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Establishment and Evaluation of a Rat Model of Non-Puerperal Mastitis

Yulian YIN ; Lina MA ; Siyuan TU ; Ling CHEN ; Meina YE ; Hongfeng CHEN

Laboratory Animal and Comparative Medicine.2024;44(6):587-596. doi:10.12300/j.issn.1674-5817.2024.065

Objective This study aims to establish a non-puerperal mastitis (NPM) rat model by simulating hyperprolactinemia and immune-inflammatory states, and to evaluate its local inflammatory characteristics in the mammary gland, thereby laying the foundation for research on the diagnosis and treatment of this clinically challenging disease. Methods Twelve SPF-grade Wistar female rats were evenly divided into a control group and a model group. During the experiment, the control group received no experimental treatment or medication. The model group received daily subcutaneous injections of 100 mg/kg metoclopramide hydrochloride for 7 consecutive days. Serum prolactin (PRL) levels were measured using ELISA on the 10th, 20th, and 30th days after the first injection. After 7 days of injections, 200 μL of lactating SD rat milk was mixed with 200 μL of complete Freund's adjuvant to prepare an oil-in-water emulsion, which was administered by multiple subcutaneous injections into the back of the Wistar rats for the initial immunization. Seven days after the initial immunization, the emulsion was injected subcutaneously into the third, fourth, and fifth mammary glands for the final immunization. After the final immunization, the rats were observed for 28 days for changes in mammary gland appearance, and the size of mammary nodules was calculated. On the 3rd, 7th, 14th, and 28th days, hematoxylin-eosin (HE) staining was used to analyze mammary tissue morphology. Immunohistochemistry was employed to detect CD138 expression levels. ELISA was used to measure the levels of interleukin (IL)-6, IL-1β, tumor necrosis factor (TNF)-α, and inducible nitric oxide synthase (iNOS) in mammary tissue to comprehensively assess the model. Results Rats in the model group exhibited mammary skin ulceration and foul odor at the ulcer sites. Palpation and ultrasound revealed the formation of mammary nodules. HE staining showed that on the 3rd day after the final immunization, normal ductal and lobular structures in the mammary glands disappeared, with significant infiltration of plasma cells. On the 7th day, ductal dilation, epithelial necrosis and detachment, and pronounced periductal plasma cell and lymphocyte (predominantly T-lymphocytes) infiltration were observed. On the 14th day, there was a proliferation of fibrofatty tissue, small blood vessels, and granulation tissue, with scattered plasma cells in the interstitium. By the 28th day, inflammatory cell infiltration and fibrous tissue proliferation were reduced, with granuloma formation. Serum PRL levels in the model group were significantly increased on the 10th day (P<0.05) and the 20th day (P<0.001). IL-6 and TNF-α levels in mammary tissue were higher in the model group compared to the control group on the 3rd, 7th, 14th, and 28th days (P<0.05). IL-1β levels were higher on the 3rd, 7th, and 14th days compared with the control group (P<0.01) but lower than the control group on the 28th day (P>0.05). iNOS levels were significantly higher on the 7th day after the final immunization (P<0.001). Conclusion A successful NPM model was established in rats, which exhibited typical pathological features such as local mammary masses, abscesses, ulcers, ductal dilation and plasma cell infiltration. This model can serve as a foundation for further research into the diagnosis and treatment of this clinically challenging disease.

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Establishment and Evaluation of a Moderate-to-Severe Knee Osteoarthritis Model in Rats Induced by Surgery

Xiaorong SUN ; Dan SU ; Wenjuan GUI ; Yue CHEN

Laboratory Animal and Comparative Medicine.2024;44(6):597-604. doi:10.12300/j.issn.1674-5817.2024.066

