Artificial nerve grafts made from spider silk

Every year, hundreds of thousands of people suffer from paralyzed limbs as a result of peripheral nerve injury. Recently, implantation of artificial nerve grafts has become the method of choice for repairing damaged peripheral nerves. Grafts can lead to some degree of functional recovery when a short segment of nerve is damaged. But they are of little use when it comes to regenerating nerves over distances greater than a few millimeters, and such injuries therefore often lead to permanent paralysis.

Now though, surgeons from Germany have made what could be a significant advance in nerve tissue engineering. They have developed artificial nerve grafts made from hollowed-out pig veins filled with spider silk fibres and, in a series of animal experiments, showed that the grafts can enhance the regeneration of peripheral nerves over distances of up to 6cm. Their findings have just been published in the open access journal PLoS One.

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Bladders grown in the lab for transplant

American physicians and scientists have rebuilt parts of human bladders in the laboratory and successfully transplanted them into patients.

Although simple tissues such as skin and bone have been engineered before, this is the first time a complex, fully functional organ has been successfully grown. The work, published on The Lancet’s website today, is therefore a breakthrough in tissue engineering and transplant surgery.

The work, carried out on seven teenagers at Boston Children’s Hospital, was led by Dr. Anthony Atala, who has since become director of the Institute for Regenerative Medicine at Wake Forest University School of Medicine in North Carolina. 

Patients first had damaged bladder tissue surgically removed. Several thousand progenitor cells from the bladder of each patient were then removed, placed on bladder-shaped collagen scaffolds, and left to divide for several weeks, after which they numbered approximately 1.5 billion. This lab-grown tissue was then sewn back onto what remained of the patients’ bladders, where it continued to grow and reform a functioning organ once again.

During the 1990s scientists tried xenotransplantation – using organs from genetically engineered pigs for transplants into humans. This proved unsuccessful because of the immune response of patients and because of the dangers of infection with animal viruses.

Because the current work involved bladders being rebuilt from cells belonging to the patients, there was no danger of them being rejected by the patients’ immune systems.

However, only parts of the organs were grown in the study and engineering and transplanting an entire bladder may prove more difficult as it would involve reconnecting the urethra and blood and nerve supplies.

“It is [nevertheless] an exciting development,” says Professor Catherine Kielty of the Centre for Tissue Engineering at Manchester University, because “it is an engineered organ which has proved functional.”

In the UK, approximately 6,700 are on the waiting list for an organ transplant, and 2,180 such operations were performed last year. Organs for transplantation are in short supply because of improvements in road safety and fewer accidents.

“This suggests that tissue engineering may one day be a solution to the shortage of donor organs,” says Dr. Atala.