Development of an acute pancreatitis porcine model based on endoscopic retrograde infusion of contrast medium or sodium taurocholate

Embolization of the Pancreas Using Microspheres: A Proof-of-Safety Study in a Porcine Model

PURPOSE

To evaluate safety and impact of particle embolization on pancreatic function in a pig model.

MATERIALS AND METHODS

Embolization of the dorsal pancreatic artery using 100-300-μm particles was performed on 14 Yorkshire pigs. Baseline and post-embolization glucose tolerance testing results and serum amylase/lipase levels were obtained. Pigs were observed for 2 weeks to assess for behavioral signs of pain/distress, bowel changes, and changes to intake/output. After 2 weeks, euthanasia and necropsy with gross and histopathologic assessment of the pancreas were performed.

RESULTS

Embolization was technically successful in all pigs. All animals survived the 2-week follow-up without evidence of pain/distress. There were significant increases in amylase and lipase at 24 and 48 hours (P < .001), which normalized by 2 weeks. There was minimal change in glucose tolerance testing at 2 weeks. Bowel habits were unchanged without diarrhea. At necropsy, all examined pancreases had fibrosis in the distal body and tail, without gross evidence of ongoing inflammation. On histopathologic evaluation, all pancreases demonstrated fibrosis in the embolized portions without evidence of active inflammation in treated or adjacent pancreatic tissue.

CONCLUSIONS

Particle embolization of the pancreas was feasible and tolerated by all tested pigs with transient amylasemia, lipasemia, and mildly impaired glucose tolerance but without clinical or histopathologic evidence of acute pancreatitis and no evident impact on pancreatic endocrine or exocrine function.

Ultrasound-guided noninvasive pancreas ablation using histotripsy: feasibility study in an in vivo porcine model

Pancreatic cancer is a malignant disease associated with poor survival and nearly 80% present with unresectable tumors. Treatments such as chemotherapy and radiation therapy have shown overall improved survival benefits, albeit limited. Histotripsy is a noninvasive, non-ionizing, and non-thermal focused ultrasound ablation modality that has shown efficacy in treating hepatic tumors and other malignancies. In this novel study, we investigate histotripsy for noninvasive pancreas ablation in a pig model. In two studies, histotripsy was applied to the healthy pancreas in 11 pigs using a custom 32-element, 500 kHz histotripsy transducer attached to a clinical histotripsy system, with treatments guided by real-time ultrasound imaging. A pilot study was conducted in 3 fasted pigs with histotripsy applied at a pulse repetition frequency (PRF) of 500 Hz. Results showed no pancreas visualization on coaxial ultrasound imaging due to overlying intestinal gas, resulting in off-target injury and no pancreas damage. To minimize gas, a second group of pigs (n = 8) were fed a custard diet containing simethicone and bisacodyl. Pigs were euthanized immediately (n = 4) or survived for 1 week (n = 4) post-treatment. Damage to the pancreas and surrounding tissue was characterized using gross morphology, histological analysis, and CT imaging. Results showed histotripsy bubble clouds were generated inside pancreases that were visually maintained on coaxial ultrasound (n = 4), with 2 pigs exhibiting off-target damage. For chronic animals, results showed the treatments were well-tolerated with no complication signs or changes in blood markers. This study provides initial evidence suggesting histotripsy's potential for noninvasive pancreas ablation and warrants further evaluation in more comprehensive studies.

[Large Animal Models in Pancreas and Biliary Disease]

Rodent models, which have played important roles in preclinical research of pancreas and biliary diseases, have some limitations to translating data from rodent models to human diseases. Large animal models have recently been developed to overcome these limitations and perform translational research of medical devices and drugs in pancreas and biliary diseases. Preclinical studies using large animal models are necessary before clinical application, especially for the research and development of equipment, instrumentation, and techniques in pancreato-biliary diseases. As long as the endoscope used in humans can enter an organ, there appears to be no limitation in terms of species or organ for endoscopic experiments of large animal models. Investigators have mainly used swine for pancreas and biliary endoscopic experiments. Until now, unique swine models that investigators have been established include the normal bile duct model, bile duct dilation model, bile duct dilation+direct peroral cholangioscopy model, benign biliary stricture model, hilar biliary obstruction model, and acute pancreatitis (post-ERCP pancreatitis) model. Many preclinical studies have been performed using these established endoscopy-based large animal models to develop novel medical devices. Furthermore, porcine pancreatic cancer models induced by a transgenic or orthotopic method are currently under development. These models appear to be available for general use in the future and will have multiple potential preclinical and clinical applications.