Acrosomeless sperm. A cause of primary male infertility

Area of Science:

• Reproductive Biology
• Andrology
• Human Genetics

Background:

• Male infertility affects a significant portion of couples seeking conception.
• The acrosome plays a critical role in sperm-egg interaction and fertilization.
• Understanding sperm defects is crucial for diagnosing and treating male infertility.

Purpose of the Study:

• To investigate the characteristics and fertility potential of sperm completely lacking an acrosome.
• To determine the impact of acrosome absence on sperm function and fertilization capacity.

Main Methods:

• Analysis of Papanicolaou stained smears and electron microscopy to confirm acrosome absence.
• Assessment of sperm membrane integrity using vital staining and hypoosmotic swelling tests.
• Enzyme assays for acrosin and proacrosin levels.
• In vitro fertilization assays using zone-free hamster oocytes and in vivo postcoital testing.

Main Results:

• Confirmed absence of the acrosome and post-acrosomal sheath in sperm from two infertile males.
• Sperm exhibited compromised membrane integrity (72% unstained, 69% swollen).
• Significantly reduced acrosin (5-fold decrease) and proacrosin (8-fold decrease) levels were observed.
• Acrosomeless sperm, despite 46% progressive motility, failed to penetrate hamster oocytes.

Conclusions:

• Complete absence of the acrosome is a primary cause of male infertility.
• Acrosomal deficiency severely impairs sperm function, including the ability to fertilize oocytes.
• Further research into acrosomal development and function is warranted for fertility treatments.