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BackgroundLarge animal models of human neurological disorders are advantageous compared to rodent models due to their neuroanatomical complexity, longevity and their ability to be maintained in naturalised environments. Some large animal models spontaneously develop behaviours that closely resemble the symptoms of neural and psychiatric disorders. The horse is an example of this; the domestic form of this species consistently develops spontaneous stereotypic behaviours akin to the compulsive and impulsive behaviours observed in human neurological disorders such as Tourette’s syndrome. The ability to non-invasively probe normal and abnormal equine brain function through cognitive testing may provide an extremely useful methodological tool to assess brain changes associated with certain human neurological and psychiatric conditions.New methodAn automated operant system with the ability to present visual and auditory stimuli as well as dispense salient food reward was developed. To validate the system, ten horses were trained and tested using a standard cognitive task (three choice serial reaction time task (3-CSRTT)).ResultsAll animals achieved total learning criterion and performed six probe sessions. Learning criterion was met within 16.30 ± 0.79 sessions over a three day period. During six probe sessions, level of performance was maintained at 80.67 ± 0.57% (mean ± SEM) accuracy.Comparison with existing method(s)This is the first mobile fully automated system developed to examine cognitive function in the horse.ConclusionsA fully-automated operant system for mobile cognitive function of a large animal model has been designed and validated. Horses pose an interesting complementary model to rodents for the examination of human neurological dysfunction.

Background As novel treatment approaches for Huntington's disease (HD) evolve, the use of transgenic (tg) large animal models has been considered for preclinical safety and efficacy assessments. It is hoped that large animal models may provide higher reliability in translating preclinical findings to humans, e.g., by using similar endpoints and biomarkers. New method We here investigated the feasibility to conduct MRI assessments in a recently developed tgHD model in the Libechov minipig. The model is characterized by high genetic homology to humans and a similar body mass and compartments. The minipig brain provides anatomical features that are attractive for imaging studies and could be used as endpoints for disease modifying preclinical studies similar to human HD. Results We demonstrate that complex MRI protocols can be successfully acquired with tgHD and wild type (wt) Libechov minipigs. We show that acquisition of anatomical images applicable for volumetric assessments is feasible and outline the development of a segmented MRI brain atlas. Similarly diffusion-weighted imaging (DWI) including fiber tractography is presented. We also demonstrate the feasibility to conduct in vivo metabolic assessments using MR spectroscopy. Comparison with existing methods In human HD, these MRI methods are already validated and used as reliable biomarker of disease progression even before the onset of a clinical motor phenotype. Conclusions The results show that the minipig brain is well suited for MRI assessments in preclinical studies. We conclude that further characterization of phenotypical differences between tg and wt animals in sufficiently powered cross-sectional and longitudinal studies is warranted.

Background Development of new analgesic drugs or gene therapy vectors for spinal delivery will be facilitated by “hyperlocal” targeting of small therapeutic injectate volumes if spine imaging technology can be used that is ready for future clinical translation. New Method This study provides methods for MRI-guided drug delivery to the periganglionic epidural space and the dorsal root ganglion (DRG) in the Yucatan swine. Results Phantom studies showed artifact-corrected needle localization with frequency encoding parallel to the needle shaft, while maximizing bandwidth (125 KHz) minimized needle artifact. A custom constructed 8–12 element surface coil (phased array) wrapped over the spine in conjunction with lateral recumbent positioning achieved diagnostic quality signal to noise ratio at the depth of the DRG and afforded transforaminal access via anterolateral or posterolateral vectors, as well as interlaminar access. Swine epidural anatomy was homologous with human anatomy. Injectate containing 2% gadolinium allowed imaging of injectate volumes in increments as small as 10 microliters and discrimination of epidural flow from intraparenchymal injectate delivery into a DRG. All technical and technological elements of the procedure appear clinically translatable. Comparison with Existing Methods Computed tomographic or fluoroscopic guidance cannot directly visualize drug delivery into the DRG due to contrast medium toxicity, nor reliably identify epidural injection volumes of Conclusions MRI-guided hyperlocal delivery in swine provides a translatable and faithful model of future human spinal novel drug- or gene therapy vector delivery.

