Transplanted immune cells donate mitochondria to brain cells
Immune cells delivered via bone marrow transplantation do more than restore the body’s defenses. They also transfer their own energy-producing organelles (mitochondria) to neighboring brain cells. That is the finding of a new mouse study published in Nature Communications.
Mitochondrial dysfunction, in which cells produce insufficient energy, is one of the hallmarks of aging. It also plays a central role in rare conditions such as Friedreich’s ataxia, a genetic disease in which the protein frataxin is absent. Without frataxin, heart muscle cells and neurons run into energy deficits. Researchers at Stanford asked whether bone marrow transplantation could go beyond replacing defective immune cells and also restore energy metabolism in non-immune cells through mitochondrial transfer.
Fluorescent labels trace the transfer
To track the transfer, the researchers labeled donor cells with two fluorescent markers: a green signal throughout the whole cell and a red signal targeting only the mitochondria. Five months after transplantation, roughly 82 percent of the measured brain immune cells were donor-derived. But red-labeled mitochondria also appeared in brain cells that lacked the green donor-cell label. Those cells were therefore not donor cells themselves, yet they had received donor mitochondria. Neurons as well as supporting brain cells showed this pattern.
Notably, affected mice took up more donor mitochondria than healthy mice did. This suggests that energy-deprived cells may actively seek additional mitochondria. The researchers found traces of mitochondrial transfer outside the brain as well.
What this means for aging research
Mitochondrial decline is not unique to rare genetic diseases. It is one of the measurable hallmarks of ordinary aging. The finding that transplanted immune cells can share mitochondria with surrounding cells therefore carries broader relevance. If mitochondrial transfer can be harnessed systematically, it may open new avenues for addressing energy deficits in aging tissues. This study does not prove that yet, and it was conducted in mice, but the proof of concept is remarkably clear.
The results also help explain earlier observations that bone marrow transplants sometimes benefit tissues beyond the immune system. The mechanism behind that broader recovery had until now remained unclear.
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