Biomedical Porcine Models for the Study of Surgical Hemostasis, Hindlimb Ischemia, and Pancreatic Cancer

Murine models have dominated the world of biomedical research and comparative medicine since their development in the early 1900s. [1] While they may be suitable models to study proteomics and genomics, they may not serve as effective translational models. [2-4] Murine models do not accurately model the pathophysiology of human disease and are limited by their size, application of medical imaging and intervention, which reduces their overall preclinical predictive value. [2-4] Porcine models on the other hand, are slowly and steadily bridging the gap between murine models and human patients. [5] Pigs are more similar to humans than rodents in terms of size, anatomy, physiology, longevity and genetics. [5-7] In the world of translational research, swine models have been replacing commonly used mammalian and primate models (for instance dogs, monkeys) for preclinical toxicologic testing of medicinal drugs. [5, 8-10] Additionally, swine models can be used as unique tools to study medical imaging (Xray, CT, MRI etc.) to better characterize and understand pathology and interventional efficacy. [11] Our lab has been interested in producing new protocols and procedures to develop biomedical porcine models that can recapitulate human disease. In this dissertation we will present three porcine surgical models that have been developed to study human conditions with the ultimate intention to have a platform for the testing of new treatment strategies. 1) Surgical Hemostasis. In a non-survival, non-compressible hepatic resection swine model, our objective was to evaluate the acute efficacy of a hemostatic patch consisting of custom-made nano-engineered resorbable polycaprolactone (PCL) mesh embedded with human clotting factors. Normovolemic normothermic domestic swine were anesthetized, splenectomized, given a grade V liver injury and then randomized into different treatment groups of 1-hour duration. In this model of porcine hepatic resection, previously studied and standardized in our laboratory, we show that the resorbable PCL mesh, either alone or in combination with biologics, appeared to have equivalent hemostatic efficacy as the traditional surgical technique. 2) Hindlimb Ischemia. In a porcine model of hindlimb ischemia, our aim was to develop an animal model of end-organ disease for peripheral arterial disease, in order to have a platform to develop and optimize regenerative therapies. Here the domestic swine underwent open induction of right hind-limb ischemia via ligation of different arteries involved in the iliofemoral complex. FDA approved medical grade real-time X-ray fluoroscopy was used to shoot peripheral angiographies pre- and post-ligation on day zero, and then immediately prior to euthanasia on day 30, followed by necropsy. Cross comparison of the different ligation models produced measurable difference in end points - arterial pressure, muscle oxygen saturation, and treadmill stamina. We provide histological evidence of myopathy in the porcine model were comparable with human counterparts. 3) Pancreatic Cancer. In a novel porcine model of pancreatic cancer, our intention was to induce pancreatic ductal adenocarcinoma in a large animal (transgenic KRAS/p53 Oncopig) whose size was comparable with humans, which would provide us with a platform to use and test diagnostic and therapeutic strategies. AdCre injection of the transformed cells into the pancreatic duct and the parenchyma of five Oncopigs after four months failed to produce gross tumors but did show histological evidence cell proliferation with transgene expression. In conclusion, we show that these porcine surgical models are potential translational animal models that can mimic human disease and may provide more relevant data compared to rodent models. In these large animal models, we were able to use clinically relevant techniques, such as advanced medical imaging, to characterize and quantify the disease process which would not have been possible in murine models. Additionally, we demonstrated that these models could provide unique opportunities to test and develop novel diagnostic methods and therapies

Induction of pancreatic neoplasia in the KRAS/TP53 Oncopig

The 5-year survival of pancreatic cancer (PC) remains low. Murine models may not adequately mimic human PC and can be too small for medical device development. A large-animal PC model could address these issues. We induced and characterized pancreatic tumors in Oncopigs (transgenic swine containing KRAS(G12D) and TP53(R167H)). The oncopigs underwent injection of adenovirus expressing Cre recombinase (AdCre) into one of the main pancreatic ducts. Resultant tumors were characterized by histology, cytokine expression, exome sequencing and transcriptome analysis. Ten of 14 Oncopigs (71%) had gross tumor within 3 weeks. At necropsy, all of these subjects had gastric outlet obstruction secondary to pancreatic tumor and phlegmon. Oncopigs with injections without Cre recombinase and wild-type pigs with AdCre injection did not show notable effect. Exome and transcriptome analysis of the porcine pancreatic tumors revealed similarity to the molecular signatures and pathways of human PC. Although further optimization and validation of this porcine PC model would be beneficial, it is anticipated that this model will be useful for focused research and development of diagnostic and therapeutic technologies for PC. This article has an associated First Person interview with the joint first authors of the paper