New hope for dialysis: Bioengineered blood vessels

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Posted: Thursday, May 29, 2014 4:00 pm

DURHAM, N.C. (Ivanhoe Newswire) – Nearly 400-thousand Americans are on dialysis for kidney failure. The treatment uses a special machine to filter toxins from the blood and often requires a graft to connect an artery to a vein to speed blood flow. But in many patients, synthetic grafts lead to infection and frequent hospitalizations. Now a first of its kind bioengineered blood vessel is changing that.

William Alexander has suffered with kidney failure for 15 years. Dialysis keeps him alive.

“[It’s not] like you can’t do it,” Alexander told Ivanhoe. “You’ve got to have dialysis to live.”

However, his arm tells the story of failed blood vessel grafts used to help clean his blood.

“It’s disfiguring,” Jeffrey Lawson, MD, PhD, Professor of Vascular Surgery and Pathology at Duke University Medical Center, Durham, N.C., told Ivanhoe.

It’s a reality Dr. Lawson says most patients face.

“I tell many of my patients they can expect to have a procedure related to dialysis at least once a year,” Dr. Lawson explained.

Now, a new bioengineered blood vessel using donated human cells could change that.

“We’ll be able to reduce the number of interventions they have to have,” Dr. Lawson said.

At the lab, Dr. Shannon Dahl says donated cells are placed in a bioreactor and cultured for two months.

“So we’re growing the cells and we’re putting the bioreactor parts together,” Shannon L.M. Dahl, PhD, Vice-President, Scientific Operations, cofounder, Humacyte, Inc., Durham, N.C., told Ivanhoe.

Once the vessel is formed, it’s cleansed of the donor cells, leaving a collagen structure that the body readily accepts as its own.

“It then becomes your blood vessel as your body grows into it, which is very, very exciting,” Dr. Dahl explained.

Alexander had the bioengineered vessel placed in his right arm eight months ago.

“I don’t have any trouble and it’s doing good, and I’m glad it’s doing good,” Alexander said.


BACKGROUND: Dialysis is a treatment that does some of the things done by healthy kidneys. It is needed when your own kidneys can no longer take care of your body's needs. You need dialysis when you develop end stage kidney failure --usually by the time you lose about 85 to 90 percent of your kidney function. When your kidneys fail, dialysis keeps your body in balance by: removing waste, salt and extra water to prevent them from building up in the body; keeping a safe level of certain chemicals in your blood, such as potassium, sodium and bicarbonate; and helping to control blood pressure. (Source: kidney.org)

DR. LAWSON: “We’ve been involved in developing a bioengineered blood vessel really since the late 1990s. It’s been very exciting work. The developed tube is intended to be used as a general blood vessel for sort ovascularf replacements anywhere in the body. This past year, we started our first in man clinical trials using this blood vessel and that’s been used in a unique application for what’s called vascular access for hemodialysis. That is really used as a prototype model for blood vessels in many applications, but this dialysis situation is a safe and easy way to begin to test the new vascular technology. So, we started using these blood vessels in that area. We hope to ultimately someday be able to use these blood vessels in things like the heart and the brain and really throughout the body.” (Source: Dr. Lawson)


Jeffrey Lawson, MD, PhD, Professor of Surgery and Pathology, Duke University, talks about bioengineering blood vessels.

We’re talking about the bioengineered blood vessel, which is pretty exciting. Can you talk about some of its application here?

Dr. Lawson: Sure, so we’ve been involved in developing a bioengineered blood vessel really sense the late 1990s. It’s been very exciting work. The developed tube is intended to be used as a general blood vessel for vascular replacements anywhere in the body. This past year, we started our first in man clinical trials using this blood vessel and that’s been used in a unique application for what’s called vascular access for hemodialysis. That is really used as a prototype model for blood vessels in many applications, but this dialysis situation is a safe and easy way to begin to test the new vascular technology. So, we started using these blood vessels in that area. We hope to ultimately someday be able to use these blood vessels in things like the heart and the brain and really throughout the body.

So even in the heart and the brain, at what capacity?

Dr. Lawson: When people have blockages in the heart arteries, there are many ways to treat those blockages. One of which you can do you can treat them with a balloon angioplasty or a stent, but some patients can’t be reconstructed using those techniques and require a bypass surgery. Currently that bypass is done with a vein that’s usually taken out of the leg which requires an additional incision and then the leg veins are sewn as bypasses on the major blood vessels in the heart. That causes patients to have a second incision and increases the morbidity operation. If our bioengineered blood vessels work for the heart bypass operation, that would reduce the need to harvest the patients own vein and make the procedure both safer and faster.

So for this particular trial though is being used for dialysis patients?

Dr. Lawson: Yes. In Europe, we actually are using them both for dialysis patients and peripheral vascular patients. In the US, currently we’re just testing them for vascular access for dialysis. We hope that maybe the coming year to begin to do peripheral arterial disease cases in the United States.

Can you talk about the need for this for dialysis patients?

Dr. Lawson: Our dialysis patients really have a significant problem. You know dialysis is a special situation that requires a lot of engineering on to itself. We figured out years ago how to clean people’s blood in a machine. Basically we have to wash their blood three times a week in a machine and we call that process hemodialysis. However, that means we have to get their blood out of their body to a machine, which requires a number of logistical problems. The way that we’ve solved that through operationally is to place a large blood vessel in the arm that can be accessed or cannulated by the dialysis team. However, that blood vessel has to have a continuous high flow that they can run this dialysis machine. So, we make an artificial circuit where we connect and artery and a vein in the arm using various materials, but the current materials we use are most often either the patient’s own vein, which has problems with their own vein maturing and working and when those don’t work we use artificial veins and the artificial veins we use are primarily a Teflon material, which unfortunately have both a high rate of failure by clotting and or infection.

It appears that there’s not much risk of rejection, correct?

Dr. Lawson: We have not seen rejection in any of the animals or humans that have been exposed to this tissue, which is actually quite remarkable. The tissue engineered vessels are intended to be a universal donor. We had to come up with a platform that allowed us to make blood vessels that would function like your blood vessel but could be available off the shelf in any hospital, anywhere in the country or the world. And so we had to take an approach of taking a universal donor, taking cells from in this case organ donors who donated aortic tissue just like they donate their hearts and their kidneys and their lungs. However to avoid rejection, we have to remove the donor cell and leave a decellularized matrix of tissue that the body doesn't reject and is actually repopulated by the patients own cells

So the patient that we saw that came in I noticed on the arm that didn’t have this bioengineered blood vessel he must’ve had a graft or several grafts?

Dr. Lawson: So that patient I’ve worked with for a number of years. In his left arm where he had, had initially what was called a fistula, that’s his own vein that was used for dialysis in his forearm, that then failed and that was replaced by an artificial vein in that area that again lasted for a period of time but then failed. Some of artificial grafts that were used in his arm became infected and had to be removed as we know can happen with the artificial vascular materials. Then, he had two other grafts placed in his upper arm that each worked for a period of time and that ultimately failed. I think both of them developed blood clots in them.

Those weren’t there before that happened because of the grafts?

Dr. Lawson: Exactly, so the things that you saw in his arms and particularly I think there’s one area where there’s a very large what looks like a knot and that’s what these patients live with. It’s very disfiguring. He’s had multiple, multiple operations over a number of years and remarkably he’s continued to do well. But when I asked him if he wanted to participate in this trial to test a new type of vascular graft, he was very interested.

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