Technical Feasibility and Histological Analysis of Balloon-Expandable Metallic Stent Placement in a Porcine Eustachian Tube

Abstract

There is a clinical need to develop a stent to treat obstructive and refractory Eustachian tube dysfunction (ETD) after balloon Eustachian tuboplasty. An animal model for stent placement in the Eustachian tube (ET) is needed to develop optimal designs and materials, as stents for ETD have not been clinically applied. The purpose of this study was to evaluate the technical feasibility of stent placement and histological changes in a porcine ET model. Six ETs were evaluated in three pigs. Cobalt–chrome alloy stents with two different diameters were placed in the left and right ET of each animal (right, 3.5 mm; left, 2.5 mm). The outcomes were assessed by endoscopic and fluoroscopic imaging during the procedure, computed tomography after the procedure, and by histological examinations. Stent placement was technically successful in all specimens after metallic guiding sheaths were located in the nasopharyngeal end of the ET. The mean luminal diameters of the proximal, middle, and distal portions of the larger stents in the right ETs were 3.48 mm, 2.54 mm, and 2.15 mm, respectively. In the left ETs using smaller stents, these values were 2.49 mm, 1.73 mm, and 1.42 mm, respectively. The diameters of the inserted stents differed by stent location and the original diameter. Histological findings showed tissue hyperplasia with severe inflammatory cell infiltration at 4 weeks after stent placement. In conclusion, stent placement into the porcine ET was technically feasible, and stent-induced tissue hyperplasia was significantly evident. The luminal configuration of the placed ET stent changed according to its non-elastic nature and anatomical features of the porcine ET. Using this model, ET stents of various materials and designs with anti-inflammatory or anti-proliferative drugs can be optimized for future treatments of ET dysfunction.

Sirolimus-eluting cobalt–chrome alloy stent suppresses stent-induced tissue hyperplasia in a porcine Eustachian tube model

“…In a previous study, stent-induced tissue hyperplasia was observed in the porcine ET model. Although stent development in the ET has not been sufficiently investigated, tissue responses after stent placement similar to those of other nonvascular luminal organs have been observed 19 . In the present study, SES was used to suppress stent-induced tissue hyperplasia in the porcine ET model.…”

“…Moreover, a sheep model was established to evaluate the in vivo profile of a balloon-expandable metallic stent 15 . Our previous study developed a porcine ET model to investigate technical feasibility and assess stent-induced complications 19 , which laid a solid foundation for this study to examine the efficacy of SES using the previously established technique. In the present study, SES was successfully located in the cartilaginous portion to effectively suppress tissue hyperplasia.…”

“…2 a). The Co–Cr alloy stent size was determined based on our previous study 19 .

Figure 2 Cobalt–chrome (Co–Cr) alloy stent and metallic guiding sheath for Eustachian tube stent placement.

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“…Thus, stent placement can serve as an effective therapeutic option 12 , 13 . Despite many ongoing preclinical studies that evaluate the technical feasibility and tissue response after stent placement in ET, stent-induced tissue hyperplasia caused by mechanical injury still represents a significant postprocedural complication 14 – 19 . Drug-eluting stents loaded with antiproliferative agents are believed to improve this situation.…”

Tapered self-expandable metallic stent optimized for Eustachian tube morphology in a porcine ET model

“…Thus, finding other effective therapeutic options remains a therapeutic challenge. Previous studies proposed the use of ET stenting as an alternative option for patients with ETD, and preclinical studies were conducted to develop an ET stent for relieving ETD 13 – 18 . However, the tubular structure of the ET stents used in the previous studies may not be appropriate for the morphology of the ET.…”