The Pig as a Translational Animal Model for Biobehavioral and Neurotrauma Research

Brains in space: impact of microgravity and cosmic radiation on the CNS during space exploration

Solar system exploration is a grand endeavour of humankind. Space agencies have been planning crewed missions to the Moon and Mars for several decades. However, several environmental stress factors in space, such as microgravity and cosmic radiation, confer health risks for human explorers. This Review examines the effects of microgravity and exposure to cosmic radiation on the CNS. Microgravity presents challenges for the brain, necessitating the development of adaptive movement and orientation strategies to cope with alterations in sensory information. Exposure to microgravity also affects cognitive function to a certain extent. Recent MRI results show that microgravity affects brain structure and function. Post-flight recovery from these changes is gradual, with some lasting up to a year. Regarding cosmic radiation, animal experiments suggest that the brain could be much more sensitive to this stressor than may be expected from experiences on Earth. This may be due to the presence of energetic heavy ions in space that have an impact on cognitive function, even at low doses. However, all data about space radiation risk stem from rodent experiments, and extrapolation of these data to humans carries a high degree of uncertainty. Here, after presenting an overview of current knowledge in the above areas, we provide a concise description of possible counter-measures to protect the brain against microgravity and cosmic radiation during future space missions.

Distribution of ganciclovir in the porcine central nervous system

Ganciclovir is often used compassionately for encephalitis due to cytomegalovirus (CMV) and human herpes virus 6b (HHV-6b). Ganciclovir pharmacokinetic studies in the central nervous system (CNS) generally rely on single measurements in the cerebrospinal fluid (CSF) or homogenized brain tissue. Therefore the objective was to compare brain extracellular fluid (ECF) concentrations of ganciclovir with plasma and CSF concentrations in a porcine model, using microdialysis during a 24 h period. Six Danish landrace pigs (female, age 4 months, 31-37 kg) received two weight-adjusted intravenous doses of ganciclovir. Unbound ganciclovir concentrations were determined by microdialysis over 24 h in five compartments: CSF (lateral ventricle, cisterna magna, and lumbar) and brain ECF (cortical and subcortical). Data were compared with paired plasma samples. Ganciclovir concentrations >IC50 for CMV (1.6 µg/mL) were achieved in all compartments. Concentrations >IC90 for CMV (8.3 µg/mL) were only achieved in plasma and the lumbar CSF compartment. The concentration time curves indicated higher lumbar and cisternal CSF concentrations than ECF concentrations. The ECF compartments achieved greater maximum concentration (Cmax), area under the concentration time curve (AUC), and time >IC50 after the second dose, and an accumulation ratio (Rac) >1. The greater Cmax, AUC, time >IC50, and Rac >1 in the ECF compartments with repeated dosages suggest that therapeutic concentrations may be achieved during long-term treatment. A higher loading dose might be warranted to improve early viral inhibition.

Unravelling Secondary Brain Injury: Insights from a Human-Sized Porcine Model of Acute Subdural Haematoma

Traumatic brain injury (TBI) remains one of the leading causes of death. Because of the individual nature of the trauma (brain, circumstances and forces), humans experience individual TBIs. This makes it difficult to generalise therapies. Clinical management issues such as whether intracranial pressure (ICP), cerebral perfusion pressure (CPP) or decompressive craniectomy improve patient outcome remain partly unanswered. Experimental drug approaches for the treatment of secondary brain injury (SBI) have not found clinical application. The complex, cellular and molecular pathways of SBI remain incompletely understood, and there are insufficient experimental (animal) models that reflect the pathophysiology of human TBI to develop translational therapeutic approaches. Therefore, we investigated different injury patterns after acute subdural hematoma (ASDH) as TBI in a post-hoc approach to assess the impact on SBI in a long-term, human-sized porcine TBI animal model. Post-mortem brain tissue analysis, after ASDH, bilateral ICP, CPP, cerebral oxygenation and temperature monitoring, and biomarker analysis were performed. Extracerebral, intraparenchymal-extraventricular and intraventricular blood, combined with brainstem and basal ganglia injury, influenced the experiment and its outcome. Basal ganglia injury affects the duration of the experiment. Recognition of these different injury patterns is important for translational interpretation of results in this animal model of SBI after TBI.

