Epidermal growth factor activates cytosolic [Ca2+] elevations and subsequent membrane permeabilization in mouse...

Area of Science:

• Reproductive Biology
• Cell Biology
• Developmental Biology

Background:

• Epidermal growth factor (EGF) is known to enhance mammalian oocyte maturation in vitro.
• EGF stimulation of cumulus-oocyte complexes (COCs) is associated with pulsatile calcium efflux.
• The precise mechanisms underlying EGF's effects on COCs are not fully characterized.

Purpose of the Study:

• To investigate the role of EGF in intracellular calcium dynamics within COCs.
• To elucidate the cellular mechanisms linking EGF stimulation to calcium release and cell membrane changes.
• To understand the consequences of EGF-induced cellular events on cumulus cell fate and function.

Main Methods:

• Quantitative Fura-2 imaging was employed to measure intracellular calcium levels in murine COCs.
• Experiments involved EGF stimulation and treatment with calcium ionophore, thimerosal, and thapsigargin.
• Changes in plasma membrane integrity were assessed in response to various stimuli.

Main Results:

• EGF stimulation induced intracellular calcium increases in a subpopulation of cooperative cumulus cells within COCs.
• Oocytes did not respond to EGF stimulus directly.
• EGF-induced calcium release was linked to plasma membrane permeabilization and presumptive cumulus cell death in responding cells.

Conclusions:

• EGF triggers calcium release from intracellular stores in cumulus cells, leading to plasma membrane permeabilization.
• This permeabilization results in cell death and contributes to the previously observed pulsatile calcium efflux.
• The observed cellular events may play a role in promoting cumulus cell expansion during oocyte maturation.