METTL14/YTHDF2 m6A Axis Protects Against M2 Macrophage Polarization in Endometriosis by Regulating KLF4 Stability.

Endometriosis (EMs) is a chronic inflammatory disorder featured by infertility and pain. The role of N6-methyladenosine (m6A) in EMs has been evidenced. This study investigated the molecular mechanism of METTL14-m6A-KLF4 modulating macrophage polarization in EMs. RT-qPCR assay was conducted to test METTL14 levels in tissues and cells and the relative mRNA levels of M2 (Arg-1, Fizz1) and M1 (iNOS, IL-1β) factors in the supernatant after co-culture of macrophages with normal endometrial stromal cells (nESCs) or ectopic endometrial stromal cells (eESCs). CD206 and CD86 expression, as well as Arg-1, IL-10, and IL-4 levels, were assessed. Meanwhile, the relationship between METTL14 and the m6A modification of KLF4 was analyzed. Additionally, the effect of KLF4-activated M2 macrophages on in vitro ESC progression was observed. Cellular and tissue METTL14 was under-expressed in EMs. METTL14 expression might be related to macrophage M2 polarization. Co-culture of eESCs overexpressing METTL14 and macrophages downregulated Arg-1, Fizz1, CD206, IL-10, and IL-4 levels. Mechanistically, METTL14 could mediate KLF4 m6A modification through the m6A reading protein YTHDF2. KLF4 overexpression could nullify METTL14 re-expression-repressed M2 macrophage polarization. In addition, KLF4-activated M2 macrophages accelerated the proliferation and migration of ESCs in vitro. METTL14-m6A-KLF4 regulated macrophage polarization in EMs.