A rat tracheal model to investigate stent-induced tissue hyperplasia: a pilot study

To evaluate the feasibility of stent placement and the formation of stent-induced tissue hyperplasia and to verify matrix metalloproteinase (MMP) expression in stent-induced tissue hyperplasia in a rat tracheal model.

In a pilot study, four rats were used to verify MMP expression in stent-induced tracheal tissue hyperplasia based on zymography and Western blot analysis. In the main experiment, 12 rats were divided into two groups with different stent-mesh gap sizes (group I, 1.23 × 1.92 mm; group II, 0.80 × 1.80 mm). The stent was 4 mm in diameter and 8 mm long. Follow-up tracheogram was performed before sacrifice 3 weeks after stent placement. The gross and the microscopic findings were evaluated.

Stent placement was technically successful in all rats. During follow-up, two rats (one from each group) died within 4 days after stent placement, and one stent in group II was placed outside the trachea. MMP-9 expression was significantly higher in tissue hyperplasia than in control normal tissue. The excised specimens showed tissue hyperplasia through the mesh, and all of the stents had become incorporated into the wall of the trachea. The papillary projection thickness, granulation tissue area, percentage of granulation tissue area, and degree of inflammatory cell infiltration were higher in group II than in group I, but there was no statistically significant difference.

In this study, stent placement was feasible, and the formation of stent-induced tissue hyperplasia was evident in a rat tracheal model. MMP-9 overexpression was evident in the stent-induced tracheal tissue hyperplasia.