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Transcript: NIH Researchers Develop Nanoprobe Treatment for Animal Model of Cerebral Palsy

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Audio News Briefing

April 17, 2012
2:00 PM ET

Operator: Good afternoon, ladies and gentlemen, and thank you for waiting. Welcome to the Nanoprobe Study Media Call. All lines have been placed on listen only mode and the floor will be open for your questions following the presentation. Without further ado, it is my pleasure to turn the floor over to your host, Mr. Robert Bock. Mr. Bock, the floor is yours.

Robert Bock: Thank you and welcome to the National Institutes of Health. I'm Bob Bock, the press officer for the Eunice Kennedy Shriver National Institute of Child Health and Human Development. This briefing will be on the forthcoming Science Translational Medicine paper, “Dendrimer-based postnatal therapy for neuroinflammation and cerebral palsy in a rabbit model.” 

Our briefing is being held under the terms of the journal embargo which lifts tomorrow at 2:00 pm Eastern Daylight Time, Wednesday, April 18th, 2012. This study was conducted by the Perinatology Research Branch of the NIH’s Eunice Kennedy Shriver National Institute of Child Health and Human Development. I would now like to introduce our first speaker, Dr. Roberto Romero, Chief of the Perinatology Research Branch, who will introduce his co-authors on the paper, who will briefly talk about the study. Dr. Romero.

Dr. Romero: Thank you, Bob. And thank you all of you who are joining us today. I am Roberto Romero. I am an obstetrician and I serve as Chief of the Perinatology Research Branch. Our branch focuses on pregnancy and pregnancy complications and is housed in Detroit, Michigan, at Wayne State University and the Detroit Medical Center.

Now the other physicians and scientists who are with us on the conference call are Dr. Sujatha Kannan, an Associate Professor of Pediatrics. She is the first author in this report and she developed the animal model for cerebral palsy and has evaluated the evidence for neuroinflammation in this experimental model. 

Also with us is Dr. R. Kannan who is Professor of Chemical Engineering of Imperial Science and developed the nanotechnology approach by preparing and characterizing the nano device that we have used in this study. 

Now, as a way of introduction, I would just like to say a few words about cerebral palsy and why we conducted this study. Cerebral palsy is a group of conditions. It is not one condition but a group of conditions that are characterized by motor disabilities and the key features of cerebral palsy, I would say, are number one: the presence of movement disorders of the lower extremities, the upper extremities, but children often have difficulties with posture and sometimes difficulties with swallowing. 

The second feature of cerebral palsy is a developmental abnormality. That means that is the result of an insult that occurs in early life, be that fetal life or early childhood. 

The third feature is that cerebral palsy is non-progressive in nature and is not considered a degenerative disorder. An example of a degenerative disorder would be Alzheimer's disease. Cerebral palsy is a lifelong condition for which there is no known cure and that is the significance of the paper that we are publishing tomorrow.

Now often (inaudible) children with cerebral palsy have a developmental delay with cognitive disorder and I want to emphasize at the outset that not all children with cerebral palsy have a developmental delay. Some children have the motor disorder but have normal intellectual performance.

Now, in terms of the magnitude of the problem, cerebral palsy affects approximately 750,000 children and adults in the United States and the Center for Disease Control has estimated there are approximately 100,000 babies born in the United States that develop cerebral palsy every year.  And the prevalence of the condition is 3.3 per 1,000 live births.

Now the leading identifiable cause of cerebral palsy is premature birth, so the lower the gestational age at delivery, the greater the risk of cerebral palsy and this is particularly the case for babies who are born less than 32 weeks of gestation. 

Now our branch has been interested in the problem of cerebral palsy and premature birth for a number of years and what we have established is that one of every three premature babies is born to a mother with sub-clinical intraamniotic infection. So there are bacteria in the amniotic cavity but the mother doesn't have a fever. The only way of presentation is an episode of premature labor or the membranes have ruptured.

