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Analysis of the Progress in Identification and Evaluation of Laboratory Animal Resources in China

Laboratory Animal and Comparative Medicine.2024;44(5):469-474.

Laboratory animals are not only a national strategic resource but also an important support for development of science and technology. The Committee of Identification and Evaluation for Laboratory Animal Resources, organized by Chinese Association for Laboratory Animal Sciences and established in May 2019, is currently the only specialized academic agency dedicated to the identification and evaluation of laboratory animal resources in China. This paper first discusses the significance of identifying and evaluating laboratory animal resources, summarizes three new approaches to developing these resources, including the domestication and standardization of laboratory animals (economic, ornamental, agricultural, and wild animals, etc.), the acquisition of new strains (species) through natural mutation and induced mutation, and the creation of new laboratory animal resources through gene editing technology. It then introduces the workflow for resource identification and evaluation, including preliminary review (format review), written review (expert review), joint review or on-site inspection, final review (voting and public announcement)，and the issuance of certificates. The required materials to be submitted include application, summary report, research or identification reports, appendices and other necessary documents. The paper further discusses related requirements for resource identification and evaluation, including population, genetic classification, biological characteristics, genetic stability, and application value. Finally, the current status of newly identified laboratory animal strains (species) and issues in current work practices are analyzed, as well as solutions to these issues. This paper aims to provide a valuable reference for further research in this field.

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Evaluation of Simulated Weightlessness Model of Hindlimb Unloading Miniature Pigs and Their Tissue Damage

Yingxin TU ; Yilan JI ; Fei WANG ; Dongming YANG ; Dongdong WANG ; Zhixin SUN ; Yuexin DAI ; Yanji WANG ; KAN GUANGHAN ; Bin WU ; Deming ZHAO ; Lifeng YANG

Laboratory Animal and Comparative Medicine.2024;44(5):475-486.

Objective To establish a weightlessness simulation animal model using miniature pigs, leveraging the characteristic of multiple systems’ tissue structures and functions similar to those of humans, and to observe pathophysiological changes, providing a new method for aerospace research. Methods Nine standard-grade miniature pigs were selected and randomly divided into an experimental group (n=7) and a control group (n=2). The experimental group was fixed using customized metal cages, with canvas slings suspending their hind limbs off the ground, and the body positioned at a -20° angle relative to the ground to simulate unloading for 30 days (24 hours a day). Data on body weight, blood volume, and blood biochemistry indicators were collected at different time points for statistical analysis of basic physiological changes. After the experiment, the miniature pigs were euthanized and tissue samples were collected for histopathological observation of the cardiovascular, skeletal and muscle systems HE and Masson staining. Statistical analysis was also conducted on the thickness of arterial vessels and the diameter of skeletal muscle fibers. Additionally, western blotting was employed to detect the expression levels of skeletal muscle atrophy-related proteins, including muscle-specific RING finger protein 1 (MuRf-1) and muscle atrophy F-box (MAFbx, as known as Atrogin-1), while immunohistochemistry was used to detect the expression of glial fibrillary acidic protein (GFAP), an indicator of astrocyte activation in the brain, reflecting the pathophysiological functional changes across systems. Results After hindlimb unloading, the experimental group showed significant decreases in body weight (P<0.001) and blood volume (P<0.01). During the experiment, hemoglobin, hematocrit, and red blood cell count levels significantly decreased (P<0.05) but gradually recovered. The expression levels of alanine aminotransferase and γ-glutamyltransferase initially decreased (P<0.05) before rebounding, while albumin significantly decreased (P<0.001) and globulin significantly increased (P<0.01). Creatinine significantly decreased (P<0.05). The average diameter of gastrocnemius muscle fibers in the experimental group significantly shortened (P<0.05), with a leftward shift in the distribution of muscle fiber diameters and an increase in small-diameter muscle fibers. Simultaneously, Atrogin-1 expression in the gastrocnemius and paravertebral muscles significantly increased (P<0.05). These changes are generally consistent with the effects of weightlessness on humans and animals in space. Furthermore, degenerative changes were observed in some neurons of the cortical parietal lobe, frontal lobe, and hippocampal regions of the experimental group, with a slight reduction in the number of Purkinje cells in the cerebellar region, and a significant enhancement of GFAP-positive signals in the hippocampal area (P<0.05). Conclusion Miniature pigs subjected to a -20° angle hind limb unloading for 30 days maybe serve as a new animal model for simulating weightlessness, applicable to related aerospace research.

