Non-human primates (NHP) are valuable models for late translational pre-clinical studies, often seen as a last step before clinical application. The unique similarity between NHPs and humans is often the subject of ethical concerns. However, it is precisely this analogy in anatomy, physiology, and the immune system that narrows the translational gap to other animal models in the cardiovascular field. Cell and gene therapy approaches are two dominant strategies investigated in the research field of cardiac regeneration. Focusing on the cell therapy approach, several xeno- and allogeneic cell transplantation studies with a translational motivation have been realized in macaque species. This is based on the pressing need for novel therapeutic options for heart failure patients. Stem cell-based remuscularization of the injured heart can be achieved via direct injection of cardiomyocytes (CMs) or patch application. Both CM delivery approaches are in the late preclinical stage, and the first clinical trials have started. However, are we already ready for the clinical area? The present review concentrates on CM transplantation studies conducted in NHPs, discusses the main sources and discoveries, and provides a perspective about human translation.

OBJECTIVE: Mechanical valves still require life-long anticoagulation. Preclinical animal testing is a crucial step in the assessment of valves; however, the chosen animal model should be carefully considered, and a well-controlled animal model of mechanical valve thrombosis has not been established yet. In this study, a histopathologic comparison was performed to evaluate the representativity of pigs and sheep as large animal models in bileaflet mechanical valve thrombosis research.
METHODS: 10 pigs and 8 sheep were implanted with a bileaflet mechanical valve in pulmonary position. During follow-up, no anticoagulative therapy was administered. Pigs were sacrificed between 14 and 38 days for explantation and assessment of the valve. Sheep were sacrificed between 71 and 155 days. Thrombus samples were processed and (immuno)histochemical stainings were applied. A pathologist evaluated the samples morphologically and semiquantitatively and compared these samples to available slides from 3 human patients who underwent redo surgery for acute bileaflet mechanical valve thrombosis, caused by insufficient anticoagulation.
RESULTS: All pigs showed macroscopically evident thrombi on the mechanical valve surface at sacrifice. In contrast, none of the sheep showed any sign of thrombus formation. Histology showed a high fibrin content in thrombi of both human and porcine cases (3/3 vs 8/10). Porcine thrombi showed more cellular organization (0/3 vs 6/10), more calcification (0/3 vs 9/10) and more endothelialization (0/3 vs 6/10). Inflammatory cells were present in all samples and were considered physiological.
CONCLUSIONS: Contrary to sheep, pigs develop thrombi on their mechanical valves in the short-term if no anticoagulation is administered. Histologic comparison of human and porcine thrombi shows comparable findings. The pig model might serve interestingly for further research on valve thrombosis, if it shows not to be an overly aggressive model.

Huntington\'s disease (HD) is a hereditary neurodegenerative disorder for which there is currently no effective treatment available. Consequently, the development of appropriate disease models is critical to thoroughly investigate disease progression. The genetic basis of HD involves the abnormal expansion of CAG repeats in the huntingtin ( HTT) gene, leading to the expansion of a polyglutamine repeat in the HTT protein. Mutant HTT carrying the expanded polyglutamine repeat undergoes misfolding and forms aggregates in the brain, which precipitate selective neuronal loss in specific brain regions. Animal models play an important role in elucidating the pathogenesis of neurodegenerative disorders such as HD and in identifying potential therapeutic targets. Due to the marked species differences between rodents and larger animals, substantial efforts have been directed toward establishing large animal models for HD research. These models are pivotal for advancing the discovery of novel therapeutic targets, enhancing effective drug delivery methods, and improving treatment outcomes. We have explored the advantages of utilizing large animal models, particularly pigs, in previous reviews. Since then, however, significant progress has been made in developing more sophisticated animal models that faithfully replicate the typical pathology of HD. In the current review, we provide a comprehensive overview of large animal models of HD, incorporating recent findings regarding the establishment of HD knock-in (KI) pigs and their genetic therapy. We also explore the utilization of large animal models in HD research, with a focus on sheep, non-human primates (NHPs), and pigs. Our objective is to provide valuable insights into the application of these large animal models for the investigation and treatment of neurodegenerative disorders.
亨廷顿舞蹈症(HD)是一种遗传性神经退行性疾病，目前尚无有效的治疗方法。因此，建立合适的动物疾病模型，对疾病进行深入、全面研究非常重要。HD是由亨廷顿( HTT)基因中CAG重复序列的异常扩增（≥36），导致HTT蛋白中多聚谷氨酰胺重复序列的扩增。突变HTT在大脑中发生错误折叠并聚集，导致特定脑区神经元选择性丧失。动物模型在阐明包括HD在内的神经退行性疾病发病机制以及探索潜在的治疗靶点方面发挥着重要作用。鉴于啮齿类动物与人类之间较大的物种差异，因此建立大动物模型是研究HD发病机制的重要手段，这将有助于新治疗靶点的发现，有效的药物递送方法探究，最终改善治疗效果。本综述旨在结合近年来关于HD大动物模型的建立及其基因治疗的研究进展，对HD大动物模型进行更全面的概述。在此我们探讨了大型动物模型，特别是绵羊、非人灵长类动物和猪在亨廷顿研究中的应用。我们期望这些在大动物模型上的发现，为研究和治疗神经退行性疾病提供有价值的见解。.

