Extent of nuclear DNA damage in ejaculated spermatozoa impacts on blastocyst development after in vitro fertilization

Abstract

Objective: To determine whether the extent of ongoing apoptotic cell death measured as the presence of DNA strand breaks in spermatozoa affects embryo development to the blastocyst stage in IVF.

Design: A prospective comparative study.

Setting: A university IVF clinic and a private IVF clinic.

Patient(s): Men (n = 49) undergoing infertility treatment with IVF.

Intervention(s): After density gradient centrifugation preparation, part of the sperm sample was used for infertility treatment, and the rest was fixed in paraformaldehyde. Strand breaks in DNA that are indicative of apoptosis were detected by the in situ DNA nick end labeling (TUNEL) technique. A total of 15,000 spermatozoa from each sample were evaluated for TUNEL reactivity by flow cytometry.

Main outcome measure(s): Percentage of ejaculated spermatozoa with DNA strand breaks indicative of apoptosis, blastocyst development rate, and pregnancy rate.

Result(s): Blastocyst development showed a significant negative correlation with percentage TUNEL positivity in spermatozoa. When 20% was used as a cutoff for TUNEL positivity in sperm samples, the percentage of blastocyst development was 50% higher in the <20% TUNEL-positivity group (n = 27) compared with those with >/=20% TUNEL positivity (n = 22; 44.7% blastocyst development vs. 29.8%). Clinical pregnancy rates in these two groups were 52% vs. 44%, respectively.

Conclusion(s): The extent of nuclear DNA fragmentation in prepared ejaculated spermatozoa used in IVF negatively correlates with blastocyst development. A larger series of patients needs to be assessed to determine whether this paternal effect on blastocyst development may also affect pregnancy outcome.