Genetically modified pigs:Emerging animal models for hereditary hearing loss

Hereditary hearing loss(HHL),a genetic disorder that impairs auditory function,significantly affects quality of life and incurs substantial economic losses for society.To investigate the underlying causes of HHL and evaluate therapeutic outcomes,appropriate animal models are necessary.Pigs have been extensively used as valuable large animal models in biomedical research.In this review,we highlight the advantages of pig models in terms of ear anatomy,inner ear morphology,and electrophysiological characteristics,as well as recent advancements in the development of distinct genetically modified porcine models of hearing loss.Additionally,we discuss the prospects,challenges,and recommendations regarding the use pig models in HHL research.Overall,this review provides insights and perspectives for future studies on HHL using porcine models.

Large animal models for Huntington's disease research

Huntington'sdisease(HD)isahereditary neurodegenerative disorder for which there is currently no effectivetreatmentavailable.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.

Neurophysiological, histological, and behavioral characterization of animal models of distraction spinal cord injury: a systematic review

Distraction spinal cord injury is caused by some degree of distraction or longitudinal tension on the spinal cord and commonly occurs in patients who undergo corrective operation for severe spinal deformity.With the increased degree and duration of distraction,spinal cord injuries become more serious in terms of their neurophysiology,histology,and behavior.Very few studies have been published on the specific characteristics of distraction spinal cord injury.In this study,we systematically review 22 related studies involving animal models of distraction spinal cord injury,focusing particularly on the neurophysiological,histological,and behavioral characteristics of this disease.In addition,we summarize the mechanisms underlying primary and secondary injuries caused by distraction spinal cord injury and clarify the effects of different degrees and durations of distraction on the primary injuries associated with spinal cord injury.We provide new concepts for the establishment of a model of distraction spinal cord injury and related basic research,and provide reference guidelines for the clinical diagnosis and treatment of this disease.

Animal models of hepatitis E infection: Advances and challenges

Hepatitis E virus(HEV)is one of the leading causes of acute viral hepatitis worldwide.Although most of HEV infections are asymptomatic,some patients will develop the symptoms,especially pregnant women,the elderly,and patients with preexisting liver diseases,who often experience anorexia,nausea,vom-iting,malaise,abdominal pain,and jaundice.HEV infection may become chronic in immunosuppressed individuals.In addition,HEV infection can also cause several extrahepatic manifestations.HEV exists in a wide range of hosts in nature and can be transmitted across species.Hence,animals susceptible to HEV can be used as models.The establishment of animal models is of great significance for studying HEV transmission,clinical symptoms,extrahepatic manifestations,and therapeutic strategies,which will help us understand the pathogenesis,prevention,and treatment of hepatitis E.This review summarized the animal models of HEV,including pigs,monkeys,rabbits,mice,rats,and other animals.For each animal species,we provided a concise summary of the HEV genotypes that they can be infected with,the cross-species transmission pathways,as well as their role in studying extrahepatic manifestations,prevention,and treatment of HEV infection.The advantages and disadvantages of these animal models were also emphasized.This review offers new perspectives to enhance the current understanding of the research landscape surrounding HEV animal models.

Knee osteoarthritis:A review of animal models and intervention of traditional Chinese medicine

Background:Knee osteoarthritis(KOA)characterized by degeneration of knee cartilage and subsequent bone hyperplasia is a prevalent joint condition primarily affecting aging adults.The pathophysiology of KOA remains poorly understood,as it involves complex mechanisms that result in the same outcome.Consequently,researchers are interested in studying KOA and require appropriate animal models for basic research.Chinese herbal compounds,which consist of multiple herbs with diverse pharmacological properties,possess characteristics such as multicomponent,multipathway,and multitarget effects.The potential benefits in the treatment of KOA continue to attract attention.Purpose:This study aims to provide a comprehensive overview of the advantages,limitations,and specific considerations in selecting different species and methods for KOA animal models.This will help researchers make informed decisions when choosing an animal model.Methods:Online academic databases(e.g.,PubMed,Google Scholar,Web of Science,and CNKI)were searched using the search terms“knee osteoarthritis,”“animal models,”“traditional Chinese medicine,”and their combinations,primarily including KOA studies published from 2010 to 2023.Results:Based on literature retrieval,this review provides a comprehensive overview of the methods of establishing KOA animal models;introduces the current status of advantages and disadvantages of various animal models,including mice,rats,rabbits,dogs,and sheep/goats;and presents the current status of methods used to establish KOA animal models.Conclusion:This study provides a review of the animal models used in recent KOA research,discusses the common modeling methods,and emphasizes the role of traditional Chinese medicine compounds in the treatment of KOA.

