Interactions Between the Breast Tissue Microbiota and Host Gene Regulation in Nonpuerperal Mastitis

Abstract

Background: Nonpuerperal mastitis (NPM) causes considerable psychological distress in females, since it is difficult to diagnose and treat. A spectrum of etiological factors, ranging from infection to autoimmune disorders, can lead to NPM. However, the pathogenesis of NPM remains unclear. Here, we aimed to dissect the role of host gene-microbe interactions in NPM. Methods: We performed 16S rRNA sequencing to characterize the breast tissue microbiome and identify bacteria that were differentially abundant between NPM patients and controls. We also performed 16S rRNA sequencing to characterize the gut microbiome and identify gut microbes with different abundances between NPM patients and healthy controls. Moreover, we investigated whether the breast tissue microbiome was associated with an altered gut microbiome in patients with NPM. We analyzed differentially expressed genes in inflammatory tissues of mammary gland from patients with NPM and normal mammary gland tissues from patients with benign and non-infectious breast disease by RNA-sequencing (RNA-seq). The landscape of infiltrating immune cell subtypes in the breast tissue immune microenvironment was analyzed using CIBERSORT, based on the gene expression profiling of breast tissues. Lastly, we modeled associations of relative abundances of specific bacterial taxa with differential expression of immune-related genes and differences in infiltrating immune cells. Results: The composition and functions of the breast tissue microbiota communities differed between NPM patients and controls. The breast tissue shared a relatively small proportion of bacterial communities with the gut in patients with NPM. The relative abundance of Ruminococcus (family Ruminococcaceae) of breast tissue was positively correlated with the differentially expression of immune-related genes between NPM patients and controls, including antigen processing and presentation genes (ICAM1, LGMN, THBS1, TAP1, HSPA1B and HSPA1A), cytokine receptor gene IL15RA, and chemokine gene CCN1. The relative abundances of Rhizobium of breast tissue was negatively correlated with the differentially expression of the antigen processing and presentation gene HSPA6 between NPM patients and controls. We also found that the relative abundance of Ruminococcus (family Ruminococcaceae), Coprococcus, and Clostridium of breast tissue positively correlated with the difference of CD8+ T cells between NPM patients and controls. The relative abundance of Ruminococcus (family Ruminococcaceae) of breast tissue positively correlated with resting memory CD4+ T cells. The relative abundance of Leucobacter of breast tissue negatively correlated with CD8+ T cells. The relative abundance of Caulobacter of breast tissue positively correlated with activated memory CD4+ T cells. Conclusions: Our results explored the potential role of host-microbe interactions in the etiology of NPM. We demonstrate cross-talk between the breast tissue microbiome and the gut microbiome in patients with NPM. We suggest that NPM microbiome composition influences the immune microenvironment and natural history of the disease by affecting the transcriptome, which merits further study. Funding Information: This study was supported by the Youth Science Fund Project of Jiangxi Provincial Department of Science and Technology (20192BAB215037), the Science and Technology Project of Education Department of Jiangxi Province (GJJ180057) and the Science and Technology Project of Education Department of Jiangxi Province (GJJ180056). Declaration of Interests: The authors declare that they have no competing interests. Ethics Approval Statement: The study was approved by the Ethics Committee of the First Affiliated Hospital of Nanchang University (Nanchang, China), and informed consent was obtained from all subjects.