 Rene Choi is going to talk to us about stem cell transplantation in dry AMD Give a second to get his computer all fired up here All right, hello everybody So I'm Rene Choi. I just want to thanks thank Zach again for reminding me that my huge geek as well. I Knew that he thought that of me as I entered residency because one of the first questions he asked me was why are your glasses so thick? I'm not saying that we're really gonna miss you Zach All right, so let's get started today I'd like to cover a topic that I find personally to be very interesting, you know the last number of years I've been to Arvo and that's this topic of stem cells and they're Involvement in regenerating the retina So to begin this journey we really have to define what exactly stem cells are Stem cells are a group of cells right that are not committed toward any specific cell fate They have the limitless potential to regenerate proliferate cell for new and they can become any cell type in the body Now aside from embryonic stem cells There are also what are known as adult stem cells these are endogenous stem cells that are in our body throughout our lives That regenerate or replace lost tissue from everyday wear and tear Some of these include bone marrow stem cells Intestinal stem cells corneal stem cells which everybody hears particularly Familiar with as well as even neural stem cells in the brain However to date there are no identified retinal stem cells in the human eye And that and that's particularly Disappointing because there are a number of diseases that affect the retina an impaired vision by reducing the elements here That are responsible for processing vision many of these include retinitis pigmentosa cone-raw dystrophies age-related macular degeneration Diabetic retinopathy as well as glaucoma Now to emphasize the gravity of these diseases I'd like to demonstrate to you how somebody who's afflicted with retinitis pigment pigmentosa how this disease Manifests visually in this patient. There is a beautiful picture of a Teton National Park For all of us who are not afflicted with this disease. We have no problems seeing this image in its entirety, but over time somebody with retinitis pigmentosa Slowly loses their peripheral vision until They reach irreversible blindness, okay? So I thought to myself How amazing would it be if just like the cornea? We're able to regenerate lost Photoreceptors any other cell type you're interested in the retina just like in the cornea when the epithelial cells You know are abraded those new corneal stem cells grow in and replace that tissue so the first question I asked when I did my literature search was to Determine is there any evidence of regeneration that takes place in the retina regardless of the species? To begin this journey we first have to go into the history of stem cell regeneration 1744 Abraham Tremblay. He was a Swiss naturalist He was the first to observe that when you surgically resect a limb from a hydra It's able to regenerate that limb almost as if no intervention ever took place Few years later in 1781 Charles Benet is actually a cousin of Abraham Tremblay Realized that when he surgically resected the eye Then an anew anew was able to regenerate the lens as well as parts of the retina as well now this discovery set essentially Led to the in the next two centuries all the all the further investigations that took place in retinal regeneration So let's get to the core. What are the source of newly generated cells in the retina? Well, it depends on two things it depends on the species and also depends on where you're looking in the retina now in the Very center of the retina in amphibians the putative stem cells are thought to be the retinal pigmented epithelial cells and the fish It's thought to be the molar glial cells However, in both species in the peripheral retina There's an area known as the sillier marginal zone actually gives rise to new retina progenitors throughout the life of the animal Let's talk about that a little bit more. So here's the sillier marginal zone It lies in between the sillier epithelium and the neural retina and throughout the life of the animal It gives rise to new retina progenitors and cells of all type that are specific to the retina Now what's remarkable about the CMZ is that there's this feedback loop when you damage the retina in amphibians and fish The CMZ is able to to pick up on that and actually increase proliferation in the CMZ But what's even more remarkable? Is that if you ablate a specific cell type if you ablate for instance Amicron cells the CMZ picks up on that and actually generates a higher proportion of amicron cells compared to the other cell types Now what about in mammals, you know including humans. Do we have a CMZ? Unfortunately, we don't Now as I alluded to earlier the source of newly generated cells in the central retina are thought to be the retinal pigmented epithelial cells in amphibians Let's just cover touch a little bit about what retinal pigment to epithelial cells are responsible for it mainly serves as a Has a supportive role for the photoreceptor cells in the retina some of them include providing nutrients for the photoreceptor cells Absorbing UV light to protect the photoreceptor cells Recycling photopigment that's part of the visual phototransduction cascade as well as being responsible for Faggocytosing the photoreceptor outer segments as well Now in the amphibian retina in newts as well as frogs. It's quite amazing. What happens when you perform a retinectomy That's when you physically scoop out the retina you give the animal 30 days to recover. Okay It'll reestablish the retina almost as as if no intervention took place. It's quite remarkable Now what is this process entail? It's something known as RP trans differentiation. It's a two-step process Once the RP cells notice that the retina has been damaged it starts to undergo De-differentiation it becomes an earlier retinal progenitor cell type and then it starts to proliferate and then the second step is to Redifferentiate into all the different cell types within the