Feasibility of in vivo swine models using guide wire-assisted intraductal radiofrequency ablation for benign biliary stricture

www.nature.com/scientificreports OPEN Feasibility of in vivo swine models using guide wire‑assisted intraductal radiofrequency ablation for benign biliary stricture Jae Keun Park 1, Ju‑Il Yang 2, Joo Kyung Park 2, Kwang Hyuck Lee 2, Jong Kyun Lee 2 & Kyu Taek Lee 2* Several in vivo swine models of benign biliary stenosis (BBS) have been recently reported for preclinical studies of novel endoscopic techniques and devices. The aim of this study was to evaluate the efficacy and feasibility of large animal models of BBS by using intraductal radiofrequency ablation (RFA) assisted by guide wire. Six in vivo swine models were made by using an intraductal RFA for cauterization at 10 W, 80 °C, 90 s in the common bile duct (CBD). Endoscopic retrograde cholangiopancreatography (ERCP) was performed with cholangiography and histologic evaluation was done for the common bile duct. Blood tests were examined before, after, and at the final follow-up. Guide wire assisted RFA electrode produced BBS in all (6/6, 100%) animal models without severe complications. Fluoroscopy findings at 2 weeks after intraductal RFA in every model revealed BBS in the common bile duct. In histologic evaluations, fibrosis and chronic inflammatory changes were noted. After the procedure, ALP, GGT, and CRP were elevated and decreased after an appropriate drain. A swine model of BBS is developed by inducing intraductal thermal injury using intraductal RFA assisted by guide wire. This novel technique for inducing BBS in swine is effective and feasible. Abbreviations BBS Benign biliary stenosis RFA Radiofrequency ablation ERCP Endoscopic retrograde cholangiopancreatography WBC White blood cell AST Aspartate transaminase ALT Alanine transaminase ALP Alkaline phosphatase GGT Gamma-glutamyl transferase CRP C-reactive protein H–E Hematoxylin eosin M-T Masson trichrome CK 19 Cytokeratin 19 Endoscopic biliary drainage has been used as an initial treatment for benign biliary stricture (BBS). Recently, multiple plastic stents and covered self-expandable metal stents have been reported to show promising outcomes for the management of B BS1,2. However, adequate biliary drainage over the long-term using biliary stents is still challenging. Many biliary endoscopic devices including biliary stents have been recently developed to improve the patency of devices3–5. However, these attempts to increase the long-term drainage effect by changing the shape or material of plastic stents do not have satisfactory effects. Therefore, there are increasing requirements for new devices that can improve limitations of conducting endoscopic management in BBS. Before applying to endoscopic devices in humans, appropriate animal models are important for preclinical study to evaluate the efficacy of endoscopic devices. In the past, previous studies mostly reported surgically 1 Department of Internal Medicine, Kangnam Sacred Heart Hospital, Hallym University College of Medicine, Seoul, South Korea. 2Division of Gastroenterology, Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, 81 Irwon‑ro, Gangnam‑gu, Seoul 06351, South Korea. *email: ktcool.lee@ samsung.com Scientific Reports | (2023) 13:7185 | https://doi.org/10.1038/s41598-023-33867-9 1 Vol.:(0123456789) www.nature.com/scientificreports/ created percutaneous a pproaches6–8. However, procedures of making animal models using surgically created percutaneous approaches were laborious. Recently, several studies have reported the development of in vivo and in vitro animal models for BBS using an endoscopic biliary approach9–11. The first endoscopic biliary approach by Rumella et al. used heat probe and multipolar probe to produce BBS12. However, these studies were conducted using methods including heat probe and multipolar probe other than intraductal radiofrequency ablation (RFA) for BBS. Even if an endoscopic approach was used, the experiment was conducted using a non-thermal injury method such as endoscopic detachable snare. Some studies have reported a short observation time without performing follow-up liver function tests commonly conducted in clinical practice. Comparing other thermal injury methods for animal models of BBS, using intraductal RFA device is comfortable and easy to control energy dose (W), temperature (°C), and exposure time (sec). Using guide wire methods, intraductal RFA devices might more easily control the location and degree of bile duct injury. However, there were only a few investigations for intraductal application of RFA. In addition, an effective and safe energy dose for intraductal thermal injury with RFA is still not established. Thus, the aim of this study to assess the development of reproducible large animal models of BBS using endo biliary RFA and to investigate an effective and safe energy option for application in producing BBS. Results Fluoroscopic analysis via ERCP and blood analysis. In all six swine animal models, we succeeded in generating BSS using intraductal RFA without any complications such as bleeding or perforation (success rate = 100% (6/6), severe complication rate = 0%). Blood levels of WBC, AST, ALT, ALP, GGT, and CRP of all experimental animals were measured before the intraductal RFA procedure, after the intraductal RFA procedure (2 weeks after RFA), and before euthanizing animals (Figs. 1, 2, 3A–G). Blood levels of WBC, AST, ALT, ALP, GGT, and CRP were elevated after the intraductal RFA procedure but decreased after biliary stenting. Figure 1H,I are biliary fluoroscopy findings at 2 weeks after RFA in experimental animals 1 and 2, demonstrating biliary stenosis. The same trend of blood test results as in Fig. 1 was observed in Fig. 2. The difference between Figs. 1 and 2 was that the follow-up was performed at 3 months after biliary stenting in Fig. 2. Biliary stenosis was confirmed by fluoroscopy findings at 2 weeks after RFA in experimental animals 3 and 4 (Fig. 2H,I). Experimental animals 5 and 6 were followed for 5 months after biliary stenting. They showed the same tendency of blood test results (Fig. 3A–G). Biliary stenosis was also confirmed by fluoroscopy findings at 2 weeks after RFA in experimental animals 5 and 6 (Fig. 3H,I). Macroscopic and microscopic histopathological evaluation. The common bile duct (CBD) diameter was 2.5 ± 0.5 mm in macroscopic findings. The biliary stricture length measured after harvesting of experimental animals was 36 mm ± 0.5 mm in macroscopic findings. Using H&E-stained tissue sections, the degree of histological damage was compared by examining the depth of inflammation, the degree of deposition of neutrophils, the presence of mucosal ulceration, and the overall score (Figs. 4, 5 and Tables 1, 2). The total histological score indicating histological damage of plastic stents was observed to be higher for the 3-month point than that for the 1-month point total score, median (range) of 1-month pigs vs. 3-month pigs: 6 (6–8) vs. 6.5 (6–8) (...truncated)