Feasibility and effectiveness of endoscopic irreversible electroporation for the upper gastrointestinal tract: an experimental animal study

Biphasic Regulation of Apoptosis Following Gastric Irreversible Electroporation Using Tissue Immunohistochemistry of Activated Caspase-3 with TUNEL Method

The regulation of apoptosis is the primary goal of ablation therapy. Irreversible electroporation (IRE) is a promising non-thermal tissue ablation-based therapy that induces apoptosis by manipulating electrical conditions. This study aimed to investigate IRE-induced gastric tissue apoptosis in response to changes in the electric field intensity, followed by the repair process. Among the 52 rats used in this study, 24 were used to explore apoptosis, and 28 were used to study regeneration. The apoptosis-to-necrosis ratio of the electrical field strength was evaluated using terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling and caspase-3 immunohistochemistry. The size of IRE-induced ulcers in the gastric tissue continuously increased with increasing electrical intensity (r2 = 0.830, p < 0.001). The level of apoptosis gradually decreased after peaking at 200 V (1000 V/cm). The size of the 400 V-ablated ulcers continued to decrease, and they were not visible by day 14. The proliferation and migration of epithelial cells with fibroblasts were observed on day 3 and augmented on day 7 post-ablation. This investigation demonstrated the biphasic activation of apoptosis with respect to the electrical field strength. Visually and histologically, IRE-induced gastric ulcers demonstrated complete tissue regeneration after two weeks.

Balloon-assisted laser application for endoscopic treatment of biliary stricture

OBJECTIVES

Malignant biliary stricture is a ductal narrowing of the bile duct that is often diagnosed at an advanced stage, leading to difficulty in resection. The current study aims to evaluate the feasibility of endobiliary laser treatment by quantifying the extent of coagulative necrosis in tissue under various conditions.

METHODS

Ex vivo and in vivo porcine bile tissues were used for endobiliary laser treatment to characterize the dosimetric responses of the tissue to various treatment conditions: power level, irradiation time, and number of treatments. 532 nm laser light was coupled with a balloon-integrated diffusing applicator (BDA) to deliver the laser light endoscopically for tissue coagulation. The coagulated regions (maximum length and depth) in the treated tissues were evaluated histologically for quantitative comparison.

RESULTS

Dosimetric evaluations with ex vivo liver tissue confirmed that both maximum length and depth of coagulative necrosis (CN) increased with applied power and number of treatments. Ex vivo bile duct tests demonstrated that BDA-assisted laser treatment at 10 W for 12 s reproducibly yielded CN with a length of 5.8 ± 1.6 mm and a depth of 0.6 ± 0.2 mm. In vivo tests presented that endoscopic laser treatment using the BDA created CN on the ductal surface without any perforation. Microscopic examinations revealed that a dense inflammatory cell infiltration and eosinophilic area in the in vivo treated tissue. The extent of CN in the in vivo tissue was 40% longer and 120% deeper (length: 8.1 ± 0.7 mm; depth: 1.3 ± 0.2 mm), compared to that in the ex vivo tissue.

CONCLUSION

BDA-assisted laser treatment could be a feasible option for endoscopic treatment of biliary stricture with uniform ablation at the circumference of bile duct. Further in vivo studies will be performed in a large number of stricture-developed porcine models to examine both efficacy and safety of the proposed endobiliary laser treatment for clinical translations.

