit animal model in which stenosis will be induced chemically. The following treatment groups will be included: (1) stenosis with no stent, (2) stenosis treated with a commercially available silicone stent, (3) stenosis treated with a PCL-collagen stent, (4) stenosis treated with a PCL-collagen-mometasone eluting stent. Stents will remain for 24 weeks in situ and longitudinally monitored for inflammatory changes, epithelialization, healing tendency, stent migration, and airway obstruction. At the completion of this project we will have obtained valuable pre-clinical data regarding optimum stent biomechanics and composition, which will prepare us for further long-term experiments in larger animals.
The incidence of tracheal stenosis in the VA patient population has not been studied but is presumably higher compared to the non-VA patient population considering higher rates of chronic conditions than the general population resulting in increased rates of intubation and intubation injuries. Also, soldiers have a greater risk of combat trauma sometimes demanding long-term intubation to manage their injuries. A bioabsorbable, drug eluting tracheal stent has the potential to improve respiratory rehabilitation. It can shorten the treatment time of tracheal stenosis, reduce number of airway surgeries and as a result this stent can reduce the morbidity and mortality. This new device has the potential to save many affected patients and veterans from repeat airway surgeries or even a permanent tracheostomy. If successfully applied, this tracheal stent has the potential to not only improve outcome of affected patients, but also to lower all over overall costs.