ObjectiveTo establish a rat model of moderate-to-severe knee osteoarthritis, laying the foundation for studying the pathogenesis of moderate-to-severe knee osteoarthritis and its prevention and treatment methods. MethodsThirty male SD rats were randomly divided into three groups: a sham surgery group, an 8-week model group, and a 20-week model group, with 10 rats in each group. Rats in the 8-week and 20-week model groups underwent surgery to cut the anterior and posterior cruciate ligaments and medial collateral ligament of the right knee joint, and remove the medial and lateral menisci. After surgery, the rats were allowed to move freely. The rats in the sham surgery group had only skin incisions to expose the joint without any surgical treatment. At 8 and 20 weeks post-surgery, Micro-CT scans were performed to analyze the femoral osteoporosis in the rats. After euthanizing the rats, gross observations of the knee joints were made, and the cartilage of the joint surface was scored using the Pelletier scoring system. The knee joints were collected for hematoxylin and eosin (HE) staining and safranin O-fast green staining to observe changes in cartilage morphology. The modified Mankin's scoring system was used to assess the tissue pathology of the joint surface. Immunohistochemical staining was used to detect the expression of type II collagen and matrix metalloproteinase 13 (MMP13), reflecting the anabolic and catabolic metabolism of the knee joint cartilage. ResultsThe knee joint cartilage in the 8-week and 20-week model groups was severely damaged, with Pelletier and modified Mankin's scores significantly higher than those in the sham surgery group (both P<0.01). The Pelletier and modified Mankin's scores in the 20-week model group were significantly higher than those in the 8-week model group (P<0.01). Micro-CT observations revealed irregular joint surfaces, osteophyte formation, and signs of osteoporosis in both the 8-week and 20-week model groups, with the 20-week model group showing more loose bodies around the knee joints. Immunohistochemical staining showed increased expression of MMP13 and decreased expression of type II collagen in the knee joint tissues of the model groups, indicating that the balance of anabolic and catabolic metabolism in the joint cartilage was disrupted. MMP13 increased while type II collagen decreased. ConclusionThe surgical method of cutting the anterior and posterior cruciate ligaments and medial collateral ligament and removing the medial and lateral menisci successfully creates a moderate-to-severe knee osteoarthritis model in rats. Imaging examinations reveal osteophytes, osteoporosis, and loose bodies in the knee joints, while pathological observations show a reduction or even disappearance of joint cartilage, with a disruption in the balance of cartilage anabolic and catabolic metabolism.

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Establishment of a New Hyperglycemic Obesity Cardiac Dysfunction Mouse Model with Triacsin C

Xiaona ZHAO ; Peng WANG ; Maoqing YE ; Xinkai QU

Laboratory Animal and Comparative Medicine.2024;44(6):605-612. doi:10.12300/j.issn.1674-5817.2024.078

Objective This study aims to establish a novel hyperglycemic obesity mouse model by utilizing Triacsin C, an inhibitor of acyl-CoA synthetase long-chain family member 1 (ACSL1), combined with a high-fat diet, to simulate the changes in adipose tissue and cardiac function observed in patients with obesity-related type 2 diabetes. MethodsTwenty adult SPF-grade male C57BL/6J mice were randomly divided into two groups: the Control group (injected intraperitoneally with citric acid-sodium citrate buffer, Con group) and the TC group (injected intraperitoneally with Triacsin C, TC group). After four consecutive weeks of intraperitoneal injections, both groups were fed high-fat diets. Body weight and glucose tolerance of the mice were assessed every eight weeks. The models were considered successful if fasting blood glucose exceeded 8 mmol/L or blood glucose was above 15 mmol/L two hours after glucose injection. Cardiac function, including ventricular end-diastolic diameter (LVEDD), left ventricular end systolic diameter (LVESD), end-diastolic interventricular septal thickness (EDIVS), left ventricular ejection fraction (LVEF), and left ventricular short-axis fractional shortening (FS), was measured by echocardiography. HE staining was used to detect the changes in epididymal white adipose tissue (WAT) and brown adipose tissue (BAT). Immunofluorescence technology was used to analyze changes in CD31 and UCP1 in BAT. ACSL1 expression in myocardial tissue was tested by Western blotting. ResultsThe fasting blood glucose levels were (8.14±1.43) mmol/L in the Con group and (8.18±0.85) mmol/L in the TC group (P>0.05) , and the 2-hour postprandial blood glucose levels were (19.8±4.01) mmol/L in the Con group and (22.60±3.97) mmol/L in the TC group (P<0.05). This indicated that both groups of diabetic mouse models were successfully established. Compared to the Con group, the TC group showed poor glucose tolerance; significant decreases in LVEDD, LVEF and FS (P<0.05); significant increases in WAT and BAT areas (P<0.05); significant decreases in CD31 and UCP1 expression (P<0.05); and a significant decrease in the expression of ACSL1 in myocardial tissues (P<0.05). ConclusionCompared with the high-fat diet-induced type 2 diabetes model, the new hyperglycemic obesity and cardiac dysfunction mouse model, created by the combination of Triacsin C and a high-fat diet, is feasible and allows for easier observation of brown adipose tissue whitening, insulin resistance and cardiac dysfunction.

