They are made by the body to sustain and repair itself and have important roles in cell survival. Many research groups are investigating growth factors either when used alone, or in combination with other therapies, such as stem cell therapy and gene therapy, in the treatment of retinal diseases.
One of the main growth factors that has received attention is CNTF – Ciliary Neurotrophic Factor – a substance that has a specific role in nourishing nerve cells. CNTF has been shown to be successful in slowing retinal degeneration in animal models of retinitis pigmentosa. Safety was also demonstrated.
Early clinical trials in patients have taken place in the hope that the growth factor would “rescue” retinal cells and reduce vision loss. The CNTF was delivered to the retina via a tiny implant containing retinal cells, which release the growth factor into the eye. This technique is known as encapsulated cell therapy.
There has been some evidence, from high-resolution advanced retinal imaging, suggesting that CNTF promotes photoreceptor survival. However, there was no clear benefit to vision in these early phase, relatively short-term trials.
Work is advancing on discovering new growth factors, on understanding how they influence retinal cells, their role in different retinal diseases and on developing methods for delivering growth factors to the eye. This may result in new avenues for therapy, in addition to other growth factors being investigated in clinical trials using a similar approach to that used for CNTF.