PTGS2 and Infertility: On the other hand, increased COX2 expression involves with inflammation and COX2-derived prostaglandin E2 (PGE2) biosynthesis contributes to EMS-related pain and infertility (1, 13), while increased MMP1 expression is involved with tissue degradation, menstrual bleeding, and invasion of seeded endometriotic explants (14, 15).