Hyaluronan is another critical component of the ECM, and the enzymes for hyaluronan synthesis, hyaluronan synthase HAS1, HAS2 and HAS3, were also highly expressed in the endometrium of women with adenomyosis (P = 0.016, P = 0.049 and P = 0.015, respectively) without changes in their receptor, CD44, a cell-surface glycoprotein involved in cell–cell interactions, cell adhesion and migration (FIGURE 3D). Here, HAS3 is linked to adenomyosis.