Study on the Contact Stress Concentration and the Hyperplasia of the Canine Trachea Granulation Tissue after Stenting

Tracheal stenosis is a common respiratory disease and is usually treated by stent implantation. However, the implanted stent often causes excessive hyperplasia of trachea granulation tissue, leading to the restenosis. Although surgical removal or chemical suppression can be used to alleviate the restenosis, the efficacy is limited. Thus, restenosis remains a thorny complication. We investigated this issue from the perspective of the “stress-growth” relationship. Firstly, the lower airway of 5 experimental dogs were CT-scanned to reconstruct the 3D numerical models; secondly, the implantations of the Nitinol alloy stents were numerically simulated; thirdly, 45 days after the stenting, the dogs were evaluated for the hyperplasia of the trachea granulation tissue by CT imaging, bronchoscopy and histological sectioning; finally, the correlation analysis was performed between the contact stress and the hyperplasic thickness of the granulation tissue. Results show that the hyperplasia of the trachea granulation tissue and the local contact stress are positively correlated (R=0.82) and the high local dilation stress can promote the hyperplasia of the trachea granulation tissue, probably through the recombination of basic fibroblast growth factor or the dysfunction of plasminogen activator inhibitor-1. Therefore, contact stress concentration should be prevented in the future design of the tracheal stent.