Selected Spermatozoa at Conventional Magnification Cannot Guarantee in Obtaining Spermatozoa With Long Telomere Length in Severe Teratozoospermia Patients

Background Sperm selection from the population of processed spermatozoa cells after density gradient centrifugation (DGC) can assist embryologists in selecting high-quality sperm. Sperm selection of low-quality and chromatin-damaged spermatozoa is inevitable in severe teratozoospermia semen specimens. This study was conducted to evaluate whether sperm selection at ×400 magnification enables embryologists to select a population of spermatozoa with low DNA fragmentation and high sperm telomere length (STL) in semen samples with severe teratozoospermia. Methods A total of 23 infertile men characterized by severe teratozoospermia were selected. Sperm DNA fragmentation (SDF) and relative STL (r-STL) were evaluated at three stages: specimen collection, after DGC, and during the single selection of spermatozoa at ×400 magnification (single selection). The 23 patients were divided into two groups, including 14 with normal morphology ≤1% and nine with normal morphology of 2%. SDF and r-STL were compared between the two groups at three stages. Results The results of this study showed that although SDF decreased remarkably after DGC and single selection (F=64.327, P-value=0.000), the DNA fragmentation index obtained for each semen sample was more than the cutoff point of 18% based on the Halo sperm test. No statistically significant differences were observed in r-STL after DGC and single selection (F=1.978, P-value=0.163). Meanwhile, the pairwise comparison of r-STL showed that in the 2% normal morphology group, the mean relative telomere length was significantly higher in the selected spermatozoa compared to the semen specimen (P=0.014). This increase can be attributed to DGC and single selection by the embryologist. Also, there was no correlation between SDF and r-STL in the semen samples with severe teratozoospermia (r=0.01, P-value=0.964). Conclusions This study suggests that investing more time in sperm selection can decrease SDF, but r-STL of spermatozoa selected by the embryologist does not increase in severe teratozoospermia semen samples with morphology ≤1%.