SDF-1α Induces Angiogenesis After Traumatic Brain Injury

BackgroundTraumatic brain injury (TBI) is one of the most important global public health problem. About100million people around the world are hospitalized or dead of TBI, and more than570million people world wide have been hospitalized with one or more TBI[1]. Despite the research progression of pathophysiological mechanism after TBI and the treatment strategies on TBI animal models, the effective clinical therapy is still limited. The previous research of TBI therapies focused more on the neurogenesis, but less on the angiogenesis after the initial injury. The angiogenesis and neurogenesis after TBI are co-regulated. Neurovascular niche, a unit that include neuron and microvessel draw more and more researchers’ attention. The angiogenesis promoting strategies after TBI may be a promising field for TBI treatment.ObjectiveTo evaluated the angiogenesis and also the local brain tissue expression of CD34、 CXCR4mRNA and protein after rhSDF-1α treatment in TBI animal model.To evaluated the angiogenesis and also the local brain tissue expression of CD34、 CXCR4mRNA and protein after SDF-1α neutralizing antibody treatment in TBI animal model.To evaluate the correlation of angiogenesis and neurological outcome in different treatment groups.MethodsYouth male Wistar rats received fluid percussion and were divided into3groups, the rhSDF-1α treated group, the SDF-1α neutralizing antibody treated group and the normal saline treated group.30minutes after TBI, the rhSDF-1α group received stereotactic cortical injection of rhSDF-1α4μg/4μl, the SDF-1α neutralizing antibody group received stereotactic cortical injection of SDF-1α neutralizing antibody4μg/4μl, the controlled group received stereotactic cortical injection of normal saline4μl. Modified neurological severity score (mNSS) was used to evaluate the neurological functional outcome before trauma and1,3,7,14and21days post trauma. The Morris water maze was used to evaluate the special learning memory deficit14days after injury. Flow cytometry was used to analyze the peripheral CD34+cells1,3,7,14days after injury. The brain tissues were harvest from the3groups14days post injury for histological and molecular biological assessment. The immunochemistry and immunofluorescence staining were used to assess the CD34positive microvessel density (MVD) and CD34/CXCR4double positive microvessels. Quantitative real time polymerase chain reaction (qRT-PCR) and western blot were used to assess the mRNA and protein expression of CD34and CXCR4. The role of SDF-1/CXCR4axis in angiogenesis was evaluated and the correlation of angiogenesis and neurological outcome was also assessed.ResultsNo significant differences of the number of peripheral blood CD34+cells were observed among the three different treated groups by flow cytometry analysis. The histology staining results showed that the MVD and CD34/CXCR4double positive mivrovessels of the rhSDF-1α treated group increased significantly, whereas, decreased in the SDF-1α neutralizing antibody treated group compared with that of normal saline treated group (P<0.05). The results of qRT-PCR and western blot demonstrated that the expression of mRNA and protein of CD34and CXCR4in injured tissue increased compared to that of normal saline treated animals, however, in SDF-1α neutralizing antibody treated animals, the mRNA and protein expression of CD34and CXCR4decreased compared to that of normal saline treated animals (P <0.05). All of the3group animals displayed low mNSS before injury, but high mNSS lday post injury. The mNSS result indicated that the fluid percussion induced neurological dysfunction to the rats. The mNSS decreased dramatically in the subsequent evaluation days, demonstrating that there was a neurological recovery process after injury. The neurological outcome of rhSDF-1α treated group was better that of SDF-1α neutralizing antibody treated group (P<0.01) or normal saline treated group (P<0.05)14and21days after injury. The mNSS of SDF-la neutralizing antibody treated group had no significant difference compared to that of normal saline treated animals in14days after injury (P>0.05). However, the mNSS of neutralizing antibody treated group was worse than that of normal saline treated animals (P<0.05). The Morris water maze (MWM) was used to assess the special learning memory ability after injury. The latency of the3groups animals were similar at the beginning of the test, but decreased in the subsequent special acquisition test (P<0.001) This indicated that the special learning memory was established. The rhSDF-1α treated animals had shorter latency compared to that of normal saline treated group, whereas, the SDF-1α antibody treated group had longer latency compared to that of normal saline treated group (P<0.05). In the probe trial, the rhSDF-1α treated animals spend more time in the target quadrant, in the contrary, the SDF-1α neutralizing antibody treated animals spend less time in the target quadrant compared to that of the normal saline treated animals (P<0.05). The swimming speed of the3groups rats had no significant differences demonstrated that the special learning deficit was not due to the injury induced limb impairment. The Spearman rank correlation coefficient test showed that there was a significant negative correlation between mNSS and MVD14days after TBI in the3differently treated groups.ConclusionLocal distribution of rhSDF-1α after TBI could enhance the migration of CD34+cells to the injured site, increase the expression of mRNA and protein of CD34and CXCR4, promote angiogenesis, ameliorate neurological outcome via SDF-1/CXCR4axis.Local distribution of SDF-1α neutralizing antibody after TBI could suppress the migration of CD34+cells to the injured site, decrease the expression of mRNA and protein of CD34and CXCR4, inhibit angiogenesis, exacerbate neurological outcome via blocking SDF-1/CXCR4axis.SDF-1/CXCR4axis may be a new promising therapeutic target for TBI.