Faculty Editor: Dr. Heather Olins
In the pursuit of examining extraordinary beings that inhabit the planet, it would be remiss not to investigate the elemental juggernaut known as the naked mole rat. As its name suggests, the naked mole rat is a hairless rodent resembling a sausage with loose, wrinkly skin and large, prominent teeth made for digging. Heterocephalus glaber is a native of East Africa, and its species exhibits burrowing and living underground in bee hive-like colonies. Despite its strange appearance, naked mole rats possess a set of extraordinary characteristics that distinguish it from other organisms.
One surprising quality of the naked mole rat is its resistance to most pain. Naked mole rats showed no response to pain-inducing agents like low-pH saline solution or capsaicin, the active component of chili peppers that produces burning sensations, even when the former was injected directly into the skin of their paws (Park, 2008). In attempts to explain such pain tolerance, studies conducted at the University of Texas, Austin point to the lack of an important neurotransmitter. Isolation of single nerve cells found that a receptor called TrkA, responsible for relaying messages of pain throughout the cell, activates molecular pores, known as TRPV1 ion channels, that result in the cell’s increased sensitivity to touch or heat. However, the TrkA in naked mole rats does not activate the ion channels as efficiently as in other animals (Pennisi, 2016). The rat’s pain resistance, especially to acid, makes it well-suited to its habitat: underground tunnels and burrows reach toxic levels of carbon dioxide that cause acid to accumulate in body tissues.
Another remarkable characteristic of naked mole rates is their exceptionally low rates of cancer. Although not completely impervious to tumors, naked mole rats possess a combination of genes that enhance the regulation of cell division, thus reducing the risk of cancerous growths (Delaney). Research has also pointed to the presence of a complex sugar, hyaluronan, produced by the rat’s cells that prevent cells from clumping into tumors. The main purpose of hyaluronan in naked mole rats is likely to improve skin flexibility, allowing them to move about more easily in the confines of their underground tunnels (Pennisi, 2013). However, a study by researchers at the University of Rochester has found the hyaluronan in naked mole rats to be five times larger in molecular mass than that found in humans and mice (Tian, 2013).
Further evidence of the naked mole rat’s superhero quality can be found in its ability to survive in environments deprived of oxygen. While mice died quickly in chambers without oxygen, naked mole rats were able to significantly drop their heart rates, survive for up to 18 minutes, and make full recoveries after having oxygen reintroduced. Additionally, naked mole rats were able to continue regular activity without showing significant signs of distress for up to 5 hours in only 5% oxygen atmospheres (Kupferschmidt, 2017). This level of resistance is likely due to naked mole rats’ efficient oxygen intake and low metabolisms that don’t require high levels of oxygen. Another reason is that naked mole rats do not thermoregulate, which requires significant amounts of oxygen. Unlike other mammals, naked mole rats are cold-blooded in terms of their temperature regulation; the body temperatures of naked mole rats are dependent on their environment (Park, 2018).
Although the traits described above are certainly astonishing, recent findings further solidify the naked mole rat’s superhero status. A study shows that naked mole rats defy the biological law of aging: the naked mole rat’s daily chance of dying stays at 1 out of 10,000 for its entire life after reaching sexual maturity (Kupferschmidt, 2018). Humans, for example, experience an exponentially increasing chance of death every year after age 30 (INED, 2004). Such findings are even more incredible when paired with the fact naked mole rats are the longest living rodent, with lifespans of up to 32 years in captivity. For perspective, brown rats only live for 2 years. Both humans and the naked mole rats experience greater longevity with the help of increased expression of DNA repair genes compared to mice. This helps to combat the damage and mutations in DNA associated with aging (MacRae, 2015)
These traits of the naked mole rat provide exciting opportunities for improvement and development in a vast array of human applications. Greater understanding of the naked mole rat’s pain resistance could have helpful applications in the field of anesthesia and the development of treatments of pain. More research on the role of hyaluronan and the rat’s abilities in evading cancer could have a monumental effect on cancer prevention and treatment. Study of the naked mole rat’s relation with oxygen can be highly beneficial for exploring the situations and medical emergencies in which humans encounter oxygen deprivation. Even current perceptions of the inevitability of aging can be transformed through study of the naked mole rat. The relevance of the naked mole rat’s abilities concerning pain, cancer, oxygen, and aging to the advancement of human health has momentous potential.
- Delaney, M. A., Ward, J. M., Walsh, T. F., Chinnadurai, S. K., Kerns, K., Kinsel, M. J., & Treuting, P. M. (2016, February 4). Initial Case Reports of Cancer in Naked Mole-rats (Heterocephalus glaber). Retrieved from https://journals.sagepub.com/doi/full/10.1177/0300985816630796
- French Institute for Demographic Studies (INED). (2018, August). Age-specific mortality rates. Retrieved from https://www.ined.fr/en/everything_about_population/graphs-maps/interpreted-graphs/age-risk-mortality/
- Kupferschmidt, K. (2017, April 20). Naked mole rats can survive 18 minutes without oxygen. Here’s how they do it. Retrieved from https://www.sciencemag.org/news/2017/04/naked-mole-rats-can-survive-18-minutes-without-oxygen-here-s-how-they-do-it
- Kupferschmidt, K. (2018, January 29). Naked mole rats defy the biological law of aging. Retrieved from https://www.sciencemag.org/news/2018/01/naked-mole-rats-defy-biological-law-aging
- MacRae, S. L., Croken, M. M. K., Calder, R. B., Aliper, A., Milholland, B., White, R. R., … Vijg, J. (2015, December 30). DNA repair in species with extreme lifespan differences. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4712340/
- Park, T. J., Lu, Y., Jüttner, R., Smith, E. S. J., Hu, J., Brand, A., … Lewin, G. R. (2008, January 29). Selective inflammatory pain insensitivity in the African naked mole-rat (Heterocephalus glaber). Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2214810/
- Park, T., & Lundgren, C. (2018, May 29). Are naked mole rats the strangest mammals? Retrieved from https://www.youtube.com/watch?v=2sKADUBfdMk
- Pennisi, E. (2016, October 11). How naked mole rats conquered pain-and what it could mean for us. Retrieved from https://www.sciencemag.org/news/2016/10/how-naked-mole-rats-conquered-pain-and-what-it-could-mean-us
- Pennisi, E. (2013, June 19). Why Naked Mole Rats Don’t Get Cancer. Retrieved from https://www.sciencemag.org/news/2013/06/why-naked-mole-rats-dont-get-cancer
- Tian, X., Azpurua, J., Hine, C., Vaidya, A., Myakishev-Rempel, M., Ablaeva, J., … Seluanov, A. (2013, June 19). High-molecular-mass hyaluronan mediates the cancer resistance of the naked mole rat. Retrieved from https://www.nature.com/articles/nature12234