A Translational 'Humanised' Porcine Model for Trans-Septal Mitral Valve Interventions: the Right Pulmonary Vein Approach.

There is an important need to develop a transcatheter/trans-septal-like model which will allow deliverability of mitral valve devices at the right angulation and height above the mitral annulus similar to the human patient. A ministernotomy allowing for TEE probe to be introduced transpericardially was performed in seven animals. In three, a standard trans-septal approach was used to attempt to deliver a device to the level of the mitral plane with a human delivery system. In four cases, a Dacron tube was connected to the RPV and the device introduced to the LA. Under TEE equivalent imaging, the device was then successfully steered to the mitral plane in all cases, having failed in all trans-septal attempts. A combination of transpericardial echocardiographic imaging (TPE) and RPV approach to the LA facilitated successful human-like mitral valve device implantation.

Development of a porcine hard-to-heal wound model: evaluation of a bromelain-based enzymatic debriding agent.

AIMS: We describe the development of a novel porcine eschar model and compare the debridement efficacy of various concentrations of a novel bromelain-based enzymatic agent with collagenase. METHODS: Full thickness excisional wounds were created on pigs and injected intradermally with various doses of doxorubicin. Wounds were monitored for a period of 46 days for the development of eschar and wound closure. After determining the optimal concentration and dose of doxorubicin resulting in non-healing eschars, these conditions were used to create additional wounds on another set of animals. The resulting eschars were treated with various concentrations of a novel bromelain-based enzymatic agent (EscharEx-02) or collagenase. The primary endpoint was greater than 95% removal of the central eschar. RESULTS: Consistent eschars composed of two distinct areas (a central area of exudate and slough representing the hard-to-heal wound bed, and a peripheral area of full-thickness mummified necrosis) were seen after injection of doxorubicin (0.5 ml/cm2 of stock solution 0.75mg/ml) at one and six days after wound creation. Complete removal of the central eschar was achieved in all wounds after five and eight treatments with 5% and 2% EscharEx-02 respectively. Complete removal of the central eschar with collagenase was achieved in 0% and 82% of the wounds after 10 and 16 treatments respectively. CONCLUSIONS: We describe a porcine model for creating eschars similar to hard-to-heal wounds in humans. A novel bromelain-based enzymatic debridement agent was more effective than a commercially available collagenase in removing eschars in this wound model.

A novel fully tapered, self-cutting tissue-level implant: non-inferiority study in minipigs.

OBJECTIVES: To assess the osseointegration and crestal bone level maintenance of a novel fully tapered self-cutting tissue-level implant for immediate placement (test) compared to a clinically established tissue-level implant (control) in moderate bone quality. MATERIALS AND METHODS: Test and control implants were compared in 3 groups, i.e., small-, medium-, and large-diameter implants in an edentulous mandibular minipig model with moderate bone quality after 12 weeks of healing. Histometrically derived bone-to-implant contact (BIC) and first bone-to-implant contact (fBIC) were subjected to statistical non-inferiority testing. Maximum insertion torque values in artificial bone were assessed for comparison. RESULTS: BIC values for the tests and control implants for all 3 diameters were comparable and non-inferior: small diameter (61.30 ± 10.63% vs. 54.46 ± 18.31%) (p=0.99), medium diameter (60.91 ± 14.42 vs. 54.68 ± 9.16) (p=0.55), and large diameter (45.60 ± 14.67 vs. 52.52 ± 14.76) (p=0.31). fBIC values for test implants were higher and non-inferior compared to control implants in all three groups. Test implants further showed distinctly higher maximum insertion torque values compared to control implants. CONCLUSION: The investigated novel tissue-level implant is able to achieve high levels of primary and secondary implant stability under simultaneous preservation of crestal bone levels. This qualifies the studied implant as an attractive candidate for immediate placement in bone of limited quality. CLINICAL RELEVANCE: This pilot pre-clinical study investigated a novel tissue-level implant for immediate placement. With the aim of translating the studied prototype into clinical application pre-clinical models, procedures and controls have been chosen with the aim of reflecting its future clinical indication and use.

