[Overwork Affects Extracellular Matrix of Arterial Vessel Wall in Rats]

Objective To explore the effect of overwork (OW) on extracellular matrix of arterial vessel wall in rats. Methods Random number grouping method was employed to assign 18 Sprague-Dawley rats into three groups(n=6):the control group(no special treatment),group OW(forced swimming twice a day for 15 days),and sleep deficiency(SD)+OW group(in addition to forced swimming twice a day,the rats were put on the platforms in water to limit sleep for 15 days).On the 16th day,the abdominal aorta and common carotid artery were collected after blood sampling from heart under deep anesthesia.A part of the abdominal aorta sample was taken for Masson staining of collagen fiber,and Verhoeff-Van Gieson staining was carried out for the elastic fiber of common carotid artery.Image J was employed for the quantitative analysis of collagen fiber and elastic fiber content.The expression of collagen 1(Col-1) protein was quantified by immunohistochemistry and the ultrastructure of vascular matrix was examined by transmission electron microscopy.The other part of the abdominal aorta sample was used to determine the mRNA levels of matrix metalloproteinase(MMP)-1,MMP-2,MMP-9,tissue inhibitor of metalloproteinases-1(TIMP-1),and Col-1 by quantitative real-time polymerase chain reaction. Results Compared with that in control group,the content of collagen fiber in groups OW and SD+OW had no significant change(all P>0.05);the content of elastic fiber in groups OW and SD+OW decreased(all P<0.001) and had no significant difference between each other(P>0.05).The vascular vessel wall of group OW showed slight fiber breakage,while that of group SD+OW presented wormhole-like or spongy fiber fragmentation.The mRNA levels of MMP-1 and MMP-2 in groups OW and SD+OW had no significant difference between each other(P>0.05) but were higher than that in control group(all P<0.001).The mRNA levels of MMP-9 and TIMP-1 had no significant difference among the three groups(all P>0.05).Groups OW and SD+OW had lower mRNA level(all P<0.001) and protein level(all P<0.001) of Col-1 than control group,while the mRNA and protein levels of Col-1 had no significant difference between groups OW and SD+OW(P>0.05). Conclusion OW can reduce the content of Col-1 and elastic fibers in the extracellular matrix of arterial vessels,destroy the elastic lamina of vascular wall,up-regulate the expression of MMP-1 and MMP-2,thereby injuring arterial vessels.