Blind Mice Shed Light On Human retinitis pigmentosa

"Mutant mice could provide genetic clues to understanding incurable human sight loss resulting from retinal degeneration. New research uncovers a role for microRNA in retinal disease, and may point the way to future therapies.

A team from the Trinity College Dublin and the Sanger Institute, Cambridge (UK), led by Dr Arpad Palfi and Dr Jane Farrar of the Smurfit Institute of Genetics, Trinity College Dublin used mutant mice that model the human eye disease retinitis pigmentosa (RP).
The researchers compared these mice with wild-type mice, testing their hypothesis that changes in microRNA expression may be evident in retinal degeneration.
The team found very similar patterns of microRNA expression in retinas of two wild-type mouse strains, but, microarray profiling revealed that in these wildtype mice the patterns of microRNA expression differed between the brain and retina. Furthermore, there were clear differences in the microRNA expression patterns between wild type and mutant mice. The researchers found alterations greater than two-fold in the expression of 9 microRNAs in mutant mouse retinas compared with those of the wild-type mice. These microRNAs potentially regulate genes implicated in retinal diseases and genes encoding components involved in cell death and intracellular trafficking.
The results from the study suggest that miRNA expression is perturbed during retinal degeneration" says Dr Jane Farrar of Trinity College Dublin. "Modulation of expression of retinal microRNAs may possibly represent a future therapeutic strategy for retinopathies such as retinitis pigmentosa."

Innovative Implant to Patients with Retinitis Pigmentosa

"Ten persons with retinitis pigmentosa (RP) from across the U.S. and Mexico have been selected to participate in a 'compassionate trial' at Emory Eye Center.

These individuals will receive an innovative implant that has shown promising results in halting the progression of RP in National Eye Institute-sponsored Phase I trials.
Each patient will make 10 visits to Emory Eye Center beginning in early December, with all exams and surgeries to be completed by mid-December. Neurotech identified the patients and is donating the implants, and Emory Eye Center will cover most of the costs involved, including the cost of the surgeries. The patients, all of whom have profound RP visual loss, were not eligible for the Phase II portion of the study.

The implant, NT-501, is the only one of its type and provides a long-term release of the therapeutic protein, ciliary neurotrophic factor (CNTF), directly into the back of the eye by means of the company’s proprietary Encapsulated Cell Technology (ECT).

The new implant has shown promising results in halting the progression of RP among the patients who have received it in a clinical trial conducted by the implant’s maker, Neurotech. Emory retina specialists Daniel F. Martin, MD, and Jiong Yan, MD, will perform the surgeries. Emory Eye Center Director Thomas M. Aaberg, Sr., MD, is the principal investigator of the Emory study.

"I am pleased to be able to use this new technology on these 10 patients" says Dr. Aaberg. "Emory Eye Center is uniquely poised to pull together its talented staff and surgical resources to make these procedures happen on a timely basis. We are excited to be a part of this process for these deserving patients"

Drs. Aaberg, Martin and Yan have no financial interest in Neurotech.

Retinitis pigmentosa advice + support

"Advice and support

British Retinitis Pigmentosa Society
Helpline: 0845 123 2354
Website: helpline@brps.org.uk
Website: www.brps.org.uk"

Can retinitis pigmentosa be treated

"Currently, no treatment is available to cure RP or arrest its progress. It is the result of incorrect instructions being passed to the body’s chemistry by faulty inherited genes.

However, co-ordinated research, in many centres around the world, has been expanding for around 20 years. Many of the genes responsible for the numerous types of RP have been located and their defects identified. Scientists are following many lines of research, among which is the development of a safe system for introducing corrective genetic material to the appropriate cells of an eye. There is some evidence that this will take hold and assist cell regrowth.

There have also been some very positive developments in stem cell and retinal cell transplantation. However, research in these areas is still in the very early stages. It could take a number of years before these new developments might become available as treatments."

Can retinitis pigmentosa be detected by an eye test?

"The types of RP which cause loss of central vision become apparent through an inability to read a test card (eye test chart), but peripheral loss, or loss of side vision, is not so obvious and a person may be able to read an optician’s test card for many years.

The condition is best detected through an eye test or examination by an optometrist (optician) or ophthalmologist (eye doctor). By looking through the front of the eye with a piece of equipment called an ophthalmoscope, an optometrist or ophthalmologist can see clearly to the back of the eye. Normally they would see an orange-coloured area called the fundus. When the patient has RP, the orange surface is broken by black or brown clumps of pigment.

Other tests are available which measure the area of visual field which is still useable and the ability to adapt to low light levels."

When does retinitis pigmentosa develop:

"There is no hard and fast rule, but in most cases the early symptoms of RP develop between the ages of 10 and 30."

How is retinitis pigmentosa inherited:

"There are three ways in which RP can be inherited:
Autosomal dominant inheritance:
This is the pattern of inheritance where RP is known to exist in a family, affecting both males and females. The probability of RP being passed from an affected parent to a child is exactly 50 per cent.
Autosomal recessive inheritance:
There will usually be no known history of RP in the family but if two carriers who show no obvious symptoms have a child, there is a 25 per cent chance that he or she will have RP.
X-linked inheritance:
This is a pattern of inheritance where only males develop the disease, but female members of a family are carriers. Some carriers can develop a mild form of RP.
For example, if a man has X-linked RP, his sons will not develop RP, but all of his daughters will become carriers. These daughters will each have a 50 per cent chance of producing an affected son and a 50 per cent chance of daughters who will be carriers. This inheritance pattern is sometimes difficult to identify in a family where there have been no sons for several generations, as the faulty gene could have passed down a line of female carriers and then suddenly affect a male child."

Symptoms of retinitis pigmentosa

"The most common first symptom is difficulty in seeing in poor light, for example outdoors at dusk, or in a dimly lit room. A second symptom is reduction of the visual field, in which sight is lost from the sides, or from above and below. This is often referred to as tunnel vision and means that the rod cells, and some of the outer cone cells, have been affected first.
In some RP-related conditions central vision is lost first. The first signs of this are difficulty in reading print or carrying out detailed work. All RP conditions are progressive, but the speed at which deterioration takes place varies from one person to another.
In many types of RP, glare from bright lights is an increasing problem, although some people do not experience this until the more advanced stages."

What Causes retinitis pigmentosa

"It is now known that there are many different inherited problems causing RP. In all RP-related conditions however, the ability of the retina to respond to light is affected. The problem can be in many parts of the retina such as the rod or cone cells, or in the connections between the cells of the retina."

Retinitis pigmentosa

"Retinitis pigmentosa (RP) is the name given to a group of hereditary eye disorders. These disorders affect the retina, which is the light-sensitive tissue lining the back of the eye, in which the first stages of seeing take place. In RP, sight loss is gradual but progressive. It is unusual for people with RP to become totally blind as most retain some useful vision well into old age."