Preliminary exploration of animal models of congenital choledochal cysts

BACKGROUND Various animal models have been used to explore the pathogenesis of choledochal cysts(CCs),but with little convincing results.Current surgical techniques can achieve satisfactory outcomes for treatment of CCs.Consequently,recent studies have focused more on clinical issues rather than basic research.Therefore,we need appropriate animal models to further basic research.AIM To establish an appropriate animal model that may contribute to the investigation of the pathogenesis of CCs.METHODS Eighty-four specific pathogen-free female Sprague-Dawley rats were randomly allocated to a surgical group,sham surgical group,or control group.A rat model of CC was established by partial ligation of the bile duct.The reliability of the model was confirmed by measurements of serum biochemical indices,morpho-logy of common bile ducts of the rats as well as molecular biology experiments in rat and human tissues.RESULTS Dilation classified as mild(diameter,≥1 mm to<3 mm),moderate(≥3 mm to<10 mm),and severe(≥10 mm)was observed in 17,17,and 2 rats in the surgical group,respectively,while no dilation was observed in the control and sham surgical groups.Serum levels of alanine aminotransferase,aspartate aminotrans-ferase,total bilirubin,direct bilirubin,and total bile acids were significantly elevated in the surgical group as compared to the control group 7 d after surgery,while direct bilirubin,total bilirubin,and gamma-glutamyltransferase were further increased 14 d after surgery.Most of the biochemical indices gradually decreased to normal ranges 28 d after surgery.The protein expression trend of signal transducer and activator of transcription 3 in rat model was consistent with the human CC tissues.CONCLUSION The model of partial ligation of the bile duct of juvenile rats could morphologically simulate the cystic or fusiform CC,which may contribute to investigating the pathogenesis of CC.

Advances in viral encephalitis:Viral transmission,host immunity,and experimental animal models

Viral infections have led to many public health crises and pandemics in the last few centuries.Neurotropic virus infection-induced viral encephalitis(VE),especially the symptomatic inflammation of the meninges and brain parenchyma,has attracted growing attention due to its high mortality and disability rates.Understanding the infectious routes of neurotropic viruses and the mechanism underlying the host immune response is critical to reduce viral spread and improve antiviral therapy outcomes.In this review,we summarize the common categories of neurotropic viruses,viral transmission routes in the body,host immune responses,and experimental animal models used for VE study to gain a deeper understanding of recent progress in the pathogenic and immunological mechanisms under neurotropic viral infection.This review should provide valuable resources and perspectives on how to cope with pandemic infections.

Research progress on animal models of corneal epithelial-stromal injury

A corneal epithelial-stromal defect is recognized as a major contributor to corneal scarring.Given the rising prevalence of blindness caused by corneal scarring,increasing attention has been focused on corneal epithelialstromal defects.Currently,the etiology and pathogenesis of these defects remain inadequately understood,necessitating further investigation through experimental research.Various modeling methods exist both domestically and internationally,each with distinct adaptive conditions,advantages,and disadvantages.This review primarily aims to summarize the techniques used to establish optimal animal models of corneal epithelial-stromal injury,including mechanical modeling,chemical alkali burns,post-refractive surgery infections,and genetic engineering.The intention is to provide valuable insights for studying the mechanisms underlying corneal epithelial-stromal injury and the development of corresponding therapeutic interventions.