Now this is important for two reasons. Number one, premature babies, particularly those born inside 32 weeks, are more prone to develop cerebral palsy because the brain is immature. And the other reason is because the bacteria can invade the human fetus. The fetus's non-systemic inflammatory response, and if there is an exaggerated inflammatory response in the brain, that leads to the damage that eventually will manifest itself as cerebral palsy. 

Now an important point to have these findings in context is that the human newborn is born premature so it doesn't walk and this is in contrast to, let's say, animals like rabbits, in this particular case. That is, they are able to walk at the time of birth. So in humans we do not make the diagnosis for cerebral palsy until the age of two and three. And the reason why that is important is because if we have an insult that occurs in fetal life or in early neo-natal life, that inflammatory process can be taking place for months and is clinically silent and perhaps this is one of the reasons why, when we make the diagnosis, there is very little that we can do. 

Now, in a nutshell, where we are going to present today and Sujatha is going to present the biological part and then Kannan is going to present the nanotechnology part. We've developed an animal model for cerebral palsy by exposing mothers who were pregnant to bacterial endotoxin which is a component of ground negative bacteria. So, no live bacteria but a microbial product. 

Then these babies were born at term and have the features of cerebral palsy which you can see in the videos that are posted in Science Translational Medicine, and the intervention was to give a nano device which is an anti-inflammatory agent coupled with a dendrimer. And the key result is that in five days there was reversal for the motor disorder, the motor impairment and you can verify that by looking at the videos in Science Translational Medicine. 

So the importance of this work is that it indicates that there is a window, a window in time immediately after birth when neuroinflammation can be identified and that treatment with a nano device can reverse the features of cerebral palsy. Sujatha, can you take it out from here.

Dr. Sujatha Kannan: Thank you. Hi, this is Sujatha Kannan. Thank you, Bob, and Dr. Romero for the introduction and thank you, everyone, for being here. I'm a pediatrician and a pediatric critical care physician. What we have developed is a rabbit model of cerebral palsy which is induced by introduction of endotoxin or a bacterial product along the uterus and this creates an environment of inflammation in the uterus of the mother, resulting in inflammation of the fetus. 

So one of the responses of the brain to any injury is activation of cells called microglia and astrocytes. Normally in the developing brain, these microglia are present in white matter tracts and when there is an insult or any injury during development, these microglia saw-- the normal function of the microglia cells is to remodel and help the brain develop normally. So in the presence of any insult, these microglia cells change the function. They become pro-inflammatory, or they create this rampant neuroinflammation that-- instead of doing their normal job of creating white matter and helping the brain develop-- normally they start destroying the cells around them. And this is one of the reasons that we think there is brain injury resulting in features such as cerebral palsy with motor deficit. 

So our goal was to see if we try and target these microglia cells, and if we suppress the process of inflammation at an early phase, would this result in improvement and would this stop the damage and help the normal brain repair take over? 

So the reason we used rabbits in the study is because of the parallels in brain development between rabbits and humans. In humans, a lot of the brain development is perinatal, that means it starts before birth and continues for a period after birth and that is similarly the case in rabbits. And the microglia distribution in the white matter region in the rabbits is also similar to that in humans. So this makes the animal model very unique because this has a phenotype of cerebral palsy which other animal models do not have and the advantage of that is that we can test therapies and look at the improvement in motor function in using this kind of an animal model.

So what we found is that when we use these dendrimers to target an anti-inflammatory agent which specifically delivers the drug to active microglia and astrocytes, there was an improvement in motor function, there was a decrease in inflammation and oxidative injury.

Dr. Romero: Also an improvement in the motor function of the babies. That was, right?

Dr. Sujatha Kannan: A dramatic improvement in the motor functions.

Dr. R Kannan: Thank you, everyone, for your interest. I am (inaudible) Kannan. Since there are two of us, I'm the last person in this article. So as Sujatha mentioned, neuroinflammation plays a key role, not only in cerebral palsy, but in many neuro-degenerative disorders and it is mediated by activation of microglia and astrocytes. So the hypothesis was that if we can somehow itinerate the ongoing neuroinflammation, perhaps we could affect that pocket of therapeutic response in these animals. However, targeting these cells in the brain in a diffused injury is a major challenge. First you have to traffic the drug across the blood-brain barrier. After the drug has crossed the blood-brain barrier, they have to find the target cells and they have to be able to deliver enough drugs to the target cells so that we can effect a therapeutic response in this debilitating disease.

