NS3736

Cytotoxicity assays are usually based on the assessment of cell membrane damage, which can also be indirectly detected by measuring cell viability. Detection methods include MTT assay, CKK-8 assay, LDH assay and ATP assay, etc.

Selecting a suitable non-mouse animal model is a structured decision based on the research question, required anatomy or physiology, disease mechanism, endpoint feasibility, translational relevance, and ethical justification. Non-mouse models are preferred when mice cannot reproduce key human-relevant features, such as organ size, surgical anatomy, cardiovascular physiology, neuroanatomy, immune features, pharmacology, toxicology, or long-term clinical procedures. Candidate species may include rats, rabbits, guinea pigs, ferrets, zebrafish, pigs, sheep, goats, dogs, cats, horses, and non-human primates, but each species must be justified by its specific scientific advantage rather than convenience or tradition. Unresolved questions include how to quantify translational superiority across species, how to balance increased biological relevance against higher ethical burden, and when human-derived systems or new approach methodologies should replace animal use.

Osteoclast differentiation is an in vitro induction assay in which monocyte/macrophage-lineage precursors are exposed to macrophage colony-stimulating factor (M-CSF) and receptor activator of NF-κB ligand (RANKL), generating multinucleated osteoclasts that are commonly identified by tartrate-resistant acid phosphatase (TRAP) staining and functionally confirmed by resorption pits on dentin, bone, or mineralized substrates. M-CSF supports survival and expansion of osteoclast precursors, while RANKL binding to RANK drives osteoclast commitment, fusion, maturation, and resorptive function; osteoprotegerin inhibits this pathway by binding RANKL and preventing RANK activation. The main readouts are the number of TRAP-positive multinucleated cells, formation of F-actin rings, and resorbed surface area; TRAP-positive multinucleated cells indicate osteoclast differentiation, whereas pit formation on dentin, bone, or mineralized coating indicates functional bone-resorbing activity.

Choosing the right model animal is a validity-driven decision in which the species, strain, sex, age, genetic background, disease-induction method, outcome measures, and welfare burden must match the scientific question rather than laboratory tradition or convenience. A model should be selected by judging face validity, construct validity, and predictive validity: whether it resembles the human phenotype, whether it reproduces relevant mechanisms, and whether results are likely to predict human biology or treatment response. Animal studies often fail to translate because of species differences, weak disease resemblance, poor experimental design, inadequate reporting, publication bias, and underuse of randomization, blinding, and sample-size justification. Unresolved questions include how to rank competing models objectively, how much human-disease complexity must be reproduced for a given objective, and when non-animal systems such as organoids, ex vivo tissue, or computational models