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Stem Cells Reported to Improve Vision

Two patients receiving embryonic stem cells for their blinding retinal diseases reported improvement in their vision. The results were released just last week online in the medical journal Lancet.

Each patient received retinal epithelial pigment cells (aka RPE cells) grown from human embryonic stem cells. RPE cells are the faulty cells in macular diseases such as ARMD and Stargardt’s Disease. In healthy patients, these cells are normal and function appropriately.

Dysfunctional, sick or degenerated retinal epithelial cells lead to progressive loss of vision. As the healthy RPE cells begin to dwindle, so does the vision. The RPE cells are a key component to translating light to vision.

Researchers have been hopeful to replace sick RPE cells with the healthy replacements derived from the stem cells.

Hence, the excitement. Two individuals, one with dry ARMD and the other with Stargardt’s underwent RPE cell transplantation and the reports at 4 months after the operation are encouraging. Both noted improvement and, according to the report, no complications occurred either to the eye or to the patient.

Both patients underwent surgery at UCLA. The research was funded by Advanced Cell Technology, the same company conducting stem cell research on patients with Stargardt’s Disease.

What Does This Mean?

At most, this is encouraging news.  This does NOT mean that stem cell transplantation works.

There are lots of flaws; only 2 patients involved, inability to objectively measure improvement in vision, funding company (Advanced Cell Technology) is involved and adds bias to the study results, etc.

On the other hand, I am very excited that the research seems to be moving forward. Yes, the results are tainted, but it does demonstrate several “successes” in solving some of the technical challenges of stem cell research;

  • This is pioneering work. Regardless of visual outcomes, researchers have designed techniques to deliver the RPE cells to the correct anatomic location. That is, retinal surgeons have figured out how to transplant the cells effectively.
  • The cells may indeed remain “alive” when transplanted. How long? We don’t know, but it seems to be at least 4 months!
  • This is great news in the face of recent failures of stem cells used in spinal cord injury.
  • There were apparently no complications.

This certainly is enlightening and exciting.  With time, we will need more extensive research and objective data.  This is no different than a new “drug” fighting for FDA approval.

There is still many questions to answer the ultimate questions;  Is the technique safe?  Is the technique effective?

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Stem Cells for Stargardt's Macular Dystrophy and Macular Degeneration

RPE Transplantation for Stargardts Disease

 

Advanced Cell Technology recently announced the beginning of their landmark trial where stem cells are transplanted into patients with Stargardt’s Macular Dystrophy (aka Stargardt’s Disease) and dry macular degeneration.

Clinical Trials for Stargardt’s Begin

The company announced that their phase I/II clinical trials started in mid-July with one patient each of either Stargardt’s or macular degeneration.  Each patient received a relatively small dose of cells and subsequent patients will receive larger amounts of cells.  The first patients received about 50,000 cells.

The goal of the study, at this phase, is to test the safety and tolerability of the stem cell treatment over a 12 month period, that is, phase I/II will answer the question as to “how safe is the procedure?” and will also asses if this is a viable way to transplant stem cells.

Retinal RPE Cells are Replaced

The cells to be replaced are called RPE (retinal pigment epithelial) cells and are located underneath the top layer of the retina.  If you liken the retina to be an open faced sandwich with a slice of ham with cheese on top, the RPE cells are the slice of ham.  The “rods and cones” (otherwise known as photoreceptors) are located on the underside of the cheese.  The RPE cells nourish the photorecptors.

In cases of Stargardt’s disease and dry macular degeneration, the faulty RPE cells can no longer nurture, or feed, the photoreceptors, hence, the loss of vision.  It is hoped that by replacing the sick retinal pigment epithielial cells with stem cells, the vision can return.

What Does This Mean? This is really promising and exciting news.  On the horizon is the potential for a true “fix” for two of the most common forms of “blindness” in the world.  Actually, most of these patients are legally blind as you remember that the macula gives us central vision.  Thus, RPE transplantation should improve the central vision.

In my view, there are two large variables or areas of concern.  First, the actual technique of implanting the cells must be refined and perfected and at the same time, we need to see how long the stem cells can live or remain healthy.

While this is very promising, this may still be years away from becoming a viable treatment option.

Here is further information about patient inclusion into the study for either Stargardt’s Macular Dystrophy and dry ARMD.

 

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Part 2: Transplanting Stem Cells to Treat Macular Degeneration

In the last post, we identified the Retinal Pigment Epithelium as the layer in the retina that becomes diseased in macular degeneration.  The cells, once damaged, do not have the ability to divide, regenerate or regrow.  Thus, permanent damage (i.e. loss of vision) ensues.

