Toll-Like Receptor 4 Gene Knockout Increases the Function of Exogenous Bone Marrow Stem Cells in Ischemic Brain

Abstract

The present study was to investigate the effects of toll-like receptor 4 on transplanted bone marrow stem cells in the ischemic brain. Focal cerebral ischemia was induced by permanent occlusion of middle cerebral artery in toll-like receptor 4 gene knockout mice and wild type control mice. Bone marrow stem cells were injected into lateral cerebral ventricle. The cylinder tests, in vivo image, polymerase chain reaction array, etc. were applied to evaluate the neurological function and the underlying mechanisms. On the 10th d after permanent occlusion of middle cerebral artery, the ratio of right limb movement in group 1 was significantly higher than that in wild type and toll-like receptor 4 gene knockout mice without injection of bone marrow stem cells (p<0.05). In vivo imaging showed that on the 3rd d after injection of bone marrow stem cells, the fluorescence intensities in group 3 and group 1 were significantly enhanced compared with that on the 1st d and 7th d. There were more green fluorescent protein positive cells in group 3 and group 1 compared with sham controls (p<0.05). Amount of green fluorescent protein positive cells in group 1 was significantly higher compared with group 3. In toll-like receptor 4 gene knockout mice, bone morphogenetic protein 2 messenger ribonucleic acid and fibroblast growth factor 9 messenger ribonucleic acid were up-regulated and interleukin-1-beta protein was decreased, compared with wild type mice. The present study firstly demonstrated that toll-like receptor 4 deficiency further increased the amount of intracerebroventricularly injected bone marrow stem cells in ischemic brain areas, thereby improved neurological function after focal cerebral infarction. The increased expression of bone morphogenetic protein 2 and fibroblast growth factor 9 in the environment of toll-like receptor 4 deficiency might be one of the molecular mechanisms.