A Demonstration of Tissue Engineering Nerve Grafts
Researchers in the field of tissue engineering are making steady progress towards repair of larger sections of nerve damage caused by injury, here demonstrating a little restoration of function in pigs:
Nerve cells or neurons work by growing axons, long fibrous projections that connect neurons and form the body's signal transmission and communication structure. Although new neurons are born, the long axon cables that connect them do not regenerate effectively over long distances, yet they are necessary for normal function. Researchers have been working for decades to coax damaged axons to regenerate, with little success in getting enough axons to grow to the right places.There are currently no commercially available nerve grafts capable of consistently facilitating axon regeneration across major nerve lesions, generally considered to be a loss of a nerve segment five centimeters or longer. Researchers have now demonstrated the success of tissue-engineered nerve grafts (TENGs) in driving axon regeneration across five centimeter nerve lesions in the legs of pigs (in 10 out of 10 subjects). TENGs are lab-grown nervous tissue comprised of long axonal tracts spanning neurons. The ability to generate TENGs is based upon a mechanism of axon "stretch growth". These tissues are not only similar in structure to endogenous nerves, but suitable for transplantation upon removal from custom bioreactors.
The living TENGs were surgically attached to bridge a missing segment of nerve and were shown to accelerate the regeneration of axons, allowing a population of axons to cross the graft within five weeks. At three months, the bulk of axons had crossed the graft into the existing nerve structures opposite the lesion. Target muscle reinnervation was confirmed via an evoked hoof twitch as early as seven months following TENG repair, and over nine to eleven months post-repair there were steady increases in muscle electrical activity and muscle force generation. Microscopic examination of the regenerated nerves revealed a high density of regrown axons bridging the lesion zone and progressing the length of the repaired nerve to innervate target muscle.