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Transplantation Stem Cells

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					       Current and Upcoming
           Clinical Trials
Now, let’s consider 2 treatments where
  few or no photoreceptor cells remain
  alive.
Possible treatments here would include:
• Donor Photoreceptor Cell and Stem
  Cell Transplantation
• The use of Electronic Prosthetic
  Devices
Photoreceptor Cell Transplantation
          Clinical Trial
• The idea of replacing dead photoreceptor
  cells with new, donor photoreceptors by
  transplantation has long been worked on.
• There is a small human Clinical Trial on
  transplantation of photoreceptor cells being
  conducted by Dr. Norman Radtke in the USA.
• It has proven the relatively safety of the
  technique. BUT, unfortunately, there has not
  been much good news from the study as to
  improvement in vision in the patients.
Thus, with only very modest positive results
  from both animal and human studies, it is
  difficult to see how this will be a viable
  treatment in the future.
       Transplantation: Stem Cells
An exciting new area of research is in the
  study of Stem Cell transplantation.
• Stem cells are cells that have the potential of
  multiplying and developing into almost any
  type of cell in the body.
• Thus, theoretically, stem cells could be
  transplanted into the retinal space where
  photoreceptor cells have died and could
  develop and replace them.
• However, proper and complex biological
  signals have to be given to the stem cells
  such that they develop into mature,
  functional photoreceptor cells – instead of
  other cell types.
    A Stem Cell Clinical Trial?
• There are some reports that a clinical trial
  using stem cells on RP patients has been
  stopped in the USA. However, the company
  has not confirmed that stem cells were
  actually being used.
• There are also reports of commercial stem
  cell therapy in some other countries but
  these are not well documented as to
  scientific safety and efficacy.
• Much more work needs to be done on stem
  cells before they can be used as an RD
  treatment.
 Electronic Prosthetic Devices
     for Sight Restoration
These fall into 2 categories:
1) Brain (cortical) electronic implants
2) Retinal implants – in front or behind
   the retina
For the retinal implants, there are many
   different designs and surgical
   approaches from groups around the
   world.
   Brain Prosthetic Devices
Three main groups of investigators have worked
  or are working on brain prosthetic devices that
  will have the potential to bypass the eye
  completely.
• One group has prematurely done human
  implants with poor results.
• A second group continues to do mainly basic
  lab work.
• The third group is doing excellent work in
  monkey and is planning a human clinical trial.
  How Does the Retinal Prosthesis
              Work?
• The device uses electrical signals to
  bypass defective or dead photoreceptors
  and stimulate remaining viable, non-
  photoreceptor cells of the retina.
• Images comes from an external video
  camera worn behind the patient’s glasses.
• The images are transmitted through a
  computer to electrodes (called an array)
  attached to the retina to reproduce the
  visual image in the brain.
       Retinal Prosthesis Trials
Groups in many countries are developing
  retinal prostheses.
There are 4 groups around the world that have
  implanted human subjects with retinal
  prosthetic devices of different design.
• Optobionics Co. (Chicago, IL) – poor design
  such that it does not function well or at all.
• 2 excellent German companies – early stages
  of human testing – e.g., Retina Implant AG.
• Second Sight (Sylmar, CA) – with Dr.
  Humayun, has already implanted 6 subjects
  in a Phase 1 study and now over 10 subjects
  in a Phase 2 Clinical Trial that recently
  started.
        Phase 1 Patient Update
Chronic studies on human implants have
  been done on an early electrode device
  with 16 electrodes -- from 2/02.
 Six patients were implanted. There were
  NO device failures.
 All subjects saw discrete visual images
  (called phosphenes) and could perform
  visual spatial and motion tasks.
 Mobility (walking and navigation) has been
  improved.

   The remaining 5 patients use the device at
    home.
Retinal Prostheses – The Future
• Several clinical trials have been started. If
  successful, commercial models should soon
  become available for implant.
• Designs are improving to increase the
  number of electrodes touching the retina.
• Theoretically, a design with about 1,000
  electrodes is needed to give reading ability
  and face recognition.
• The prosthetic device may be the best hope
  for restoring sight to severely affected RP
  and dry AMD patients.
    In Conclusion for RP….
Several Clinical Trials are in progress. Proof of
  Principle for several other types of therapies
  has been established.
• For example, Gene Therapy work on a dog
  model of RP-LCA shows not only sight
  restoration but a long term, positive effect.
• Other basic work in the fields of gene
  therapy, stem cell research, pharmaceutical
  therapy, nutrition and electronic implants
  show promise in current and future Clinical
  Trials.

				
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posted:10/5/2012
language:English
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