Harvard neuroscientists explore the science of acupuncture

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Researchers have discovered the neurons necessary for the anti-inflammatory response to acupuncture,

Acupuncture is a traditional Chinese technique that has been used for millennia to treat chronic pain and other health problems associated with inflammation, but the scientific basis for the technique remains poorly understood.

Today, a team of researchers led by neuroscientists from Harvard Medical School elucidated the underlying neuroanatomy of acupuncture that activates a specific signaling pathway.

In a study conducted in mice and published on October 13, 2021 in Nature, the team identified a subset of neurons that must be present for acupuncture to trigger an anti-inflammatory response via this signaling pathway.

Scientists have determined that these neurons only occur in a specific area of ​​the hind limb region, which is why acupuncture in the hind limbs works, while acupuncture in the abdomen does not.

“This study addresses one of the most fundamental questions in the field of acupuncture: What is the neuroanatomical basis of body region selectivity, or acupuncture point?” Said lead researcher Qiufu Ma, HMS professor of neurobiology at the Dana-Farber Cancer Institute.

One area of ​​particular interest to the research team is the so-called cytokine storm – the rapid release of large amounts of cytokines that frequently lead to severe systemic inflammation and can be triggered by many factors, including COVID-19[female[feminine, treatment for cancer or sepsis.

“This exuberant immune response is a major medical problem with a very high death rate of 15% to 30%,” Ma said. Even so, drugs to treat the cytokine storm are lacking.

Adapting an old technique to treat aberrant inflammation

Over the past few decades, acupuncture has been increasingly adopted in Western medicine as a potential treatment for inflammation.

In this technique, acupuncture points on the surface of the body are mechanically stimulated, triggering nerve signaling that affects the functioning of other parts of the body, including organs.

In a 2014 study, researchers reported that electroacupuncture, a modern version of traditional acupuncture that uses electrical stimulation, could reduce the cytokine storm in mice by activating the vagal-adrenal axis, a pathway in which the vagus nerve signals to the adrenal glands to release dopamine.

In a study published in 2020, Ma and her team found that this electroacupuncture effect was region specific: it was effective when given to the hind limb region, but had no effect when administered to the hind limb region. it was administered in the abdominal region. The team hypothesized that there may be sensory neurons unique to the hind limb region responsible for this difference in response.

In their new study, the researchers conducted a series of experiments on mice to investigate this hypothesis. First, they identified a small subset of sensory neurons marked by the expression of PROKR2Creat receiver. They determined that these neurons were three to four times more numerous in the deep fascia tissue of the hind limb than in the fascia of the abdomen.

Then the team created mice that lacked these sensory neurons. They found that electroacupuncture in the hind limbs did not activate the vagal-adrenal axis in these mice. In another experiment, the team used light-based stimulation to directly target these sensory neurons in the deep fascia of the hind limb.

This stimulation activated the vagal-adrenal axis in a manner similar to electroacupuncture. “Basically, activating these neurons is both necessary and sufficient to activate this vagal-adrenal axis,” Ma said.

In a final experiment, scientists explored the distribution of neurons in the hind limb. They found that there are many more neurons in the anterior muscles of the hind limb than in the posterior muscles, resulting in a stronger response to electroacupuncture in the anterior region.

“Based on this distribution of nerve fibers, we can almost accurately predict where the electrical stimulation will be effective and where it won’t,” Ma explained.

Taken together, these results provide “the first concrete neuroanatomical explanation for the selectivity and specificity of acupuncture points,” added Ma. “They tell us the parameters of acupuncture, so where to go, how deep to go, what depth to go must be the intensity. “

He noted that although the study was performed in mice, the basic organization of neurons is likely conserved throughout evolution in mammals, including humans.

However, an important next step will be the clinical testing of electroacupuncture in humans with inflammation caused by real-world infections such as COVID-19. Ma is also interested in exploring other signaling pathways that could be stimulated by acupuncture to treat conditions causing excessive inflammation.

“We have a lot of difficult chronic diseases that need even better treatment,” he said, such as inflammatory bowel syndrome and arthritis. Another area of ​​need, he added, relates to excessive immune reactions which can be a side effect of cancer immunotherapy.

Ma hopes her research will advance the scientific understanding of acupuncture and provide practical information that can be used to improve and refine the technique.

Reference: “A neuroanatomical basic for electroacupuncture to drive the vagal – adrenal axis” by Shenbin Liu, Zhifu Wang, Yangshuai Su, Lu Qi, Wei Yang, Mingzhou Fu, Xianghong Jing, Yanqing Wang and Qiufu Ma, October 13, 2021, Nature.
DOI: 10.1038 / s41586-021-04001-4

The work was primarily supported by the National Institutes of Health (grant R01AT010629), and partially supported by Harvard /MIT Joint Fundamental Neuroscience Research Grants Program and Wellcome Trust (Grant 200183 / Z / 15 / Z). For more information on salary support for researchers, please refer to the article.

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