gms | German Medical Science

Objective: After spinal cord injury (SCI), primary and secondary damage occur due to several endogenous processes including inflammation and the development of a glial scar, which inhibit axonal reconnection from supralesional structures and lead to misrouting of nerve fibers. So far many different approaches have been tried to boost regeneration, including enhancing or decreasing endogenous processes, the injection of cells and the use of polymeric devices in mice after SCI. We are introducing a new technique with a tissue graft (1 mm³), extracted from the subventricular zone (SVZ) with neurogenic stem cells (NSC), to give neurons an orientation matrix to grow in a specific direction. Through the use of green fluorescent protein (GFP) expressing mice under the β-actin promoter as donor mice, we can easily distinguish donor from host neurons and cells, thus being able to study their role in the regulation of endogenous regenerative processes.

Methods: 20 C57 black6 mice underwent SCI at the Th7 level as described by the Michael Schwarz group, receiving either SVZ grafts or cortex grafts, from mice expressing GFP under the β-actin promoter. Motor impairment and functional regeneration were measured with the Basso Mouse scale (BMS). After 14 days the mice were sacrificed and 20μm sections cut on a cryostat. Using immunhistochemical techniques the survival of the grafted cells, axonal regrowth, newly established connections and the size of the glial scar was counted and measured.

Results: We found GFP expressing neurons, astrocytes and blood vessels in and around the lesion scar. Some axons extend over the scar growing into the caudal spinal column. In the control group, we could distinguish astrocytes and blood vessels, but only seldom neurons. Behavioral tests showed a slightly better outcome of the experimental group, which was not statistically significant. The BMS showed a slightly better outcome of the experimental group, which was not statistically significant. Through the stable expression of GFP in the transplants we are perfectly able to distinguish host cells from implanted cells.

Conclusions: We hope to find a new way to overcome some of the detrimentally effects of SCI und gain entirely new insights into regeneration after SCI. We present a new technique that allows the stable monitoring of the fate of a transplanted tissue graft, derived from the SVZ with NSC, allowing us now to further study the role of this tissue graft in the regulation of endogenous regenerative processes.