BACKGROUND:Endothelin has been found to be involved in the breakdown of the blood-spinal cord barrier after spinal cord injury,and stem cell-derived exosomes can reduce the permeability of the blood-spinal cord barrier and repair spinal cord injury. OBJECTIVE:To investigate whether exosomes produced by human umbilical cord mesenchymal stem cells can reduce the permeability of the blood-spinal cord barrier by inhibiting endothelin-1 expression,thus repairing spinal cord injury. METHODS:Exosomes were extracted from the cultured supernatant by the hyperspeed centrifugation method.The morphology of exosomes was observed by transmission electron microscope.The expression levels of tsg101 and CD63 were detected by western blot assay.Eighty SD rats were randomly divided into sham operation group,model group,exosome group,and endothelin-1 group(n=20).The modified Allen's method was used to create the rat model of spinal cord injury.In the endothelin-1 group,10 μL(1 μg/mL)endothelin-1 was injected directly into the injured area with a microsyringe.Immediately,1 day,2 days after operation,sham operation group and model group were injected with 200 μL PBS solution through the tail vein;the exosome group and endothelin-1 group were injected with 200 μL exosome(200 μg/mL)solution through the tail vein,respectively.Hind limb motor function scores were performed on days 1,3,7,14 and 21 after spinal cord injury.The blood-spinal cord barrier permeability was observed by Evans blue staining on day 7 after injury.The expression levels of tight junction proteins β-Catenin,ZO-1,Occludin and endothelin-1 in the spinal cord were detected by western blot assay. RESULTS AND CONCLUSION:(1)Basso-Beattie-Bresnahan score in the exosome group was significantly higher than that in the model group at 3-21 days after injury(P<0.05).Hematoxylin-eosin staining showed that spinal cord injury was greatly reduced in the exosome group compared with the model group.Basso-Beattie-Bresnahan score in the endothelin-1 group was significantly decreased compared with the exosome group(P<0.05).Spinal cord injury was more severe in the endothelin-1 group than that in the exosome group.(2)The expression of endothelin-1 in the model group was significantly increased compared with the sham operation group(P<0.05),and the expression of endothelin-1 in the exosome group was significantly decreased compared with the model group(P<0.05).(3)The blood-spinal cord barrier Evans blue exudate in the exosome group was significantly decreased compared with the model group(P<0.05).The expression levels of the tight junction proteins β-Catenin,Occludin and ZO-1 in the exosome group were increased(P<0.05);the Evans blue exudate in the endothelin-1 group was significantly increased compared with the exosome group(P<0.05).The expression level of tight junction protein was significantly decreased compared with the exosome group(P<0.05).(4)The results show that human umbilical cord mesenchymal cell-derived exosomes protect the permeability of the blood-spinal cord barrier by down-regulating the expression of endothelin-1 and play a role in the repair of spinal cord injury.

Objective:To discuss the influence of high load and weightlessness environment on intervertebral disc by observing and analyzing the imaging changes of the spines in New Zealand white rabbits and the content changes of matrix metalloproteinase (MMP) and tissue inhibitor of metalloproteinase (TIMP) in the intervertebral disc under high load and weightlessness environment, and to provide theoretical basis for prevention and delay of lumbar intervertebral disc degeneration under high load and weightlessness environment.Methods:A total of 120 New Zealand white rabbits with balanced age and body weight were randomly and averagely divided into control groups (further grouped by 30 d, 60 d and 90 d) and high load/weightlessness groups (further grouped by 30 d, 60 d and 90 d) with residual single-blind method. High load was simulated by animal centrifuge and weightlessness was simulated by tail suspension. The imaging changes and the positive expression rates of MMP1, MMP3 and TIMP1 in intervertebral disc were detected, and the statistical differences between the high load/weightlessness group and the control group in different time periods were compared, as well as among the different exposure time in load/weightlessness groups.Results:From the imaging observation, the T2-weighted images of lumbar 6 sacral 1 intervertebral disc in experimental animals decreased to some extent. The positive rates of MMP1 and MMP3 in each high load/weightlessness group were higher than those in the control group for the same exposure time, and the differences were statistically significant ( t=22.97-145.51,all P<0.001). The positive rates of MMP1 and MMP3 increased with the extension of exposure time, and there were statistically differences among the groups with different exposure time in high load/weightlessness group ( F=2531.10, 1758.80, both P<0.001). The positive rate of TIMP1 in each high load/weightlessness group was higher than that in the control group for the same exposure time, and the difference was statistically significant ( t=29.34-65.05, all P<0.001). There was statistically difference on TIMP1 positive rate among different load/weightlessness exposure time groups ( F=462.20, P<0.001). Conclusions:High load/weightlessness can cause the MMP1, MMP3 and TIMP1 content changes in animal lumbar disc. The changes of TIMP1 are obvious in the early stage and the sensitivity is decreased in the late stage. High load/weightlessness may lead to changes in the contents of MMP and TIMP in intervertebral discs, which may accelerate intervertebral disc degeneration.

