BACKGROUND: Olfactory ensheathing cells (OECs) and bone marrow mesenchymal stem cells (BMSCs) repair the function of injured spine cord. Whether their combination can have better repair effect is unclear. OBJECTIVE: To investigate effects of OEC and BMSC transplantation for treating injured spine cord.DESIGN, TIME AND SETTING: The randomized control animal experiment was performed at the Linyi People’ s Hospital and Kunming Medical College from June 2006 to October 2007. MATERIALS: Healthy clean adult female Sprague Dawley rats with the body mass of 220-280 g were enrolled and divided into a normal control group (n=5), a OEC group (n=10), a BMSC group (n=10), a co-transplantation group (n=10) and a operation control group (n=10). METHODS: OECs and BMSCs were harvested from the olfactory bulb and femoral bone. Animal models of complete spinal cord injury were established by cutting rat spinal cord. Rats in the normal control group only received vertebral plate unfolding, but no spinal cord transaction. Rats in the OEC group, BMSC group and co-transplantation group were respectively injected with OECs, BMSCs and their combination at the broken ends and proximal and distal ends. Using three points injection, the injection depth was separately 0.5 mm, 1.0 mm and 1.5 mm. Rats in the operation control group only received medium following spinal cord transaction. MAIN OUTCOME MEASURES: OECs and MSCs were co-cultured after being digested. Cells were identified by P75 and BrdU immunofluorenscence. Spinal cord functional recovery was assessed, and pathological changes and cell survival were observed after transplantation. RESULTS: One proportion of co-cultured cells wove into net with their processes linking. The other proportion grew like strip-shaped. OECs were identified on the cell membrane (green fluorescence) and on the cell core (red fluorescence), whereas BMSCs were identified on the cell core (red fluorescence) without cell membrane (green fluorescence). Spinal cord function was improved in rats treated with OECs and BMSCs. Four weeks later, the spinal cord function was better in the co-transplantation group compared to the OEC and BMSC groups. Pathology observation showed that spinal cord structure was severely destroyed in the operation control group, showing a mass of cavitates and pericaryon atrophy, surrounded by many cavitates and tissue fluids; cell number became small; nerve fibers arranged disordered. Following OEC and BMSC transplantation, spinal cord structure was still severely damaged, but cavitas area was small, with many cells; nerve cells arranged orderly. Under a fluorescent microscope, many cell nuclei stained red at the injured spinal cord, and many positive cells were seen at the proximal and distal ends of the injured spinal cord. OECs and BMSCs were both found in the co-transplantation group, but cells were disordered, no significant arrangement or significant movement. CONCLUSION: OECs and BMSCs are co-cultured well in vitro for repairing spinal cord injury. Their combination obtains a better outcome compared to OECs or BMSCs alone.