Interestingly, in the E2 plus P4-treated lesions there was a significant reduction in uterine cell proliferation (KI67), perimeters of supporting blood vessels as well as expression of CD31 (an endothelial cell marker also known as PECAM-1) and CCN1/Cyr61, a critical angiogenic regulator in pathogenesis of endometriosis [39]. Here, CCN1 is linked to endometriosis.