The relationship between morphology, motility and zona pellucida binding potential of human spermatozoa

Summary. Prediction of the fertilizing potential of human gametes under in vitro conditions has been a major field of interest of assisted reproductive programmes. However, sperm morphology has been regarded as a predictor of human in vitro fertilization rate. This paper prospectively evaluates the relationships among normal sperm morphology and (1) motion characteristics viz. curvilinear velocity (VCL), straight line velocity (VSL), and linearity (LIN) (n = 37) and (2) spermzona pellucida binding capacity under HZA conditions (n = 144) of two separate groups of infertile couples. Semen was evaluated for sperm concentration, percentage motility, forward progression, and percentage normal morphology (strict criteria). The motility characteristics were measured using a computerized Sperm Motility Quantifier (SMQ). The zona binding potential of sperm was evaluated using the hemizona assay. Firstly, the VCL significantly differred between the P-pattern and both the G (72.9 ± 7 vs. 86.3±16 μm s^?1; P = 0.04) and N patterns (72.9 ± 7 vs. 91.0 ± 15 μm s^?1; P = 0.002). The VSL differed only between the P and N patterns, being 19.7 ± 7 vs. 32.6±15 μm s^?1 (P = 0.02), respectively. No significant differences in LIN were noted between any of the three patterns. The sperm concentration differed significantly between the P and both the G (37.9±35 vs. 80.8 ± 9 × 10⁶ ml^?1; P = 0.03) and the N patterns (37.9 ± 35 vs. 89.7 ± 72 × 10⁶ ml^?1; P = 0.05). Significant differences were observed in the percentage motility between the P and both the G (38.0 ± 21% vs. 43.7 ±9%; P = 0.03) and the N patterns (38.0 ± 21% vs. 52.1±8%; P = 0.04). In the second study, the hemizona indices (HZI) differed significantly between the P and both the G (29.3 ± 26% vs. 57.6 ± 62%; P = 0.01) and the N patterns (29.3 ± 26% vs. 102.4 ± 80%; P < 0.001). The G and N patterns also differed significantly in their HZI (57.6 ± 62% vs. 102.4 ± 80%; P = 0.005). Sperm concentration differed between the P and both the G (32.8 ± 29 vs. 76.1±54 × 10⁶ ml^?1; P < 0.001) and the N patterns (32.8 ± 29 vs. 95.44 ± 61 × 10⁶ ml^?1; P < 0.001). The percentage motility differs significantly between the P pattern and both the G (41.2± 17% vs. 50.9±11%; P = 0.002) and the N patterns (41.2±17% vs. 53.4±11%; P = 0.001). Sperm morphology seems to be indicative of important functional characteristics of spermatozoa, for example motility and zona pellucida binding.