Stem Cells and Their Promise
We've all heard about stem cells. I remember that during my teens in the early 2000s, there was not a single night that we would not have heard this hot topic on the evening news. “Promises of revolutionary therapies!”. But where are we today? Well, fast forward to today, and we've seen quite significant progress, especially in treating diseases in animal models, with some advancements translating to human clinical trials. This is a quite complex theme, so I will try to summarise this in a more simplistic manner. And by the way, we have a full podcast episode on stem cell therapies, which I will embed below. Feel free to check it out as I dive much deeper in it.
The Eye is Arguably Ideal for Stem Cell Therapy
The eye, and particularly the retina, is very much suited for novel technologies like stem cell therapy (and gene therapy for that matter!) for several reasons:
- Compartmentalisation: Different sections of the eye are, for the lack of a better word, separated/segregated, allowing targeted treatments to specific tissues. Think, for instance, about a group of genetic conditions that affect the light-sensitive cells of the retina (aka photoreceptors) named inherited retinal diseases. Treatments can be directed to a specific region of the retina which is immediately adjacent or proximal to these photoreceptors that are not working properly. This allows for a targeted treatment, with less risks of affecting other tissues, or in other words, “off-site” events.
- Observation: We can easily observe the eye in real-time using any slit lamp microscope and a set of lens (if the treatment is located in the retina), but also high-resolution devices like the optical coherence tomography (OCT). When the treatments are in organs like the liver or lungs, we do have great resolution imaging, but not with the simplicity and the real-time advantages that the ophthalmic microscopes carry.
- Functional Testing: We have well-established tests for eye functions, such as visual acuity, visual fields, color vision, and even measuring the electrical activity sent to the brain. These are very accurate tests, even though they may carry a degree of subjectiveness. But the point is that we can directly measure the effect of a certain treatment in the function of the eye. Did it increase vision? Did it change the visual field? Is there any change in how the light-sensitive cells are reacting to light? All very relevant questions that we can answer thoroughly.
What are stem cells?
And again, I do apologise for how simplistic this reads, but remember that the aim of Eyes On Research – simplify complex themes relating to vision research to make it more accessible.
Anyway, stem cells are pluripotent and undifferentiated, meaning they can transform, or differentiate into various types of cells. They offer a regenerative approach, providing new cells to areas where cells have been lost. This means that, in theory, a cell that does not work properly anymore due to a disease could be reintroduced in the game. Indeed, we think stem cells have the potential to be differentiated (or grown) into new tissues, that would then be transplanted into a specific tissue. Currently, stem cells are being studied to treat common diseases affecting a variety of organs in the body, from type 1 diabetes to Parkinson's disease, amyotrophic lateral sclerosis, heart failure, amongst others.
It’s true that I am quite optimistic, but would you agree how promising this looks? This is different from other therapies, like gene therapy, which requires existing cells to be alive and functional. I talk a bit more about this in a specific podcast episode on gene therapy, so feel free to check it out if this interests you.
Retinal Diseases and Stem Cell Therapy
Retinal diseases, such as diabetic retinopathy and age-related macular degeneration, lead to vision loss and affect millions of people. Stem cell therapy holds promise for these conditions because:
- Regeneration: Stem cells can regenerate retinal tissues that do not naturally regenerate, such as, for instance, certain neurons present in the retina.
- Types of Stem Cells: A variety of stem cells are currently being studied. Types of cells that have been used include embryonic stem cells, induced pluripotent stem cells, and bone-marrow-derived stem cells.
But how does it work? Well, the current line of thought is that transplanting healthy retinal tissue or using stem cells can create retinal epithelium, which can then be delivered to the retina. Some studies have shown that these transplants are generally safe and well-tolerated. The efficacy of these approaches is mixed in most studies, although there was improvement in vision in a few of these. This has the potential to change as technology and our understanding of the procedure evolve.
Challenges and Future Directions
While there is evidence supporting the safety of these therapies, we still need more information on their long-term efficacy. Challenges include optimizing photoreceptor transplantation and managing risks like rejection. Despite these hurdles, the field is moving in the right direction, with many promising studies underway.
The wrap up
Currently, there are no FDA-approved stem cell therapies for retinal conditions. Be very wary of unregulated clinics, as they pose risks to patients. It's crucial for patients to stay informed and for regulations to be strict. At the same time, given how novel the treatment is, and how strict the regulations rightfully are, we are still in very early stages. Regenerative medicine shows great promise, and while challenges remain, the future is bright.
That’s right, my friends, the future is indeed bright. Read this again!
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Thales A. C. de Guimaraes, MD, PhD
Host and Founder | Eyes On Research