This is a big challenge, not only for the drug, but also for the larger moleculed nano particles, because the blood-brain barrier is very selective. We discovered that these globular tree-like nano- structured polymers called dendrimers-- specifically poly amidoamine dendrimers-- these are synthetic macro molecules that are made of beta alanine-like building blocks. They are about four nanometers in size and they have hydroxyl groups on them. 

When we injected them into animals that have cerebral palsy, we found that, not only did they go across the blood-brain barrier, but they quickly localized in these very cells that caused the problem. Surprisingly, when we attached this drug called N-acetylcysteine, which is a safe, anti-inflammatory antioxidant drug that is clinically approved and is being used in pregnant women and neo-natal for accidental poisoning, we found that the dendrimer drug conjugate nano device was not only able to reach the target cells, but it was able effect the worst of motor function in newborn rabbits. Specifically, one administration of a dendrimer drug nano device was able to effect a very significant response by day five whereas given a ten-fold higher free drug was not effective in producing motor function improvement, improving neuro injury or improving myelination. 

So this shows that nano-technology can actually be a powerful way to target these hard-to-reach cells in the brain. Shall I stop at that and we'll be happy to take questions?

Robert Bock: Operator, we can now open it up for questions.

Operator: Certainly, the floor is now open for questions. If you do have a question, please press the number 7 on your telephone keypad. Questions will be taken in the order they are received. If, at any point, your question has been answered, you may press 7 again to disable your request. If you are using a speakerphone, we ask that, while posing your question, you pick up your handset to provide favorable sound quality. Please hold while we wait for the first question.

If you have a question, please press the number 7 on your telephone keypad.

We have a question on the line from Kim Kozlowski of Detroit News. Kim, go ahead.

Kim Kozlowski: Hello. Thank you for presenting this information to us today. Could one of you please summarize what this might mean for parents who might have children with cerebral palsy or children who might in the future contract this?

Dr. Sujatha Kannan: We think there is a lot of promise that says that there might be a window of opportunity for treatment, even after birth, for patients who are at risk for cerebral palsy. Of course, this work is pre-clinical and we have to do a lot more work to explore this further and we might have to -- we would have to do long-term safety studies and also long-term therapeutic responses but the important thing to take away from this is that there appears to be a window of opportunity for treatment, even after birth.

Dr. Romero: So, Kim, this is Roberto Romero. In direct answer to your question, if what you’re asking is can parents call us tomorrow to giet these N-acetylcysteine dendrimers, this is not ready for implementation in humans. This study is a study that proves the concept that neuroinflammation can cause cerebral palsy, that in other papers that we have done together we can identify that neuroinflammation and that treatment can reverse this. And this is a very important concept because cerebral palsy has traditionally been considered a lifelong disease that doesn't have any treatment. So our expectation is that we will be able to take advantage of this window of opportunity, develop this treatment further in animals, and then begin clinical trials in the future.

Kim Kozlowski: Thank you. And how soon in the future do you expect people might see the therapy?

Dr. Romero: So, Kim, that's a very difficult question.

Kim Kozlowski: I know.

Dr. Romero: What we -- let me tell you, the immediate steps are to find out what is the optimal dose, what is the optimal duration of treatment, and then to prove that there is a safety margin to these treatments and the safety margins are -- there are two components. N-acetylcysteine, as you heard before, we use it in mothers who have been poisoned with an overdose of Tylenol so it a small molecule that has been used for pregnant women in this country and the main indication is intoxication with Tylenol. So we're very confident that that part of the treatment is safe and the other part that we need to treat, to examine, is the dendrimers. We need to do those studies before we begin clinical studies. I can tell you this will serve you as sort of an index that the study that we are reporting tomorrow in Science Translational Medicine took approximately three years. Sujatha and Kannan, is that fair?