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Advances in Nucleic Acid Drugs and Gene Therapies based on Animal Models of Duchenne Muscular Dystrophy

Siyu LIU ; Yuezhao LAI ; Wenting GUO ; Xuejin CHEN

Laboratory Animal and Comparative Medicine.2024;44(6):613-625. doi:10.12300/j.issn.1674-5817.2024.168

Duchenne muscular dystrophy (DMD) is a severe X-linked recessive genetic disorder caused by mutations in the DMD gene, making it one of the most common forms of hereditary muscular dystrophy. The DMD gene, which encodes dystrophin, is the largest known gene in the human genome. Mutations in the DMD gene are highly diverse, including exon deletions, duplications, point mutations, and small insertions or deletions, posing significant challenges for treatment. Currently, there is no cure for DMD, and existing treatment strategies focus primarily on symptom management, which cannot reverse or halt disease progression. Advances in biotechnology position nucleic acid drugs and gene therapies at the forefront of DMD treatment research. These treatments aim to restore dystrophin expression by repairing or replacing mutated genes, thereby improving muscle function or slowing muscle degeneration. Preclinical studies in animal models and early-phase clinical trials demonstrate promising efficacy and offer new hope for DMD patients. This review briefly outlines the pathological mechanisms and genetic characteristics of DMD before delving into recent progress in therapeutic strategies, with a particular focus on nucleic acid drugs (including antisense oligonucleotides for exon skipping therapy and translation readthrough inducers) and gene therapy approaches (including gene replacement therapy and gene editing). The development and application of these therapies not only provide new treatment options for DMD patients, but also offer valuable insights for addressing other genetic disorders. However, numerous challenges impede the clinical translation of DMD treatments. Future studies must optimize existing therapeutic strategies, improve their efficacy and applicability, and explore innovative approaches to deliver more effective and sustainable treatments for DMD patients.

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Advances in Development of PM2.5-Exposed Animal Models and Their Application in Reproductive Toxicity Research

Fang TIAN ; Bin PAN ; Jiayi SHI ; Yanyi XU ; Weihua LI

Laboratory Animal and Comparative Medicine.2024;44(6):626-635. doi:10.12300/j.issn.1674-5817.2024.068

