| Objective: A variety of methods of psychological stress were applied to stimulate the rats,A control study on the blank control group and psychological stress group was carried out through the observation on the histological change in condyle of rats and the changes in MMP-13 and TIMP-1 inside the condyle from the blank control group and psychological stress group,the data results were collated,added up and analyzed in order to explore the influence of psychological stress on the temporomandibular joint.Method:1Laboratory animal: 42 healthy-and-clean-grade Wistar rats,weighing 200g±20g,provided by Laboratory Animal Center of Hebei Medical University.2 Stimulating method: Stimulation time was accordingly two weeks,four weeks and six weeks,the random-number method was applied to randomly arrange the seven kinds of method for each week,the stress treatment was performed in each morning,one stimulation for each day,same kind of stimulation was not allowed to appear continuously,so as to prevent the rats from foreseeing the stimulation.The seven stimulating methods are respectively:(1)binding for an hour;(2)flushing for an hour;(3)food deprivation for 24 hours;(4)one-hour use of e-mouse repeller;(5)soaking in water for an hour;(6)water deprivation for 24 hours;(7)wet padding for 24 hours.3 Experimental method: 42 rats were randomly divided into two groups,21 rats for blank control group,21 rats for psychological stress group,each group was then divided into three subgroups based on the experimental duration,namely,two-week,four-week and six-week subgroup with 7 rats in each subgroup.The weight of rats in each group had been tested by equilibrium test and confirmed to be indiscriminate.And the rats in each group were separately fed under identical feeding condition and environment.Each group of rats was placed into the feeding box prior to the experiment to allow them to get used to the environment,during which,no stimulation was applied to them.After the experiment began,no stimulation was applied to the blank control group,while the stimulation was applied to the psychological stress group according to the stimulating method,each group of rats was respectively put to death according to the duration of 2 weeks,4 weeks and 6 weeks when the experiment has been finished,then samples were taken for HE staining and immunohistochemical staining.4 Research method: HE staining and immunohistochemical staining was equally performed on the blank control group and psychological stress group,the histological change in the condyle of the rats was displayed by HE staining,the content of MMP-13 and TIMP-1 in the condyle was measured by immunohistochemical staining.The influence of psychological stress on temporomandibular joint was studied through the changes in the two abovementioned aspects.5 Statistical method: The measured data of each index was statistically analyzed with SPSS21.0 software,the measurement results of MMP-13 was statistically analyzed with rank sum test,the measurement results of TIMP-1 was statistically analyzed with variance analysis,and the test level was set at P < 0.05.Result:1 The histological change in condyle: the surface of condylar cartilage of the control group was neat and smooth,the cartilage layer had a regular arrangement,no fibrosis was found,and the bone trabecula was normal.Regarding the two-week experimental group,the surface of condylar cartilage was slightly rough,the cartilage layer developed a fibrosis,the collagen fiber of the surface band was degenerated,its developing direction was unclear,which presents a diffuse and structureless homogeneous matter.Regarding the four-week experimental group,the surface of condylar cartilage was clearly rough,the cartilage matrix dissolved,the osteocyte disappeared,the bone lacuna was empty,the bone trabecula had a tiny irregular crack,even disintegration,to which the adjacent marrow cavities were fused.Regarding the six-week experimental group,a reparative response had been developed,the surface of condylar cartilage was slightly rough,the cartilage layer developed a slight fibrosis,the collagen fiber of the surface band was slightly degenerated,the osteocyte disappeared occasionally.2 The immunohistochemical testing result of MMP-13 in the condyle: a pairwise comparison of MMP-13 positive cells count was conducted between the control group,two-week subgroup,four-week subgroup and six-week subgroup of the experimental group.The MMP-13 positive cells count of control group compared with that of two-week subgroup of the experimental group was statistically significant(P﹤0.05),the MMP-13 positive cells count of control group compared with that of four-week subgroup of the experimental group was statistically significant(P﹤0.05),the MMP-13 positive cells count of two-week subgroup compared with that of four-week subgroup was statistically significant(P<0.05),the MMP-13 positive cells count of four-week group compared with that of six-week subgroup was statistically significant(P<0.05),the MMP-13 positive cells count of control group compared with that of six-week subgroup of the experimental group was not statistically significant(P>0.05),the MMP-13 positive cells count of two-week subgroup compared with that of six-week subgroup was not statistically significant(P>0.05).3 The immunohistochemical testing result of TIMP-1 in the condyle: a pairwise comparison of TIMP-1 positive cells count was conducted between the control group,two-week subgroup,four-week subgroup and six-week subgroup of the experimental group.The TIMP-1 positive cells count of control group compared with that of two-week subgroup of the experimental group was statistically significant(P<0.05),the TIMP-1 positive cells count of control group compared with that of four-week subgroup of the experimental group was statistically significant(P<0.05),the TIMP-1 positive cells count of two-week subgroup compared with that of four-week subgroup was statistically significant(P<0.05),the TIMP-1 positive cells count of four-week group compared with that of six-week subgroup was statistically significant(P<0.05),the TIMP-1 positive cells count of control group compared with that of six-week subgroup of the experimental group was not statistically significant(P>0.05),the TIMP-1 positive cells count of two-week subgroup compared with that of six-week subgroup was not statistically significant(P>0.05).Conclusion:1 The psychological stress can induce pathological change of rat condylar,and with the psychological stress time prolongation,the pathological change of rat condylar become more serious within 4weeks.2 The psychological stress can induce pathological change of rat condylar,and with the psychological stress time prolongation,the pathological change of rat condylar become more serious,But afterwards(4 weeks later),the condyle will be repaired to some extent.3 MMP-13 and TIMP-1 may be involved in the process of development of pathological change in the condylar tissue of rats under a condition of psychological stress. |
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