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Morphological Changes of Renal Corpuscles in Male Mongolian Gerbils at Different Ages

Meng LI ; Bai'an CHEN ; Jing LU

Laboratory Animal and Comparative Medicine.2024;44(5):487-494.

Objective By observing and comparing the changes in renal corpuscles at the largest longitudinal section in male Mongolian gerbils of different ages, this study preliminarily explored potential patterns of renal corpuscle changes, providing foundational data for the selection of male Mongolian gerbils for research on the pathogenic mechanisms and drug screening of nephropathy. Methods Kidney samples were collected from male Mongolian gerbils aged 12, 48, and 72 weeks. After making longitudinal cuts along the largest coronal plane in the middle, kidney tissue sections were prepared. Following HE staining, panoramic electronic tissue sections were scanned, and images of renal corpuscles at the largest longitudinal plane were captured using CaseViewer. The areas of renal corpuscles and their glomeruli and renal vesicles were measured. Statistical analysis was performed using IBM SPSS Statistics 27, and figures were created using GraphPad Prism 8. Results Compared with the 12-week group, both the area of renal corpuscle (P=0.029) and glomerulus (P=0.001) significantly increased in the 48-week group, while there was no significant change in the area of renal vesicle (P=0.478). The proportion of glomerular area within the renal corpuscle showed an increasing trend but the difference was not statistically significant (P=0.163). Compared to the 48-week group, the areas of renal corpuscle, glomerulus, and renal vesicle were all significantly larger in the 72-week group (P<0.001), but the proportion of glomerular area within renal corpuscle decreased significantly (P<0.001). Conclusion The renal corpuscles in male Mongolian gerbils continued to increase from 12 to 72 weeks of age. There might be a certain pattern in this process of enlargement, where the trends of glomerular and renal corpuscle enlargement were relatively consistent. However, the enlargement of renal vesicles appeared to lag behind that of the renal corpuscle. It was speculated that the enlargement of renal corpuscles was mainly caused by the passive enlargement of renal vesicles due to glomerular enlargement. The enlargement of renal corpuscles might be achieved through multiple cycles of "glomerular enlargement - triggering renal vesicle enlargement".

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Perioperative Animal Care for Xenotransplantation from Genetically Edited Pigs to Monkeys

Chan ZHU ; Dongliang ZHANG ; Deli ZHAO ; Xueqin SHI ; Lei QIAN ; Xuan ZHANG ; Yan JIN ; Wei DUAN ; Ruocheng QI ; Chaohua LIU ; Xuekang YANG ; Juntao HAN ; Dengke PAN

Laboratory Animal and Comparative Medicine.2024;44(5):495-501.

Objective To discuss the perioperative care and wound protection of xenotransplantation from genetically edited pigs to monkeys, with the goal of improving the success rate of such experimental procedures. Methods From October 2022 to October 2023, perioperative care and wound protection were performed on 7 recipient rhesus monkeys undergoing xenotransplantation of genetically edited pig tissues and organs. Customized wound protective garments were designed based on monkeys' size and surgical area to protect the wounds, alongside meticulous perioperative care. This included preoperative preparation and medication, intraoperative monitoring of physiological indicators and anesthesia management, and postoperative care comprising wound protection, observation and monitoring, and nutritional support. Results All seven monkeys successfully underwent xenotransplantation. With the aid of protective garments and detailed care, all surgical wounds healed by first intention, and postoperative recovery was satisfactory. Conclusion Proper care and wound protection during xenotransplantation from genetically edited pigs to monkeys not only promote wound healing, but also alleviate pain and harm to animals. This has significant implications for advancing experimental research in pig-monkey xenotransplantation and enhancing animal welfare.

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Optimal Adaptation Period for Metabolic Cage Experiments in Mice at Different Developmental Stages

He TAN ; Xiaohui YANG ; Daxiu ZHANG ; Guicheng WANG

Laboratory Animal and Comparative Medicine.2024;44(5):502-510.

