An estimated 15% of couples in the world suffer from infertility. According to a survey in 2013 by the National Institute of Health and Clinical Optimization (NICE) in the United Kingdom, male factors have become the main reason for infertile couples to use assisted reproductive therapy (ART).
Male infertility is mainly diagnosed by routine semen analysis (WHO standard), including semen volume, concentration, vitality and morphology.
Although studies have shown that semen quality and ART outcome are correlated, until now, we have not found a conventional semen threshold that can predict the success of ART.
Recent studies have shown that sperm DNA fragmentation (SDF), including sperm DNA single-strand breaks and double-strand breaks, are all related to male infertility factors, which can adversely affect the male reproductive system and increase the risk of genetic diseases in offspring .
Two previous Meta-analysis studies have shown that SDF is related to ART failure and repeated pregnancy loss.
However, human sperm itself does not have DNA repair activity (DRA). Once fertilised, DRA mainly depends on the transcripts produced during the maturation of the oocyte to repair it. The ability of oocytes to repair SDF depends on the degree of fragmentation of SDF and the quality of oocytes.
Therefore, reproductive medicine researchers from Sao Paulo, Brazil, conducted research on women’s age and SDF and the outcome of intra-cytoplasmic sperm injection (ICSI) assisted pregnancy.
Amanda Souza Setti et al. collected 540 couples who underwent ICSI at the centre from May 2017 to December 2019, and divided the ICSI cycle into three groups according to the age of the woman: ≤36 years old (285 cases), 37-40 years old ( 147 cases) and >40 years old (108 cases).
Sperm chromatin diffusion test was used to evaluate the SDF of semen specimens.
For each age group, according to the SDF index, the ICSI cycle is divided into two subgroups: low fragmentation index (SDF <30%) and high fragmentation index (SDF ≥ 30%).
Summarised and analysed the outcome indicators such as embryo implantation rate, pregnancy rate and abortion rate.
The study found that: for young patients (36 years old) and patients between 37-40 years old, whether SDF <30% or SDF ≥ 30%, the laboratory and clinical results of the ICSI cycle were not significantly different.
When female patients are older than 40 years old, compared with SDF<30%, in an ICSI cycle with SDF ≥ 30%, the rate of D3 high-quality embryo acquisition (54.4% vs 33.1%) and the rate of blastocyst formation (49.6% vs 30. 2%), pregnancy rate (20.0%vs7.7%) and implantation rate (19.7%vs11.9%) were significantly reduced, while miscarriage rate (12.5%vs100.0%) increased.
The results of the study showed that, Older oocytes, when injected with sperm derived from samples with high SDF (Sperm DNA Fragmentation) index, develop into embryos of poor quality that lead consequently to lower implantation and pregnancy rates and higher miscarriage rates, in intracytoplasmic sperm injection cycles from women with advanced maternal age.
The results of this study are of great significance to clinical work. Women’s age cannot be changed, but male SDF can be improved through diet, environment, lifestyle changes, antioxidant and other therapies. This study may provide new ideas for improving the ART pregnancy rate of elderly couples and reducing the abortion rate.
Oocyte ability to repair sperm DNA fragmentation: the impact of maternal age on intracytoplasmic sperm injection outcomes
Fertility and Sterility (IF7.329), Pub Date : 2021-02-13, DOI: 10.1016/j.fertnstert.2020.10.045
Amanda Souza Setti, Daniela Paes de Almeida Ferreira Braga, Rodrigo Rosa Provenza, Assumpto Iaconelli, Edson Borges