Catechins down-regulate p-NF-κB p65-mediated inflammation in the uterus and inhibit MMP2 and MMP9-mediated endometrial damage, which improves uterine function in PCOS mice, and the inhibition of STAT3 signaling and up-regulation of IRS1/PI3K expression by catechins may play a key role on insulin resistance and uterine function in PCOS mice. Here, MMP9 is linked to polycystic ovary syndrome.