Objective To investigate the optimal adaptation period for mice at different developmental stages during metabolic cage experiments, aiming to provide a reference for conducting metabolic research using mice. Methods A total of 80 male C57BL/6J mice at three developmental stages (weaning period M1, adolescent M2, and adulthood M3) were subjected to a 7-day metabolic cage experiment. Data on food intake, water intake, energy expenditure, respiratory quotient, body weight, and activity levels were recorded every five minutes. The collected data were processed using time series decomposition and comprehensive cluster analysis. Statistical differences were compared using repeated measures ANOVA combined with t-test to determine the optimal adaptation period. Results Significant differences in metabolism were observed among mice in different developmental stages (P<0.01). Compared with adolescent (M2) and adult (M3) mice, weaned mice (M1) exhibited lower activity level (P<0.01) and less distinct circadian rhythm. M1 mice had higher oxygen consumption, carbon dioxide production, and energy expenditure, as well as a lower respiratory quotient (all P<0.001), indicating that they mainly relied on fat as an energy source. Analysis of food intake, water intake, and energy expenditure revealed significant differences between the first light cycle (0-12 h) and the second light cycle (24-36 h) across all developmental stages (all P<0.05) . However, there was no significant difference in daily food intake or water intake after 24 hours (both P>0.05). Comprehensive cluster analysis of multiple indicators showed that the overall indicators of mice during the first 24 hours in the metabolic cages did not cluster with those of the subsequent 6 days, demonstrating significant differences. Conclusion Metabolic cage experiment can be used to detect continuous physiological changes in mice. The results suggest that mice can adapt to new metabolic cages environment within 24 hours, providing a theoretical basis for the design of metabolic experiments using mice.

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Optimization and Evaluation of Conditions for Orthotopic Nude Mouse Models of Human Liver Tumor Cells

Yu MENG ; Dongli LIANG ; Linlin ZHENG ; Yuanyuan ZHOU ; Zhaoxia WANG

Laboratory Animal and Comparative Medicine.2024;44(5):511-522.

Objective The study aims to optimize the conditions for constructing orthotopic nude mouse models of liver cancer by injecting human liver tumor cell lines and to explore appropriate timings for drug administration. Methods Human hepatocellular carcinoma Hep3B and hepatoblastoma HepG2 cell lines, which stably expressing the luciferase reporter gene (LUC), were selected. The linear correlation between the luciferase luminescence intensity and the number of liver tumor cells was analyzed using a Small Animal In Vivo Imaging system to verify the luminescent efficiency of the human liver tumor cells. Different concentrations (8×10⁶, 2.4×10⁷, 7.2×10⁷ cells/mL) and resuspension media (PBS, Matrigel) of human liver tumor cell suspensions HepG2-LUC and Hep3B-LUC were orthotopically inoculated into the liver lobes of 5-week-old female BALB/c nude mice (12 groups, 7 mice each) to construct human liver tumor nude mouse orthotopic cancer models. Every 7 days, the weights of mice were recorded, and the growth of orthotopic tumors was monitored using the Small Animal In Vivo Imaging system. On day 35 post-cell inoculation, mouse livers were dissected, and pathological slices were prepared for HE staining to observe histopathological changes in liver tissues. Results The luminescence intensity of human liver tumor cell lines was positively correlated with the number of cells (R²=0.983 1, R²=0.970 5), indicating their suitability for orthotopic model construction. Successful modeling was achieved in the high-concentration groups of HepG2-LUC, the low-, medium-, and high-concentration groups of HepG2-LUC+Matrigel, the medium- and high-concentration groups of Hep3B-LUC, and the low-, medium-, and high-concentration groups of Hep3B-LUC+Matrigel. For both HepG2-LUC+Matrigel and Hep3B-LUC+Matrigel groups, mice in the high-concentration groups exhibited significantly reduced body weight compared to the low- and medium-concentration groups (both with P<0.05). The luminescence intensity of successfully modeled mice increased exponentially over time (R²>0.950 0), and reached a minimum of 1.0×10⁷ p/(s·cm²·sr) by day 14 post-transplantation. Mice in the low- and medium-concentration groups of HepG2-LUC and the low-concentration group of Hep3B-LUC showed no significant pathological changes, while the other groups exhibited evident liver tumors and hepatocyte lesions. Conclusion For the HepG2-LUC cell line, the recommended injection volume is 50 µL with a cell density of 2.4×10⁷ cells/mL, resuspended with Matrigel, followed by drug administration or prognostic measures on day 7 post-modeling. For the Hep3B-LUC cell line, the recommended injection volume is 50 µL with a cell density of 7.2×10⁷ cells/mL, not resuspended with Matrigel, with administration or prognostic measures on day 14 post-modeling.

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Effect of Modified Duodenal Exclusion Surgery on Glucose Metabolism in Rats with Type 2 Diabetes Mellitus

Jin YANG ; Shiya YU ; Nan LIN ; Yongchao FANG ; Hu ZHAO ; Jinwei QIU ; Hongming LIN ; Huiyan CHEN ; Yu WANG ; Weihang WU

Laboratory Animal and Comparative Medicine.2024;44(5):523-530.