Dr. Kannan: That's a very good point. I wanted to just add that how far -- I think research is a component of how fast things can move. From a nano technology point of view. There are also regulatory components. We need to air on the part of large number of constituents to advance promising technologies further and those approaches must take into account, not only the risk of new treatments, but also the reward of new treatments. So the risk-reward ratio of an (inaudible) nano-technology-based treatment must be a balanced one. 

So I think research is an important component. Identifying the right methodologies, right combination of therapies that could be beneficial to this approach, identifying who are the right candidates after birth who could be administered these therapies is important. More-- I think more that there has to be a collective approach once the science is validated and then that will determine how fast it can be moved clinically.

Kim Kozlowski: Thank you.

Operator: There are no other questions in the queue at this time. Again, if you do have a question, please press number 7 on your telephone keypad. And we just had a question come in from Rachel Rettner of MyHealthNewsDaily. Rachel?

Rachel Rettner: Hi, thank you for answering my question. I was wondering if this treatment could be translated to humans, how would you identify which children would need the treatment if cerebral palsy isn't diagnosed until much later in life?

Dr. Romero: Great question. So, Rachel, this is Roberto Romero. We have two methods to identify the baby who may benefit. Today, when we have a patient in premature labor, and our branch of the Detroit Medical Center and Wayne State, one of the questions that we have is: is that premature labor due to infection? We assess that by doing an amniocentesis and determining if they have bacteria in the amniotic fluid and if there is inflammation. And we can make that determination of whether there is inflammation quickly, in a matter of hours, looking at the white blood cell count, measuring (inaudible) the amniotic fluid. Now that will tell us that there is inflammation in the amniotic cavity, not necessarily in the fetus. 

When the baby is born we can do a second test and that is to measure inflammatory markers in umbilical cord blood and that tells us that baby has systemic inflammation. 

The third line of diagnostic, to identify the baby who has neuroinflammation, is to examine the brain with imaging techniques and what we have used in the past is PET scan -- Positron Emission Tomography. And the first unit in the world that developed this is here at Children's Hospital in Michigan and it is possible to identify activation of the microglia that Sujatha mentioned to you before that are the hallmark of inflammation in the brain. 

So we have three ways to do it. Number one, to ask is there any inflammation or infection in the amniotic cavity with amniocentesis? The second one is to measure markers in the blood, and the third is to use imaging techniques with a PET or Positron Emission Tomography after the baby is born, or MRI to see if there is evidence of inflammation. And those will be the babies that will be candidates who have neuroinflammation, that are clinically silent; those are the babies who can benefit from this therapy.

Dr. Kannan: Rachel, this is Sujatha Kannan, just to add to what Dr. Romero said, and those are the excellent ways to be able to identify the - the PET imaging idea helps identify the molecular level. It helps identify the cells specifically that are involved in neuroinflammation that has activated microglia. And there are ligands that can specifically bind it and we've already published this in the animal model. It is also used-- these ligands are also used-- currently being used in humans to identify microglia activation in other disorders. So this is something that could imminently be translatable in the clinical study.

Dr. Romero: And can I just to give you the reference so that you can look it up. It’s the Journal of Nuclear Medicine, Volume 48, Number 6, and the page of the paper is 946. Any reports-- these are sectional microglia activation in this model that we are reporting tomorrow.

Rachel Rettner: Thank you. That answers my question.

Operator: There are no other questions in the queue at this time. Again if you have a question, please press 7 on your touch-tone keypad. And we did just have another question come in from Kim Kozlowski of Detroit News. Kim?

Kim Kozlowski: Thank you for taking another question from me. Doctors, could you please go over how some drugs do not cross the blood-brain barrier and is it that nano device that allows for this particular drug to cross this barrier? And could you explain to me how this nano device works?

Dr. Romero: Could I just begin by-- the blood-brain barrier is, as the name indicates, is a barrier. It is intended to protect the brain from-- anything that is outside the brain can be toxic so the brain has a mechanism to protect itself. One of them is this blood-brain barrier. 

