Stem cells to treat blindness caused by AMD

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Dr Anniken Burés: “We are laying the foundations for tissue regeneration, which once seemed impossible even to imagine.”

Since they managed to grow them for the first time in a laboratory at the University of Cambridge, the scientific community has been studying for three decades the possibilities stem cell use opens up for the treatment of diseases that, until now, were considered incurable or very difficult to cure. It seems that, finally, the first positive results can be discerned after all these years of research: US scientists have successfully tested a stem cell transplant to treat age-related macular degeneration (AMD), the leading cause of blindness in the Western world.

As Dr Anniken Burés, from IMO Retina Department, stated when being asked by the newspaper El Mundo about this news: “We are laying the foundations for tissue regeneration, which once seemed impossible even to imagine.” In fact, these good results were already pointed out at the Trends in Surgical & Medical Retina conference, which was organised by IMO Retina Department in June last year, where Marco Zarbin from the US explained that Phase I studies in humans already seemed to be proving that the use of stem cells to replace damaged retinal cells could improve visual acuity of patients.ntes.

Stem cells – a cell source for almost everything?

Stem cells have the capacity to differentiate into any specialised tissue and to renew themselves to produce more stem cells; hence much of the medical community considers them a potential cell source for treating a large number of diseases. But their very main virtues are also the factors that greatly impede their therapeutic use: on the one hand, the ability to transform into any specialised tissue ("plasticity") could lead to specialisation into an unwanted cell type, whereas the ability of self-renewal, if it gets out of control, could lead to tumour growth.

Thus, the secret for stem cells to begin to meet the expectations placed in them lies in being able to control these two features, while also proving the safety of using this biological material in humans.

The Advanced Cell Technology study

The work carried out in the United States by one of the world leaders in regenerative medicine, Advanced Cell Technology, points in that direction. The study, led by Robert Lanza, has achieved positive results in the treatment of two of the eye diseases causing a significant percentage of blindness cases in the developed world: AMD and Stargardt's macular dystrophy.

The study, a Phase I clinical trial, only intended to prove the safety of using stem cells in humans, which is why it was only performed with 18 people (9 with AMD and 9 with Stargardt's macular dystrophy), an insufficient number to assess the validity of the medical therapy applied.

Thus, given that no statistically valid conclusions can be drawn from this study, the results were as follows:

- Of the 9 patients suffering from Stargardt's macular dystrophy, 3 substantially improved their visual acuity, 4 maintained it or improved it slightly, in one case it worsened and in another the 6-month follow-up was not completed.

- Of the 9 patients suffering from AMD, 6 substantially improved their visual acuity and 3 maintained it or improved it slightly.

AMD and Stargardt's macular dystrophy are diseases that attack the retinal pigment epithelium, causing the photoreceptors' death, which causes blindness. In this case, Robert Lanza's team was able to make stem cells transform into cells of the retinal pigment epithelium, which were then transplanted to the patients' retina, with the results shown above. One factor that is favourable to the success of this technique is the fact that the eyes are organs which are quite isolated from the immune system, which substantially reduces the risk of rejection of the implanted cells. Be it as it may, it seems that scientific efforts are on track.

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