Hyaluronan in the bovine oviduct—modulation of synthases and receptors during the estrous cycle

The extracellular matrix (ECM) component hyaluronan (HA) is considered to contribute to the optimal development of the gametes and the embryo. In this study, the regulation and localization of HA, its synthases (HAS 1–3) and the receptors CD44, RHAMM, and putative HARE were investigated in bovine oviducts during the estrous cycle. HA could be demonstrated in the entire lamina propria of the oviduct. Immunoreactive CD44 was found in the muscle layer additionally to the lamina propria. As for HA the luminal epithelium was devoid of CD44. Introducing quantitative real-time RT–PCR, a remarkable cyclic change of CD44 occurred. In addition, CD44 expression was much higher in the isthmus than in the ampulla. RHAMM transcripts were elevated particularly in the ampulla during estrus. A major part of the bovine putative HARE coding sequence was characterized. An analysis of the tissue distribution revealed transcripts not restricted to liver, spleen, and lymph node, providing evidence for a local putative HARE-mediated turnover of HA. These results suggest that in the bovine oviduct the cell surface receptor CD44 in particular might inversely regulate HA during the estrous cycle. The local turnover of HA through synthases and receptors may indicate its participation in the bovine oviduct supporting gamete maturation and early embryonic development.