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Ed. Note: The following is a press
release from the University of Pennsylvania School Of Medicine.
February 16, 2006 --
Researchers at the University of
Pennsylvania School of Medicine have created – in a rodent model – a
completely new way to engineer nerve structures, or constructs, in culture.
This proof-of-principle research has implications for eventually becoming a
new method to repair spinal cord injury in humans. The work appears in the
latest issue of Tissue Engineering.
“We have created a three-dimensional neural network, a mini nervous system
in culture, which can be transplanted en masse,” explains senior author
Douglas H. Smith, MD, Professor, Department of Neurosurgery and Director of
the Center for Brain Injury and Repair at Penn. Previously, Smith’s group
showed that they could grow 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.
In this study, the neurons were elongated to 10mm over seven days – after
which they were embedded in a collagen matrix (with growth factors), rolled
into a form resembling a jelly roll, and then implanted into a rat model of
spinal cord injury.
“That creates what we call a nervous-tissue construct,” says Smith. “We have
designed a geometrical arrangement that looks similar to the longitudinal
arrangement that the spinal cord had before it was damaged. The long bundles
of axons span two populations of neurons, and these neuron constructs can
grow axons in two directions – toward each other and into the host spinal
cord at each side. That way they can integrate and connect the ‘cables’ to
the host tissue in order to bridge a spinal cord lesion.”
After the four-week study period, the researchers found that the geometry of
the construct was maintained and that the neurons at both ends and all the
axons spanning these neurons survived transplantation. More importantly, the
axons at the ends of the construct adjacent to the host tissue did extend
through the collagen barrier, penetrating into the host tissue. Future
studies will measure neuronal electrical conductivity across the newly
engineered bridge and restoration of motor activity.
“The really great news – and there’s still much work to be done – is that
the construct survives and also integrates with host tissue,” says Smith.
“We find this very promising. In particular, this new technique provides a
means to bridge even very long spinal lesions that are common in humans with
spinal cord injury. Now we have to test whether the transplanted constructs
convey a signal all the way through, and we’re developing and testing a new
animal model to allow us to test whether this new technique improves
function.”
Study co-authors are Akira Iwata, Kevin D. Browne, Bryan J. Pfister, all
from Penn; and John A. Gruner, from Cephalon Inc., West Chester, PA. The
research was funded by the National Institutes of Health and the Sharpe
Trust.
This release and related images can be found at http://www.uphs.upenn.edu/news/
PENN Medicine is a $2.7 billion enterprise dedicated to the related missions
of medical education, biomedical research, and high-quality patient care.
PENN Medicine consists of the University of Pennsylvania School of Medicine
(founded in 1765 as the nation's first medical school) and the University of
Pennsylvania Health System.
Penn’s School of Medicine is ranked #2 in the nation for receipt of NIH
research funds; and ranked #4 in the nation in U.S. News & World Report’s
most recent ranking of top research-oriented medical schools. Supporting
1,400 fulltime faculty and 700 students, the School of Medicine is
recognized worldwide for its superior education and training of the next
generation of physician-scientists and leaders of academic medicine.
The University of Pennsylvania Health System comprises: its flagship
hospital, the Hospital of the University of Pennsylvania, consistently rated
one of the nation’s “Honor Roll” hospitals by U.S. News & World Report;
Pennsylvania Hospital, the nation's first hospital; Penn Presbyterian
Medical Center; a faculty practice plan; a primary-care provider network;
two multispecialty satellite facilities; and home health care and hospice.
Images Available:
http://www.uphs.upenn.edu/news/News_Releases/feb06/axonspnrpr_photo.htm
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