Implantable microsystem for the adaptation of the spinal cord after paraplegia

Status:

completed 04/2010

Aims:

- Enhancement of lately developed biochemical methods by a surgical procedure for the adaptation of the injured spinal cord structures towards an entire concept of the treatment after paraplegia.
- Development of a biocompatible microsystem ("chip") which allows directed growing of axons and a mechanical connection of the tissue structures as well as targeted drug delivery to the connection area.

Activities/Methods:

- Producing of a connecting element based on microsystem technologies which consists of microstructures with numerous parallel tubes as well as additional transverse canals.
- Development of a moulding method for bioabsorbable materials which permits an accurate moulding of the microstructures. The implants are tested in animal experiments on rats.
- Histologic and behavioral investigations to proof the function of the system.
- Development of potential clinical application procedures together with the establishment of a valid surgical methodology.

Results:

After spinal cord injury (SCI) neuronal structures form sprouts in an attempt to regenerate. Concomitantly, the release of inhibitory factors prevents any further regenerative axon growth. Both the expression of inhibitory molecules as well as scar formation can be influenced on a molecular basis to provide a possible cure for spinal cord injury, a goal which appeared out of reach in the past. There is a lack of possibilities of mechanical adaption of the severed spinal cord in the submillimeter range. Therefore, our long-term research objective is the adaption of injured spinal cord tissue stumps via an implantable biodegradable microsystem, which was developed in a collaboration of the BG Trauma Center Hamburg and the institute of Microsystems Technology of the Technical University Hamburg-Harburg. The device is further intended to promote regenerative axon growth and improve motor and sensory function after SCI.
In this project, a protocol for the standardized implantation of the mechanical microsystem (mMS) into the partially or completely transected rat spinal cord was developed. The surgical setup with integrated pressure measurement allows optimal control of the applied negative pressure used for the suction of the spinal cord stumps. Two weeks after mMS implantation a tissue bridge has formed in the mMS lumen, which contains numerous axons. Both descending (motor) and ascending (sensory) axon fibers grow into the implant. mMS implantation does not have any noticeable negative side effects on the rats' motor function. Moreover, motor function improvement of implanted animals could be detected and was more prominent than in transection-only controls. Based on the results of our recent animal experiments the adaptation of the spinal cord stumps via implantation of the highly innovative mechanical microsystem represents a promising strategy for the development of a visionary curative treatment of patients suffering from traumatic spinal cord injury. With its integrated delivery channels the novel micromechanical system further holds the additional possibility for combinatory treatment strategies with pharmacological agents. For the Berufsgenossenschaften as the provider of the centers for injuries of the spinal column and spinal cord this subject is of particular importance, especially in regard to the alleviation of the suffering of affected patients by any appropriate means.

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