The effects of bone marrow stromal cells (BMSCs) on the repair of injured spinal cord and on the behavioral improvement were studied in the rat. The spinal cord was injured by contusion using a weight-drop at the level of T8-9, and the BMSCs from the bone marrow of the same strain were infused into the cerebrospinal fluid (CSF) through the 4th ventricle. BMSCs were conveyed through the CSF to the spinal cord, where most BMSCs attached to the spinal surface although a few invaded the lesion. The BBB score was higher, and the cavity volume was smaller in the rats with transplantation than in the control rats. Transplanted cells gradually decreased in number and disappeared from the spinal cord 3 weeks after injection. The medium supplemented by CSF (250 microl in 3 ml medium) harvested from the rats in which BMSCs had been injected 2 days previously promoted the neurosphere cells to adhere to the culture dish and to spread into the periphery. These results suggest that BMSCs can exert effects by producing some trophic factors into the CSF or by contacting with host spinal tissues on the reduction of cavities and on the improvement of behavioral function in the rat. Considering that BMSCs can be used for autologous transplantation, and that the CSF infusion of transplants imposes a minimal burden on patients, the results of the present study are important and promising for the clinical use of BMSCs in spinal cord injury treatment.

Reconstruction of a severed mammalian spinal cord with restoration of function has so far not been achieved, although structural and functional restitution after spinal transection has been successful in some lower vertebrates. In quail-chick and chick-chick chimaeras, spinal cord segments were found to be functional after replacement by isotopic and isochronic grafting of the neural tube. Here we achieve such a replacement in neonatal rats under less restricted topological and temporal conditions than were necessary for the avian chimaeras. The replaced segments united with the host spinal cord and promoted robust growth and regrowth of axons across the graft, enabling neural connections to be reconstructed that were hardly distinguishable from normal. The animals with replaced segments could walk, run and climb with almost normal hind-forelimb coordination. This functional restoration in these animals appeared to be permanent, raising the possibility of therapeutic application in humans.

It is possible to insert a screw safely, even into the narrow isthmus with a high-riding vertebral artery, if the surgeon realizes where the screw should be inserted and has the requisite insertion technique. Bilateral screw fixation should provide a high fusion rate.

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