Effect of Mucosal Sutures on the Muscularis Propria Layer at the Gastroesophageal Junction

Abstract

Purpose: Endoscopic gastroplications can improve gastroesophageal reflux symptoms in patients, and have been reported to reduce esophageal acid exposure and increase in lower esophageal sphincter pressure in a swine model. The Endoscopic Suturing DeviceTM (ESD, Wilson-Cook, Winston-Salem, NC) is a flexible transoral suturing system available for intraluminal soft tissue apposition. The aim of this study is to investigate the effect of mucosal sutures created using ESD on the muscularis propria layer at the gastroesophageal junction (GEJ) in a swine model. Methods: Female domestic pigs weighing 30 kg were used as control (n=6) and study (n=6) animals. An upper endoscopy with endoscopic ultrasound (EGD/EUS) was performed in all animals at baseline. The appearance and thickness of the muscularis propria layer at the GEJ was imaged and measured endosonographically. In each study animal, two gastroplications were created using ESD at the squamo-columnar junction. EGD/EUS was repeated at 3 weeks after the suturing procedure and then the animal was sacrifice. The distal esophagus and proximal stomach were fixed in formalin while the intraluminal diameter were kept constant for all specimens. The thickness of the muscularis propria layer was measured histologically and correlated with EUS findings. Ultra-structural changes were evaluated with electron microscopy (EM). Results: Mucosal sutures induced a focal increase in the muscularis propria layer thickness at the GEJ near the suture site. The baseline thickness measured 1.12 ± 0.14 mm by EUS, 3 weeks after the procedure the thickness increased to 3.84 ± 0.69 mm (p<0.01) near the suture site. The length of the focal increase in thickness measured 13.2 ± 4.9 mm by EUS. Histologic examination confirmed this localized increase in thickness of the muscularis propria layer near the mucosal suture when compared to the control, 8.0 ± 1.9 mm vs. 5.7 ± 1.6 mm (p=0.03). The increase in smooth muscle cell mass was due entirely to hypertrophy of the circular smooth muscle layer, 6.2 ± 1.7 mm vs. 4.2 ± 1.6 (p=0.04). The thickness of the longitudinal smooth muscle layer remained unchanged. Transmission EM of the smooth muscle cells revealed cellular and nuclear changes as well as intra-cellular collagen deposition. Conclusions: In a swine model, mucosal sutures placed by the Endoscopic Suturing Device led to focal hypertrophy of the muscularis propria layer at the gastroesophageal junction.