Chondroitin sulfate (CS) is the most abundant
glycosaminoglycan species in the human endometrium, but the expression profile of CS
proteoglycans (PGs) in this mucosal tissue remains fully undetermined. In this study, we aimed to clarify the expression of CSPGs including
aggrecan,
neurocan,
melanoma-associated CSPG, neuroglycan C, and
brevican in the human cycling endometrium. By reverse transcription-polymerase chain reaction, the gene transcripts for
aggrecan core
protein were detected in all samples examined, while other CSPGs were not. Western blotting showed the immunoreactivity for
aggrecan core
protein at approximately 370 kDa size after enzymatic digestion of CS-A and CS-C side chains. The expression level of
aggrecan core
protein was significantly higher in the secretory phase than in the proliferative phase. The immunostaining for
aggrecan was detected in the endometrial microvascular endothelium throughout the menstrual cycle. The immunostaining in the glandular epithelium was faint during the proliferative and early secretory phase, but distinct during the mid-to-late-secretory phase.
Progesterone, but not 17β-estradiol, induced
aggrecan core
protein expression in cultured endometrial epithelial cells. The endometrial expression pattern of
aggrecan was distinct from that of other known CSPGs, suggesting the unique role of this
proteoglycan at the implantation site.