Role of SAA1 in endometrial extracellular matrix remodeling in polycystic ovary syndrome: implication for pregnancy loss

Abstract Context Abnormal endometrial extracellular matrix (ECM) remodeling compromises endometrial receptivity and diminishes the probability of a successful live birth. Serum amyloid A1 (SAA1), a modulator of inflammation, is elevated in the circulation of polycystic ovary syndrome (PCOS) patients and involved in ECM remodeling during tissue repair. However, the specific role of SAA1 in endometrial ECM remodeling and subsequent risk of pregnancy loss in PCOS patients remains unclear. Objective To examine the role and underlying mechanism of SAA1 in ECM remodeling in the endometrium of PCOS patients. Design Serum samples from PCOS and control patients were utilized to investigate the relationship between the abundance of SAA1 and pregnancy loss. Human endometrial tissues and primary human endometrial stromal cells were used to examine the role and underlying mechanism of SAA1 in ECM remodeling. Results Serum SAA1 concentration was elevated and could serve as an independent risk of pregnancy loss in PCOS patients. Increased SAA1 abundance was also observed in endometrium obtained from these patients. Further mechanistic studies showed that SAA1 stimulated collagen I chains synthesis (COL1A1 and COL1A2) in endometrial stromal cells, suggesting excessive SAA1 may contribute to endometrial ECM remodeling, resulting in a non-supportive environment for ongoing pregnancy. This effect was abolished by either a toll-like receptors 2/4 antagonist or a nuclear factor κB inhibitor. Conclusions The locally elevated levels of SAA1 in endometrium contribute to ECM over-deposition by inducing collagen I synthesis in PCOS patients, which may hamper embryo implantation and increase the risk of pregnancy loss. These observations highlight the crucial role of heightened SAA1 in orchestrating endometrial dysfunction and shed light on potential therapeutic avenues for improving reproductive outcomes in PCOS patients.