May 14, 2007
Is this the diabetes silver bullet?
My father was diagnosed with a rare form of adult-onset juvenile diabetes during the Korean War, forcing him to inject himself with insulin several times a day for the last 54 years. Recently Dad started wearing an insulin pump, which allowed him to administer small, precisely metered doses through a small needle under his skin by clicking a button.
Although a little inconvenient, it prevented the large swings in his blood-sugar levels that sometimes sent him into severe insulin shock.
But it looks like a better solution may be close at hand, a technological blend of man-made materials and life-saving cells, creating an artificial pancreas, thanks to some researchers and students at Johns Hopkins.
The press release offers hope to people like my Dad, as well as some pretty mind-boggling science.
Johns Hopkins undergraduates have invented a device to improve cell therapy for diabetes patients by anchoring transplanted insulin-producing cells inside a major blood vessel.
A team of five seniors and two freshmen, working with Johns Hopkins doctors and engineers, devised a protective "pouch" that should fit inside the portal vein, which feeds into the liver. This pouch would keep microcapsules of therapeutic cells in one place, allowing them to thrive and send out needed insulin. The inventors say the same approach could be used in cell therapy for other ailments, including liver disease.
[...]
The pouch is formed by sandwiching a porous band of nylon mesh between two concentric metal stents, similar to the ones used to keep clogged blood vessels open. Once the stents are in place, microcapsules filled with helpful cells are injected into the gap between the stents, where they become trapped within the nylon mesh. Blood flowing through the vessel should nourish the encapsulated cells and circulate the proteins, such as insulin, produced by these cells.
[...]
Progress in cell therapy has been slow for several reasons. First, the injected cells are often attacked by a patient's immune system. Also, the injected cells cannot survive long without plentiful oxygen and nutrients, which are not available throughout the body. Finally, once they are inside the patient, the injected cells need to settle in a place where they can provide effective treatment without interfering with healthy body functions.
Something about the device -- described in greater detail below -- reminds me of Isaac Asimov's Fantastic Voyage, with killer antibodies threatening the lifesaving intruders.
Anyhow, it would be nice if this technology entered the human testing phase soon; I know of several diabetics (and those at risk -- are you listening, Wild Bill?), much younger than my father, who would have a much better chance of reaching their senior years if something like this becomes practical.
Arepally and Bulte have overcome some of these hurdles by working with semi-permeable alginate microcapsules - tiny spheres that surround the injected cells and protect them from the body's immune system. At the same time, the spheres allow beneficial proteins to flow out and oxygen and glucose to flow freely in. Arepally and Bulte, both faculty members in the Russell H. Morgan Department of Radiology and Radiological Science of the Johns Hopkins School of Medicine, also have developed ways, covered by a pending patent, to track the microcapsules with various imaging technologies.
They and researchers elsewhere have struggled, however, to keep these encapsulated cells alive within the body, mainly because the cells often situate themselves where they do not have access to a plentiful blood supply. To address this challenge, the radiologists last year asked undergraduates in the university's BME Design Team course to devise a way to keep the microcapsules in one place where their cells could thrive and deliver effective therapy.
During the past school year, the engineering students researched the topic, tested biomaterials and constructed the prototype, designed to fit inside the portal vein. This large blood vessel, about the diameter of an index finger, carries blood from the digestive system into the liver.
The pouch components are made to be compressed and inserted with catheters that a physician can snake into the abdomen through the femoral vein in the leg. Using real-time imaging technology, an interventional radiologist can view and guide the minimally invasive procedure as it takes place. First, the doctor would insert the stainless steel outer stent, which would push out harmlessly on the elastic interior of the vein. Next, the doctor would insert the inner stent, surrounded by the porous nylon mesh. The inner stent is made of nitinol, a metal that snaps back into its original shape after being compressed for insertion. The inner stent matches the interior diameter of the vein. When all of the pieces are inserted, the nylon mesh is held snugly against the inner stent. A gap forms between the mesh and the outer stent, allowing blood to pass through.
At this point, the physician would use another catheter to inject the encapsulated cells between the stents, where the mesh would hold them in place. The tiny openings in the mesh, each about 250 microns in diameter, would allow blood to pass through to nourish the cells and disperse helpful proteins. But the openings are too small to allow the microcapsules to escape.
In lab tests using latex tubing to represent a vein, the students used ultrasound imaging to confirm that fluid can flow smoothly through the mesh and can spread the microcapsules throughout pouch. They also demonstrated that the device causes no pressure drop in the model blood vessels and that the microcapsules can easily be injected and withdrawn.
Posted by Mike Lief at May 14, 2007 10:28 PM
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Comments
Incredible! Incredible! My sister has diabetes and I look at this as a potentially incredible gift of unimaginable beauty.
Posted by: Tom C. at May 15, 2007 07:53 AM
Mike, I am sure that I am one of the younger diabetics that you were referring to. You and I have spoken about this issue several times. This type of treatment would be a godsend.
There are a lot of misconceptions regarding Type I diabetes, which I was diagnosed with at the ripe old age of 6. The first misconception is that we must have eaten too much sugar or been too fat and that is why we got this disease. Ahhh, wrong. In fact, neither of those two things contribute to Type I, which is the type that most insulin pumps are prescribed for.
Growing up with diabetes is very difficult. It affects every part of your life. The lovely side effects that you get to experience years later are also a serious burden. My eyes and my heart have been severely affected (hey, but at least I have my limbs and kidneys for now...).
Most of these treatments that have been introduced in the past few years will likely be too late for me. By the time they get through clinical trials, I will likely be beyond what they can do for me.
However, when I look in the eyes of my 6, 4 and 10 month old, I know that they are all statistically at much greater risk of developing this dreaded disease and so are their children. I am encouraged by the progress that is being made.
There was recently an article on Drudge regarding Diabetes and stem cell research. The article reported about the promising new developments, specifically for people with heart and eye problems related to diabetes that may be treatable as a result of stem cells.
I know its a controversial subject, but try telling a Diabetic with heart and eye problems like me what a bad idea stem cell research is. (By the way I am a church-going Christian as well...)
Mike, thank you for putting this on your site and giving me a chance to vent. Keep up the good work.
RW
Posted by: Ryan at May 15, 2007 11:13 PM