Accurately and promptly assessing pain in experimental animals is extremely important to avoid unnecessary suffering of the animals and to enhance the reproducibility of experiments. This is a key concern for veterinarians, animal caretakers, and researchers from the perspectives of veterinary care and animal welfare. Various methods including ethology, immunohistochemistry, electrophysiology, and molecular biology are used for pain assessment. However, the grimace scale, which was developed by taking cues from interpreting pain through facial expressions of non-verbal infants, has become recognized as a very simple and practical method for objectively evaluating pain levels by scoring changes in an animal’s expressions. This method, which was first implemented with mice approximately 10 years ago, is now being applied to various experimental animals and is widely used in research settings. This review focuses on the usability of the grimace scale from the “cage-side” perspective, aiming to make it a more user-friendly tool for those involved in animal experiments. Differences in facial expressions in response to pain in various animals, examples of applying the grimace scale, current automated analytical methods, and future prospects are discussed.

Japan's largest platform for academic e-journals: J-STAGE is a full text database for reviewed academic papers published by Japanese societies

The Adriamycin-induced nephropathy (AN) model plays a crucial role in advancing our understanding of and research on chronic kidney disease (CKD). This review outlines methodologies for generating AN models in mice and rats, discusses their pathophysiologic and molecular characteristics, highlights their advantages and limitations, describes therapeutic interventions that have been evaluated in these models, and presents future research perspectives. The AN model replicates key features observed in human CKD, such as proteinuria, podocyte injury, glomerulosclerosis, and tubulointerstitial fibrosis. Notably, genetic factors significantly influence the onset and severity of AN, with mutations in the Prkdc gene linked to nephrotoxicity and systemic toxicity. To evaluate therapeutic interventions for CKD, agents such as ACE inhibitors, corticosteroids, and SGLT2 inhibitors have been tested in the AN model, demonstrating promising renoprotective effects. However, the systemic toxicity of Adriamycin and variability across models pose limitations, highlighting the need for caution when translating findings to human CKD. Future advancements in genetic engineering and the application of CRISPR-Cas9 technology are expected to improve the fidelity of AN models to human disease. Additionally, Discovery of biomarkers by using the AN model enables us to improve early diagnosis. These efforts are anticipated to deepen our understanding of CKD pathophysiology and contribute to developing more effective diagnostic tools and targeted therapies.

Tensin2 is a focal adhesion-localized multidomain protein expressed in various tissues, and its dysfunction leads to alterations in podocytes. However, these podocyte-related manifestations are dependent on murine strain. Tensin2 dysfunction results in susceptible strains developing podocyte foot process effacement and massive albuminuria, whereas podocytes in resistant strains remain almost intact. In our previous studies, quantitative trait loci analysis and congenic analysis using resistant C57BL/6J and susceptible ICGN mice identified a modifier locus associated with podocyte injury caused by tensin2 dysfunction on chromosome 2. However, the effect of this modifier locus on chromosome 2 is insufficient to explain the resistance of C57BL/6J mice to tensin2 dysfunction, indicating the existence of other modifier genes. Whereas previous studies focused on the severity of chronic kidney disease, the present study focused on podocyte injury. We performed a genome-wide linkage analysis of backcrosses between two tensin2-deficient mouse strains, B6.ICGN-Tns2 ^nph and FVB.ICGN-Tns2 ^nph , and detected a novel major modifier locus on chromosome 10. The combined effect of the C57BL/6J alleles of the two loci on chromosomes 2 and 10 reduced the urinary albumin excretion caused by tensin2 dysfunction to a level comparable to that of C57BL/6J mice. These data indicate that the resistance to podocyte injury caused by tensin2 dysfunction is mainly produced by the effects of the modifier genes on the two loci. The identification of these modifier genes is expected to help elucidate the mechanism underlying podocyte injury.

Animal models of podocytopathy and chronic kidney diseases (CKD) help elucidate these pathologies. Adriamycin (ADR)-induced nephropathy is a common rodent model of podocytopathy. BALB/c mice are sensitive to ADR, whereas C57BL/6 (B6) mice, the most commonly used strain, are resistant to ADR. Therefore, mouse strains with the B6 genetic background cannot be used as an ADR nephropathy model. We previously generated DNA-dependent protein kinase catalytic subunit (Prkdc) mutant B6 mice (B6-PrkdcR2140C) carrying the R2140C mutation that causes ADR nephropathy. However, whether ADR nephropathy in the novel strain progresses to CKD after ADR administration has not been evaluated. Therefore, we examined whether the B6-PrkdcR2140C mice develop CKD after ADR administration. We also evaluated whether differences existed in the genetic background in ADR nephropathy by comparing the B6-PrkdcR2140C mice with BALB/c mice. Our findings demonstrated that B6-PrkdcR2140C progresses to CKD and is resistant to nephropathy compared with the BALB/c mice. The B6-PrkdcR2140C and BALB/c mice differed in the expression of genes related to inflammatory mediators, and further analysis is required to identify factors that contribute to resistance to nephropathy.