Human stem cell-derived retinal cells show promise as treatment for macular diseases

Note: The post below is  from the study (pdf) published in The Lancet.

Since 1981, when pluripotential cell cultures were first derived by Evans and Kauffman, embryonic stem cells (ESC) have been regarded as a potential source of therapeutic cells for a wide range of diseases caused by tissue loss or dysfunction. Despite the great therapeutic potential, their plasticity and unlimited capacity for self-renewal raise concerns about serious safety issues, including the ability to form teratomas and other tumours, potential immune reactions, and the risk of differentiating into unwanted cell types. 

Sildenafil (Viagra) may not be safe in Retinitis Pigmentosa

Sildenafil (Viagra) is a PDE5 inhibitor in wide use for the treatment of erectile dysfunction. It is known to increase the level of cGMP, and ultimately increases penile response to sexual stimulation. Sildenafil preferentially inhibits PDE5 more than PDE6, both of which are expressed in the retina. Therefore, there is a potential for this drug to alter retinal function, not only in normal subjects, but also in patients with PDE6 gene mutations such as in some forms of RP. 

Stem cells close to cornea may help treat Macular Degeneration or Retinitis Pigmentosa

Scientists at the Southampton General Hospital and the University of Southampton have found a pool of stem cells around the corneal limbus that can be induced to become retinal cells. Such cells can then potentially be transplanted into the eye of the patient of macular degeneration or retinitis pigmentosa to stop the disease or even cure it.