Pathologic cardiac hypertrophy is a common consequence of many cardiovascular diseases, including aortic stenosis (AS). AS is known to increase the pressure load of the left ventricle, causing a compensative response of the cardiac muscle, which progressively will lead to dilation and heart failure. At a cellular level, this corresponds to a considerable increase in the size of cardiomyocytes, known as cardiomyocyte hypertrophy, while their proliferation capacity is attenuated upon the first developmental stages. Cardiomyocytes, in order to cope with the increased workload (overload), suffer alterations in their morphology, nuclear content, energy metabolism, intracellular homeostatic mechanisms, contractile activity, and cell death mechanisms. Moreover, modifications in the cardiomyocyte niche, involving inflammation, immune infiltration, fibrosis, and angiogenesis, contribute to the subsequent events of a pathologic hypertrophic response. Considering the emerging need for a better understanding of the condition and treatment improvement, as the only available treatment option of AS consists of surgical interventions at a late stage of the disease, when the cardiac muscle state is irreversible, large animal models have been developed to mimic the human condition, to the greatest extend. Smaller animal models lack physiological, cellular and molecular mechanisms that sufficiently resemblance humans and in vitro techniques yet fail to provide adequate complexity. Animals, such as the ferret (Mustello purtorius furo), lapine (rabbit, Oryctolagus cunigulus), feline (cat, Felis catus), canine (dog, Canis lupus familiaris), ovine (sheep, Ovis aries), and porcine (pig, Sus scrofa), have contributed to research by elucidating implicated cellular and molecular mechanisms of the condition. Essential discoveries of each model are reported and discussed briefly in this review. Results of large animal experimentation could further be interpreted aiming at prevention of the disease progress or, alternatively, at regression of the implicated pathologic mechanisms to a physiologic state. This review summarizes the important aspects of the pathophysiology of LV hypertrophy and the applied surgical large animal models that currently better mimic the condition.

Delivery of therapeutics to solid tumors with high bioavailability remains a challenge and is likely the main contributor to the ineffectiveness of immunotherapy and chemotherapy. Here, a catheter-directed ionic liquid embolic (ILE) is bioengineered to achieve durable vascular embolization, uniform tissue ablation, and drug delivery in non-survival and survival porcine models of embolization, outperforming the clinically used embolic agents. To simulate the clinical scenario, rabbit VX2 orthotopic liver tumors are treated showing successful trans-arterial delivery of Nivolumab and effective tumor ablation. Furthermore, similar results are also observed in human ex vivo tumor tissue as well as significant susceptibility of highly resistant patient-derived bacteria is seen to ILE, suggesting that ILE can prevent abscess formation in embolized tissue. ILE represents a new class of liquid embolic agents that can treat tumors, improve the delivery of therapeutics, prevent infectious complications, and potentially increase chemo- and immunotherapy response in solid tumors.

The reconstruction of critical-size bone defects in long bones remains a challenge for clinicians. A new osteoinductive medical device is developed here for long bone repair by combining a 3D-printed architectured cylindrical scaffold made of clinical-grade polylactic acid (PLA) with a polyelectrolyte film coating delivering the osteogenic bone morphogenetic protein 2 (BMP-2). This film-coated scaffold is used to repair a sheep metatarsal 25-mm long critical-size bone defect. In vitro and in vivo biocompatibility of the film-coated PLA material is proved according to ISO standards. Scaffold geometry is found to influence BMP-2 incorporation. Bone regeneration is followed using X-ray scans, µCT scans, and histology. It is shown that scaffold internal geometry, notably pore shape, influenced bone regeneration, which is homogenous longitudinally. Scaffolds with cubic pores of ≈870 µm and a low BMP-2 dose of ≈120 µg cm-3 induce the best bone regeneration without any adverse effects. The visual score given by clinicians during animal follow-up is found to be an easy way to predict bone regeneration. This work opens perspectives for a clinical application in personalized bone regeneration.

