Scientists test eye injections of mitochondria to restore vision

Researchers’ first attempt to treat vision loss by injecting mitochondria into the eye was safe, but the effect on vision was temporary, ERR reported. The result nevertheless raises hopes that the procedure could eventually have clinical benefits.

Mitochondria, organelles that produce energy in cells, are being studied as a possible treatment for diseases that damage tissues. The idea is that damaged cells could absorb healthy transplanted mitochondria and partially restore tissue function.

In earlier human trials, mitochondria were transplanted into the heart and brain. In a paper that has not yet undergone peer review, researchers describe the first successful transplantation into the eye.

The patient’s optic nerve and retina had been damaged by a cerebral haemorrhage, causing almost complete loss of vision. Light entering the eye had not triggered a pupil response. After mitochondria were injected, the pupils did respond to light, but the effect lasted about four weeks.

Temurkhan Ayupov, a biologist at the Basel-based Institute of Molecular and Clinical Ophthalmology, said the trial demonstrated the relative safety of injecting the patient’s own mitochondria into the eye. He added that it did not confirm a long-term therapeutic effect.

David Putrino, a neuroscientist at the Icahn School of Medicine in New York and a co-author of the study, said the trial was intended to assess safety rather than effectiveness. Physiological changes in the eye were nevertheless observed, he said.

Limited success

Putrino and his colleagues wanted to determine whether injecting mitochondria directly into the eye could restore the function of ganglion cells in the inner layer of the retina. Earlier studies in mice had produced promising results. In May, the researchers received special permission from the US Food and Drug Administration to transplant mitochondria into the eye of a human patient.

The researchers were most concerned about an immune reaction in which the immune system would attack the foreign material injected into the body. Tests carried out after the procedures found no signs of inflammation or damage in either eye.

Although the pupil response was not sustained, Putrino said the patient was able to distinguish shapes and shadows with the left eye during the post-transplant assessment.

Neuro-ophthalmologist Patrick Yu-Wai-Man of the University of Cambridge said it remained unclear whether the pupil responses were directly caused by the mitochondrial transplant, or reflected the recovery or fluctuation of remaining neuronal function. There is also no direct evidence that the injected mitochondria entered cells and continued to function there, he said.

Ayupov said it was likewise unclear which cells had taken up the injected mitochondria. He added that it was very difficult to determine what would be needed to make the therapeutic effect permanent.