VOLUME 11, NUMBER 1
JUNE, 1985
SVM Researcher Studies Regeneration
Research Provides Clues to Spinal Cord Trauma and Fracture Healing
Have you ever wondered why some animals can regenerate a limb or a tail, while
others cannot? Or what the specific
mechanisms are which prevent most paraplegics from regaining full use of their
legs?
Richard B. Borgens, Ph.D., has been pondering these questions since childhood,
and is now studying them on a full-time
basis at the Purdue University School of
Veterinary Medicine.
Dr. Borgens investigates the role of the
natural flow of electricity common in all
developing and regenerating tissues, finding clues to the nature of wound-healing
and tissue regeneration, as well as embryonic development and cell differentiation.
Wounds of any sort produce an electrical
field adjacent to the lesion, and a weak,
steady flow of electric current out of the
wound, Dr. Borgens said. For example,
when the limb of a salamander is amputated, Dr. Borgens, and others, have
fuund and measuied an electrical cuneni
leaving the stump and returning to the
undamaged portions of the limb and
body. This current steadily declines until
disappearing upon the appearance of new
limb growth.
Whereas the amputation of an adult salamander's limb may initiate limb regeneration, Borgens' research indicates that a
developmentally programmed "wound"
may initiate limb generation in salamander larvae. Upon finding a small increase
in current along the flank of a larva, Dr.
Borgens has been able to pinpoint the location at which a limb bud will form.
In salamanders, according to Dr. Borgens,
skin is the electromotive force which
drives electric current out of the regenerating limb stump or out of presumptive
limb regions and developing buds. Indeed, if a skin flap is sewn over the face
of the limb stump, limb regeneration is
inhibited.
Among chordates, regenerative ability is
thought to have reached its peak in the
tailed amphibians, such as salamanders.
However,   Dr.   Borgens   has found  that
mice can regrow the tip of a foretoe when
it has been amputated distal to the last
joint. And, in humans, especially children, regrowth of the tips of fingers has
been reported after accidental amputation. If the finger is severed somewhere
between the last joint and nail, a nearly
perfect replacement may regrow within a
few months, often complete with nail and
fingerprint. However, the attending physician must not sew the finger closed, for
if closed, no regrowth will occur.
The natural flow of current, similar in
most respects to that leaving salamander
limb stumps, has been measured leaving
the finger stumps of children and foretoe
studied certain regrowth mechanisms in
the lamprey, a small, primitive vertebrate
with giant neurons. Upon transection of
its spinal cord, a lamprey has the natural
ability to eventually regenerate neurons
across the lesion, restoring its ability to
swim. However, Dr. Borgens has found
that a weak, steady electrical current imposed across the severed spinal cord
speeds the regeneration of neurons up to
and across the lesion.
In addition to laboratory animal models,
working in the Veterinary Medical School
may provide Dr. Borgens the opportunity
to study spontaneously-occurring spinal
injuries in small companion animals.   Es-
Ongoing research in Dr. Borgens' lab tests whether an applied electrical field can Induce substantial amounts of nerve regeneration within the mammalian spinal cord.
stumps of mice. In addition, Dr. Borgens
said the regeneration of amphibian limbs
and the regrowth of the mammalian digits
share at least two other similarities. First,
the level of amputation is critical. Second, a skinflap sewn over the stump inhibits both the regeneration of amphibian
limbs and the regrowth of human fingertips.
"But we're not in the business just to
grow limbs back on animals and people,"
Dr. Borgens said.    Dr. Borgens has also
pecially common in basset hounds and
dachshunds, these injuries could provide
information needed to further understand
spinal injuries in humans. Dr. Borgens is
now involved in the next step: applying
electric current to the spinal cord of small
laboratory mammals to try to initiate regeneration. So far, Dr. Borgens said, the
results are promising.
Outgrowths of other's electrophysiologic
research include the clinical use of electricity to speed regeneration of various tis-
A surgically implanted battery imposes an
electrical field across a hemisected guinea
pig spinal cord.
sues in animals and humans. For example, adhesive bandages and casts with
built-in electrodes are presently being
tested. In addition, electricity is sometimes used to help treat persons with
chronic non-union bone fractures. If several bone grafts or pins fail to produce
union, then sometimes a portion of the
limb must be amputated. However, two
different types of electrical stimulating
devices, both approved by the U. S. Food
and Drug Administration, are now increasing the success rate in such cases.
Dr. Borgens has found that bone is an
electrically dynamic tissue, driving a
steady electric current into the site of injury after a fracture. According to Dr.
Borgens, the healing potential of artificially applied electric current probably resides in its action on the natural electrical
mechanisms already present in growing
and healing bone.
A Texan, Dr. Borgens received the doctorate in developmental biology and biophysics in 1976 from Purdue under the
direction of embryologist, Lionel F.
Jaffe. Before returning to Purdue in
1982, Dr. Borgens worked in laboratories
on both the east and west coasts.
Laura L. Voss, M.A.
-
.
^
*
A regenerating neuron within a transected guinea pig spinal cord.   The spear shaped
ending with a tuft is called the growth cone.
Search For New Dean Begins
Dean Jack Stockton has announced his intention to
retire as dean in December of this year. President
Beering has appointed a Search Committee to recommend candidates for the deanship. Members of the
Search Committee are Drs. William Blevins, Gerald
Bottoms, John Fessler, Kenneth Meyer, Ralph Richardson, David Van Sickle, John Van Vleet, all representing the School; Vice President Struther Arnott,
Graduate School; Professor William Fuller, University
Senate; Dean Bernard Liska, Agriculture; Ms. Lynda
Rhodes, 3rd year student; and Dr. Robert Ferguson,
alumnus.
The committee has been meeting regularly and has begun to shorten the long list
of potential candidates. Your comments to the committee will be welcomed at any
time.