Development and evaluation of an autism pig model

Developing cost-effective and disease-relevant animal models is essential for advancing biomedical research into human disorders. Here we investigate the feasibility of a pig model for autism spectrum disorder (ASD) using embryonic exposure to valproic acid (VPA), an antiepileptic drug known to increase ASD risk. We established experimental paradigms to assess the behavioral characteristics of these pig models. Administration of VPA to Bama miniature pigs (Sus scrofa domestica) during critical embryonic stages resulted in abnormal gait, increased anxiety levels, reduced learning capabilities and altered social patterns, while largely preserving social preference of treated piglets. Notably, we detected significant neuroanatomical changes in cortical regions associated with ASD in the VPA-treated pigs, including cortical malformation, increased neuronal soma size, decreased dendritic complexity and reduced dendritic spine maturation. Transcriptome analysis of the prefrontal cortex of VPA-treated pigs further revealed substantial alterations in the expression of genes linked to ASD, especially genes of the dopamine signaling pathway, highlighting the model's relevance and potential for shedding light on ASD's underlying neuropathological and molecular mechanisms. These findings suggest that pig models could serve as a promising alternative to traditional rodent models and provide a more ethical substitute for the use of primates in translational research on neurodevelopmental disorders.

Approachability and Sensory Changes Following Mild Traumatic Brain Injury in Pigs

BACKGROUND/OBJECTIVES

Traumatic brain injury (TBI) is a global healthcare concern affecting millions, with wide-ranging symptoms including sensory and behavioral changes that can persist long-term. Due to similarities with human brain cytoarchitecture and inflammation, minipig models are advantageous for translational TBI research. However, gaps in knowledge exist regarding their behavioral and sensory sequelae following injury.

METHODS

Therefore, in this study, we assessed changes in approachability using a forced human approach task (FHAT) and mechanical nociception using the von Frey test in adult male and female Yucatan minipigs for up to one week following a sham or central fluid percussion injury (cFPI). Specifically, the FHAT assessed each animal's response to a forced interaction with either a known or unknown experimenter. To evaluate changes in nociceptive sensory sensitivity, von Frey monofilaments ranging from 0.008 to 300 g of force were applied to the pinna of the ear or base of the tail.

RESULTS

We found that forced approachability was affected by experimenter familiarity as well as cFPI in a sex-specific manner at subacute timepoints. We also found reductions in sensitivity following cFPI on the ear in male minipigs and on the tail in female minipigs.

CONCLUSION

Overall, the current study demonstrates that cFPI produces both behavioral and sensory changes in minipigs up to one-week post-injury.

Development and optical characterisation of agarose-based phantoms mimicking biological tissues for studies of light penetration in the brain

Searching for materials that accurately mimic the optical properties of biological tissues is essential, particularly for transcranial photobiomodulation (PBM) research, where it is necessary to comprehend how light propagates through the head tissues. In this research, we characterised, in the 500-1200 nm range, the transmittance spectra of porcine tissues (skin, muscle, cranium, brain, and cerebellum) and different agarose-based phantoms. These phantoms were developed using different combinations of titanium dioxide (TiO2), India ink, organometallic compounds, and laser-ablated gold and zinc oxide nanoparticles. The surface and mechanical properties of these phantoms were also characterized. The results showed that an increased TiO2 concentration decreased the optical transmittance of the phantoms. However, when TiO2 was added to the India ink and laser-ablated nanoparticles' phantoms, not only did it reduce transmittance amplitude, but it also flattened its spectra. Comparing the phantoms and biological tissues' results, the spectral profiles of TiO2 samples appeared similar to those of muscle, skin, and brain/cerebellum; organometallic compounds replicated the skin and muscle curves; India ink emulated skin and cranium; and the laser-ablated nanoparticles mimicked the muscle. Although it was possible to establish qualitative similarities between the phantoms and the biological tissues' optical transmittance spectra, there is a need for further studies with different components' combinations to ascertain curves that more closely mimic the biological tissues.

