Mannose-binding sites on human spermatozoa and sperm morphology.

OBJECTIVE

To verify a possible association between the expression of sperm head mannose-binding sites and sperm morphology.

DESIGN

Prospective in vitro study.

SETTING

University-based sperm biology and andrology laboratories.

PARTICIPANTS

Twenty-seven fertile donors and 45 patients consulting for infertility.

INTERVENTIONS

D-mannose-binding sites were identified using a fluoresceinated mannose-enriched bovine serum albumin. Hoechst 33258 was included to confirm sperm viability and hypo-osmotic swelling test to assess plasma membrane integrity. Sperm morphology was judged by strict criteria and semen samples were classified into three groups: normal (group N, > 10% morphologically normal sperm, n = 27), good prognosis (group G, 5% to 10%, n = 23), or poor prognosis (group P, < or = 4%, n = 22).

RESULTS

Only viable (Hoechst 33258 negative) spermatozoa with intact plasma membrane (hypo-osmotic swelling test positive)were considered in the evaluation of mannose-binding sites. The incidence of spermatozoa showing surface mannose-binding sites was higher in the N group (48.1% +/- 1.9%; mean +/- SEM) then in the G (17.6% +/- 4.4%) or P (7.6% +/- 2.3%) groups. Total mannose-binding site expression and percentage of morphologically normal sperm showed a high positive correlation (r = 0.80).

CONCLUSION

Altered expression of mannose-binding sites, putative zona receptors, may be one of the molecular defects causing decreased fertility in morphologically abnormal human sperm.