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Neural tissue transplantation.

The January 1996 column reviewed promising new drug treatments for acute spinal-cord injury (SCI). This month we will review another exciting research strategy--treating SCI by transplanting neural tissue directly into the site of injury. Although still in experimental stages, this strategy may yet be fruitful in bringing about effective new therapies.

OBJECTIVES

The science of organ and tissue transplantation has advanced remarkably in the past 30 years. Transplanting a human heart used to make news around the world, but today the operation is almost routine and barely receives notice in the local paper.

The successes continue--liver, lung, bone marrow, and kidney transplants prolong many lives. Tissue transplantation is increasingly common. Physicians use skin grafts to treat serious burns or pressure sores, muscle or tendon transplants to treat various movement disorders, and fat transplants for cosmetic purposes in plastic surgery.

Achieving functional recovery after SCI by transplanting neural tissue, however, remains a complex challenge. Physicians and scientists pursue their intense efforts, and effective neural transplantation could bring immense benefits to people with neural injury.

Researchers have narrowed the broad goal of achieving recovery into more specific objectives:

* Physical or functional replacement of dead or injured cells with newly transplanted ones

* Reduction of damage caused by secondary injury processes

* Reduction of scarring at the injury site

* Introduction of additional support cells

* Introduction and formation of a physical or functional "bridge" between the disconnected ends of traumatically cut tissue

RESEARCH IN ANIMAL MODELS

Research studies analyzing the effect of neural transplants in animals following SCI have achieved the following promising results:

* Transplants can help save immature damaged nerve cells from dying.

* Transplants can support axon growth into and through the injury site.

* Transplants can promote limited motor recovery. Some animals with transplants perform better than those with SCI and no transplant but not as well as noninjured animals.

* Newborn-rats receiving transplants usually show better recovery than adults.

The amount of cell-to-cell connectivity is greater in newborn animals: Extensions of the host spinal cord (axons) can grow through the transplant to reach spinal-cord tissue on the other side. Dr. Barbara S. Bregman and colleagues of Georgetown University School of Medicine refer to this transplant function as a "bridge." In adult rats, this type of growth does not occur. However, in adult animals transplants can receive axons from the host neurons and send out axons to the host. Dr. Bregman calls this a "relay" function. Scientists hope they will be able to isolate the factors that contribute to the better growth in newborns and find ways to enhance the regrowth that does occur in adult animals.

This research provides encouraging evidence that it may he possible to use neuronal transplants to treat neural-system dysfunctions. Will this strategy be tested in people with SCI? Most scientists involved in neural transplantation are hopeful that someday this procedure will be ready for evaluation in people with SCI. Most are also quick to caution, however, that this day is not yet here.
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Title Annotation:for spinal cord injury treatment
Author:Chanaud, Cheryl M.
Publication:PN - Paraplegia News
Date:Jul 1, 1996
Words:493
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