retina now as I stated earlier in it's in fish It's thought to be the molar glial cells that are the putative stem cells after retinal damage Now I wanted to look in a literature and find out how exactly did they determine this It was a genius experiment that Pamela Raymond's group from the University of Michigan performed What they did was they developed the transgenic line of zebra fish where they had the GFAP promoter That's a molar glial cell specific promoter driving green fluorescent protein Thus all this all the molar glial cells were lit up with were lit up green essentially Now after they damaged the retina specifically ablating the cone and rod footer receptors They found out that there was co-localization between GFP as well as a marker for rod footer receptors as well as GFP GFP as well as a Marker for cone footer receptors thus suggesting that these cells have actually come from the molar glial cells How about in mammals? Well, we know in mice After damage to the retina there's a very limited response of proliferation of the molar glial cells, but they don't actually De-differentiate into a retinal progenitor cells however De-differentiation can take place or can be induced by misexpression of retinal stem cells specific genes However, after de-differentiation The re-differentiation phase is somewhat limited in terms of its profile It can only become certain cell types such as amocrine cells as well as bipolar cells However, what's noted is, you know the evidence is somewhat equivocal because Lineage tracing studies as has been done in fish have not been done in the mammal or in the mice specifically Now in humans as I stated to date There are no identified retinal stem cells in humans So the field has really come up with two translational approaches All right using stem cell stem cell transplantation in order to help Treat the retina and there comes in two approaches one is cell replacement where you use stem cells to actively Replace the lost retinal photoreceptors or other cell types that you're interested in and the other one is cell protection Where the stem cells provide a trophic factor for the remaining retina? There's a seminal paper Published by McLaren and colleagues back in The University College of London and what they noticed was that what they did was they had a retinitis pigmentosa model In mice and they transplanted rod progenitor cells into the sub retinal space of these mice They found out that these progenitor cells were able to differentiate into mature rod photoreceptors Structurally as well as functionally integrate into the retina as well And I should also mention that using the cell replacement Technique right now there are phase one and two trials of taking human embryonic stem cell derived RP cells Transplanting it into the sub retinal space of patients with geographic atrophy And so it's quite amazing, you know Now there's this new cohort of stem cells known as human derived neural stem cells All right, and it's obtained from fetuses from the second trimester There's this two seminal papers published by a group in KC I institute where they took the RCS rat That's a specific retinal degeneration modeling rat The primary defect in these rats is that they had they lack the ability to phagocytose the photoreceptor outer segments And thus this leads to toxic debris in the eventual death of the photoreceptor cells and when they take this this new this human derived neural stem cells and Transplanted into the sub retinal space of these these rats. They find out that not only do they preserve photoreceptor viability also synaptic connections with the second-order neurons and lastly also Functional vision as well based on a behavioral assay that's visually mediated And they found out actually that the mechanism that's responsible for this preservation of the photoreceptors and the rest of retina is twofold one is it actually acts or adopts the RPE's ability to phagocytose the Shed outer segments from the photoreceptors and it also provides trophic factors for the rest of the retina Now we know in geographic atrophy in patients with dry ARMD that part of the primary pathology involves the loss of the RPE loss of the RPE cells and therefore it can't provide those supportive function Or roles for the photoreceptor cells that's leading to further photoreceptor death There's a particular group Stem cell incorporated they performed or organized a multi-center phase one study To determine the safety profile of transplanting these human derived neural stem cells into patients with geographic atrophy And they found out that there was no adverse side effects with transplantation of these cells in eight patients or 15 patients So the question they asked us they asked a number of centers across the country to be part of their phase two trial specifically asking can sub retinal transplantation of these human derived CNS cells Decrease the rate of geographic atrophy and patients afflicted with this with geographic atrophy methods eight macular degeneration patients with geographic atrophy in both eyes They were going to choose the worst the eye with the worst best corrected visual acuity to transplant These human derived CNS cells into the sub-retinal space have them follow up on day zero one seven twenty eight and months 369 12 after transplantation where they would receive a complete eye examination as well as retinal imaging Including fundus autofluorescence OCT as well as photography Their primary outcome measures include Determining the rate of progression of geographic atrophy in these patients as well as secondarily Determine their best corrective visual acuity low luminance visual acuity as well as contrast sensitivity Now I should stop here and just tell you that this project has been put on hold right now because the company is actually Focusing their efforts on using these stem cells for spinal cord as well as brain trauma injury patients Okay, so this this project has not started yet At this point in my talk, I just want to take everybody and bring them to look at the big picture Okay, and