Researchers have discovered a cluster of sensory neurons that link the brain and heart, triggering an immune response crucial for recovery after a heart attack. This finding reveals a feedback loop involving the nervous and immune systems that could lead to new therapies. Experiments in mice showed that manipulating these neurons speeds up healing and reduces scarring.
A team led by Vineet Augustine at the University of California, San Diego, has uncovered how the brain contributes to heart repair following a heart attack. Their study, published in Cell, identifies a previously unknown group of sensory neurons originating from the vagus nerve. These neurons wrap around the heart's ventricle wall, particularly in areas damaged by oxygen deprivation.
In experiments, the researchers made mouse hearts transparent using tissue clearing to observe neural activity after inducing a heart attack by blocking blood flow. Before the injury, few such nerve fibers existed, but their numbers increased dramatically afterward, indicating the heart signals growth in response to damage.
"The body and the brain do not exist in isolation. There is immense crosstalk between different organ systems, the nervous system and the immune system," Augustine explained.
When the team genetically silenced these neurons, preventing signals from reaching the brain, the mice experienced rapid healing. The damaged heart tissue shrank significantly, demonstrating a "remarkable" recovery. These signals reach a brain region linked to stress responses, activating the fight-or-flight mode and mobilizing immune cells to the heart. While these cells form scar tissue to mend the muscle, excessive scarring can impair function and cause heart failure.
Blocking the early immune activation offered another path to improved outcomes. This builds on prior knowledge of cardiac sensory neurons that manage blood pressure and fainting.
Experts not involved in the research praised the precision enabled by modern tools. "This gives us really exciting opportunities to develop new therapies for patients that have heart attacks," said Matthew Kay at George Washington University, noting potential for gene therapies.
The discovery may explain how beta blockers, commonly prescribed post-heart attack, aid recovery by targeting this neuroimmune pathway. However, Robin Choudhury at the University of Oxford cautioned that the response is complex, influenced by factors like genetics, sex, diabetes, and hypertension. Further work is needed to assess its activity across diverse patients before new drugs can be developed.