Now one of the key observations that was made during the course of this study is that when you have neuroinflammation, the blood -brain barrier becomes porous, becomes more permeable. And if you look at the paper, there is a figure in which, that is in blue color, in which the animals were injected with a dye that is called Evans Blue that forms a complex with albumin. And under normal circumstances, that complex does not cross the blood-brain barrier. But when there is neuroinflammation, that is induced by exposure to endotoxins, that blood-brain barrier opens a little and it becomes more permeable. And it was because of that, that the dendrimers were effective in crossing the blood-brain barrier. 

In previous papers published by the three of us, in the absence of that permeability, the dendrimers did not go to the brain and that is an important feature because it says that if there is no neuroinflammation, the dendrimers are not going to go to the brain. So in many ways the dendrimers are acting in a stem cell-like fashion, that the dendrimers know to go to the brain when there is inflammation.

Now the other part of your question is how do dendrimers execute this feat? And that is a question for Kannan that he is ready to answer. Kannan?

Dr. Kannan: Thank you. I think that blood- brain barrier is selective so, in fact, even small drugs, many of them do not cross the blood-brain barrier because they need a receptor to be transported across this tight junction into the brain. Even drugs that are reported to cross the blood-brain barrier are often not effective. A key component of this work is that if, for example, a lot of the brain defoggers are (inaudible) too much could be cured by simply delivering the drug into the brain, we would have significant advancement in therapeutics of the brain. The unfortunate part is, even if you inject a small drug into the brain, it doesn’t move much in the brain. That is why it is not effective. 

So the first problem is that the drug has to be transported across but that, in itself, is not sufficient to evoke a therapeutic response especially in a diffused neuroinflammatory challenging disease like cerebral palsy. So our study, like Dr. Romero mentioned, showed that there is an impairment of the blood-brain barrier that allowed the dendrimer to get into the brain. But this is only one of the major hurdles. 

What was a rather surprising finding was that, in fact, many nano particles have been shown to cross the impaired blood-brain barrier but most of these nano particles, they get stuck to very near the blood vessel so they really do not deliver drugs away from the blood vessel. Interestingly, we found that these dendrimers, they are not found near the blood vessel, actually they are found in the very cells that cause the problem. This could be either because the dendrimers diffused very quickly and the cells ate them up because they are (inaudible) or the cells themselves migrated and ate up the drug. 

So reaching the target cells is only the second aspect of the problem. Once you reach the target cells, the drug has to actually be released from the nano device. So we did a lot of work to engineer that release from the dendrimer and we have published many papers on how to do this inside the cell. And that is what is effective. 

So to summarize, not only do you need to transport the drug. If the drug goes through the impaired blood-brain barrier, that in itself is not sufficient. You need the drug to be trafficked across the blood-brain barrier, into the target cells, released in a timely fashion to produce the effect. And that is what we think-- that's what we have shown the inert nano carriers called dendrimers do.

Dr. Romero: And, Kim, there is a picture in the paper where you can see the second point. So the first point is that they cross the blood-brain barrier but there is a picture in color in the paper that shows that the dendrimers are localized to the microglia and to the astrocytes so the difference is, if you give N-acetylcysteine or a free drug, it diffuses into the brain. This one, imagine an airplane crossing the blood-brain barrier, find the target, and then attach into the target and release the cargo. That is the N-acetylcysteine through the cells of interest.

Kim Kozlowski: That's a great analogy. Thank you, doctor.

Operator: We have a question on the line from Kerry Sheridan of AFP. Kerry, go ahead.

Kerry Sheridan: Hi, thanks for taking my call. I was just wondering if I could clarify, you mentioned there are different types of cerebral palsy. Do you have any indication that this would work on types that also involve the developmental delays or is this something that mainly seems to be working on the motor deficits? And just one second question, I know you haven’t tested it yet, but is there any hint or any possibility that this sort of treatment could one day reverse cerebral palsy in children who already have it? Older children.

