Mannose-binding sites on human spermatozoa and sperm morphology

Area of Science:

• Reproductive Biology
• Andrology
• Spermatozoa Function

Background:

• Mannose-binding sites on sperm heads are implicated in fertilization.
• Sperm morphology is a key indicator of male fertility.
• The relationship between mannose-binding sites and sperm morphology requires further investigation.

Purpose of the Study:

• To investigate the association between the expression of sperm head mannose-binding sites and sperm morphology.
• To determine if altered mannose-binding site expression correlates with reduced sperm quality.

Main Methods:

• Prospective in vitro study involving 27 fertile donors and 45 infertile patients.
• Assessed D-mannose-binding sites using fluoresceinated mannose-enriched bovine serum albumin.
• Evaluated sperm viability (Hoechst 33258) and plasma membrane integrity (hypo-osmotic swelling test).
• Classified semen samples into normal, good prognosis, and poor prognosis groups based on strict morphological criteria.

Main Results:

• A higher incidence of spermatozoa with mannose-binding sites was observed in the normal morphology group (48.1%) compared to the good (17.6%) and poor prognosis groups (7.6%).
• Total mannose-binding site expression showed a strong positive correlation (r = 0.80) with the percentage of morphologically normal sperm.
• Viability and membrane integrity were confirmed before mannose-binding site evaluation.

Conclusions:

• Altered expression of mannose-binding sites, potentially acting as zona receptors, may contribute to decreased fertility in men with morphologically abnormal sperm.
• Mannose-binding sites represent a potential molecular marker for assessing sperm fertilizing capacity.
• This finding highlights a molecular basis for infertility linked to sperm defects.