The Initial Study Of Exosomes In The Pathogenesis Of Plasma Cell Mastitis

Background:Plasma cell mastitis(PCM)is a rare benign breast disease,characterized by limitless mass forming in the nonlactational breast.Clinically,plasma cell mastitis,granulomatous lobular mastitis,and non-specific mastitis are thought to be a different period of one disease.PCM is a pathological diagnostic and the main diagnostic factors of PCM were dilated ducts and abundant inflammatory cell infiltrate,including plenty of plasma cells.Its clinical importance lies in the fact that the clinical presentations are not specific and are easily confused with breast carcinoma in imaging manifestations.Surgical resection,usually an extended excision,is typically made for PCM and can reduce the rate of recur.Although in this comparatively drastic way,there is still recur reports and the rate were almost 28%.Such a begin disease leads to an excision of their breast,likening breast cancer.Unquestionable,it comes at a high cost.Not only that,the incidence of PCM kept increasing in recent years.Therefore,it is particularly important to study the etiology of PCM.The etiology of PCM remains unclear.There are many different hypotheses about PCM,for example,bacterial infection or autoimmune disease and so on some articles indicated that overweight or obesity and later onset of menarche may the risk factors for PCM.On the other hand,one of the major predisposing factors is obstructed lactiferous duct,furthermore,it is nipple retraction that is the most common reason.Besides,smoking is thought to be one of the main predisposing factors for PCM because of ductal damage.What's more,some chronic diseases,such as diabetes mellitus,prolactinoma,psychological problem,or rheumatoid arthritis were also be reported to be found in PCM patientsIn this study,we summarized the etiologies reported in the literature that may be associated with plasma cell mastitis and observed the proportion of these indicators in our patients.What's more,through transmission electron microscopy,we finished the first observation of submicroscopic structure of PCM,and found that the exosomes were highly expressed in PCM.At the meantime,RNA gene sequencing around outside secrete body work,at the same time for differences in gene,we through immunohistochemical method to detect the expression of MMP9,MMP15,MMP24,in plasma cell mastitis,acute mastitis,and non-pathological breast tissue,and analyzes each index expression differences in three groupsMethod:Data regarding patients with the histologic diagnosis of PCM from January 2013 to August 2018 were obtained from the computer database at the Department of Pathology,Binzhou Medical University Hospital,Shandong,China.The basic information of the corresponding patients including age,personal history,marriage and child history,family history and so on was collected at the admission to hospital.At the same time,10 tissue specimens of acute mastitis(AM)patients and 10 tissue specimens of non-pathological(NP)breast tissue were selected as the control group.Through transmission electron microscopy,we observed the submicroscopic structure of plasma cell mastitis tissue for the first time.At the meantime,we found that there were more exosomes in the intercellular space than the normal group.We extracted the exosomes and made the RNA-Seq.According to the results of RNA-Seq,total differentially expressed genes were screened one by one through GO categories,KEGG database,and PPI network.And we found some different expressed gens,between PCM and NP.Finally,we detected the expression of these differentially expressed proteins by immunohistochemistry.Result:Obesity and nipple reaction have been considered as significant risk factors for this disease in previous studies.Our result meets the previous studies.However,active smoking and passive smoking have a low percentage in our patients.The different conclusion may be caused by the low smoking rate of women in China.The result of RNA-seq:A total of 2978 DEGs including 2397 up-regulated genes and 581 down-regulated genes were screened.The main pathways in PCM were cAMP signaling pathway,Calcium signaling pathway,Oxytocin signaling pathway,cGMP-PKG signaling pathway,PI3K-Akt signaling pathway.The PPI network showed that mTOR?HSP90AA1?EEF2?MMP9?MMP15 and MMP24 showed a higher expression in PCM.Immunohistochemical resultsThe MMP15 immunoreactivity was significantly higher in neutrophils and plasma cells in PCM than in AM and NP(P<0.05,for both).MMP9 was significantly higher in neutrophils and plasma cells in PCM than in NP(P<0.05),however,there was no statistical significance of MMP9 immunoreactivity between the PCM group and AM group(P>0.05),and MMP9 and MMP24 showed no statistically significant difference between the plasma and non-pathological tissues(P>0.05).As for the result of MMP24,there were no statistical significance neither PCM and AM(P>0.05)or PCM and Non-pathological(P>0.05).Conclusion:Overweight or obesity and nipple retraction are the risk factors for plasma cell mastitis.The basilar membrane of ductal epithelial cells in PCM patients was severely damaged,and there were fewer gap junctions and Mosaic junctions than normal tissues.The secretion of exosomes is increased in plasma cell mastitis.Meanwhile,MMP15 is highly expressed in plasma cell mastitis.We speculate that MMP15 is involved in the disease progression of plasma cell mastitis through the ability of degrading extracellular matrix,comparing with neutrophils and plasma cells when homing to the glandular epithelium.