Background Many current neuroscience studies in large animal models have focused on recordings from cortical structures. While sufficient for analyzing sensorimotor systems, many processes are modulated by subcortical nuclei. Large animal models, such as nonhuman primates (NHP), provide an optimal model for studying these circuits, but the ability to target subcortical structures has been hampered by lack of a straightforward approach to targeting. New Method Here we present a method of subcortical targeting in NHP that uses MRI-compatible titanium screws as fiducials. The in vivo study used a cellular marker for histologic confirmation of accuracy. Results Histologic results are presented showing a cellular stem cell marker within targeted structures, with mean errors ± standard deviations (SD) of 1.40 ± 1.19 mm in the X-axis and 0.9 ± 0.97 mm in the Z-axis. The Y-axis errors ± SD ranged from 1.5 ± 0.43 to 4.2 ± 1.72 mm. Comparison with existing methods This method is easy and inexpensive, and requires no fabrication of equipment, keeping in mind the goal of optimizing a technique for implantation or injection into multiple interconnected areas. Conclusion This procedure will enable primate researchers to target deep, subcortical structures more precisely in animals of varying ages and weights.

The prognosis of glioblastoma remains poor despite significant improvement in cytoreductive surgery, external irradiation and new approach of systemic treatment as antiangiogenic therapy. One of the issues is the low concentration in the infiltrated parenchyma of therapeutic agent administered intravenously mainly due to the blood–brain barrier. An intracerebral injection is advocated to overpass this barrier, this kind of administration need a low flow and continuous injection. The development of sophisticated implanted devices for convection-enhanced delivery is a mandatory step to have a controlled released of a therapeutic agent in glioblastoma treatment. Before testing such a device in a clinical trial a serious preclinical studies are required, in order to test it in realistic conditions we have develop the first induced high grade glioma model in a non-rodent animal: the pig. 21 pigs have been implanted in the parietal lobe with human glioblastoma cell lineage under a chemical immunosuppression by ciclosporine. A MRI follow up was then realized. 15 pigs have been implanted with U87MG, 14 have presented a macroscopic significant tumor, with radiological and anatomapathological characteristics of high grade glioma. 6 pigs were implanted with G6, stem-like cells tumors of glioblastoma, 1 pig develops a macroscopic tumor. This is the first reproducible glioma model in a large animal described, it open the way to preclinical studies to test implanted devices in anatomic realistic conditions, without the ethical issues of a primate use.

Background Deep brain stimulation (DBS) in experimental animals has promoted new indications and refined existing treatments. Implantation of downscaled clinical DBS leads directly compatible with commercially available implantable pulse generators can however be challenging. Accordingly, we have developed a lead implantation device (LID) and technique for minimally invasive implantation of experimental multicontact DBS leads in large research animals. Materials and methods The LID carries a small-diameter biocompatible polyimide guide tube which is first used for inserting the stimulating end of the lead and then implanted subcutaneously with the rest of the lead. The functionality of the device was tested by implanting 2 different designs of experimental DBS leads in 12 Gottingen minipigs for up to 12 weeks. The brains were histologically analyzed in order to assess implantation accuracy and local tissue reaction. Results and conclusions The LID was easy to handle and capable of accurate stereotaxic implantation of downscaled experimental DBS leads in the predetermined target brain structures with minimal surrounding tissue reaction. The device may benefit future large animal DBS research as it allows for precise implantation of DBS leads and may have implications for further refinement of clinical DBS leads.

