INFLUENCE OF SPERM MOVEMENT PARAMETERS ON HUMAN SPERM-OOLEMMA FUSION

Flagellar dyskinesia is characterized by abnormal sperm movement param eters and a negative sperm mucus penetration test. It is associated wi th structural pathologies of the axonemal complex (lack of outer dynei n arms), of the periaxonemal complex (sliding spermatozoa and periaxon emal dyskinesia), or of both structures (short flagella). Even during in vivo fertilization, dyskinesia prevents the spermatozoon from getti ng through the egg vestment. However, in some cases, fertilization has been achieved using subzonal insemination. Flagellar dyskinesia is th erefore an interesting model for investigating the role of sperm movem ent in the fusion process between the spermatozoon and the oolemma. Th irty-one patients requiring assisted fertilization were included in th e study. Fifteen had spermatozoa in which the flagellum lacked outer d ynein arms, II had anomalies of the periaxonemal complex (five with sl iding spermatozoa and six with periaxonemal dyskinesia) and five had s permatozoa with short flagella. Seven men who produced spermatozoa wit h normal movement were selected as controls. Movement was evaluated us ing a computer-assisted analyser, and penetration was assessed using z ona-free hamster eggs. At 37 degrees C in semen, the dyskinetic sperma tozoa had reduced straight line and curvilinear velocity and lateral h ead displacement compared with controls (P < 0.01). In the Percoll-sel ected sperm suspension, the only difference was that spermatozoa with periaxonemal anomalies maintained a narrow lateral head displacement c ompared with the controls (P < 0.001). After 3 h of incubation at 37 d egrees C, the lateral head displacement of dyskinetic spermatozoa had not changed, while that of the controls showed a significant increase (4.5 to 5.6 mu m; P< 0.05). The results from the sperm penetration ass ay for the spermatozoa lacking outer dynein arms were lower than those of the controls (47% versus 77%; P < 0.05) and the results for slidin g spermatozoa and spermatozoa with periaxonemal dyskinesia were even l ower (25% and 34%, respectively; P < 0.01). The fertilization rates af ter subzonal insemination were 46.5% for spermatozoa lacking outer dyn ein arms, 36.1% for spermatozoa with short flagella, 24.8% for sliding spermatozoa and 17.3% for spermatozoa with periaxonemal dyskinesia. T here was a significant correlation between the curvilinear velocity of the Percoll-selected sperm suspensions and their fertilization rates after subzonal insemination (r = 0.5; P < 0.05) and their sperm penetr ation assays (r = 0.7; P < 0.001). The data provide evidence that sper m velocity is correlated with the ability to fuse with the oolemma.