Methodological Approaches to Experimental Evaluation of Neuroprotective Action of Potential Drugs

The authors propose a novel approach to a comprehensive evaluation of neuroprotective effects using both in vitro and in vivo methods. This approach allows for the initial screening of numerous newly synthesized chemical compounds and substances from plant and animal sources while saving animal life by reducing the number of animals used in research. In vitro techniques, including mitochondrial suspensions and neuronal cell cultures, enable the assessment of neuroprotective activity, which can be challenging in intact organisms. The preliminary methods help outline the neuroprotection mechanism depending on the neurodestruction agent. The authors have validated a model of acute cerebrovascular accident, which simulates key cerebrovascular phenomena such as reduced cerebral blood flow, energy deficit, glutamate-calcium excitotoxicity, oxidative stress, and early gene expression. A significant advantage of this model is its ability to reproduce the clinical picture of cerebral ischemia: impaired motor activity; signs of neurological deficits (paresis, paralysis, etc.); as well as disturbances in attention, learning, and memory. Crucial to this approach is the selection of biochemical, molecular, and cellular markers to evaluate nerve tissue damage and characterize potential neuroprotective agents. Additionally, a comprehensive set of molecular, biochemical, histological, and immunohistochemical methods is proposed for evaluating neuroprotective effects and underlying mechanisms of potential pharmaceutical compounds.

Stroke studies in large animals: Prospects of mitochondrial transplantation and enhancing efficiency using hydrogels and nanoparticle-assisted delivery

One of the most frequent reasons for mortality and disability today is acute ischemic stroke, which occurs by an abrupt disruption of cerebral circulation. The intricate damage mechanism involves several factors, such as inflammatory response, disturbance of ion balance, loss of energy production, excessive reactive oxygen species and glutamate release, and finally, neuronal death. Stroke research is now carried out using several experimental models and potential therapeutics. Furthermore, studies are being conducted to address the shortcomings of clinical care. A great deal of research is being done on novel pharmacological drugs, mitochondria targeting compounds, and different approaches including brain cooling and new technologies. Still, there are many unanswered questions about disease modeling and treatment strategies. Before these new approaches may be used in therapeutic settings, they must first be tested on large animals, as most of them have been done on rodents. However, there are several limitations to large animal stroke models used for research. In this review, the damage mechanisms in acute ischemic stroke and experimental acute ischemic stroke models are addressed. The current treatment approaches and promising experimental methods such as mitochondrial transplantation, hydrogel-based interventions, and strategies like mitochondria encapsulation and chemical modification, are also examined in this work.

Development of the PD9-9 Monoclonal Antibody for Identifying Porcine Bone Marrow-Derived Dendritic Cells

The purpose of this study was to develop a monoclonal antibody (mAb) that can identify porcine dendritic cells (DCs) that have differentiated from bone marrow progenitor cells. Hybridoma technology was used to obtain mAbs, and bone marrow-derived DCs (BMDCs) were employed as immunogens for producing antibodies. The generated PD9-9 mAbs exhibited considerable reactivity towards porcine BMDCs with applications in flow cytometry and immunostaining. The antibody was composed of heavy immunoglobulin gamma-1 chains and light kappa chains. The PD9-9 mAb recognized fully differentiated porcine BMDCs and cells undergoing DC differentiation. In contrast, bone marrow cells and macrophages were not recognized by PD9-9. In addition, the PD9-9 mAb promoted porcine DC proliferation. Consequently, the PD9-9 mAb may be a biomarker for porcine DCs and will be advantageous for investigating porcine DC biology.