Pulsed Electric Fields in Oncology: A Snapshot of Current Clinical Practices and Research Directions from the 4th World Congress of Electroporation

The 4th World Congress of Electroporation (Copenhagen, 9-13 October 2022) provided a unique opportunity to convene leading experts in pulsed electric fields (PEF). PEF-based therapies harness electric fields to produce therapeutically useful effects on cancers and represent a valuable option for a variety of patients. As such, irreversible electroporation (IRE), gene electrotransfer (GET), electrochemotherapy (ECT), calcium electroporation (Ca-EP), and tumour-treating fields (TTF) are on the rise. Still, their full therapeutic potential remains underappreciated, and the field faces fragmentation, as shown by parallel maturation and differences in the stages of development and regulatory approval worldwide. This narrative review provides a glimpse of PEF-based techniques, including key mechanisms, clinical indications, and advances in therapy; finally, it offers insights into current research directions. By highlighting a common ground, the authors aim to break silos, strengthen cross-functional collaboration, and pave the way to novel possibilities for intervention. Intriguingly, beyond their peculiar mechanism of action, PEF-based therapies share technical interconnections and multifaceted biological effects (e.g., vascular, immunological) worth exploiting in combinatorial strategies.

Assessment of efficacy and safety of advanced endoscopic irreversible electroporation catheter in the esophagus

Nonthermal irreversible electroporation (NTIRE) is emerging as a promising tissue ablation technique. However, maintaining irreversible electroporation (IRE) electrodes against displacement during strong esophageal spasms remains an obstacle. The present study aimed to evaluate the efficacy and safety of newly designed balloon-type endoscopic IRE catheters. Six pigs were randomly allocated to each catheter group, and each pig was subjected to four ablations at alternating voltages of 1500 V and 2000 V. Esophagogastroscopy was performed during the IRE. The ability of balloon-type catheters to execute complete IRE with 40 pulses was assessed. The success rate was higher for the balloon-type catheter than that for the basket-type (12/12 [100%] vs. 2/12 [16.7%], p < 0.001). Following gross inspection and histologic analysis of the 1500-V vs. 2000-V balloon-type catheter revealed a larger mucosal damage area (105.3 mm2 vs. 140.8 mm2, p = 0.004) and greater damage depth (476 μm vs. 900 μm, p = 0.02). Histopathology of the ablated tissue revealed separated epithelium, inflamed lamina propria, congested muscularis mucosa, necrotized submucosa, and disorganized muscularis propria. Balloon-type catheters demonstrated efficacy, achieving full electrical pulse sequences under NTIRE conditions, and a safe histological profile below 2000 V (1274 V/cm). Optimal electrical conditions and electrode arrays pose ongoing challenges.

Image-guided stent-directed irreversible electroporation for circumferential ablation in the rat esophagus

Background: Irreversible electroporation (IRE) has been investigated in the alimentary tract; however, the lack of dedicated electrodes and insufficient tissue responses made its application limited. The aim of this study was to investigate the efficacy and safety of image-guided stent-directed IRE in the rat esophagus. Methods: The bipolar self-expandable electrode (SE) was developed using the braiding technique. A finite element analysis was performed to validate optimal electrical field strength for the rat esophagus. A total of 40 out of 50 rats received stent-directed IRE and were sacrificed at 10 h, 3 days, 7 days, and 28 days of 10 each. The remaining ten rats underwent a sham procedure. The outcomes of stent-directed IRE were assessed by esophagography and histological responses. Results: Stent-directed IRE was technically successful in all rats with mild muscle contraction. The heart rate dropped immediately and gradually recovered at 180 s. TUNEL and caspase-3 with submucosal thickness significantly increased at 10 h and Day 3 compared with those of the sham control (all p < 0.001). The thickness of epithelial layers with collagen deposition significantly decreased at 10 h and Day 3 (all p < 0.001), however, increased at Day 7 compared with that of the sham control (all p < 0.05). The Ki67-positive deposition significantly increased at Day 3 and 7 compared with that of the sham control (all p < 0.001). All variables were similar to those of the sham control at Day 28. Conclusion: Image-guided stent-directed IRE was effective and safe in the rat esophagus. It seems to have effectively and evenly induced cell death and gradually recovered with cellular regeneration.