Animal models of vascularized nerve grafts:a systematic review

The aim of this review is to present and compare the various animal models of vascularized nerve grafts described in the literature as well as to summarize preclinical evidence for superior functional results compared to non-vascularized free nerve grafts. We also will present the state of the art on prefabricated vascularized nerve grafts. A systematic literature review on vascularized nerve graft models was conducted via the retrieval with the Pub Med database on March 30, 2019. Data on the animal, nerve, and vascularization model, the recipient bed, the evaluation time points and methods, and the results of the study results were extracted and analyzed from selected articles. The rat sciatic nerve was the most popular model for vascularized nerve grafts, followed by the rabbit;however, rabbit models allow for longer nerve grafts, which are suitable for translational evaluation, and produced more cautious results on the superiority of vascularized nerve grafts. Compared to free nerve grafts, vascularized nerve grafts have better early but similar long-term results, especially in an avascular bed. There are few studies on avascular receiving beds and prefabricated nerve grafts. The clinical translation potential of available animal models is limited, and current experimental knowledge cannot fully support that the differences between vascularized nerve grafts and free nerve grafts yield a clinical advantage that justifies the complexity of the procedure.

Targeting autophagy in Alzheimer's disease:Animal models and mechanisms

Alzheimer's disease(AD)is an age-related progressive neurodegenerative disorder that leads to cognitive impairment and memory loss.Emerging evidence suggests that autophagy plays an important role in the pathogenesis of AD through the regulation of amyloid-beta(Aβ)and tau metabolism,and that autophagy dysfunction exacerbates amyloidosis and tau pathology.Therefore,targeting autophagy may be an effective approach for the treatment of AD.Animal models are considered useful tools for investigating the pathogenic mechanisms and therapeutic strategies of diseases.This review aims to summarize the pathological alterations in autophagy in representative AD animal models and to present recent studies on newly discovered autophagy-stimulating interventions in animal AD models.Finally,the opportunities,difficulties,and future directions of autophagy targeting in AD therapy are discussed.

Recent advances in anxiety disorders:Focus on animal models and pathological mechanisms

Anxiety disorders have become one of the most severe psychiatric disorders,and the incidence is increasing every year.They impose an extraordinary personal and socioeconomic burden.Anxiety disorders are influenced by multiple complex and interacting genetic,psychological,social,and environmental factors,which contribute to disruption or imbalance in homeostasis and eventually cause pathologic anxiety.The selection of a suitable animal model is important for the exploration of disease etiology and pathophysiology,and the development of new drugs.Therefore,a more comprehensive understanding of the advantages and limitations of existing animal models of anxiety disorders is helpful to further study the underlying pathological mechanisms of the disease.This review summarizes animal models and the pathogenesis of anxiety disorders,and discusses the current research status to provide insights for further study of anxiety disorders.

Fundus photography,fluorescein angiography,optical coherence tomography and electroretinography of preclinical animal models of ocular diseases

The eye is an immune-privileged and sensory organ in humans and animals.Anatomical,physiological,and pathobiological features share significant similarities across divergent species(1).Each compartment of the eye has a unique structure and function.The anterior and posterior compartments of the eye contain endothelium(cornea),epithelium(cornea,ciliary body,iris),muscle(ciliary body),vitreous and neuronal(retina)tissues,which make the eye suitable to evaluate efficacy and safety of tissue specific drugs(2).

Large animal models of cardiac ischemia-reperfusion injury:Where are we now?

Large animal models of cardiac ischemia-reperfusion are critical for evaluation of the efficacy of cardioprotective interventions prior to clinical translation.Nonetheless,current cardioprotective strategies/interventions formulated in preclinical cardiovascular research are often limited to small animal models,which are not transferable or reproducible in large animal models due to different factors such as:(i)complex and varied features of human ischemic cardiac disease(ICD),which are challenging to mimic in animal models,(ii)significant differences in surgical techniques applied,and(iii)differences in cardiovascular anatomy and physiology between small versus large animals.This article highlights the advantages and disadvantages of different large animal models of preclinical cardiac ischemic reperfusion injury(IRI),as well as the different methods used to induce and assess IRI,and the obstacles faced in using large animals for translational research in the settings of cardiac IR.