Atmospheric fine particulate matter (particulate matter 2.5,PM_2.5) is a major component of haze, and its potential hazards to human reproductive health have garnered widespread attention. Establishing appropriate animal models is crucial for in-depth research into the reproductive toxicity of PM_2.5 exposure and its underlying mechanisms. This paper, based on recent literature, summarizes current methods for establishing PM_2.5-exposed animal models and the evaluation criteria for reproductive toxicity research. The primary modeling methods for PM_2.5 exposure include whole-body inhalation exposure and intratracheal instillation exposure. While whole-body inhalation exposure effectively simulates real-life human inhalation environments, it requires sophisticated experimental equipment. Conversely, intratracheal instillation exposure is more cost-effective and easier to operate but faces challenges in accurately mimicking the distribution and deposition of PM_2.5 during natural inhalation. Therefore, researchers must carefully weigh these exposure methods to enhance model rigor and achieve the most realistic simulation of human exposure conditions. When summarizing the application evaluation indicators of PM_2.5-induced reproductive toxicity, this review finds that the main indicators of male reproductive toxicity include reduced sperm quality, testicular tissue damage, and hormonal imbalances. For female reproductive toxicity, the primary indicators are reduced ovarian reserve, endocrine dysfunction, endometrial damage, and adverse perinatal reactions. Additionally, this review highlights the need for detailed chemical composition analysis of PM_2.5, exploring the reproductive toxic targets and mechanisms of particles containing different chemical components, such as heavy metals and polycyclic aromatic hydrocarbons. Long-term studies are also necessary to assess the effects of PM_2.5 exposure on reproductive health and transgenerational effects, to predict potential long-term risks for humans. Additionally, interdisciplinary collaboration should be encouraged, involving cooperation between environmental science, toxicology, reproductive medicine, and other disciplines, to comprehensively assess the environmental health risks of PM_2.5 and provide scientific support for the development of integrated prevention and control strategies. This review summarizes animal modeling methods, evaluation criteria, and their applications, providing valuable methodological references for future reproductive toxicity research on PM_2.5.

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Research Progress on Animal Models of Sepsis-Related Organ Injury

Jiahao YANG ; Chunlei DING ; Fenghua QIAN ; Qi SUN ; Xusheng JIANG ; Wen CHEN ; Mengwen SHEN

Laboratory Animal and Comparative Medicine.2024;44(6):636-644. doi:10.12300/j.issn.1674-5817.2024.087

Sepsis is a multi-organ dysfunction syndrome caused by infection and immune dysfunction, with a high mortality rate. It affects multiple important organs such as the heart, lungs, kidneys, liver, and brain. Establishing corresponding animal models of organ dysfunction syndrome is an essential step in clarifying its pathogenesis, researching potential effective drugs, and evaluating the effectiveness and safety of treatment plans. This article first summarizes classic modeling methods for sepsis related organ injury, including the destruction of intestinal barrier tissue integrity and the implantation of pathogens or toxic drugs. The former mainly includes cecal ligation and puncture, ascending colon stent implantation, and cecal ligation incision. The latter is divided into intraperitoneal injection, intravenous injection, and intratracheal administration based on the clinical infection route being simulated. Cecal ligation and puncture and lipopolysaccharide intraperitoneal injection are the most commonly used methods. Secondly, this article summarizes the common modeling methods and evaluation methods for animal models of sepsis-induced cardiomyopathy, acute lung injury, acute kidney injury, acute liver injury, and brain dysfunction. It points out that almost all organ injuries use classic modeling methods, and different organ injury models have additional modifications according to their different pathogenesis. For example, in addition to the classic modeling methods, lipopolysaccharide instillation in the trachea is more effective in modeling acute lung injury as it better simulates lung barrier dysfunction. Cecal ligation and puncture followed by Pseudomonas instillation in the trachea in a secondary challenge model better represents sepsis-induced acute kidney injury. Intraperitoneal injection of galactosamine is a mature modeling method of sepsis-induced acute liver injury. Intracerebral injection of lipopolysaccharide is a feasible model of sepsis-associated encephalopathy. In addition to the different modeling methods, there are differences in the administration time, dosage and experimental time points according to the different experimental purposes. This article reviews the research progress of animal experimental models for sepsis-induced cardiomyopathy, acute lung injury, acute kidney injury, acute liver injury, and brain dysfunction, aiming to provide a reference for the selection of animal experimental models and optimization of experimental design.