Objective To investigate the impact of anti-reflux modified duodenal exclusion surgery on glucose metabolism in rats with type 2 diabetes mellitus (T2DM), and to elucidate the role of the duodenum in maintaining glucose homeostasis. MethodsForty male Sprague-Dawley rats aged 5 weeks were fed a high-fat diet and induced with T2DM using low-dose streptozotocin. Thirty-six rats that met the T2DM model criteria were randomly divided into three groups: the simple duodenal exclusion surgery group (DE group), the anti-reflux modified duodenal exclusion group (MDE group), and the sham operation group (SO group), with 12 rats in each group. Gastroenterography was performed 4 weeks after surgery, and the body weight, fasting blood glucose levels, and serum glucagon-like peptide-1 (GLP-1) concentrations were measured before surgery and at 1, 2, 4, and 8 weeks post-surgery. Eight weeks post-surgery, the rats were euthanized, and a 1 cm segment of the biliopancreatic loop was collected from each group for pathological sectioning and HE staining to observe the intestinal mucosal villus length under an optical microscope. Results Gastroenterography showed that there was significant reflux of the contrast agent into the duodenal lumen in the DE group, while no reflux was observed in the MDE group. At one week post-surgery, the body weights of rats in all three groups significantly decreased compared to before surgery (P<0.05), and then the body weights of all groups increased over time, with no significant differences between the groups (P>0.05). Compared with the SO group, the fasting blood glucose levels in the MDE and DE groups significantly decreased at all time points post-surgery (P<0.05), while GLP-1 concentrations significantly increased (P<0.05). The fasting blood glucose levels in the MDE group were lower than those in the DE group at all time points post-surgery (P<0.05), but there were no significant differences in serum GLP-1 concentrations between the MDE and DE groups (P>0.05). Regarding intestinal mucosal morphology, the villus lengths of the biliopancreatic loops in the MDE group were significantly shorter than those in the DE and SO groups (P<0.05). Conclusion Anti-reflux modified duodenal exclusion surgery effectively improves glucose metabolism in T2DM rats by preventing the reflux of chyme into the diverted duodenum, thereby enhancing its hypoglycemic effect.

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Transcriptomic Analysis of Menstrual Blood-Derived Stem Cells Transplantation Combined with Exercise Training in Promoting Spinal Cord Injury Recovery in Rats

Longju QI ; Shiyuan CHEN ; Zehua LIAO ; Yuanhu SHI ; Yuyu SUN ; Qinghua WANG

Laboratory Animal and Comparative Medicine.2024;44(5):531-542.

ObjectiveTo explore the potential therapeutic targets and molecular mechanisms of menstrual blood-derived stem cells (MenSCs) transplantation combined with exercise training in promoting recovery in rats with spinal cord injury (SCI) through transcriptome sequencing analysis. MethodsFemale SD rats aged two months were selected and a SCI model was established by a hemisection at the tenth thoracic vertebra (T10). The rats were then divided into two groups: the Cell and Treadmill Training (CTMT) group, which received MenSCs transplantation and treadmill training after SCI, and the SCI group (control), with 12 rats in each group. One week after modeling, the CTMT group received a microinjection of 1×10⁵ MenSCs at the injury site, followed by two weeks of weight-supported aerobic exercise training. Spinal cord tissue from the injury site was selected for transcriptome sequencing, and mRNA expression data from both the SCI and CTMT groups were analyzed. Differential gene expression, GO (Gene Ontology) functional enrichment, KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway enrichment, and protein-protein interaction (PPI) network analyses were performed. Motor function recovery was assessed using the Basso, Beattie, and Bresnahan (BBB) score, while histopathological changes at the injury site were evaluated through hematoxylin-eosin (HE) staining. Real-time fluorescent quantitative PCR and Western blotting were used to verify the expression of differentially expressed genes. ResultsTranscriptome sequencing analysis showed 247 upregulated genes and 174 downregulated genes in the CTMT group compared to the SCI group. Notably, genes such as Bdnf, Hmox1, Sd4, Mmp3, and Cd163 were significantly upregulated [|log2(FoldChange)|≥0.66, P<0.05]. KEGG pathway enrichment analysis and GO functional enrichment analysis indicated that these differentially expressed genes were mainly involved in growth and development, metabolic reactions, and immune-inflammatory processes, such as axon growth and the electron transport chain. The Bdnf gene was notably enriched in the PI3K-Akt signaling pathway. The BBB score showed that MenSCs transplantation combined with exercise training significantly improved the motor function of SCI rats. HE staining revealed that pathological changes at the injury site were significantly reduced in the treatment group. Furthermore, real-time quantitative PCR and Western blotting confirmed that brain-derived neurotrophic factor (BDNF) mRNA and protein expression levels in the CTMT group were significantly higher than those in the SCI group (P<0.001). ConclusionThe combined exercise training with MenSCs effectively promotes the recovery of motor function in SCI rats by upregulating BDNF expression, providing a novel strategy for SCI treatment.