Establishment and evaluation of animal models of sepsis-associated encephalopathy

BACKGROUND:Sepsis-associated encephalopathy(SAE) is a critical disease caused by sepsis.In addition to high mortality,SAE can also adversely aff ect life quality and lead to significant socioeconomic costs.This review aims to explore the development of evaluation animal models of SAE,giving insight into the direction of future research in terms of its pathophysiology and therapy.METHODS:We performed a literature search from January 1,2000,to December 31,2022,in MEDLINE,PubMed,EMBASE,and Web of Science using related keywords.Two independent researchers screened all the accessible articles based on the inclusion and exclusion criteria and collected the relevant data of the studies.RESULTS:The animal models for sepsis are commonly induced through cecal ligation and puncture(CLP) or lipopolysaccharide(LPS) injection.SAE can be evaluated using nervous reflex scores and sepsis evaluation during the acute phase,or through Morris water maze(MWM),openfield test,fear condition(FC) test,inhibitory avoidance,and other tests during the late phase.CONCLUSION:CLP and LPS injection are the most common methods for establishing SAE animal models.Nervous reflexs cores,MWM,FC test,and inhibitory avoidance are widely used in SAE model analysis.Future research should focus on establishing a standardized system for SAE development and analysis.

Acute liver failure:A systematic review and network meta-analysis of optimal type of stem cells in animal models

BACKGROUND The therapeutic effects of various stem cells in acute liver failure(ALF)have been demonstrated in preclinical studies.However,the specific type of stem cells with the highest therapeutic potential has not been determined.AIM To validate the efficacy of stem cells in ALF model and to identify the most promising stem cells.METHODS A search was conducted on the PubMed,Web of Science,Embase,Scopus,and Cochrane databases from inception to May 3,2022,and updated on November 16,2022 to identify relevant studies.Two independent reviewers performed the literature search,identification,screening,quality assessment,and data extraction.RESULTS A total of 89 animal studies were included in the analysis.The results of traditional meta-analysis showed that stem cell therapy could significantly reduce the serum levels of alanine aminotransferase[weighted mean difference(WMD)=-181.05(-191.71,-170.39)],aspartate aminotransferase[WMD=-309.04(-328.45,-289.63)],tumor necrosis factor-alpha[WMD=-8.75(-9.93,-7.56)],and interleukin-6[WMD=-10.43(-12.11,-8.76)]in animal models of ALF.Further subgroup analysis and network meta-analysis showed that although mesenchymal stem cells are the current research hotspot,the effect of liver stem cells(LSCs)on improving liver function is significantly better than that of the other five types of stem cells.In addition,the ranking results showed that the possibility of LSCs improving liver function ranked first.This fully proves the great therapeutic potential of LSCs,which needs to be paid more attention in the future.CONCLUSION LSCs may have a higher therapeutic potential.Further high-quality animal experiments are needed to explore the most effective stem cells for ALF.

Optimizing diabetic kidney disease animal models:Insights from a meta-analytic approach

Diabetic kidney disease(DKD)is a prevalent complication of diabetes,often leading to end-stage renal disease.Animal models have been widely used to study the pathogenesis of DKD and evaluate potential therapies.However,current animal models often fail to fully capture the pathological characteristics of renal injury observed in clinical patients with DKD.Additionally,modeling DKD is often a time-consuming,costly,and labor-intensive process.The current review aims to summarize modeling strategies in the establishment of DKD animal models by utilizing meta-analysis related methods and to aid in the optimization of these models for future research.A total of 1215 articles were retrieved with the keywords of“diabetic kidney disease”and“animal experiment”in the past 10 years.Following screening,84 articles were selected for inclusion in the meta-analysis.Review manager 5.4.1 was employed to analyze the changes in blood glucose,glycosylated hemoglobin,total cholesterol,triglyceride,serum creatinine,blood urea nitrogen,and urinary albumin excretion rate in each model.Renal lesions shown in different models that were not suitable to be included in the metaanalysis were also extensively discussed.The above analysis suggested that combining various stimuli or introducing additional renal injuries to current models would be a promising avenue to overcome existing challenges and limitations.In conclusion,our review article provides an in-depth analysis of the limitations in current DKD animal models and proposes strategies for improving the accuracy and reliability of these models that will inspire future research efforts in the DKD research field.