Objective:To discuss the influence of high load and weightlessness environment on intervertebral disc by observing and analyzing the imaging changes of the spines in New Zealand white rabbits and the content changes of matrix metalloproteinase (MMP) and tissue inhibitor of metalloproteinase (TIMP) in the intervertebral disc under high load and weightlessness environment, and to provide theoretical basis for prevention and delay of lumbar intervertebral disc degeneration under high load and weightlessness environment.Methods:A total of 120 New Zealand white rabbits with balanced age and body weight were randomly and averagely divided into control groups (further grouped by 30 d, 60 d and 90 d) and high load/weightlessness groups (further grouped by 30 d, 60 d and 90 d) with residual single-blind method. High load was simulated by animal centrifuge and weightlessness was simulated by tail suspension. The imaging changes and the positive expression rates of MMP1, MMP3 and TIMP1 in intervertebral disc were detected, and the statistical differences between the high load/weightlessness group and the control group in different time periods were compared, as well as among the different exposure time in load/weightlessness groups.Results:From the imaging observation, the T2-weighted images of lumbar 6 sacral 1 intervertebral disc in experimental animals decreased to some extent. The positive rates of MMP1 and MMP3 in each high load/weightlessness group were higher than those in the control group for the same exposure time, and the differences were statistically significant ( t=22.97-145.51,all P<0.001). The positive rates of MMP1 and MMP3 increased with the extension of exposure time, and there were statistically differences among the groups with different exposure time in high load/weightlessness group ( F=2531.10, 1758.80, both P<0.001). The positive rate of TIMP1 in each high load/weightlessness group was higher than that in the control group for the same exposure time, and the difference was statistically significant ( t=29.34-65.05, all P<0.001). There was statistically difference on TIMP1 positive rate among different load/weightlessness exposure time groups ( F=462.20, P<0.001). Conclusions:High load/weightlessness can cause the MMP1, MMP3 and TIMP1 content changes in animal lumbar disc. The changes of TIMP1 are obvious in the early stage and the sensitivity is decreased in the late stage. High load/weightlessness may lead to changes in the contents of MMP and TIMP in intervertebral discs, which may accelerate intervertebral disc degeneration.

Objective:To investigate the impact of the CD4+CD25nt/hiCD127lo regulatory T cell subset frequency on the immune status and disease progression of Chinese HIV-1 infected individuals.Methods:83 untreated HIV-infected individuals and 312 healthy control individuals of four distinct age groups were enrolled in the research. The CD4+ T cell absolute counts, phenotypes and frequency determination of CD4+CD25nt/hiCD127lo Regulatory T cell subsets was performed on freshly obtained whole blood samples by 3-color immune staining flow cytometry. The HIV-1 specific cellular immune function was test at single cell level by ELISpot. The corresponding plasma viral load was determined by NASBA.Results:The frequency of peripheral CD4+CD25nt/hiCD127lo regulatory T cells of HIV infected individuals in distinct disease progression status was dissimilar in China , and significantly increased in contrast to the healthy controls(P