Featured Research

from universities, journals, and other organizations

Lab-grown Nerves Promote Nerve Regeneration After Injury

Date:
March 20, 2009
Source:
University of Pennsylvania School of Medicine
Summary:
Researchers have engineered transplantable living nerve tissue that encourages and guides regeneration in an animal model. They have successfully grown, transplanted, and integrated axon bundles that act as "jumper cables" to the host tissue in order to bridge a damaged section of nerve.

A surviving cluster of transplanted neurons at the graft extremity (top) with axons in the center (bottom). In both images, transplanted nerve cells are labeled green and axons are stained red. These axons are a mix of the transplanted axons and host axons, which intertwined as regeneration occurred directly across the transplanted tissue.
Credit: Doug Smith, MD, University of Pennsylvania School of Medicine

Researchers at the University of Pennsylvania School of Medicine have engineered transplantable living nerve tissue that encourages and guides regeneration in an animal model. Results were published in March in the journal Tissue Engineering Part A.

About 300,000 Americans suffer peripheral nerve injuries every year, in many cases resulting in permanent loss of motor function, sensory function, or both. These injuries are a common consequence of trauma or surgery, but there are insufficient means for repair, according to neurosurgeons. In particular, surgeons need improved methods to coax nerve fibers known as axons to regrow across major nerve injuries to reconnect healthy targets, for instance muscle or skin.

“We have created a three-dimensional neural network, a living conduit in culture, which can be transplanted en masse to an injury site,” explains senior author Douglas H. Smith, MD, Professor, Department of Neurosurgery and Director of the Center for Brain Injury and Repair at Penn. Smith and colleagues have successfully grown, transplanted, and integrated axon bundles that act as ‘jumper cables’ to the host tissue in order to bridge a damaged section of nerve.

Previously, Smith and colleagues have “stretch-grown” axons by placing neurons from rat dorsal root ganglia (clusters of nerves just outside the spinal cord) on nutrient-filled plastic plates. Axons sprouted from the neurons on each plate and connected with neurons on the other plate. The plates were then slowly pulled apart over a series of days, aided by a precise computer-controlled motor system.

These nerves were elongated to over 1 cm over seven days, after which they were embedded in a protein matrix (with growth factors), rolled into a tube, and then implanted to bridge a section of nerve that was removed in a rat.

“That creates what we call a ‘nervous-tissue construct’,” says Smith. “We have designed a cylinder that looks similar to the longitudinal arrangement of the nerve axon bundles before it was damaged. The long bundles of axons span two populations of neurons, and these neurons can have axons growing in two directions - toward each other and into the host tissue at each side."

The constructs were transplanted to bridge an excised segment of the sciatic nerve in rats. Up to 16 weeks post-transplantation, the constructs still had their pre-transplant shape, with surviving transplanted neurons at the extremities of the constructs spanned by tracts of axons.

Remarkably, the host axons appeared to use the transplanted axons as a living scaffold to regenerate across the injury. The authors found host and graft axons intertwined throughout the transplant region, suggesting a new form of axon-mediated axonal regeneration. “Regenerating axons grew across the transplant bridge and became totally intertwined with the transplanted axons,” says Smith

Axons throughout the transplant region showed extensive myelination, the fatty layer surrounding axons. What’s more, graft neurons had extended axons beyond the margins of the transplanted region, penetrating deep into the host nerve. Remarkably, the constructs survived and integrated without the use of immunosuppressive drugs, challenging the conventional wisdom regarding immune tolerance in the peripheral nervous system.

The researchers suspect that the living nerve-tissue construct encourages the survival of the supporting cells left in the nerve sheath away from the injury site. These are cells that further guide regeneration and provide the overall structure of the nerve.

“This may be a new way to promote nerve regeneration where it may not have been possible before,” says co-first author D. Kacy Cullen, PhD, a post doctoral fellow in the Smith lab. “It’s a race against time - if nerve regeneration happens too slowly, as may be the case for major injuries, the support cells in the extremities can degenerate, blunting complete repair. Because our living axonal constructs actually grow into the host nerve sheath, they may ‘babysit’ these support cells to give the host more time to regenerate.”

The other co-first author is Jason Huang, MD, Assistant Professor of Neurosurgery at Rochester University, who participated in the study during his Neurosurgical residency at Penn.

This work was funded by the National Institutes of Neurological Disorders and Stroke and the Sharpe Trust.


Story Source:

The above story is based on materials provided by University of Pennsylvania School of Medicine. Note: Materials may be edited for content and length.


Journal Reference:

  1. Jason H. Huang, D. Kacy Cullen, Kevin D. Browne, Robert Groff, Jun Zhang, Bryan J. Pfister, Eric L. Zager, Douglas H. Smith. Long-Term Survival and Integration of Transplanted Engineered Nervous Tissue Constructs Promotes Peripheral Nerve Regeneration. Tissue Engineering Part A, 2009; 090220122151069 DOI: 10.1089/ten.tea.2008.0294

Cite This Page:

University of Pennsylvania School of Medicine. "Lab-grown Nerves Promote Nerve Regeneration After Injury." ScienceDaily. ScienceDaily, 20 March 2009. <www.sciencedaily.com/releases/2009/03/090319160122.htm>.
University of Pennsylvania School of Medicine. (2009, March 20). Lab-grown Nerves Promote Nerve Regeneration After Injury. ScienceDaily. Retrieved September 22, 2014 from www.sciencedaily.com/releases/2009/03/090319160122.htm
University of Pennsylvania School of Medicine. "Lab-grown Nerves Promote Nerve Regeneration After Injury." ScienceDaily. www.sciencedaily.com/releases/2009/03/090319160122.htm (accessed September 22, 2014).

Share This



More Health & Medicine News

Monday, September 22, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Sierra Leone in Lockdown to Control Ebola

Sierra Leone in Lockdown to Control Ebola

AP (Sep. 21, 2014) Sierra Leone residents remained in lockdown on Saturday as part of a massive effort to confine millions of people to their homes in a bid to stem the biggest Ebola outbreak in history. (Sept. 20) Video provided by AP
Powered by NewsLook.com
Sierra Leone's Nationwide Ebola Curfew Underway

Sierra Leone's Nationwide Ebola Curfew Underway

Newsy (Sep. 20, 2014) Sierra Leone is locked down as aid workers and volunteers look for new cases of Ebola. Video provided by Newsy
Powered by NewsLook.com
Changes Found In Brain After One Dose Of Antidepressants

Changes Found In Brain After One Dose Of Antidepressants

Newsy (Sep. 19, 2014) A study suggest antidepressants can kick in much sooner than previously thought. Video provided by Newsy
Powered by NewsLook.com
Could Grief Affect The Immune Systems Of Senior Citizens?

Could Grief Affect The Immune Systems Of Senior Citizens?

Newsy (Sep. 19, 2014) The study found elderly people are much more likely to become susceptible to infection than younger adults going though a similar situation. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins