Promising news for diabetics and others who suffer from numbness in the extremities, not to mention those who suffer from chronic pain and would prefer a natural remedy.
For the first time, scientists have converted both mouse and human skin cells into functional pain sensing nerve cells in the lab. These neurons, which are responsible for transmitting pain signals to the brain, were found to respond to various different stimuli, such as the chemical in chilies that gives them their burn. This novel model of pain, or pain in a dish, as it has been nicknamed, will hopefully advance our understanding of pain and could ultimately lead to the development of new forms of pain relief.
Basically, here’s how nerves transmit sensitivity such as pain:
Our pain sensing system may not bring much joy to us like some of our other senses, such as smell or taste, but unfortunately, we need it to survive. It tells us to withdraw from situations that could damage us — such as touching a hot surface — and alerts us when something is going awry, such as a grumbling appendix. There’s no doubt that it’s an extremely important sense, if not the most important.
Key to detecting potentially dangerous stimuli at the skin are neurons of the peripheral nervous system called nociceptors. These nerves, which project their endings to skin cells, transmit both itch and ouch signals to the brain and therefore facilitate the perception of pain. Our understanding of how the nervous system generates this sense of pain is, however, rather limited, and studying this complex system in living organisms is difficult. This is why a group of scientists from Harvard wanted to create a model system in the lab, but this was no mean feat.
The team spent three years trying to create nociceptors in the lab from stem cells, but their endeavor proved fruitless. Eventually, they gave up and decided to try a different approach, which they describe in Nature Neuroscience.
After examining mature pain sensing neurons in mice, the scientists identified a unique set of proteins, called transcription factors, which were active in these cells. Transcription factors control gene expression by binding to specific stretches of DNA, and are able to both activate and switch off certain genes. By adding this specific cocktail of transcription factors to skin cells in a dish, the researchers were able to successfully prompt them to assume their new identity as nociceptors.
The researchers then exposed these cells to several different stimuli to see if they correctly responded, and found that heating to 42oC or adding the active chemical in chili peppers caused them to fire off signals.
As well as responding to the intense ouch pain triggered by injury, the cells were also found to respond to the more subtle stimuli triggered by inflammation, which results in pain tenderness. The researchers say that reacting to both gross and fine forms of stimulation — which produce different types of pain — suggests that the cells are indeed functioning in a similar manner to naturally developed neurons.
Alongside furthering our understanding of pain sensing, it’s realistic to believe that this simple cell-conversion technique could one day be used to create patient-specific models for individuals suffering from chronic pain, which could aid the identification of potential treatments.
As well, those suffering from Type-2 diabetes have reason to hope that this breakthrough could one day assist them in returning feeling to their extremities.