Progesterone Enhances Angiogenesis And Improves Neural Regeneration In Aged TBI Rats

Backgraound and Objective:It is difficult to treat the secondary cerebral edema and inflammative cascade response secondary to the traumatic brain injury (TBI). The progesterone was reported to be able to relieve the edema, remove the inflammative substance and then improve the outcome and prognosis of the TBI. To observe the effect of progesterone on both the EPCs based angiogenesis of the injured cerebral tissue and the neurofunction restoration in the aged TBI rats. However, it has not been reported whether the progesterone induce angiogenesis in TBI. Thus, we set up the aged TBI rats to investigate if the progesterone improves both angiogenesis in the injured brain and neural function restoration.Methods:81 male aged (20-month) Wistar rats were randomly divided into sham-operated group(27 Sham Group), traumatic brain injury with DMSO-treated group (27 TBI+DMSO Group) and TBI with progesterone group (27 TBI+PR Group). The TBI model was established by the fluid percussion injury, to injury the brain over the right parietal lobe.. 1h post-TBI, progesterone and DMSO were administered intra-peritoneally at a dose of 16mg/kg(PR) and with the corresponding volumne to PR (DMSO) respectively. Then, both were daily injected subcutaneously for 14 days. 1ml whole blood was collected in EDTA tubes from retro-orbital venous plexus by glass capillary before and 3hour, 1, 7, 14, 21 days after TBI, then CD34+/CD133+ EPCs were measured in flow cytometric analysis. The mNSS was used to evaluated functional recovery at 1, 7, 14, 21 days after TBI .At the same time, The expression of both vascular endothelial marker CD34 and vWF in brain was measured with immunofluorescence staining on 7th day. Both the morris water maze and the long term potential were applied to investigate the memory recovery and the memory/learning ability retlated function at 21-25 days post-TBI.Results:1.Evaluation of angiogenesis: Compared to the sham group, the number of peripheral blood EPCs in both TBI+PR and the TBI+DMSO groups were reduced significantly(p<0.05) at 3 hours post-TBI. 3 days later, the EPCs level increased. However, the level of circulating EPCs in TBI+DMSO group gradually dropped to normal range, the one in TBI+PR group continued to increase to peak at 7 days after TBI and retained at a higher level than the normal one until 14 days post-TBI. Statistical analysis showed that the number of the circulating EPCs in TBI+PR group was significantly higher than the one in both TBI+DMSO and the SHAM group 3,7,14 days post-TBI (p<0.05). It was suggested that progesterone promote the mobilization of circulating EPCs after TBI. The CD34+ cells in the injury brain tissues and DG areas were observed to increase steadily in both DMSO-treated and progesterone-treated TBI rats when compared with the one from the sham-injured rats(p<0.05). However, the CD34+ cells in the progesterone treating injured brain was most significantly than the one in the DMSO treated TBI rats (p<0.05). The counting of the microvessel density (MVD) in the injured zone around the damaged brain tissues has shown similar result. It suggested that progesterone promote the angiogenesis in the damage zone and the ipsilateral hippocampus.2.Functional assessment of behavior: The mNSS was performed to assay the neuro-function status of the TBI rats to reveal that the progesterone-treated rats scored lower than the DMSO-treated ones at 7,14, and 21 days after TBI(p<0.05).3.Assessment of spatial learning ability:Water maze test showed that the ability of learning and memory of SHAM group gradually getting better,but there are obvious learning and memory impairment in rats after TBI. The time spent in correct quadrant of TBI+PR group was significant higher than that of TBI+DMSO group.The spatial learning ability was significantly improved in progesterone-treated rats at the 22,23,24 and 25 days after TBI (p<0.05), compared with the DMSO-treated rats.Conclusion:Progesterone improve the mobilization of endothelial progenitor cells(EPCs) of rats after TBI. These datas suggest that progesterone treatment augments TBI-induced angiogenesis, thereby leading to restoration of cognitive function after TBI in rats.