Mitochondria From a Woman’s Leg Were Injected Into Her Eyes
A 26-year-old woman arrived at a hospital nearly blind in both eyes after a severe brain bleed went untreated for roughly 18 hours. Conventional medicine had nothing left to offer her. So doctors extracted mitochondria from her own thigh muscle and injected them directly into her eyes – and within days, something in those eyes began to respond to light for the first time in more than two months.
The procedure she underwent is called mitochondria injection therapy, and it has never before been attempted in a human eye. The case was led by Dr. David Putrino, a neuroscientist and Director of Rehabilitation Innovation at the Icahn School of Medicine at Mount Sinai in New York City, and was published as a preprint on Research Square. The findings are preliminary, heavily caveated, and involve a single patient with no control group.
Mitochondria are the tiny organelles inside cells responsible for converting food and oxygen into usable energy – a molecule called ATP (adenosine triphosphate) – which powers virtually every cell function in the body. Understanding what they do, and what happens when they fail, is central to understanding this case.
What mitochondria have to do with sight
Most tissues can tolerate some degree of mitochondrial stress. The eye is less forgiving. Among the most energy-hungry cells in the nervous system are the retinal ganglion cells – neurons on the inner surface of the retina that carry vision signals from the eye to the brain. These cells depend heavily on oxidative phosphorylation, the chemical chain reaction by which mitochondria produce ATP. In animal studies, mitochondria injected into the vitreous fluid of the eye are taken up by these cells and improve their survival after optic nerve injury.
When blood and oxygen supply to the eye is suddenly cut off, that energy production collapses. Mitochondrial dysfunction is understood to be a key factor in multiple vision-related disorders, including glaucoma, hereditary optic neuropathy, and age-related macular degeneration. Retinal ganglion cells are particularly vulnerable to even brief interruptions in metabolic support, and once they die, conventional medicine currently has no way to bring them back.
Mitochondria injection therapy targets retinal ganglion cells that are damaged but not yet dead – supplying them with fresh energy rather than attempting to revive cells that have already been lost.
The patient: 18 hours too late, then one last option
The woman at the center of this case was diagnosed with bilateral optic neuropathy – damage to both optic nerves – that had been fixed and unimproving for three months following prolonged cerebral hypoperfusion, meaning severely reduced blood flow to the brain. She had suffered a major brain bleed and was not brought to a hospital for an estimated 18 hours. She survived emergency surgery, but the extended period of oxygen and blood deprivation left her nearly completely blind in both eyes.
By the eight-week mark, her optic nerves showed visible atrophy – a measurable shrinkage consistent with nerve cell death. Standard treatment options had produced no meaningful improvement in her vision. Imaging showed that while the retinal layers had thinned dramatically, they hadn’t vanished entirely, and brain recordings suggested that some visual information was still reaching her visual cortex, meaning the pathway from eye to brain hadn’t gone completely dark.
Automated pupillary reactivity – the reflex by which pupils constrict in response to bright light – had been absent across 45 separate readings taken over the 71 days preceding the procedure. Not a single normal response in more than ten weeks of measurements. For this patient, the question was whether any of her remaining retinal cells could recover function if given a fresh energy source.
The doctors decided to try.
How the procedure actually worked
Mitochondrial transplantation involves delivering viable, respiration-competent mitochondria into tissue whose own mitochondria have been damaged. It had previously been performed in the human heart and brain, but never in the eye, and no established dose, safety profile, or delivery method existed for that part of the body.
Early clinical safety data for mitochondrial transplantation came from cardiac surgery teams at Boston Children’s Hospital, Harvard Medical School, whose work on ischemia-reperfusion injuries established that mitochondria isolated from a patient’s own non-ischemic tissue could safely replace damaged ones in pediatric cardiac patients. That groundwork informed the approach used in the eye.
For this patient, the team extracted a biopsy sample from her thigh muscle – a site with abundant, healthy mitochondria. They processed that tissue to isolate tens of millions of individual mitochondria and, while they were still fresh, injected them directly into the jelly-like vitreous fluid inside each eye. The two injections were administered 24 hours apart, under emergency expanded access protocols – a regulatory pathway the FDA describes as allowing patients with serious or life-threatening conditions to access investigational treatments outside of clinical trials when no comparable alternatives exist.