Transpericardial 3D Echocardiography in the Sheep Model, Facilitating Real Time Anatomical Assessment for Planning and Guiding Transcatheter Mitral Valve Replacement and Repair.

INTRODUCTION: Symptomatic mitral regurgitation (MR) is associated with high morbidity and mortality which can be ameliorated by surgical valve replacement or repair. Despite this, many patients are excluded from surgery. Transcatheter mitral repair and replacement has emerged as a promising therapeutic option for the treatment of severe MR. The majority of these procedures rely on high definition three dimensional (3D) transesophageal echocardiographic (TEE) real time imaging. The sheep model is the model of choice for preclinical studies of transcatheter mitral valve (MV) replacement and repair. However due to the thoracic conformation TEE studies in those animals are suboptimal. METHODS AND RESULTS: In this study we tested and compared the feasibility of conventional TEE and newly described transpericardial 3D echocardiography (TPE) for assessment of the MV as a tool to plan and possibly guide transcatheter/transapical procedures in the sheep model. The conventional TEE was challenging and produced incomplete data in all of the animals. In contrast, the TPE method clearly depicted the left atria and ventricle, MV apparatus, LVOT, aortic valve and proximal ascending aorta facilitating high resolution 3D rendering in all of the animals. CONCLUSION: The value of TEE in the sheep model is limited and could not be reliable for complete assessment of the LV and mitral valve apparatus. Whereas, TPE produce reliable and similar imaging to TEE in the human patients which could allow animal testing of devices designed to be delivered in humans.

Human-like cutaneous neuropathologies associated with a porcine model of peripheral neuritis: A translational platform for neuropathic pain.

Despite enormous investment in research and development of novel treatments, there remains a lack of predictable, effective, and safe therapeutics for human chronic neuropathic pain (NP) afflictions. NP continues to increase among the population and treatments remain a major unmet public health care need. In recent years, numerous costly (time and money) failures have occurred attempting to translate successful animal pain model results, typically using rodents, to human clinical trials. These continued failures point to the essential need for better animal models of human pain conditions. To address this challenge, we have previously developed a peripheral neuritis trauma (PNT) model of chronic pain induced by a proximal sciatic nerve irritation in pigs, which have a body size, metabolism, skin structure, and cutaneous innervation more similar to humans. Here, we set out to determine the extent that the PNT model presents with cutaneous neuropathologies consistent with those associated with human chronic NP afflictions. Exactly as is performed in human skin biopsies, extensive quantitative multi-molecular immunofluorescence analyses of porcine skin biopsies were performed to assess cutaneous innervation and skin structure. ChemoMorphometric Analysis (CMA) results demonstrated a significant reduction in small caliber intraepidermal nerve fiber (IENF) innervation, altered dermal vascular innervation, and aberrant analgesic/algesic neurochemical properties among epidermal keratinocytes, which are implicated in modulating sensory innervation. These comprehensive pathologic changes very closely resemble those observed from CMA of human skin biopsies collected from NP afflictions. The results indicate that the porcine PNT model is more appropriate for translational NP research compared with commonly utilized rodent models. Because the PNT model creates cutaneous innervation and keratinocyte immunolabeling alterations consistent with human NP conditions, use of this animal model for NP testing and treatment response characteristics will likely provide more realistic results to direct successful translation to humans.

Open field and a behavior score in PNT model for neuropathic pain in pigs.