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Challenges and Development in Suzhou Laboratory Animal Industry Over the Past Five Decades

Lijuan ZHAO ; Chunlan XIAO ; Yajie SHENG ; Xi LU ; Zhengyu ZHOU

Laboratory Animal and Comparative Medicine.2024;44(6):645-653. doi:10.12300/j.issn.1674-5817.2024.113

Since the 1970s, the laboratory animal industry in Suzhou has gone through five stages: its inception, emergence, growth, transformation, and scaling up. It began with the manufacturing of caging equipment for laboratory animals, initially by imitation and later through independent innovation. The industry evolved from sporadic factories to clustered enterprises, gradually growing and opening up the export market for caging equipment. In the 21st century, with industrial upgrading and transformation, purification systems and related products began to develop, and industry organizations emerged. As China has modernized, the rise of automation and intelligent production has led to technological innovation in enterprises and the emergence of various outsourcing services in the laboratory animal industry, driving the large-scale development of the industrial chain. After nearly half a century of growth, the laboratory animal industry in Suzhou has formed a complete industrial chain, including the production of laboratory animals, caging equipment, feed and bedding materials, design and construction of laboratory animal facilities, quality testing of laboratory animals and environments, and animal experimentation services. Laboratory animal breeding equipment, the core of the industry, has reached the level of developed countries, and the industry's scale and influence are unmatched in China. Since the 21st century, biopharmaceuticals have become the "No.1 industry" in the development of Suzhou. With government support, the guidance of the local economy, and the assistance from universities and research institutes, the animal experiment outsourcing industry has begun to cluster in Suzhou. The continuous influx of CROs has driven the construction of large-scale laboratory animal facilities, and key research projects have been initiated, significantly enhancing the industry's R&D capabilities. The Suzhou laboratory animal industry has quickly expanded alongside the "No. 1 industry," creating a unique "Suzhou Path" for laboratory animals. Over nearly fifty years, the laboratory animal industry in Suzhou has been essential to the rapid development of the biopharmaceutical industry in Suzhou and China.

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Survey Report Analysis on Parasitic and Microbial Quality of Laboratory Animals in Sichuan Province, 2017-2023

Lida LIU ; Bing CHEN ; Na XIE ; Li LIU ; Siqi ZHUANG ; Yixing ZOU

Laboratory Animal and Comparative Medicine.2024;44(6):654-660. doi:10.12300/j.issn.1674-5817.2024.057

ObjectiveTo provide reference for further strengthening the management of laboratory animals in Sichuan Province by reviewing and analyzing the results of parasitic and microbial quality inspections of laboratory animals from 2017 to 2023. Methods Sichuan Province has 31 licensed laboratory animal production units, with the main species including mice, rats, guinea pigs, rabbits, dogs, monkeys, and pigs. Sampling inspections and reports were conducted for units with laboratory animal production qualifications in accordance with current national and local standards for laboratory animal classification. The quality inspection results for various laboratory animals in Sichuan Province from 2017 to 2023 were analyzed. Results With the exception of 2018, annual quality inspections of laboratory animals were conducted every year between 2017 and 2023. Mice: In 2017, positive results for helminths, flagellates, Salmonella, murine hepatitis virus antibodies, and murine pneumonia virus antibodies were detected, with a pass rate of only 42.9%. In 2019, Staphylococcus aureus and Klebsiella pneumoniae were detected, with a pass rate of 86.7%. In 2021, Sendai virus antibodies were detected, yielding a pass rate of 85.7%.The pass rate in 2020, 2022, and 2023 was 100%. Rats: In 2017, positive results were found for helminths, mycoplasma antibodies, Staphylococcus aureus, Sendai virus antibodies, murine pneumonia virus antibodies, rat parvovirus RV strain antibodies, rat parvovirus (H-1) strain antibodies, and rat coronavirus antibodies, with a pass rate of 40.0%. In 2019, mycoplasma antibodies, Staphylococcus aureus and Klebsiella pneumoniae were detected, with a pass rate of 35.0%. No positive indicators were detected in 2020. In 2021, Sendai virus antibodies and rat parvovirus RV strain antibodies were detected, with a pass rate of 50.0%. In 2022, positive results for rat parvovirus RV strain antibodies were found, yielding a pass rate of 87.5%. In 2023, Pasteurella pneumotropica and Klebsiella pneumoniae were detected, with a pass rate of 85.7%. Dogs: In 2017 and 2019, the antibody titers for rabies virus and canine distemper virus were below the required standard, with pass rates of 33.3% and 20.0%, respectively. In 2020 and 2022, the pass rate was 100%. Guinea pigs (general grade): In 2019, positive results for Toxoplasma antibodies were detected, with a pass rate of 80.0%. In all other years, the pass rate was 100%. Monkeys: In 2019, positive results for Toxoplasma gondii and rhesus herpesvirus type I antibodies were found, with a pass rate of 87.5%.In 2020 and 2022, rhesus herpesvirus type I antibodies were positively detected, yielding pass rates of 93.3% and 97.5%, respectively. The pass rates in 2021 and 2023 were 100%. Clean guinea pigs, rabbits and pigs all passed the inspection each year. ConclusionIssues related to the parasitic and microbial quality of laboratory animals persist in Sichuan Province. Supervision and sampling inspections have proven to be effective in identifying these issues promptly, serving as a critical measure to ensure the quality of laboratory animals. The results of these inspections offer valuable data to support the healthy development of the laboratory animal industry in Sichuan Province.

