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]
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.
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.