BACKGROUND: Rodent models are frequently used in the research of pain and continue to provide valuable data on the mechanisms driving pain, although they are criticized due to limited translational ability to human conditions. Previously we have suggested pigs as a model for development of drugs for neuropathic pain. In this study, we investigate the spontaneous behavior of pigs following peripheral neuritis trauma (PNT)-induced neuropathic pain. METHODS: A computerized monitoring system was used to evaluate the changes in open field test in addition to applying a composite behavior scoring system. The data suggest that the PNT operation did not affect the animal's ability to walk as the total distance walked by PNT animals was not significantly different from the total distance walked by sham-operated animals. However, PNT animals expressed a significant change in the pattern of walking. This effect was unrelated to the time that the animals spent in the open field. Following treatment with different drugs (morphine, buprenorphine, or gabapentin), the walking pattern of the animals in the open field changed in a drug-specific manner. In addition, the detailed behavior score revealed drug-specific changes following treatment. RESULTS: Pharmacokinetic analysis of the drug concentration in blood and cerebrospinal fluid correlated with the behavioral analysis. CONCLUSION: The data of this study suggest that the open field test together with the detailed behavior score applied in this model are a powerful tool to assess the spontaneous behavior of pigs following PNT-induced neuropathic pain.

The effect of local/topical analgesics on incisional pain in a pig model.

Interest in the development of new topical/local drug administration for blocking pain at peripheral sites, with maximum drug activity and minimal systemic effects, is on the rise. In the review article by Kopsky and Stahl, four critical barriers in the process of research and development of topical analgesics were indicated. The active pharmaceutical ingredient (API) and the formulation are among the major challenges. The road to the development of such drugs passes through preclinical studies. These studies, if planned correctly, should serve as guidance for choosing the right API and formulation. Although rodent models for pain continue to provide valuable data on the mechanisms driving pain, their use in developing topical and localized treatment approaches is limited for technical (intraplate injection area is small) as well as mechanical reasons (non-similarity to human skin and innervation). It has been previously shown that pigs are comparable to humans in ways that make them a better choice for evaluating topical and local analgesics. The aim of this study was to summarize several experiments that used pigs for testing postoperative pain in an incisional pain model (skin incision [SI] and skin and muscle incision [SMI]). At the end of the surgery, the animals were treated with different doses of bupivacaine solution (Marcaine®), bupivacaine liposomal formulation (Exparel®) or ropivacaine solution (Naropin). Von Frey testing demonstrated a decrease in the animals' sensitivity to mechanical stimulation expressed as an increase in the withdrawal force following local treatment. These changes reflect the clinical condition in the level as well as in the duration of the response. These data indicate a good resemblance between pig and human skin and suggest that use of these animals in the preclinical phase of developing topical analgesics can, to some extent, release the bottleneck.

Peripheral Neuritis Trauma in Pigs: A Neuropathic Pain Model.

UNLABELLED: The use of rodents in preclinical studies has contributed greatly to our understanding of the pathophysiology of chronic neuropathic pain. These animal models are limited because of their poor clinical translation. We developed a pig model for chronic pain caused by surgically induced peripheral neuritis trauma (PNT). Seventy-five percent of the animals exhibited mechanical and tactile allodynia, which are indicative of painful neuropathy, by day 28 after surgery. Importantly, the PNT-injured pigs retained their ability to walk or to stand on their injured leg. Messenger RNA analysis of acute inflammatory cytokines calcitonin gene-related peptide and brain-derived neurotrophic factor at the site of injury suggests transient inflammation followed by a persistent high level of neurologic markers. Gabapentin and morphine effectively inhibited hypersensitivity to von Frey filaments and to feather stimuli, and reversed spontaneous pain-related behavior in a dose-related manner. No analgesic effect was detected in PNT-injured pigs after treatment with aprepitant, similar to observations in humans and contrary to observations in rodents. In conclusion, PNT-induced trauma in pigs may comprise a valid preclinical model for the study of the chronification of peripheral nerve injury and for the study of new pain therapies. PERSPECTIVE: This article presents the characterization of a new peripheral neuritis trauma (PNT) model in pigs. The pig PNT model could help close the translational gap between preclinical and clinical responses and may contribute to improved efficacy or safety of candidate drugs.