Research highlights ▶ Development of a highly accurate and robust method for MRI-guided, stereotactic delivery of catheters into the brain of pigs. ▶ Reliable head immobilisation, acquisition of high-resolution MR images, precise co-registration of MRI and stereotactic spaces to facilitate accurate burr hole-generation and catheter implantation. ▶ Implants were accurately placed into the putamen with a mean Euclidean distance of 0.623 mm (standard deviation of 0.33 mm)., Achieving accurate intracranial electrode or catheter placement is critical in clinical practice in order to maximise the efficacy of deep brain stimulation and drug delivery respectively as well as to minimise side-effects. We have developed a highly accurate and robust method for MRI-guided, stereotactic delivery of catheters and electrodes to deep target structures in the brain of pigs. This study outlines the development of this equipment and animal model. Specifically this system enables reliable head immobilisation, acquisition of high-resolution MR images, precise co-registration of MRI and stereotactic spaces and overall rigidity to facilitate accurate burr hole-generation and catheter implantation. To demonstrate the utility of this system, in this study a total of twelve catheters were implanted into the putamen of six Large White Landrace pigs. All implants were accurately placed into the putamen. Target accuracy had a mean Euclidean distance of 0.623 mm (standard deviation of 0.33 mm). This method has allowed us to accurately insert fine cannulae, suitable for the administration of therapeutic agents by convection-enhanced delivery (CED), into the brain of pigs. This study provides summary evidence of a robust system for catheter implantation into the brain of a large animal model. We are currently using this stereotactic system, implantation procedure and animal model to develop catheter-based drug delivery systems that will be translated into human clinical trials, as well as to model the distribution of therapeutic agents administered by CED over large volumes of brain.

Udgivelsesdato: 2009-Oct-15 We present a stereotaxic procedure enabling MRI-guided isocentric stereotaxy in pigs. The procedure is based on the Leksell stereotaxic arch principle, and a stereotaxic localizer box with an incorporated fiducial marking system (sideplates) defining a stereotaxic space similar to the clinical Leksell system. The obtained MRIs can be imported for 3D-reconstruction and coordinate calculation in the clinical stereotaxic software planning system (Leksell SurgiPlan, Elekta AB, Sweden). After MRI the sideplates are replaced by a modified Leksell arch accommodating clinical standard manipulators for isocentric placement of DBS-electrodes, neural tracers and therapeutics in the calculated target coordinates. The mechanical accuracy of the device was within 0.3-0.5 mm. Stereotaxic MRIs were imported to the stereotaxic software planning system with a mean error of 0.4-0.5 mm and a max error of 0.8-0.9 mm. Application accuracy measured on a phantom and on inserted skull markers in nine pigs was within 1 mm in all planes. The intracerebral application accuracy found after placement of 10 manganese trajectories within the full extent of the intracerebral stereotaxic space in two minipigs was equally randomly distributed and within 0.7+/-0.4; 0.5+/-0.4; and 0.7+/-0.3mm in the X, Y, and Z plane. Injection of neural tracers in the subgenual gyrus of three minipigs and placement of encapsulated gene-modified cells in four minipigs confirmed the accuracy and functionality of the described procedure. We conclude that the devised technique and instrumentation enable high-precision stereotaxic procedures in pigs that may benefit future large animal neuroscience research and outline the technical considerations for a similar stereotaxic methodology in other animals.

Background While several novel therapeutic approaches for HD are in development, resources to conduct clinical trials are limited. Large animal models have been proposed to improve assessment of safety, tolerability and especially to increase translational reliability of efficacy signals obtained in preclinical studies. They may thus help to select candidates for translation to human studies. We here introduce a battery of novel tests designed to assess the motor, cognitive and behavioral phenotype of a transgenic (tg) HD minipig model. New methods A group of tgHD and wildtype (wt) Libechov minipigs (n = 36) was available for assessment with (1) a gait test using the GAITRite® automated acquisition system, (2) a hurdle-test, (3) a tongue coordination test, (4) a color discrimination test, (5) a startbox back and forth test and (6) a dominance test. Performance of all tests and definition of measures obtained is presented. Results Minipigs were able to learn performance of all tests. All tests were safe, well tolerated and feasible. Exploratory between group comparisons showed no differences between groups of tgHD and wt minipigs assessed, but low variability within and between groups. Comparison with existing method(s) So far there are no established or validated assessments to test minipigs in the domains described. Conclusions The data shows that the tests presented are safe, well tolerated and all measures defined can be assessed. Prospective longitudinal application of these tests is warranted to determine their test–retest reliability, sensitivity and validity in assessing motor, cognitive and behavioral features of tg and wt minipigs.