Role of hyaluronan in endometrial receptivity: key insights for implantation and reproductive success.

Infertility affects millions worldwide, and implantation failure remains a critical barrier in assisted reproduction. Endometrial receptivity, a fundamental prerequisite for successful implantation, involves precise regulation of extracellular matrix components, with hyaluronan (HA) being particularly significant due to its structural and signaling roles. This study evaluated the expression of genes involved in HA metabolism and regulation across different phases of the menstrual cycle, particularly emphasizing their role during the window of implantation in normal fertility and repeated in vitro fertilization failures. Analysis of publicly available transcriptomic datasets revealed distinct expression patterns of HA synthases (HAS2, HAS3), HA-degrading enzymes (HYAL2, CEMIP, CEMIP2), and HA receptors (CD44, RHAMM, layilin) in endometrium that dynamically change toward the receptive state. Notably, HAS enzymes and HA receptors were upregulated during the mid-secretory phase, whereas classical HA-degrading enzymes showed complex regulation, suggesting a balance between HA synthesis and degradation necessary for optimal endometrial function. In patients with repeated IVF failure, there was significant downregulation of key HA-related genes (HAS2, HAS3, CEMIP, CD44, versican, syndecans), implicating impaired HA metabolism in implantation failure. The results underscore the role of HA metabolism and HA receptors in establishing a receptive endometrial environment, highlighting HA and its associated pathways as potential therapeutic targets to enhance reproductive success rates. Further research is necessary to unravel the detailed molecular mechanisms of HA-mediated regulation and its translational implications for assisted reproduction technologies.