Effects of maturation conditions on spindle morphology in porcine MII oocytes

Area of Science:

• Reproductive Biology
• Cell Biology
• Developmental Biology

Background:

• In vitro matured (IVM) oocytes often exhibit incomplete cytoplasmic maturation.
• This can lead to microtubule and microfilament alterations, impacting pronuclear formation and embryonic development.
• Meiotic spindle morphology is crucial for successful oocyte maturation and subsequent development.

Purpose of the Study:

• To investigate the influence of various maturation conditions on meiotic spindle morphology in porcine oocytes at metaphase of meiosis II (MII).
• To compare spindle length and area under different in vitro and in vivo maturation protocols.
• To identify specific maturation factors affecting spindle organization.

Main Methods:

• Porcine oocytes were matured in vitro and in vivo under varying conditions.
• Conditions included different amounts of cumulus cells, presence/absence of hormonal supplements, and hormone exposure durations.
• Spindle morphology (interpolar spindle length and spindle area) was assessed using immunofluorescence and confocal laser microscopy.

Main Results:

• In vitro matured (IVM) oocytes had significantly shorter spindle lengths compared to in vivo matured oocytes.
• Oocytes from cumulus oocyte complexes (COCs) with fewer cumulus cells showed smaller spindle areas.
• Oocytes matured without hormonal supplements exhibited significantly reduced spindle length and area.
• Hormone exposure duration (6 vs. 22 hours) did not significantly affect spindle morphology.

Conclusions:

• Maturation conditions critically influence the morphogenesis of MII spindles in porcine oocytes.
• Suboptimal maturation conditions, such as those with poor cumulus cell support or lack of hormonal supplementation, result in abnormal spindle morphology.
• These spindle alterations may contribute to the reduced developmental potential observed in oocytes matured in vitro under suboptimal conditions.