Mice (Mus Musculus)
Mice are often used in scientific research because they share many genetic and physical traits with humans. However, since mice and humans evolved in different environments, they have distinct differences. While both species have certain shared biological processes, their reactions to experiments can vary significantly. Mice are great for studying shared biological traits and understanding how different species develop from common genes. But when it comes to mimicking human diseases, mice might not always be the best models since the connections between genes and diseases can vary between humans and mice. So, while mice are helpful in research, it's essential to consider both their similarities and differences with humans. [1]
Development of mice in the first 2 weeks of life [2]
Benefits for Longevity Research
Mice are beneficial for longevity research for several reasons:
- Short Lifespan: Mice have a relatively short lifespan, typically 2-3 years. This allows researchers to study the entire life cycle of the organism in a condensed time frame, making it feasible to observe the effects of interventions on aging within a realistic research period.
- Genetic Manipulability: Mice genomes can be easily manipulated, allowing scientists to create genetically modified strains to study specific genes or pathways related to aging.
- Conserved Aging Mechanisms: Many biological processes related to aging are conserved between mice and humans. This means that discoveries in mice often provide insights into human aging and potential interventions.
- Cost-Effective: Maintaining mice in a research setting is less expensive compared to larger animals. This makes it economically feasible to run long-term studies with large sample sizes.
- Reproducibility: Mice have relatively short reproductive cycles and produce numerous offspring. This allows for studies across multiple generations in a short time.
- Controlled Environment: It's easier to control external factors such as diet, environment, and exposure to substances in mice, ensuring that the observed effects are due to the interventions and not external variables.
- Rich Data Sets: Due to the extensive use of mice in research, there's a wealth of pre-existing data available. This enables researchers to compare and contrast findings from longevity studies with data from other domains.
- Ethical Considerations: While all animal research has ethical considerations, the use of shorter-lived organisms like mice often presents fewer ethical complexities than the use of longer-lived animals, especially primates.
Mouse Strains Relevant for Longevity Research
| Strain Name | Description | Key Traits | Use in Longevity Research |
|---|---|---|---|
| C57BL/6 | Most commonly used inbred strain | High susceptibility to diet-induced obesity | Often used as a reference strain in aging studies |
| Ames Dwarf | Mutant strain with deficiency in growth hormone, prolactin, and thyroid-stimulating hormone | Extended lifespan; reduced tumor incidence | Key model in studying hormonal effects on aging |
| Snell Dwarf | Similar to Ames Dwarf with pituitary deficiencies | Extended lifespan; improved insulin sensitivity | Used to study hormonal regulation and aging |
| SAM (Senescence-Accelerated Mouse) | Group of related strains with accelerated aging | Varies by substrain (e.g., SAMP8 shows early cognitive decline) | Widely used in aging research to study rapid aging effects |
| ApoE−/− (Apolipoprotein E-deficient) | Mutant strain deficient in ApoE protein | Prone to cardiovascular diseases; develops atherosclerosis | Widely used in cardiovascular research, providing insights into age-related cardiovascular diseases |
| C3H | Inbred strain with a propensity for certain tumors | Prone to mammary tumors; used in cancer research | Relevant in longevity research, especially in studies linking aging and cancer |
| B6C3F1 | Hybrid strain derived from C57BL/6 and C3H | High tumor incidence in old age | Used in carcinogenicity and aging studies |
| DBA/2 | Inbred strain known for early age-related hearing loss | High bone density; resistant to diet-induced obesity | Used in sensory aging studies, particularly hearing |
| BALB/c | Inbred strain with known susceptibility to certain cancers | High levels of anxiety-like behavior | Used in cancer and aging studies |