Using the patient’s own mitochondria was a deliberate safety decision. Autologous material – sourced from the patient’s own body – minimizes the risk of immune reaction. The immune system does not attack what it recognizes as self.
The injections were intravitreal, delivering the mitochondria into the fluid-filled cavity of the eye rather than directly into retinal tissue. Animal studies had already demonstrated that mitochondria introduced into this space are absorbed by the cells lining the inner retina – the exact cells the team was trying to rescue.
What happened after the injections
Neither eye developed intraocular inflammation following the procedure. Pupillary reactivity – absent across all 45 pre-treatment readings over 71 days – returned in each eye within days. Though transient, the pupil response “held at levels that were higher than they were prior to the transplant,” according to Dr. Putrino.
Brain recordings at 3, 44, and 45 days after treatment showed an organized response in the visual cortex – the region of the brain that processes sight – suggesting that some signal was traveling from the eye to the brain, even if that signal was not producing clear vision.
The pupillary responses did not last. The left eye recorded its final normal response on day 11 after the injection. The right eye continued producing sporadic normal responses until day 39. In a post-transplant low-vision assessment, the patient was noted to be “perceiving shapes and shadows” in her left eye, according to Dr. Putrino – a change not measurable before the procedure. Her visual acuity as a clinical measure remained severely impaired and did not show a statistically meaningful change.
The caveats – and why they matter
The researchers are the first to say this result cannot prove the treatment worked. This was one patient, with no control group and no way to rule out coincidence or natural fluctuation. There was no direct evidence – no microscopy or biopsy – confirming that the transplanted mitochondria actually entered the retinal ganglion cells rather than sitting inert in the vitreous fluid. The authors explicitly state the case is insufficient to establish causation.
The stated goal, according to Dr. Putrino, was to establish the safety of the approach. “We can’t prove efficacy at all, nor are we trying to,” he said, but added that “we saw a significant effect on physiological changes in the eye.”
The temporary nature of the pupillary responses raises questions about dosing. One possibility the team explored is that damaged cells may need repeated doses of healthy mitochondria to maintain any benefit – ongoing energy supplementation rather than a one-time fix.
There’s also the question of timing. This patient received her injections roughly three months after her injury, by which point considerable cell death had already occurred. Whether earlier intervention – administered closer to the initial event – might produce more sustained results is an open question that future trials will need to address.
Read More: What is Vizz? The new FDA-approved eye drop to fix near vision
What this means for you
Nature noted that injection of a person’s own mitochondria into the retina appeared safe, though the effect on restoring vision was only temporary. Dr. Putrino told Nature that his team is already working with the FDA to develop a protocol for repeated, serial mitochondrial injections – a structured approach to testing whether multiple doses can sustain the changes seen in this single case. That process will require controlled trials, more patients, and direct evidence that the transplanted mitochondria are reaching and being absorbed by target cells.
For people living with optic neuropathy, glaucoma, or other conditions rooted in retinal ganglion cell damage, this research points to a direction that has rarely been explored: not repairing or replacing dead neurons, but supporting the ones still alive with a direct energy supply. If those cells can be kept viable long enough for other therapies to take effect, the window for meaningful recovery could be extended.
The woman whose leg mitochondria were injected into her eyes remains severely visually impaired. Her case changed nothing about the current standard of care. But it may have changed what doctors think is worth asking next.
Disclaimer: The author is not a licensed medical professional. The information provided is for general informational and educational purposes only and is based on research from publicly available, reputable sources. It is not intended to constitute, and should not be relied upon as, medical advice, diagnosis, or treatment. Always consult a licensed physician or other qualified healthcare provider regarding any medical condition, symptoms, or medications. Do not disregard, avoid, or delay seeking professional medical advice or treatment because of information contained herein.
AI Disclaimer: This article was created with the assistance of AI tools and reviewed by a human editor.
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