OBJECTIVE: In this article, we review the most recent advancements in the approaches to EOS diagnosis and assessment, surgical indications and options, and basic science innovation in the space of early-onset scoliosis research.
RESULTS: Early-onset scoliosis (EOS) covers a diverse, heterogeneous range of spinal and chest wall deformities that affect children under 10 years old. Recent efforts have sought to examine the validity and reliability of a recently developed classification system to better standardize the presentation of EOS. There has also been focused attention on developing safer, informative, and readily available imaging and clinical assessment tools, from reduced micro-dose radiographs, quantitative dynamic MRIs, and pulmonary function tests. Basic science innovation in EOS has centered on developing large animal models capable of replicating scoliotic deformity to better evaluate corrective technologies. And given the increased variety in approaches to managing EOS in recent years, there exist few clear guidelines around surgical indications across EOS etiologies. Despite this, over the past two decades, there has been a considerable shift in the spinal implant landscape toward growth-friendly instrumentation, particularly the utilization of MCGR implants. With the advent of new biological and basic science treatments and therapies extending survivorship for disease etiologies associated with EOS, the treatment for EOS has steadily evolved in recent years. With this has come a rising volume and variation in management options for EOS, as well as the need for multidisciplinary and creative approaches to treating patients with these complex and heterogeneous disorders.

Implantation of engineered cartilage with soft callus features triggers remodeling to bone tissue via endochondral bone regeneration (EBR). Thus far, EBR has not progressed to the level of large animals on the axis of clinical translation. Herein, the feasibility of EBR is aimed for a critical-sized defect in a large animal model. Chondrogenesis is first induced in goat-derived multipotent mesenchymal stromal cells (MSCs) by fine-tuning the cellular differentiation process. Through a unique devitalization process, two off-the-shelf constructs aimed to recapitulate the different stages of the transient cartilaginous soft callus template in EBR are generated. To evaluate bone regeneration, the materials are implanted in an adapted bilateral iliac crest defect model in goats, featuring a novel titanium star-shaped spacer. After 3 months, the group at the more advanced differentiation stage shows remarkable regenerative capacity, with comparable amounts of bone regeneration as the autograft group. In contrast, while the biomaterial mimicking the earlier stages of chondrogenesis shows improved regeneration compared to the negative controls, this is subpar compared to the more advanced material. Concluding, EBR is attainable in large animals with a soft callus mimetic material that leads to fast conversion into centimeter-scale bone, which prospects successful implementation in the human clinics.

Traumatic brain injury (TBI) is a major contributor to morbidity and mortality in the United States as several million people visit the emergency department every year due to TBI exposures. Unfortunately, there is still no consensus on the pathology underlying mild TBI, the most common severity sub-type of TBI. Previous preclinical and post-mortem human studies have detailed the presence of diffuse axonal injury following TBI, suggesting that white matter pathology is the predominant pathology of diffuse brain injury. However, the inertial loading produced by TBI results in strain fields in both gray and white matter. In order to further characterize gray matter pathology in mild TBI, our lab used a pig model (n = 25) of closed-head rotational acceleration-induced TBI to evaluate blood-brain barrier disruptions, neurodegeneration, astrogliosis, and microglial reactivity in the cerebral cortex out to 1 year post-injury. Immunohistochemical staining revealed the presence of a hyper-ramified microglial phenotype-more branches, junctions, endpoints, and longer summed process length-at 30 days post injury (DPI) out to 1 year post injury in the cingulate gyrus (p < 0.05), and at acute and subacute timepoints in the inferior temporal gyrus (p < 0.05). Interestingly, we did not find neuronal loss or astroglial reactivity paired with these chronic microglia changes. However, we observed an increase in fibrinogen reactivity-a measure of blood-brain barrier disruption-predominately in the gray matter at 3 DPI (p = 0.0003) which resolved to sham levels by 7 DPI out to chronic timepoints. Future studies should employ gene expression assays, neuroimaging, and behavioral assays to elucidate the effects of these hyper-ramified microglia, particularly related to neuroplasticity and responses to potential subsequent insults. Further understanding of the brain\'s inflammatory activity after mild TBI will hopefully provide understanding of pathophysiology that translates to clinical treatment for TBI.

Gene therapy is a potential cure for several inherited retinal dystrophies, and adeno-associated virus (AAV) has emerged as a vector of choice for therapeutic gene delivery to the retina. However, prior exposure to AAVs can cause a humoral immune response resulting in the presence of antibodies in the serum, which can subsequently interfere with the AAV-mediated gene therapy. The antibodies bind specifically to a serotype but often display broad cross-reactivity. A subset of these antibodies called neutralizing antibodies (NABs) can render the AAV inactive, thereby reducing the efficacy of the therapy. The preexisting NAB levels against different serotypes vary by species, and these variations need to be considered while designing studies. Since large animals often serve as preclinical models to test gene therapies, in this review we compile studies reporting preexisting NABs against commonly used AAV serotypes in humans and large animal models and discuss strategies to deal with NABs.