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Title

The relationship between sperm DNA fragmentation and morphology abnormalities

Objective

It is well known that high levels of sperm DNA fragmentation could negatively impact IVF cycles, leading ultimately to higher miscarriage rates. On the other hand, some sperm morphology alterations could lead to fertilization failure, often leading to higher abortion rates. However, how the DNA fragmentation and morphology abnormalities are related in IVF outcome is still unknown. For that, the aim of this work was to study the association between high sperm DNA fragmentation and sperm morphology abnormalities.

Methods

This was a retrospective cohort study that analyzed 80 sperm samples from patients that underwent IVF cycles for DNA fragmentation by CANfrag test and sperm morphology. As recommended, 28 samples that presented more than 30% of DNA fragmentation were considered as high fragmentation samples (High group) and 62 samples with fragmentation rates lower than 30% composed the Control group). Morphology parameters were analyzed as recommended by WHO. Briefly, sperm head (macrocephaly, microcephaly, vacuoles, misshapen, elongated, fusiform, bicephalous, acephalous, round-head and piriform) acrosome (defective or absent), intermediate piece (drops, eccentric piece and vacuoles) and tail (short, curly, doble-tail and absence of tail) abnormalities were analyzed, as well as pleomorphic and amorphous sperms. Samples with  4% of normal sperm morphology were considered normal. The patients’ age was compared between groups. The fragmentation, total sperm abnormality and each sperm abnormality type were compared between groups using Chi square and Fisher’s exact test with p value ≤ 0.05 considered significant.

Results

Samples of the High group showed an increase in abnormal sperm rate (98.36%; 2754/2800) when compared to Control group (97.81%; 6064/6202). Acrosome and tail abnormalities were similar between groups (0.13% and 0.11%, and 0.28% and 0.11% for acrosome and tail abnormalities between Control and High groups, respectively). Total head abnormalities were decreased in high fragmentation samples (22.55% in High group and 25.46% in Control) and, among head abnormalities, microcephaly (8.70%) and round-head (3.54%) sperms were decreased, and acephalous (5.96%) and piriform (1.13%) sperm rates were increased in High group, comparing to Control (microcephaly; 13.67%, round-head; 6.15%, acephalous; 3.82% and piriform; 0.32%). Although the total number of intermediate piece abnormalities did not differ between groups (0.3% in Control and 0.11% in High group), among them, the presence of drops was decreased and eccentric piece rate was increased in samples with higher DNA fragmentation, comparing to control samples (drops presence; 72.22% in Control group versus 0% in High group and eccentric piece rate of 22.22% in Control versus 100% in High group). Regarding pleomorphic spermatozoa, High group showed lower rate (73.83% in Control versus 32.18% in High group). Sperm with head and acrosome abnormalities were less common in High group, with rate of 13.28% versus 23.34% in Control. Moreover, when head and tail abnormalities and 3-piece abnormalities where compared, a higher rate in high fragmentation samples (8.62% and 25.80%, respectively) comparing with control samples was observed, with 5.07% of total abnormalities with head and tail combined and 23.12% with 3-piece abnormalities.

Conclusion

Our data indicate that sperm DNA fragmentation and some sperm morphology abnormalities could be related. However, more studies are necessary to understand the impact of this association in IVF cycles outcomes.

Keywords

Sperm, DNA fragmentation, sperm morphology