| ICR (Institute of Cancer Research) | Outbred strain | Good reproductive performance; used as general multipurpose strain | Often used as a control strain in various research, including aging |
Differences Between Human and Laboratory Mice
| Feature | Mice | Human | Difference |
|---|---|---|---|
| Lifespan | ~2-3 years | ~80 years (average) | ~40x |
| Reproductive Age Start | ~6-8 weeks | ~12-15 years | ~100x |
| Growth Rate | 2-3 months to maturity | 18-25 years to reach full adult size | ~90x to ~100x |
| Genome | ~20,000-25,000 protein-coding genes | ~20,000-25,000 protein-coding genes | differences in some gene families and pathways |
| Genome Size | ~2.7 billion base pairs | ~3.2 billion base pairs | |
| Number of Chromosomes | 40 (20 pairs) | 46 (23 pairs) | |
| Heart Rate | ~500-700 beats/minute | ~60-100 beats/minute | ~8x |
| Metabolic Rate | Faster | Slower | Variable (often >10x) |
| Bone Density Decline | Begins around 1 year | Begins in late 20s | ~25x |
| Body Weight | 20-40 g (female) & 25-45 g (male) | Average 62 kg (female) & 77 kg (male) | ~2000x (average) |
| Brain Size | ~0.4 cm³ | ~1400 cm³ | ~3500x |
| Blood Volume | ~2 ml | ~5 liters | ~2500x |
| Caloric Restriction Response | Increases longevity | Increases longevity | |
| Diet | Omnivorous, often fed controlled diets in labs | Omnivorous, varied diet | |
| Telomere Length | Relatively longer in many cells | Shorter in somatic cells | |
| Reproductive Cycle | 4-5 days (Estrous cycle) | ~28 days (Menstrual cycle) | ~6x |
| Pregnancy Duration | ~19-21 days | ~280 days | ~14x |
| Immune System | Faster initial response, less memory-driven | Slower response, memory-driven | |
| Drug Metabolism | Faster drug metabolism due to differences in liver enzymes | Slower drug metabolism | |
| Blood Cell Lifespan | Red cells: ~40 days | Red cells: ~120 days | ~3x |
| Allometric Scaling Correction Factor | 3 | 37 | ~12x |
See [2] for relating the ages of men and mice.
References
- ↑ Perlman RL: Mouse models of human disease: An evolutionary perspective. Evol Med Public Health 2016. (PMID 27121451) [PubMed] [DOI] [Full text] The use of mice as model organisms to study human biology is predicated on the genetic and physiological similarities between the species. Nonetheless, mice and humans have evolved in and become adapted to different environments and so, despite their phylogenetic relatedness, they have become very different organisms. Mice often respond to experimental interventions in ways that differ strikingly from humans. Mice are invaluable for studying biological processes that have been conserved during the evolution of the rodent and primate lineages and for investigating the developmental mechanisms by which the conserved mammalian genome gives rise to a variety of different species. Mice are less reliable as models of human disease, however, because the networks linking genes to disease are likely to differ between the two species. The use of mice in biomedical research needs to take account of the evolved differences as well as the similarities between mice and humans.
- ↑ 2.0 2.1 Dutta S & Sengupta P: Men and mice: Relating their ages. Life Sci 2016. (PMID 26596563) [PubMed] [DOI] Since the late 18th century, the murine model has been widely used in biomedical research (about 59% of total animals used) as it is compact, cost-effective, and easily available, conserving almost 99% of human genes and physiologically resembling humans. Despite the similarities, mice have a diminutive lifespan compared to humans. In this study, we found that one human year is equivalent to nine mice days, although this is not the case when comparing the lifespan of mice versus humans taking the entire life at the same time without considering each phase separately. Therefore, the precise correlation of age at every point in their lifespan must be determined. Determining the age relation between mice and humans is necessary for setting up experimental murine models more analogous in age to humans. Thus, more accuracy can be obtained in the research outcome for humans of a specific age group, although current outcomes are based on mice of an approximate age. To fill this gap between approximation and accuracy, this review article is the first to establish a precise relation between mice age and human age, following our previous article, which explained the relation in ages of laboratory rats with humans in detail.