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Genetic Characteristics and Research Progress of Feline Coronavirus

Lingyun TAO

Laboratory Animal and Comparative Medicine.2024;44(6):661-666. doi:10.12300/j.issn.1674-5817.2024.069

Feline coronavirus (FCoV) is classified into two biotypes: feline infectious peritonitis virus (FIPV) and feline enteric coronavirus (FECV). FIPV and FECV might evolve and mutate via genetic recombination and mutation, leading to novel subtypes and variants. This study examined the genomic structure and biological subtyping of FCoV, analyzed the infection characteristics of FIPV and FECV, and investigated the mechanisms of FECV transforming into FIPV. The findings revealed that while their genome structures were fundamentally similar, differences in their ability to efficiently infect monocytes/macrophages significantly influenced their pathogenicity and transmission characteristics, with FIPV exhibiting higher virulence. Moreover, the analysis of the open reading frames (ORF)3/7 as well as the N/S sequences of FIPV indicated that its non-structural proteins were associated with modulation of the host immune system. These proteins enabled immune evasion, leading to more severe disease. The genomic variability of FCoV constitutes an important foundation for studying the pathogenicity and epidemiology of FIPV and FECV, and offers references for virus detection and drug development.

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Advances and Challenges of Using Experimental Pigs in Da Vinci Surgical Robot Training

Yishu LIU ; Liping CAI

Laboratory Animal and Comparative Medicine.2024;44(6):667-674. doi:10.12300/j.issn.1674-5817.2024.075

Experimental pigs occupy a crucial position in life sciences research and have been indispensable in advancing the practical application of new clinical technologies and methods. The Da Vinci Surgical Robot System, developed by Intuitive Surgical in the United States, has been widely used across various surgical fields since its approval by the U.S. Food and Drug Administration (FDA) in 2000, and is highly esteemed for its precision and accuracy. With the continuous advancement of surgical robot technology, the skill requirements for medical professionals have also increased. Consequently, surgical skills training has become an essential component of ensuring both surgical safety and effectiveness. This article briefly reviews the current status of Da Vinci surgical robot training, both domestically and internationally, with a focus on the practical application of experimental pigs in domestic Da Vinci surgical robot training. It emphasizes that experimental pigs not only effectively simulate the human surgical environment, enabling trainees to practice in a safe and controlled setting, but also help accelerate the trainees' familiarity with and mastery of the surgical robot. This, in turn, significantly shortens the learning curve, enhances the precision and stability of surgical procedures, and reduces surgical risks. However, the use of experimental animals in surgical robot training also encounters challenges, including limitations caused by the differences between experimental animals and humans, potential ethical concerns, and public opinion pressures. In response to these challenges, the paper proposes suggestions such as improving and enforcing ethical regulations, as well as advancing the development of virtual reality (VR) and augmented reality (AR) technologies. These efforts aim to reduce reliance on experimental animals in surgical training while enhancing training effectiveness, thereby contributing to the innovation and development of Da Vinci surgical robot training models.

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