Dr. Romero: So let me just begin by saying that this is a question for Sujatha but I'd like to introduce the answer by saying in the brain we have grey matter and white matter. Grey matter is where the neurons are and in white matter we have the axons or the tracks of the neurons. Now, cognitive function, intelligence, consciousness and so on, is in the grey matter. And in the white matter we have like the cables that connect one part of the brain with another. Deletion that accounts for the motor deficit is when there is neuroinflammation or there is hypoxia, there is damage of that white matter. There are some holes and you will see in the paper that we refer to periventricular leukomalacia. Periventricular means that the holes are around the ventricles -- periventricular. And malacia means destruction. So yes, cerebral palsy is mainly considered a disorder of white matter but, when there is involvement of the grey matter, then there is also the risk of cognitive impairment and other developmental delay. And Sujatha is going to tell you that we did find improvement in both grey and white matter and, specifically, in neurons. Sujatha would you?

Dr. Sujatha: Yes, I can just address both components. To start with the first one, yes, there are many causes of cerebral palsy and sometimes-- here we are looking at an inflammatory cause but there is also possible and it's been shown that, even in other causes such as in stroke or hypoxic ischemia which are other common causes, there is secondary inflammation and these cells are involved secondarily and can worsen the injury or can lead to progression beyond what was the initial injury. So it is possible that, in other causes too, this may work wherever there is involvement of these cells and, in the immature brain and injury to the immature brain, these cells play a major role. And we will be studying this in other kinds of models-- cerebral palsy models too.

But for the second part where you're asking about the cognitive impairment, we have shown-- we have looked at both components. We looked at myelin, which is mostly white matter that looks at the motor function and we found that there was an improvement in myelination which went along with the improvement in motor function in these rabbits. Now since these are animal models, it's harder to test the cognitive functions and we would probably be able to do this in as they get older, like towards adulthood, which we have studies we'll have to do later. But the neuronal injury which is injury to the grey matter and which is responsible for cognitive function and other integration of these motor and sensory functions, we found that there was improvement in the neuronal injury too. So we found that in animals that were treated with a dendrimer and N-acetylcysteine there was improvement in both the motor function, white matter injury, and improvement in neuronal injury which is related to grey matter and possible cognitive function.

Dr. Romero: (Inaudible) could I say that if you look at figure 7 in the paper, figure 7 has the evidence in support of what Sujatha just said. Improvement in myelination on the left bar graph and improvement in neuronal injury on the right bar graph. So figure 7 in the paper.

Dr. Sujatha Kannan: Now I know you had another question about if it is possible to treat patients at a later age when the diagnosis is already made.

Kerry Sheridan: That's right, yes, that's right.

Dr. Sujatha Kannan: So the thing is it is difficult for us to say now but, obviously, the earlier we suppress the neuroinflammation, the better we expect the response would be. We do know, in other disorders and not necessarily in this, but in other neuroinflammatory diseases and disorders, we know that the neuroinflammation can progress or persist for a very long time after the injury. For example, in patients with traumatic brain injury, there is a neuroinflammatory response and this can persist for months after the injury. So it is possible that the same thing happens in patients with cerebral palsy too. That there may be a component of neuroinflammation that persists for a prolonged period. We have to look further into it. It is possible that if you suppress it, even at a later stage, although there might not be complete improvement, there might be some improvement. I would think the sooner we do it the better the response would be but it's hard for me to say beyond that because we have to look into it a lot more. 

Kerry Sheridan: Okay, thank you.

Operator: No further questions in the queue at this time. Again if you do have a question, please press the number 7 on your telephone keypad. There appear to be no further questions at this time.

Robert Bock: Okay, this is Bob Bock. There do not appear to be any further questions and so we will conclude our briefing for today. Thank you very much for joining us.

Dr. Sujatha Kannan: Thank you.

Dr. Kannan: Thank you.

Dr. Romero: Thank you.

Operator: This does conclude today’s teleconference. You may now disconnect.


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Last Updated Date: 04/26/2012
Last Reviewed Date: 04/26/2012
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