Abstract: Objective To observe the effect of bone marrow stromal cells (BMSCs) transplantation on expression of COX-2 mRNA in rats following spinal cord injury. Methods BMSCs were isolated and secondarily cultured. Male Wistar rats were randomly divided into sham-operated group (group A, n=18), DMEM group (group B, n=27), and BMSCs group (group C, n=27). Rats in groups B and C were injected with BMSCs and DMEM after spinal cord injury. Expression of COX-2 mRNA and distribution of COX-2 protein in rat spinal cord tissue were detected by RT-PCR with immunofluorescence staining. Results The expression level of COX- 2 mRNA was lower in group A than in groups B and C, and significantly higher in group C than in group B after BMSCs transplantation (P＜ 0.01). Immunofluorescence staining showed that the COX-2 was expressed only in spinal cord blood vessels of group A and mainly expressed in spinal cord blood vessels and in a small number of neurons in ventral gray matter of groups B and C. Conclusion BMSCstransplantation can up-regulate the expression of COX-2 mRNA in rats after spinal cord injury.