Needle tract seeding following percutaneous irreversible electroporation for hepatocellular carcinoma

Irreversible electroporation (IRE) is a non-thermal ablative technique for unresectable liver malignancies deemed unsuitable for traditional thermal ablation due to proximity to biliary and/or vascular structures. Needle tract tumour seeding is a well-recognised complication following thermal ablation, while little is known about its risk with IRE use. We present a case of tumour seeding after IRE for unresectable hepatocellular carcinoma in a man in his 70s. The procedure was complicated by bleeding from a pseudoaneurysm, which required coil embolisation and blood transfusion. He initially progressed well, however, imaging at 12 months indicated a new tumour in the right intercostal space along the tract of one of the IRE needles; consistent with seeding. Although the patient subsequently underwent systemic therapy with sorafenib, his disease progressed, and unfortunately he passed away 20 months following IRE. This report adds to mounting evidence of needle tract tumour seeding as a complication following IRE.

Safety and feasibility of irreversible electroporation for the pancreatic head in a porcine model

BACKGROUND

Irreversible electroporation (IRE) is a local non-thermal ablative technique which has been suggested as a potential cancer therapy. However, the specific anatomic characteristics of the pancreatic head make it challenging to perform any local ablation in this region. Therefore, the safety and feasibility of IRE in the pancreatic head region should be further explored.

AIM

To evaluate the safety of IRE in pancreatic head region including its effects on pancreatic ducts, vessels, and adjacent gastrointestinal organs.

METHODS

Eight landrace miniature pigs underwent IRE of pancreatic head tissue successfully, with a total of 16 lesions created. Laboratory testing including white blood cell (WBC) count and serum amylase before IRE with follow-up laboratory analysis and pathological examination at 1, 7, 14, and 28 d postablation were performed.

RESULTS

All pigs tolerated the ablation procedure without serious perioperative complications. Transiently elevated WBC count and amylase were observed at 24 h post-IRE, suggesting an acute pancreatic tissue damage which was confirmed by pathological observations. Vascular endothelial cells and pancreatic duct epithelial cells in ablation zone were also positive in terminal deoxynucleotidyl transferase dUTP nick end labeling staining. There was extensive duodenum mucosa damage with local hemorrhage 24 h after ablation, while regeneration of new villous structures were observed at 7 and 28 d post-IRE. Masson’s trichromatic staining showed that the extracellular matrix was still intact in vessels and pancreatic ducts, and even in the duodenum.

CONCLUSION

IRE ablation to the pancreatic head may be safe and feasible without long-term damage to the surrounding vital structures. However, risks of stress injuries in acute phase should be taken into consideration to prevent severe perioperative complications.

Irreversible Electroporation: An Emerging Immunomodulatory Therapy on Solid Tumors

Irreversible electroporation (IRE), a novel non-thermal ablation technique, is utilized to ablate unresectable solid tumors and demonstrates favorable safety and efficacy in the clinic. IRE applies electric pulses to alter the cell transmembrane voltage and causes nanometer-sized membrane defects or pores in the cells, which leads to loss of cell homeostasis and ultimately results in cell death. The major drawbacks of IRE are incomplete ablation and susceptibility to recurrence, which limit its clinical application. Recent studies have shown that IRE promotes the massive release of intracellular concealed tumor antigens that become an “in-situ tumor vaccine,” inducing a potential antitumor immune response to kill residual tumor cells after ablation and inhibiting local recurrence and distant metastasis. Therefore, IRE can be regarded as a potential immunomodulatory therapy, and combined with immunotherapy, it can exhibit synergistic treatment effects on malignant tumors, which provides broad application prospects for tumor treatment. This work reviewed the current status of the clinical efficacy of IRE in tumor treatment, summarized the characteristics of local and systemic immune responses induced by IRE in tumor-bearing organisms, and analyzed the specific mechanisms of the IRE-induced immune response. Moreover, we reviewed the current research progress of IRE combined with immunotherapy in the treatment of solid tumors. Based on the findings, we present deficiencies of current preclinical studies of animal models and analyze possible reasons and solutions. We also propose possible demands for clinical research. This review aimed to provide theoretical and practical guidance for the combination of IRE with immunotherapy in the treatment of malignant tumors.