Previously unknown sensory organ identified.
Chronic pain is an out-of-control pandemic still growing after many decades. Subsequently, it is the most common reason for physician consultation in most developed countries around the world, with almost one in five people experiencing constant pain in their lifetime.
This aside, sensitivity to pain is also required for survival proffering a protective function. Additionally prompting a reflex to prevent damage to tissue. For example, when a person pulls their hand away when they feel a jab from a sharp object or when they burn themselves. To date, the exact circuitry behind this reaction is still not fully understood.
New sensory organ discovered
Now, a study from researchers at Karolinska Institutet identifies a previously unknown sensory organ in mice which detects painful mechanical damage, such as pricks and impacts. The team states their discovery changes the understanding of the cellular mechanisms of physical sensation. Furthermore, this new discovery may be of significance in the understanding of chronic pain. The study is published in the journal Science.
Previous studies show pain can be classified under various descriptions. Firstly is neuropathic pain which is initiated by a disease in the somatosensory nervous system. Secondly, there’s nociceptive pain which represents the normal response to noxious injury of tissues such as skin or bone. Thirdly and finally there is inflammatory pain which involves the activation of the nociceptive pain pathway at the site of inflammation.
All of the aforementioned types of pain are thought to be initiated by the activation of free nerve endings without end organs in the skin. The current study identifies a previously unknown mesh-like organ covering the skin in rodents which senses dangerous environmental stimuli.
The current study shows the organ, dubbed the nociceptive glio-neural complex, is made up of a network of cells called glial cells. Glial cells are found in the nervous system where they surround and support the body’s nerve cells. Results show the glial cells form a mesh-like structure or organ between the skin’s outer and inner layers, with filament-like protrusions which extend into the skin’s outer layer.
The lab tested the functionality of the sensory organ by measuring the rodents’ responses to different types of pain. Data findings show when the cells in the organ were turned off via gene editing, the animals exhibited a reduced response to mechanical pain. Additionally, the animals presented with discomfort caused by pressure, pricking, or other impacts on the skin.
Octupus-shaped sensory organ
The team states these glial cells are a type of octopus-shaped Schwann cell wrapping around and engulfing nerve cells. They go on to explain the body of the Schwann cells sitting below the outer layer of the skin has long extensions wrapped around the ends of pain-sensing nerve cells extending to the outer layer of the skin, the epidermis. The group concludes the Schwann cells are mechanosensitive and transmit nociceptive information to the nerve.
The team surmises they have identified a previously unknown sensory organ involved in the sensation of pain. For the future, the researchers state they now plan to investigate whether this sensory organ also exists in humans.
Source: Karolinska Institutet
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