The adult "paraplegic" rat: treatment with cell grafting

Spinal cord injury often results in irreversible and permanent neurologic deficits below the lesion level. Nowadays, treatment is limited to drugs and/or physiotherapy aimed at compensating disability. New experimental studies focus on the transplantation of cells capable of surviving, regenerating tissue, recovering functions and/or improving symptoms. A review of such type of studies on spinal cord reconstruction published between 1991 and 2004 is presented. In the latter years, cell transplantation appeared as the most promising approach in spinal cord regeneration research. To date, this promise has not been maintained, despite the appearance of new attractive cell populations for grafting, such as neural stem cells. The demonstration that stem cells exist in the adult brain and that they can be isolated and expanded in vitro offers the possibility to test such interesting cells in the paraplegic rat. Some neurotrophic factors can facilitate axonal regeneration and neuronal survival. Therefore, the development of strategies, such as implanting neural stem cells engineered to secrete neurotrophic factors directly in the lesion site, could be important to promote regeneration in the injured spinal cord. Despite all the strategies used till now, the problem of the paraplegic rat remains. Only the solution of such problem will authorize studies in higher mammals and, finally, the clinical application in human patients. The paraplegic adult rat with a T8 spinal cord transection should be considered the standard experimental model to be used in spinal cord reconstruction studies. Function and anatomic results are undisputed only after spinal cord transection.