Stem cells and blindness

[10/02/2012]

Stem cells and blindness

Funny how in my last post I was referring to gene therapy for treatment of an inherited blinding eye condition (retinitis pigmentosa) and now there is a recently published article about human embryonic stem cells (hESCs) used to help to patients with progressively blinding conditions (age related macular degeneration or AMD and Stargardt's macular dystrophy)! Keep the good things coming for 2012 I say!!

Stem cells has been a hot topic since it was first discovered 13 years ago. There has been enough hype about them with their potential to treat many conditions ranging from cancer to Alzheimer's to diabetes and so on. So it is not surprising there has been intense interest in this area amongst the ophthalmology community as well!

Introduction to stem cells



The retina is a tissue of many layers and it lines the inside of the eye. There are in actual fact, 10 layers in the retina but for simplicity, it can be divided into the neurosensory retina and the retinal pigment epithelium (RPE). The neurosensory retina is responsible for transmitting information to the brain for us to get the perception of vision and the RPE is a pigmented layer whose functions are many and mainly related to nutrition of the retina as well as transport of "waste material" out of the retina. It is in this layer where conditions such as AMD or Stargardt's disease where the RPE is sick or dysfunctional.

Why should the RPE become sick? It could be genetic or environmental influence (sun or smoking). Unfortunately, the damaged RPE cells cannot regenerate and as more and more cells die, the disease gets worse and the vision deteriorates further. There has been intense interest in research to find ways to replace these RPE cells and using stem cells is one way to do it.

So all the excitement about this recent breakthrough with the use of stem cells is definitely warranted! So what was all the fuss about you may ask?!

The study

RPE cells were grown from hESCs and then transplanted under the retina of 2 patients - one with AMD and the other with Stargardt's disease. This study was primarily targeted at assessing the safety of the treatment and not so much how effective it was.

The results

After 4 months, there was no evidence of unrestricted growth of cells. One of the main worries with stem cell treatment is that the cells can grow abnormally and possibly become tumors of sorts - this was not seen in this study. There was no "rejection" of the cells as one might expect in any sort of transplantation. And there were no complications from the technically challenging procedure (of injecting the cells under the retina which could result in a retinal detachment).

What was encouraging was that the 2 patients also noticed an improvement in their vision which was not the primary goal of this study.

The future?

There is still much work to be done and many more questions to be answered. This is only a short term study in a very small number of patients and what happens in the longer term to these cells remains to be seen. What are the effects in different diseases and different races of people?

Nevertheless, this is indeed a major breakthrough as stem cell therapy goes.... so definitely watch this space!!