By The Way. There are two basic types of stem cells;  embryonic stem cells and adult (or somatic) stem cells.  While there are differences between the two, I am collectively referring to both types as “stem cells” to simply highlight the uniqueness of stem cell research.

Stem Cells are Highly Clone-able. Stem cells have the potential to replicate endlessly, and therefore, represent an infinite source of “supply.”  Right now, stem cells can be cultured, or grown, in the laboratory.  Millions of cells can be cultured from just one line of stem cells.  Scientists have, to date, been successful transplanting corneas, hearts, lungs, the pancreas, etc., but there is always a severe shortage of donors.  Far too few people receive  needed, possibly life-saving, organ transplants due to short supply.  In theory, stem cell therapy could potentially alleviate the “supply” issues.

Stem cells can become specialized.  A single stem cell has no particular function.  It is has the potential; however, to differentiate, or change, into any type of cell in the body.  Stem cells can become heart cells, muscle cells, pancreas cells, etc………………and, Retinal Pigment Epithelium (RPE) cells.  Stem cells are “pluripotential” (a cell that can transform into any specialized cell).

How will this cure Macular Degneration? In theory, stem cells can be grown in the laboratory and then “turned into” RPE cells.  The RPE cells can then be inserted, or transplanted, underneath the retina.  Alternatively,  it may also be possible to transplant less specialized cells into a particular tissue, in this case, the retina, and allow the stem cells to become specialized (turned into) Retinal Pigment Epithelium cells after insertion/transplantation underneath the retina.

In theory, stem cells offer the potential be a  renewable and  infinite source of tissue.  Stem cells offer the potential to replace sick, damage RPE cells with healthy tissue.  Present therapies, e.g. diets and vitamins, are focused at nourishing diseased tissue, whereas stem cell research offers the potential of “remove and replace.”

Last Post:  Part 1:  Introduction to Stem Cells and Retinal Disease

Next Post – Obstacles to Stem Cell Therapy

“Randy”

Randall V. Wong, M.D.
Ophthalmologist, Retina Specialist
www.TotalRetina.com

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Part 1: Introduction to Stem Cells and Retinal Disease

This is the first of a small series regarding stem cells and their potential benefits to retinal diseases; principally macular degeneration and retinitis pigmentosa.

As diabetic retinopathy is primarily a disease of blood vessels, i.e.poor blood flow, loss of blood flow, leaking vessels, etc., macular degeneration is actually a disease of one of the layers of the retina.  Specifically, the layer affected is called the Retinal Pigment Epithelium (RPE).  It is a layer of cells that have numerous functions and responsibilities, one of which is keeping the photoreceptor healthy and happy.  Remember photoreceptors are also known as rods and cones.

The retina is a laminated tissue. It lines the inside of the eye in the same way that wallpaper lines the inside of a room.  Just underneath the retina is a layer of cells, the Retinal Pigment Epithelium (RPE).  The RPE layer is uniformly found underneath the entire retina, even the macula.  For us to “see,”  the retina must be attached and all the layers of the retina be healthy.  This is not so in macular degeneration.  While the retina is attached, the RPE layer becomes sick and dysfunctional; it degenerates.  It is the RPE layer that is diseased in macular degeneration.

Cross Section of Eye with Inset

In areas of the macula where the RPE has become dysfunctional, the vision is impaired.  Symptoms include blurry vision and distortion.  The actual cause of the degeneration of the RPE is not known; it may be due to poor blood supply from a vascular layer deep to the RPE (the choriocapillaris, aka choroid),  it may be purely bad genetic programming or it may be due to environmental factors (e.g. sun, smoking, etc.).

How to Replace Damaged Cells? Retinal Pigment Epithelium cells do not reproduce or regenerate.  Once the RPE is damaged, the eye can not make more.  The focus of research has been, how to replace damaged RPE cells?

Several approaches to replace Retinal Epithelium Cells are under experimentation.  Attempts at direct transplantation have had some success.  Stem cell transplantation, in theory, seems very promising.

More tomorrow.

“Randy”

Randall V. Wong, M.D.
www.TotalRetina.com
Ophthalmologist, Retina Specialist

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A detached retina is potentially blinding. The retina is the light sensitive tissue that lines the inside of the eye. A retinal tear or hole usually leads to a retinal detachment. Floaters can sometimes be the earliest, and only, symptom. Many times there is little warning and a retinal detachment usually occurs without trauma.

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