Scientists found that certain macrophages form neuron-like connections with muscle fibers and deliver calcium to jump-start repair within seconds. This rapid signaling sped healing in both injury and disease models.
The discovery could open the door to new regenerative therapies. But researchers still need to understand why this repair boost doesn’t reduce pain.
Cellular Complexities of Muscle Repair
At the microscopic scale, the process behind muscle repair becomes increasingly complex. Healing also varies depending on the type of damage involved, as the body responds very differently to an acute muscle tear from a sports injury compared to the gradual loss of muscle seen in conditions such as muscular dystrophy.
A research team at Cincinnati Children’s has now identified a shared and surprising mechanism that may enhance recovery across multiple forms of muscle damage.
Uncovering an Unexpected Synaptic-Like Twist
The eye-opening findings were published today (November 21, 2025) in Current Biology. The work was conducted by first author Gyanesh Tripathi, PhD, and corresponding author Michael Jankowski, PhD, who directs the Research Division within Cincinnati Children’s Department of Anesthesia and serves as Associate Director of Basic Science Research for the Pediatric Pain Research Center.
This newly identified process centers on a type of immune cell known as a macrophage. These cells are typically recognized for clearing out bacteria, dead cells, and assorted debris, much like tiny biological cleanup crews.
A Neuron-Like Repair System Revealed
“The biggest surprise about this was finding that a macrophage has a synaptic-like property that delivers an ion to a muscle fiber to facilitate its repair after an injury,” Jankowski says. “It’s literally like the way a neuron works, and it’s working in an extremely fast synaptic-like fashion to regulate repair.”
Scientists have long understood that macrophages play a role in the body’s response to muscle injury. They release molecules such as cytokines and chemokines that drive inflammation, influence pain, and support muscle fiber growth and regeneration.
Searching for Pain Relief, Finding Repair Instead
Jankowski’s team initially set out to better understand how to reduce pain during recovery after surgery. They were searching for new strategies that might offer safer alternatives to existing pain medications.
While their search did not reveal a pain-relieving pathway, it uncovered a fast-acting repair mechanism that could help advance treatments for muscle wasting and injury recovery. The results also point to the possibility that macrophages could become useful “delivery vehicles” for future cell-based therapies aimed at a wider range of conditions.
What These Infiltrating Macrophages Actually Do
“These are infiltrating macrophages, a very specific type. They’re not ones already residing in the tissue. These come in after damage occurs,” Jankowski says.
In a series of experiments involving mouse models of two distinct types of injury, the researchers tracked how the macrophages interacted with the myofibers that form muscle tissue. In fact, they were able to capture key moments of the activity in real time.
Fast Calcium Delivery and Rapid Muscle Activation
Using short bursts of a designer chemical to induce activation, the team watched the macrophages forming synaptic-like contacts with the myofibers. The immune cells then delivered calcium ions directly to the myofibers, which hastened an acute-injury healing process. Within 10 to 30 seconds, the researchers detected bursts of electrical activity within the affected muscles.
“This occurs in a very rapid fashion. You can activate the macrophage and make the muscle twitch subtly almost immediately,” Jankowski says.
Synaptic Response Works in Disease Models Too
Meanwhile, the connected macrophages triggered a similar process of cell regeneration, helping mice with disease-like muscle damage. After detecting damage, the immune cells flocked to the area and induced waves of muscle fiber activity. After 10 days, treated mice showed larger numbers of new muscle fibers compared to the control group.
“A similar synaptic-like response worked in both scenarios,” Jankowski says.
Next Steps Toward Human Application
More study is needed to determine whether human macrophages behave similarly after muscle injury, and, if so, how to control the process therapeutically.
The team also wants to learn more about one unexplained result of the work: Even though the infiltrating macrophages helped speed healing, their activity did not appear to reduce measures of acute pain sensation. Understanding more about why could help explain why about 20% of children who receive surgery experience longer-term pain symptoms.
Future Possibilities for Cellular Delivery
And looking forward, the researchers plan to explore more about what else a macrophage might be able to deliver to muscle cells.
Reference: “Synaptic-like coupling of macrophages to myofibers regulates muscle repair” by Gyanesh M. Tripathi, Adam J. Dourson, Fabian Montecino-Morales, Jennifer L. Wayland, Sahana Khanna, Megan C. Hofmann, Hima Bindu Durumutla, Thirupugal Govindarajan, Luis F. Queme, Douglas P. Millay and Michael P. Jankowski, 21 November 2025, Current Biology.
DOI: 10.1016/j.cub.2025.10.077
Cincinnati Children’s co-authors also included Adam Dourson, PhD, Fabian Montecino-Morales, PhD, Jennifer Wayland, MS, Sahana Khanna, Megan Hofmann, Hima Bindu Durumutla, MS, Thirupugal Govindarajan, PhD, Luis Queme, MD, PhD, and Douglas Millay, PhD. The Bioanalysis and Imaging Facility at Cincinnati Children’s also contributed to the work.
Funding sources for this study include grants from the National Institutes of Health (R01NS105715, R01NS113965, R61/R33AR078060, R01AR068286, R01AG082697) and the Cincinnati Children’s Hospital Research Foundation.
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1 Comment
thanks for this