Hyaluronan-CD44 Signalling Contributes to Gap Junction Closure and LH Receptor Expression During In Vitro Maturation...

Area of Science:

• Reproductive Biology
• Cellular Biology
• Biochemistry

Background:

• Meiotic resumption in mammals is triggered by luteinizing hormone (LH).
• Gap junctional communication disruption is an early event, halting cyclic adenosine monophosphate (cAMP) supply from cumulus cells to the oocyte.
• Cumulus expansion involves hyaluronan-rich matrix formation, crucial for oocyte maturation, but its regulatory mechanism is unclear.

Purpose of the Study:

• To investigate the role of hyaluronan in regulating gap junction closure during oocyte maturation.
• To test the hypothesis that hyaluronan contributes to gap junction closure within cumulus-oocyte complexes (COCs).

Main Methods:

• Inhibited hyaluronan synthesis or its interaction with CD44 during porcine oocyte maturation.
• Assessed intra-oocyte cAMP levels, gap junctional communication via fluorescent dye transfer, and connexin 43 tyrosine phosphorylation.
• Examined the association between hyaluronan and LH receptor expression in COCs.

Main Results:

• Inhibition of hyaluronan synthesis or CD44 interaction attenuated the decline in intra-oocyte cAMP.
• Gap junctional communication was maintained, and connexin 43 phosphorylation was reduced in inhibited COCs.
• Hyaluronan demonstrated an association with LH receptor expression in COCs.

Conclusions:

• Hyaluronan, during cumulus expansion, may work with LH to promote meiotic resumption.
• Hyaluronan likely contributes to gap junction closure, a key event in in vitro oocyte maturation.
• This mechanism is crucial for regulating cAMP levels and facilitating oocyte maturation.