PolySia: A new bioidentical structural substance  
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Polysialic acid:
A new scaffold material for nerve transplants

As part of the glycocalyx, sialic acid is an "acidic sugar" that is responsible for the negative ionisation of all animal cells. The term polysialic acid (PolySia) defines the polymerisation product of this sugar. It only occurs on few surface molecules of the nervous system. The most important carrier of PolySia is the neural cell adhesion molecule NCAM. It is found on neurons and sheath cells socalled oligodendroglia. PolySia is strongly expressed during the course of embryonic development. However, in adults the peripheral nervous system is almost free of this sugar. After nerve injury PolySia is transiently re-expressed particularly on Schwann cells that surround nerves. Numerous studies showed that PolySia expression supports regeneration of the nervous system. Impressive here are the transfection studies that demonstrate that cells, which constitutively express PolySia significantly accelerate nerve regeneration.

Regeneration correlates directly with injury severity in peripheral nerves. If the injury is mild, i.e. the gap between proximal and distal nerve stumps is small, spontaneous regeneration occurs. If the injury is more severe the injured nerves must be neurosurgically bridged. Today this is usually done using autologous nerve transplants that are taken beforehand from healthy nerves of the affected person. Aside from the additional risk of surgery, this procedure can be problematic for the patient, because only limited nerves are available for autotransplantation. Nerves that have to be extensively reconstructed may only be able to be partially restored. Therefore, especially for the treatment of large lesions alternative transplant material is necessary.

DFG Research Unit 548 has the goal to produce PolySia, which has been optimised by nature, in large scale. In addition, the aim is to use it in its natural or chemically modified form to generate biohybrid nerve transplants. Aside from unlimited availability, these transplants have the advantage that they could be specifically dissolved using PolySia-degrading enzymes after the nerves have been reconstructed. This would make repeated surgery unnecessary.

Seven task forces from the Medical School of the Leibniz University and the German Institute of Rubber Technology have been working in close cooperation in the interdisciplinary Research Unit 548 since 2004. Goals are the large-scale generation of PolySia, its chemical and biotechnological modification, the generation of PolySia-nanofibers and nanofleeces, and the testing of these materials in vitro and in vivo. Funds were granted in 2008 by the DFG for another 3 years.




DFG Research Unit 548
Polysialic Acid:
A new bioidentical structural substance


Prof. Dr. Rita Gerardy-Schahn
Medizinische Hochschule Hannover
Institut für Zelluläre Chemie



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