Experiments on naked mole-rats may lead to better treatments with fewer side effects for humans suffering from painful inflammatory arthritis, according to a new study published Friday in the journal Science.
The partially blind, hairless, wrinkly, cold-blooded mammals were good candidates for the study because of their unique insensitivity to acid-induced pain.
Native to sub-Saharan Africa, the naked mole-rat makes its home burrowed deep in huge colonies in underground tunnels, with access to very little oxygen and high levels of carbon dioxide.
“Exposure to high levels of carbon dioxide in turn would evoke acidosis, but the naked mole-rat has evolved in a way to manage this acid load and to be able to live in acidic environments, which for most other rodents in the world would be uninhabitable,” said neuroscientist Ewan St. John Smith, the lead author of the study.
Scientists say in most mammals - including humans - exposure to acid stimulates special channels at the tips of sensory neurons, called nociceptors. Once these nociceptors are activated, they transmit a signal along the spinal cord to the brain.
But among naked mole-rats, although acid triggers the nociceptors, their pain-sensing neurons contain proteins with genetic mutations that prevent neurons from firing off pain signals in response to acid.
Inflammatory disorders, such as arthritis, are normally associated with acidosis, scientists say.
“If a drug could now be developed which acts on these particular proteins on the sensory neurons, you could limit the ability of acid to cause pain in patients with arthritis and other inflammatory disorders,” Smith said.
According to the Centers for Disease Control and Prevention, an estimated 50 million U.S. adults (about 1 in 5) report doctor-diagnosed arthritis. That number is projected to increase to 67 million by 2030.
“We can learn a lot from comparative physiology. By understanding how an animal adapts to its environment, this will teach us a lot of our own biological system,” said neuroscientists Gary R. Lewin, one of the authors of the study, conducted by the Max Delbrück Center for Molecular Medicine in Germany.
The naked mole-rat has been the subject of other groundbreaking studies. The buck-tooth rodent has been found to have an unusually long life span; it can live three years longer than other rodents and is resistant to cancer.
Most recently, scientists sequenced and analyzed the entire genome, which Smith and his colleagues hope to be able to use for their next phase of research.
"It’s cool to know how things work, especially when things don’t work as you expect them to,” Smith said.
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