Influence of cumulus cell processes on oolemma permeability and lethality of isolated mouse oocytes cultured in Ca2+-free medium
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M De Felici1, S Dolci, G Siracusa
1Dipartimento di Sanità Pubblica e Biologia Cellulare, II Università di Roma, Rome, Italy.
Abstract:
Cumulus cell processes remaining in the zona pellucida of mouse oocytes mechanically isolated from the ovary have been indirectly visualized by labeling their actin microfilament core with rhodaminyl-phalloidin. If the isolation of the oocytes is performed in Ca2+-free medium, the presence of such processes allows the entry into the cell of low molecular weight molecules (such as 5-6 carboxyfluorescein) and contributes to the death of the cell in such experimental conditions. Following dissolution of the zona pellucida (by enzymatic or acidic treatment) the oocyte is no longer permeable to small molecules and becomes resistant to Ca2+-free medium, probably as a consequence of the collapse of cumulus cell processes. The role of cumulus cell processes and gap junctions in the permeability of mechanically isolated ovarian oocytes is discussed.
Insights
Cumulus cell processes in mouse oocytes allow small molecule entry and cell death in Ca2+-free conditions. Removing these processes or the zona pellucida increases oocyte survival by preventing molecule entry.
Area of Science:
- Reproductive Biology
- Cell Biology
- Oocyte Development
Background:
- Cumulus cells surround oocytes and are crucial for their development and maturation.
- The zona pellucida is the outer protective layer of the oocyte.
- Oocyte isolation methods can impact cell viability and experimental outcomes.
Purpose of the Study:
- To investigate the role of cumulus cell processes in the permeability of mechanically isolated mouse oocytes.
- To understand the impact of these processes on oocyte survival in calcium-free conditions.
- To explore the function of gap junctions in oocyte permeability.
Main Methods:
- Mechanical isolation of mouse oocytes from ovaries.
- Labeling of cumulus cell actin microfilaments using rhodaminyl-phalloidin for visualization.
- Exposure of oocytes to calcium-free medium and low molecular weight molecules (e.g., carboxyfluorescein).
- Dissolution of the zona pellucida using enzymatic or acidic treatments.
Main Results:
- Cumulus cell processes extending into the zona pellucida were visualized.
- Oocytes isolated in Ca2+-free medium with intact processes showed increased permeability to small molecules and cell death.
- Dissolving the zona pellucida rendered oocytes impermeable to small molecules and resistant to Ca2+-free medium, likely due to cumulus cell process collapse.
Conclusions:
- Cumulus cell processes play a significant role in the permeability of mechanically isolated ovarian oocytes.
- The presence of these processes contributes to oocyte vulnerability in Ca2+-free environments.
- Zona pellucida integrity and cumulus cell processes are critical for maintaining oocyte homeostasis during isolation.