| Chlamydia trachomatis genital tract infection is the most common cause of sexually transmitted bacterial diseases.The infections are often chronic and occult,and some can rise to the upper genital tract and cause pathological damage,resulting in tubal fibrosis and hydrosalpinx,eventually leading to ectopic pregnancy and infertility.In addition,clinical and animal model studies have reported that there are individual differences in the course and outcome of chlamydial infections.Chlamydiae can be quickly perceived and triggered by host cells.However,moderate inflammation is beneficial to host defense against chlamydial infection,while excessive inflammation can cause histopathological damage.Inflammatory response induced by Chlamydia trachomatis infection is the basis of its pathogenesis.The infiltration of acute and chronic inflammatory cells such as neutrophils in local tissues is closely related to genital tract injury and inflammation.Inflammatory mediators such as IL-1β and TNF-α play an important role in this process.Immunopathological damage caused by chronic chlamydia infection is also the most difficult problem in vaccine development.Progranulin(PGRN),a multifunctional secretory growth factor,is widely expressed in nerve tissue,bone tissue,reproductive tract and other organs and tissues.Studies have shown that PGRN plays an important regulatory role in acute and chronic inflammatory diseases such as rheumatoid arthritis,inflammatory bowel disease.Recent studies have shown that PGRN plays an important protective role in acute infectious diseases.However,little is known about its role in the process of chronic infectious diseases,especially its effect and mechanism on immunopathology.Therefore,the purpose of this study is to investigate the role of PGRN in chlamydial genital tract infection,especially in the chronic inflammatory pathological damage of upper genital tract.Part I:Expression characteristics of PGRN in chlamydial genital tract infection of mice with different susceptibilitiesObjective To compare the expression characteristics of PGRN in Chlamydia genital tract infection of mice with different genetic background,and explore the relationship between PGRN and inflammatory pathological damage caused by genital tract infection.Methods C57BL/6(C57)mice and C3H/HeN(C3H)mice with different susceptibility to chlamydial infection were inoculated intravaginally with Chlamydia muridarum(C.muridarum),and then the general condition and C.muridarum burden in the secretions of genital tract were assessed.The pathological changes of genital tract were compared between the two groups by gross examination and microscopic analysis.At different time points after infection,the expression of pro-inflammatory cytokines IL-1β,TNF-a and IL-6 protein in vaginal secretions and mRNA level in upper genital tract tissues were detected by ELISA and real-time quantitative PCR,respectively.Meanwhile,the expression of PGRN protein in vaginal secretions and the mRNA level in upper genital tract of two kinds of mice were detected.Results C3H mice showed higher chlamydial loads in vaginal secretions and delayed clearance of infection.Since the day 14 postinfection,C3H mice had more inflammatory cells infiltration in fallopian tube tissue,and the expressions of inflammatory cytokines IL-1β and TNF-α in vaginal secretions and upper genital tract tissues of C3H mice increased significantly compared with those of C57mice.At day 56 postinfection,C3H mice had a higher incidence rate of hydrosalpinx and a higher degree of dilatation.The expression of PGRN in vaginal secretions and upper genital tract tissues of the two strains of mice increased significantly in the early stage of infection,and gradually decreased with the chronic disease.From 14 to 56 days after infection,the level of PGRN in C3H mice was lower than that in C57 mice.The expression of PGRN was negatively correlated with the pathological inflammatoryscore and dilation score of fallopian tube in both groups,but more significantly in C3H mice.Conclusions C3H mice were susceptible to chlamydial genital tract infection because of delayed clearance of infection and more severe upper genital tract pathological damage.C.muridarum genital tract infection induce the expression of PGRN in local tissues and then decreases with the chronic course of disease.The expression level of PGRN is negatively correlated with the pathological damage of salpingitis,suggesting that PGRN may have potential protective effect in chlamydial genital tract infection.Part II:The role of PGRN in C.muridarum genital tract infectionObjective To clarify the role of PGRN in C.muridarum genital tract infection.Methods PGRN knockout(KO)mice and wild type C57 mice were intravaginally inoculated with C.muridarum.The bacteria burden in genital tract secretion were detected at different time points.The histopathological changes of genital tract tissues were compared between the two groups by gross examination and microscopic analysis.The expressions of IL-1β,TNF-α and IL-6 protein in vaginal secretions and the mRNA level of these cytokines in upper genital tract tissues were detected by ELISA and real-time quantitative PCR,respectively.After preparing mouse peritoneal macrophages and establishing C.muridarum cell infection model in vitro,the expression of inflammatory cytokines was determined in C.muridarum-infected macrophages with or without exogenous recombinant PGRN treatment.Results Gross examination and microscopic analysis showed that PGRN KO mice developed more serious disease,especially the higher incidence rate of hydrosalpinx and more serious degree of dilatation than those of wild type mice,and inflammatory cell infiltration was also more serious.However,there was no significant difference in C.muridarum loads between PGRN KO mice and wild type mice.The expressions of IL-1β,TNF-αand IL-6 in vaginal secretions and upper genital tract tissues of PGRN KO mice were significantly higher than those of wild type mice.The expressions of IL-1β,TNF-a and IL-6 were significantly lower in C.muridarum-infected macrophage with exogenous recombinant PGRN treatment.Conclusions The absence of PGRN aggravated the inflammatory pathological change of the upper genital tract tissues in mice,but have no significant effect on the chlamydial burden following C.muridarum genital tract infection.PGRN can alleviate tubal inflammatory lesions by inhibiting the secretion of proinflammatory cytokines.This study reported for the first time that PGRN has protective effect on the tubal inflammatory lesions caused by C.muridarum genital tract infection.It provided a new idea and experimental basis for the prevention and treatment of diseases caused by chlamydial genital tract infection. |
