Neurotrophic and growth factor gene expression profiling of mouse bone marrow stromal cells induced by ischemic brain extracts

Treatment of rodents after stroke with bone marrow stromal cells (BMSCs) improves functional outcome. However, the mechanisms underlying this benefit have not been ascertained. This study focused on the contribution of neurotrophic and growth factors produced by BMSCs to therapeutic benefit. Rats were subjected to middle cerebral artery occlusion and the ischemic brain extract supernatant was collected to prepare the conditioned medium. The counterpart normal brain extract from non‐ischemic rats was employed as the experimental control. Using microarray assay, we measured the changes of the neurotrophin associated gene expression profile in BMSCs cultured in different media. Furthermore, real‐time RT‐PCR and fluorescent immunocytochemistry were utilized to validate the gene changes. The morphology of BMSCs, cultured in the ischemic brain‐conditioned medium for 12 h, was dramatically altered from a polygonal and flat appearance to a fibroblast‐like long and thin cell appearance, compared to those in the normal brain‐conditioned medium and the serum replacement medium. Forty‐four neurotrophin‐associated genes in BMSCs were identified by microarray assay under all three culture media. Twelve out of the 44 genes (7 neurotrophic and growth factor genes, 5 receptor genes) increased in BMSCs cultured in the ischemic brain‐conditioned medium compared to the normal brain‐conditioned medium. Real time RT‐PCR and immunocytochemistry validated that the ischemic brain‐conditioned medium significantly increased 6/7 neurotrophic and growth factor genes, compared with the normal brain‐conditioned medium. These six genes consisted of fibroblast growth factor 2, insulin‐like growth factor 1, vascular endothelial growth factor A, nerve growth factor beta, brain‐derived neurotrophic factor and epidermal growth factor. Our results indicate that transplanted BMSCs may work as ‘small molecular factories’ by secreting neurotrophins, growth factors and other supportive substances after stroke, which may produce therapeutic benefits in the ischemic brain.