Establishing of the Transplanted Animal Models for Human Lung Cancer

Lung cancer is the leading cause of cancer mortality worldwide.Even with the applications of excision, radiotherapy, chemotherapy, and gene therapy, the 5 year survival rate is only 15% in the USA. Clinically relevant laboratory animal models of the disease could greatly facilitate understanding of the pathogenesis of lung cancer, its progression, invasion and metastasis. Transplanted lung cancer models are of special interest and are widely used today. Such models are essential tools in accelerating development of new therapies for lung cancer. In this communication we will present a brief overview of the hosts, sites and pathways used to establish transplanted animal lung tumor models.

Breast cancer animal models and applications

Breast cancer is the most common malignancy in women. Basic and translational breast cancer research relies heavily on experimental animal models. Ideally, such models for breast cancer should have commonality with human breast cancer in terms of tumor etiology, biological behavior,pathology, and response to therapeutics. This review introduces current progress in different breast cancer experimental animal models and analyzes their characteristics, advantages, disadvantages, and potential applications. Finally, we propose future research directions for breast cancer animal models.

COX-2 in liver,from regeneration to hepatocarcinogenesis:What we have learned from animal models?

The use of animals lacking genes or expressing genes under the control of cell-specific promoters has signifi cantly increased our knowledge of the genetic and molecular basis of physiopathology,allowing testing of functional hypotheses and validation of biochemical and pharmacologic approaches in order to understand cell function.However,with unexpected frequency,gene knockout animals and,more commonly,animal models of transgenesis give experimental support to even opposite conclusions on gene function.Here we summarize what we learned on the role of cyclooxygenase 2(COX-2) in liver and revise the results obtained in 3 independent models of mice expressing a COX-2 transgene specifi cally in the hepatocyte.Upon challenge with pro-inflammatory stimuli,the animals behave very differently,some transgenic models having a protective effect but others enhancing the injury.In addition,one transgene exerts differential effects on normal liver physiology depending on the transgenic animal model used.

Neuroprotection by immunomodulatory agents in animal models of Parkinson's disease

Parkinson’s disease（PD） is an age-related neurodegenerative disease for which the characteristic motor symptoms emerge after an extensive loss of dopamine containing neurons.The cell bodies of these neurons are present in the substantia nigra,with the nerve terminals being in the striatum.Both innate and adaptive immune responses may contribute to dopaminergic neurodegeneration and disease progression is potentially linked to these.Studies in the last twenty years have indicated an important role for neuroinflammation in PD through degeneration of the nigrostriatal dopaminergic pathway.Characteristic of neuroinflammation is the activation of brain glial cells,principally microglia and astrocytes that release various soluble factors.Many of these factors are proinflammatory and neurotoxic and harmful to nigral dopaminergic neurons.Recent studies have identified several different agents with immunomodulatory properties that protected dopaminergic neurons from degeneration and death in animal models of PD.All of the agents were effective in reducing the motor deficit and alleviating dopaminergic neurotoxicity and,when measured,preventing the decrease of dopamine upon being administered therapeutically after 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine,6-hydroxydopamine,rotenone-lesioning or delivery of adeno-associated virus-α-synuclein to the ventral midbrain of animals.Some of these agents were shown to exert an anti-inflammatory action,decrease oxidative stress,and reduce lipid peroxidation products.Activation of microglia and astrocytes was also decreased,as well as infiltration of T cells into the substantia nigra.Pretreatment with fingolimod,tanshinoine I,dimethyl fumarate,thalidomide,or cocaine-and amphetamine-regulated transcript peptide as a preventive strategy ameliorated motor deficits and nigral dopaminergic neurotoxicity in brain-lesioned animals.Immunomodulatory agents could be used to treat patients with early clinical signs of the disease or potentially even prior to disease onset in those identified as having pre-disposing risk,including genetic factors.