I was thinking I'm going through my literature search as well as you know looking into this this project I say it's amazing that people are looking or labs are looking into ways to activate You know possibly intrinsic regenerative mechanisms inside the eye or even use a stem cell transplantation transplantation technique in order to Treat the the eye with with a certain retinal disease as well, but I thought to myself. What is the problem? What is a big problem? You know, what's the limitation using these two approaches and that's Something I identified as retinal remodeling, okay So retinal remodeling was first described by our very own dr. Robert E mark here at the University of Utah They found out was regardless of the type of retinal degeneration model after the after the photoreceptors die The rest of the retina goes through a global massive Rewiring of the retina so the question that I came up with was even if you replace the the lost photoreceptor Or any other cell type that you're interested in how do you know the rest of the retina is Still intact to be able to process vision the same way that you and I do So if I personally were to come up with a Translational approach to help treat blinding diseases affecting the retina. I take a two-step approach first thing I would do is focus my efforts on really Elucidating the mechanisms that govern the path of etiology or the mechanism that drives that specific disease because only once we halt that progression Should we focus our efforts on regeneration or using stem cell transplantation to help replace some of those Lost cells with the hopes of one day Allowing somebody with the affected retinal disease to be able to see this image in its entirety On that note, I like to thank dr. Bernstein for giving me the opportunity to present this topic and Thank you Last but not least our QI project that dr. Jorgensen and I are actually working on Is trying to develop an electronic sign-out program for our neuro ophthalmology patients at the VA because there's such a high turnover of residents there, so it's very important that You know the patients don't fall through the cracks and that we follow up appropriately on their studies So on that note. Thank you very much Dr. Bernstein A little bit about the role of immunosuppression That's definitely true. Okay, that's a very good question. Yes, you know as part of this phase two trial They want to use tachrylimus. Yeah, I believe it was starting at seven days prior to transplantation They have never Showing that there's any side effects right from in terms of inflammation inside of the eye after transplantation But just in case they've been they wanted to use immunosuppression Yeah, and it also includes I believe cortical steroids on the day of the surgery as well And then just one other comment, you know obviously there's a lot of interest from patients about stem cells and what they can do The problem of course is dealing with the hype and the misinformation that's out there And that comes not only from the internet and things out there But even the researchers there's a lot of things because this is Market-driven as you can tell you know this study was done by stem cells Inc And then they make a business decision and withdraw the study because they're going to go do something else but there's incentive to publish very quickly and to To go beyond you know what's just proof of principle and safety Which is what a phase one study is but it gets hyped up You know if you take the worst eye of someone it's likely it's going to get a little bit better regressed to the Mean and they'll make a big deal about that This this field is still really in its infancy and there's a lot of You know people going off to China and Cuba and other places that will take your money a lot of money and inject some stem cells Actually, even Florida will do this now because you can inject abdominal stem cells Directly into a person's eye and the FDA cannot stop you or cannot stop the doctor if it's all done in the same day At the same person's cells So there's a regulatory problems and it's really an issue So it's it's the Wild West out there and you have to tell you have to tell the patients That's what it is and yet and I would certainly never recommend doing anything except under an FDA approved trial in the United States It's going to be a problem otherwise It's not even limited to rat now one of our old colleagues is now we generate crystal lenses in China and so I had a patient yesterday asked me why actually should have an implant I've got a surgery why we can't regenerate his lens Because he looked it up online and a lot of hype now online Colleagues about regenerating lenses as well. We do it every day at the rabbits, but that doesn't mean it's controlled and something we can do and so You know patients are online all the time You know the injection of interatural stem cells into the eye has had disastrous In part of the problems is dr. Bernstein as he alluded to We're just scratching the surface in terms of understanding really even the ontology as well as the epigenetics that control development so if you ask me personally, I feel like this is a very Crew form of engineering. We're just shutting cells into a certain area and praying to God or whoever, you know, that's something happens Jim to my knowledge over two major companies in the U.S. So we're doing this one with stem cells in the center. We were going to be a study site for before they diverted their funds toward final cell projects is the other one companies still focusing on Issues or is it out of the question? They're actually currently undergoing phase one and two. I forgot the name of the company, but they're Yeah, I think they're actually using human embryonic derived stem Rp cells We've seen these patients who I had one a few months ago Last note was from a year ago 2060 at dry AMD and they disappeared and then he came back and he had a total Rd with horrible PBR The result was not pretty so they May ask, sorry, they usually will find a way All right, thank you very much guys You