Exosomes Play an Important Role in the Progression of Plasma Cell Mastitis Via the PI3K-Akt-mTOR Signaling Pathway

Abstract

Background: Plasma cell mastitis (PCM) is one of the most frequently encountered inflammatory diseases of the non-lactating breast. However, its pathogenesis has remained unknown and few efforts have focused on investigating the transcriptional changes during PCM. Methods: In this study, we analyzed the distributions of age and other risk factors about PCM, and we observed the ultrastructure changes of PCM by transmission electron microscope. The transcriptome expression difference of exosomes extracted from normal (N/exo) and PCM tissues (PCM/exo), were detected by RNA-Seq, then we confirmed the key difference genes by western blot and immunohistochemistry. Finally, we established the mouse PCM model by tissue homogenate injection to validate the role of exosomes on the progression of PCM. Findings: In this study we analysised the distributions of age and other risk factors for PCM. The most frequent age of onset in the studied population was 30-39 years (65.0%) and 45% of PCM patients accompanied nipple or breast dysplasia. There were more exosomes were found in the synaptic cleft of PCM by TEM. Analysis of the transcriptome expression difference of PCM/exo and N/exo using RNA Seq showed that Rap1 signaling pathway, cAMP signaling pathway, Calcium signaling pathway, Oxytocin signaling pathway, cGMP-PKG signaling pathway and PI3K-Akt signaling pathway were involved in the course of PCM. In addition, other factors were also found to be involved, such as the decreased HSP90AA1and EEF2, excessive production of p-AKT and p-mTOR which were consistent with clinical specimens. We also found that inhibition of exosomes secretion significantly inhibited inflammatory cell infiltration and the mammary duct had maintained a better structure in PCM mouse model. Interpretation: Our results revealed the role of exosomes acting as critical signal transduction facilitators in the progression of plasma cell mastitis and identified potential key genes in the regulation of this process. These results will help to dissect the molecular mechanism of PCM and provide therapeutic targets. Funding Statement: This work was supported by National Natural Science Foundation of China (NO.81173601), Natural Science Foundation of Shandong Province (NO.ZR2017LH072 and NO.ZR2017MH033), Projects of Binzhou technology development program (NO.2015ZC0301), Scientific Research Staring Foundation of Binzhou Medical University (NO.BY2014KYQD36,NO.BY2014KJ36 and NO.BY2017KJ01). Declaration of Interests: The authors declare that no conflicts of interest exist with regard to this manuscript. Ethics Approval Statement: The study was conducted in accordance with the guidelines in the Declaration of Helsinki and it has been approved by the Medical Research Ethics Committee of Binzhou Medical University Hospital (Approval No. 2018-020-01).