Growing Replacement Blood Vessels Inside the Body

Scientists in Japan have found a new way to make replacement blood vessels by growing them inside a patient's own body. A company called Biotube Co. is working with doctors at Asahikawa Medical University to test this idea. The goal is to help patients who need bypass surgery but don't have a healthy vein available. This method could one day prevent thousands of people from losing a limb.

Vascular surgeon Nobuyoshi Azuma does about 80 leg bypass surgeries each year. In a bypass, doctors send blood around a blocked vessel using a vein taken from the patient's leg. The most common vein used is the saphenous vein, which runs the full length of the leg. Some patients, though, have already had that vein used in heart surgery, or it is simply too damaged to use again.

When no replacement vein is available, patients face serious danger. Wounds on their feet can become life-threatening, and without proper blood flow, amputation may become necessary. Man-made, or synthetic, grafts exist but don't work well for long periods of time. There are also no good artificial options for the small blood vessels needed in lower-leg surgeries.

Biomedical engineer Yasuhide Nakayama found a possible solution while working at Japan's National Cerebral and Cardiovascular Center. He noticed that when implants were placed under the skin, the body would wrap them tightly in collagen — a natural protein that helps hold the body together. He realized this process could be guided to grow useful medical tubes. Starting in 1999, he developed a technique called in-body tissue architecture, or iBTA.

The main tool used in iBTA is a stainless-steel disk roughly the size of a palm. A plastic coil sits inside the disk, just a fraction of a millimeter from the outer wall. When placed under the skin, the body fills that tiny gap with collagen, forming a tube called a 'biotube.' These biotubes can grow to more than 50 centimeters in length and are shaped precisely to match what each patient needs.

Before testing iBTA on people, researchers tried it on goats. The team at Oita University Hospital found that the biotubes were strong enough to handle the force of blood moving through arteries. Six months after being placed into the goats' neck arteries, the tubes were still fully open and working. These results gave doctors enough confidence to begin human clinical trials.

Azuma's team has now operated on three human patients who were all facing the possibility of losing a leg. Early results have been positive, though scientists say more research is needed. Doctors are watching these patients carefully over time to see how well the biotubes continue to function. Every step forward brings this promising technology closer to widespread use.

The iBTA method can also be used for things beyond blood vessels. Different molds can produce flat sheets of tissue for repairing other body parts. Researchers at Tsukuba University Hospital are studying whether these sheets could help rebuild the outer covering of the brain. They are also testing a special mix of stem cells to heal serious wounds in diabetic patients and treat other hard-to-cure conditions.

Nakayama's biggest dream is to use this technology to help children born with heart defects. Children who have heart surgery often need multiple follow-up operations because the parts used don't grow with the child. A living heart valve grown from the child's own cells might grow along with them, reducing the need for repeat surgeries. 'Growing paediatric heart valves is my ultimate objective,' says Nakayama. 'I feel a strong sense of mission to see this through.'