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Application of PNR Detection in the Diagnosis and Drug-efficacy Evaluation of Diabetic Kidney Disease in Rats

Naiqun ZHANG ; Piaopiao YUAN ; Linrong CAO ; Na YING ; Taotao YANG

Laboratory Animal and Comparative Medicine.2024;44(5):543-549.

Objective This study aims to monitor the mRNA ratio of podocin to nephrin (PNR) in glomerular podocytes of early diabetic kidney disease (DKD) rat models. The feasibility of using PNR as an early diagnostic indicator for DKD was evaluated by comparing it with the urinary albumin-to-creatinine ratio (U-ACR). Additionally, the early intervention effects of valsartan and fosinopril sodium on DKD were compared. Methods The DKD rat model was established by caudal intravenous injection of streptozotocin (STZ) at a dosage of 60 mg/kg. The early changes in PNR and U-ACR were monitored and compared, followed by timely intervention with valsartan and fosinopril sodium. Hematoxylin and eosin staining (HE) was used to observe glomerular structure, while transmission electron microscopy examined the ultrastructure of glomerular podocytes. ResultsPNR reached the critical value(≥1) on day 9 after modeling, earlier than U-ACR, which reached the critical value(≥30 mg/g) on day 15. Intervention with valsartan and fosinopril sodium on day 9 after modeling significantly reduced U-ACR (P < 0.05), with low-dose valsartan showing better results than high-dose (P>0.05), while high-dose fosinopril sodium outperformed low-dose (P>0.05). Both low doses of valsartan and fosinopril sodium significantly reduced PNR (P<0.05), with no significant effect observed for high doses. The interventions with valsartan and fosinopril sodium improved and maintained glomerular structure and podocyte arrangement. ConclusionPNR changes earlier than U-ACR, indicating its potential as an early diagnostic marker for DKD in rats. Early intervention with valsartan and fosinopril sodium demonstrates a therapeutic effect on DKD in rats.

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Establishment Methods and Application Evaluation of Animal Models in Reproductive Toxicology Research

Dongyan HUANG ; Jianhui WU

Laboratory Animal and Comparative Medicine.2024;44(5):550-559.

Reproductive toxicology is a discipline that uses toxicological methods to study the mechanisms by which foreign substances interfere with the generation of eggs or sperm and their detrimental effects on offspring. Research includes evaluating the damaging effects of test substances on reproductive function of parents and the toxicity evaluation of offspring embryos. People are exposed to a wide range of drugs, chemicals and environmental pollutants on a daily basis, and determining whether these substances have reproductive toxicity is crucial for the health of future generations. Reproductive toxicology research is therefore critical. Given the specificity and importance of reproductive toxicity evaluation, corresponding institutions both domestically and internationally have issued guidelines, national standards, or industry standards, all of which involve animal experiments. In the study of reproductive system diseases, numerous animal models have been developed to investigate key reproductive organs, such as testicles and ovaries. Each model involves the selection of animals, the establishment of methods, and the quantification of evaluation indicators, and all have advantages and limitations. The choice of model should be based on experimental needs and the characteristics of the model. This paper summarizes commonly used animal models for reproductive and development toxicity evaluation in reproductive toxicology research, including rat models for fertility and early embryonic development toxicity, rat models for embryo-fetal development toxicity, rabbit models for embryo-fetal development toxicity evaluation, minipig models for embryo-fetal development toxicity, rat models for perinatal toxicity, zebrafish models for embryonic development toxicity, and models for evaluating ovarian toxicity induced by chemical drugs, radiotherapy, autoimmunity, and ovariectomy, as well as models for evaluating testicular toxicity caused by chemical drugs and environmental factors. The methods for establishing these models, their application scope, and characteristics are reviewed in order to provide references for relevant research applications.

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