Distinct Serum Glial Fibrillary Acidic Protein and Neurofilament Light Time-Courses After Rapid Head Rotations

Traumatic brain injury (TBI) causes significant neurophysiological deficits and is typically associated with rapid head accelerations common in sports-related incidents and automobile accidents. There are over 1.5 million TBIs in the United States each year, with children aged 0-4 being particularly vulnerable. TBI diagnosis is currently achieved through interpretation of clinical signs and symptoms and neuroimaging; however, there is increasing interest in minimally invasive fluid biomarkers to detect TBI objectively across all ages. Pre-clinical porcine models offer controlled conditions to evaluate TBI with known biomechanical conditions and without comorbidities. The objective of the current study was to establish pediatric porcine healthy reference ranges (RRs) of common human serum TBI biomarkers and to report their acute time-course after nonimpact rotational head injury. A retrospective analysis was completed to quantify biomarker concentrations in porcine serum samples collected from 4-week-old female (n = 215) and uncastrated male (n = 6) Yorkshire piglets. Subjects were assigned to one of three experimental groups (sham, sagittal-single, sagittal-multiple) or to a baseline only group. A rapid nonimpact rotational head injury model was used to produce mild-to-moderate TBI in piglets following a single rotation and moderate-to-severe TBI following multiple rotations. The Quanterix Simoa Human Neurology 4-Plex A assay was used to quantify glial fibrillary acidic protein (GFAP), neurofilament light (Nf-L), tau, and ubiquitin carboxyl-terminal hydrolase L1 (UCH-L1). The 95% healthy RRs for females were calculated and validated for GFAP (6.3-69.4 pg/mL), Nf-L (9.5-67.2 pg/mL), and UCH-L1 (3.8-533.7 pg/mL). Rising early, GFAP increased significantly above the healthy RRs for sagittal-single (to 164 and 243 pg/mL) and increased significantly higher in sagittal-multiple (to 494 and 413 pg/mL) groups at 30 min and 1 h postinjury, respectively, returning to healthy RRs by 1-week postinjury. Rising later, Nf-L increased significantly above the healthy RRs by 1 day in sagittal-single (to 69 pg/mL) and sagittal-multiple groups (to 140 pg/mL) and rising further at 1 week (single = 231 pg/mL, multiple = 481 pg/mL). Sagittal-single and sagittal-multiple UCH-L1 serum samples did not differ from shams or the healthy RRs. Sex differences were observed but inconsistent. Serum GFAP and Nf-L levels had distinct time-courses following head rotations in piglets, and both corresponded to load exposure. We conclude that serum GFAP and Nf-L offer promise for early TBI diagnosis and intervention decisions for TBI and other neurological trauma.

Histology, histochemistry and ultrastructure of cornea of domestic pigs (Sus scrofa domesticus)

A comprehensive light and ultrastructural examination of the cornea in Domestic Pigs (Sus scrofa domesticus) revealed four distinct layers: the anterior epithelium, corneal stroma, Descemet's membrane and endothelium. Although Bowman's layer was not distinctly identified through histology, histochemical analysis indicated the presence of a rudimentary Bowman's layer, possibly vestigial from evolution. Scanning electron microscopy of the outer corneal surface unveiled two cell types, characterized by micro-projections, with light cells exhibiting shorter, thicker projections compared to dark cells. Examination of the inner surface via scanning electron microscopy demonstrated an endothelial layer devoid of cilia and microvilli, yet faint round to oval elevations were observed, potentially representing cell nuclei. Transmission electron microscopy unveiled that basal cells of the anterior epithelium closely adhered to the basement membrane, featuring half desmosomes along the basal surface. These basal cells extensively interconnected through interdigitations and a few desmosomes. The superficial cell layer consisted of a few rows of closely attached flat cells, forming a leak-proof layer with zona occludens. The outermost cells of this layer displayed fine projections to enhance the surface area, facilitating tear film distribution. At lower magnification, Transmission electron microscopy of the corneal stroma revealed alternating light and dark bands, with light bands representing transverse sections of collagen fibril lamellae and dark bands corresponding to longitudinal or oblique sections. Spindle-shaped keratocytes (fibroblasts) were identified as the primary stromal cells, intermingled between the lamellae, and featured long processes in close contact with neighbouring keratocytes. Overall, the histomorphology of the pig cornea resembles that of the human cornea except indistinct Bowman's membrane. This detailed understanding of the normal corneal structure in pigs hold great significance for biomedical research, providing a valuable reference for studies involving this animal model.

Porcine Models of Neurotrauma and Neurological Disorders

The translation of therapeutics from lab to clinic has a dismal record in the fields of neurotrauma and neurological disorders [...].