Decreased CCL5 expression in endometrial stromal cells induces deficient CCR5+CD4+ T cells in endometriosis

Abstract

Endometriosis (EMS) is a benign gynecological disease characterized by the growth of endometrial tissue outside the uterine cavity. Evidence shows that the survival of patients with ectopic endometrial implants is associated with a dysregulated immune microenvironment. CD4+ T cells can regulate EMS through diverse cytokines, the inflammatory response, and angiogenesis. CCR5+CD4+ T cells exhibit increased cellular immunogenicity and play a role in infectious diseases, host defense, and cancer progression. However, the specific mechanisms of CCR5+CD4+ T cells in EMS remain unknown. In the present study, flow cytometry and RNA-seq are utilized to assess the proportions and features of CCR5+CD4+ T cells in EMS patients, RT-PCR and ELISA are used to assess the production of CCL5 by ectopic endometrial stromal cells (ecESCs). Two EMS models are established through C57B6 wild-type and CCL5‒/‒ mice and utilized to explore the in vivo effects of CCR5+CD4+ T cells on ectopic lesions. Compared with CCR5‒CD4+ T cells, CCR5+CD4+ T cells display a more activated and cytotoxic phenotype. Diminished CCR5+CD4+ T cells and their impaired ability to produce IFN-γ are observed in the ectopic lesions of EMS patients and in murine EMS models. Impaired production of CCL5 has been detected in human ecESCs. Moreover, endometria stripped from CCL5‒/‒ mice are more likely to generate ectopic lesions in the peritoneum of recipient mice. These findings demonstrate that the attenuated recruitment of CCR5+CD4+ T cells in ectopic lesions caused by decreased production of CCL5 in ecESCs may facilitate the progression of EMS.

1. Introduction

Endometriosis (EMS) is a prevalent, chronic, and painful gynecological disease in which active endometrial tissue grows outside the uterine cavity. It affects approximately 15% of women and negatively impacts their quality of life (such as dysmenorrhea, dyspareunia, and chronic pelvic pain) [1‒3]. Available treatment options for EMS are limited, and the recurrence rate is alarmingly high [4]. Therefore, it is necessary to investigate the pathogenesis of EMS. Menstrual reflux is the most accepted theory used to explain the development of EMS. However, this hypothesis cannot fully explain the cause of EMS [5]. Other factors, such as stem cells, immunological factors, and epigenetics, might play a part in EMS development.

A disorganized local immune microenvironment is a pivotal promoter of EMS. The abnormal activation of T cells [6], weakened phagocytic ability of macrophages [7,8], and decreased cytotoxicity of NK cells [9] contribute to the growth of ectopic endometrial implants. Accumulating evidence has shown that systemic and local variations in CD4+ T cells are closely related to the pathogenesis and development of EMS [10‒12].

Some studies have shown that there is no significant difference in the proportion of CD4+ T cells in the peritoneal fluid between healthy women and EMS patients [13], whereas other studies have reported increased numbers of peritoneal CD4+ T cells among EMS patients [14,15]. Increased numbers of peritoneal Tregs, which can promote the growth and invasion of ectopic lesions via the induction of macrophage polarization and the production of profibrotic cytokines, are found in EMS patients [16,17]. Increased numbers of peritoneal Th17 cells in EMS patients secrete IL-17A, which promotes the inflammatory response and proliferation of ectopic endometrial stromal cells [18]. Peritoneal CD4+ T cells in EMS patients show Th2 predominance, and Th2 cells secrete IL-4 and IL-13 to promote fibrosis by mediating the differentiation of fibroblasts into myofibroblasts in ectopic lesions [19].

CCR5+CD4+ T cells are abundant in the endometrium, and CD38+HLA-DR+ CCR5+CD4+ T cells exhibit an immune-activating phenotype [20]. CCR5+CD4+ T cells can increase CD40L/CD40-mediated APC maturation and promote the activation of DCs and CD8+ T cells, thus playing an anti-tumor role [21]. However, whether CCR5+CD4+ T cells play a role in the development of EMS has not been studied.