Non-Ablative Radiofrequency (RF) Application to Smooth Muscle of Internal an al Sphincter (IAS) – A Tissue Study.

*Roman M Herman, Professor, **Dorota Wojtysiak, PhD, ***Janusz Rys, Professor, **Tomasz Schwarz, PhD, *Michal Nowakowski, MDPhD, **Maciej Murawski, PhD, **Dorota Ziemba, Professor, *Roma B Herman

*Jagiellonian University Medical College Krakow, **Agriculture University, Krakow, ***Centre of Oncology Krakow,Poland

Non-ablative radiofrequency smooth muscle remodeling has been successful in the treatments of GERD in the lower esophageal sphincter (Stretta) and fecal incontinence in the IAS (Secca). This unique, non-ablative RF therapy has demonstrated improvements in barrier function without evidence of stricture. However, the precise mechanism of non-ablative RF- induced smooth muscle remodeling has been unclear.

AIM: To investigate the pathophysiological mechanisms that lead to the clinical improvement demonstrated in patients following this non-ablative application of RF.

MATERIAL & METHODS: An experimental model of fecal incontinence (FI) was created in 10, one year old 150 lb pigs by pudendal nerve destruction+ EAS/IAS sphincterotomy. Six weeks later the study animals underwent RF application. Ten weeks post- treatment, the study animals were euthanized and the IAS and surrounding tissues were harvested for pathologic evaluation. A control group of 6 age and weight matched pigs were also sacrificed. Sections from the IAS were examined histologically using a routine H&E and trichrome stain; the architectural features of the IAS including thickness and smooth muscle/connective tissue ratio were determined using an image analyzer (Multiscan Base vers.14.02). Immunostaining of collagen I, III, and elastin were performed and the relative content of these proteins was calculated by image analysis. Semi quantitative evaluation of smooth muscle(SM) cells and myofibroblasts was done with the use of immunohistochemical stain for smooth muscle actin by image analysis.

RESULTS: Microscopic evaluation of the IAS in the control animals revealed characteristic circular muscle bundles separated by connective tissue septae. Thinner connective tissue fascicles wrapped individual cells. The basic architecture of the IAS was maintained following RF treatment. In all groups the circular muscle bundles greatly varied in diameter from 90 µm to 580 µm, although the cross section area occupied by SM within the bundles increased after RF. The amount of collagen I in the septa was statistically significantly higher than collagen III. There was no significant difference in the thickness of connective tissue septae between the FI animals before RF and the control group. An increase in the ratio of connective tissue/smooth muscle was observed in FI group before RF, compared to the controls. After RF the number of SM fibers within the muscle bundles increased. This bundles were separated by significantly larger septae. Although the IAS after RF had a greater percentage of connective tissue compared to controls, the smooth muscle layer thickness and the number of smooth muscle fibers within the IAS bundles increased. Statistically significant increase of collagen I was seen within the septa, along with an increase of SM actin within the fibroblasts after RF. This observation suggests differentiation towards a myofibroblast phenotype.

CONCLUSION: Non-ablative RF application to internal anal sphincter relevantly influences the structural arrangement of smooth muscle and connective tissue contents. The increase of the SM fibers area per muscle bundles as well as the collagen and myofibroblast contents within IAS septa are potentially responsible for sphincter reinforcement and remodeling.

Session: Poster Presentation

Program Number: P022

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