Wednesday, February 1, 2012

Sight for the Blind

Flickr Photo by Michael Dawes

     Vision is an amazing process that allows us to do a plethora of things.  Most rely on vision to do just about every daily task (like reading this blog).  Now imagine that you slowly lost your ability to see things sharply and clearly.  Imagine that you could no longer read your own watch or drive to the grocery store.  This is reality for people with macular degeneration or dystrophy.  
     People suffering from macular degeneration (watch animation here) eventually lose most of their independence as their vision deteriorates.  However for the first time, Steven Schwartz of UCLA has given a glimpse of hope to those suffering from macular degeneration (the leading cause of blindness in the US) or macular dystrophy (the leading form of pediatric macular degeneration).  The preliminary results of this stem cell therapy have recently been published in the Lancet.
     Previously human embryonic stem cells (hESCs) have been differentiated into retinal pigment epithelial (RPE) cells.  Already, scientists have implanted these hESC-derived RPE in mice and rat models with macular degeneration.  This treatment can restore photoreceptor function and prevent loss of vision in these models.  Schwartz tested this therapy in two individuals:  a 70 year old woman with dry macular degeneration and a 50 year old woman with Stardardt's macular dystrophy.   Both of these women had no negative reactions to the treatment and also showed improvement in visual tests, such as the Early Treatment Diabetic Retinopathy Study (ETDRS) visual acuity chart.  These improvements were seen in as little as two weeks after the transplantation.  Retinal evaluation also showed new growth of cell in the individual with Stardardt's macular dystrophy.    
     Although these results are only from a preliminary study and much work still needs to be done, the prospect of a new therapy to "give sight to the blind" appears promising.  


  1. What is the difference between dry macular degeneration and Stardardt's macular degeneration? Why does replacing RPE cells help, if these aren't the actual photoreceptor cells that detect light?

    1. Dry MD and Stargardt's disease are caused by different genes, and the time course of symptoms are different. Dry AMD (age-related) may also have environmental factors (sun exposure, smoking), so it is a complex genetic disorder that develops typically after age 60. Stargardt's disease can be diagnosed anytime before age 50.
      The RPE cells are like the support cells to the photoreceptors (PhR), and in several cases, by keeping RPE cells healthy will keep PhRs healthy.