Evaluation of the Clinical Treatments in Men With Severe Oligospermia, ICSI Failures and High DNA Fragmentation With the Use of Testicular Sperm

Since its first description in 1992, intracytoplasmic sperm injection (ICSI) has been widely used to overcome all forms of severe male factor infertility. Despite achieving acceptable success rates with the use of abnormal sperm, studies suggest that poor sperm quality can be detrimental to ICSI outcomes. Sperm DNA plays a critical role in normal embryonic development because the genetic information passed on to the next generation depends on its integrity (6-8). Deterioration of sperm DNA content has been associated with several conditions, including lifestyle and exposure to gonadotoxins, varicocele, infections in the male accessory glands and advanced paternal age.

Sperm DNA fragmentation (SDF) tests measure the proportion of sperm with damaged chromatin, using probes or stains to identify DNA breaks with the aid of fluorescence microscopy, light microscopy or flow cytometry depending on the type of method. Regardless of the analytical method, DNA fragmentation is more common in the sperm of infertile men than fertile men. Among couples undergoing ICSI, high SDF in the ejaculate is found in 30% of men and is generally associated with abnormal conventional semen parameters. But this high SDF is also a relatively common finding in infertile men with normal semen parameters, up to 20% - 40% according to some authors. Aside from the questionable need to routinely use SDF test during the evaluation of male infertility, recent evidence indicates that knowing the FAE can be clinically informative in estimating the results to be obtained with assisted reproductive techniques (ART). Although sperm with fragmented DNA can fertilize an oocyte with apparently similar efficacy to sperm without DNA fragmentation, the negative impact of damaged paternal chromatin is generally manifested during the development of the embryos produced, leading to developmental blockage, implantation failure or early embryo loss, thus decreasing the success of ART.

Among the many strategies proposed to overcome SDF in couples undergoing ART, the use of testicular sperm instead of ejaculate in males without azoospermia has gained increased attention, due to recent results published by various groups. The biological plausibility of using testicular sperm for ICSI in men with high SDF in the ejaculate is based on observations of less DNA fragmentation in sperm from the testis compared with sperm from the ejaculate. The alteration of sperm chromatin integrity in ejaculated sperm from infertile men may be explained, first, because chromatin compaction is still ongoing during epididymal transit. Secondly, because excessive ROS can be generated in epididymal epithelial cells under stress factors such as high temperatures and environmental conditions. Finally, certain endonucleases can cleave the DNA of mature live sperm and, as a result, sperm DNA damage can occur by different pathways, including hydroxyl radical, nitric oxide, and activation of sperm caspases and endonucleases, thus explaining the positivity for SDF in ejaculated sperm or sperm from infertile men.

Thus, the concept that oxidation-induced sperm chromatin damage can occur in the post-testicular environment or in epididymal transit and storage, and that sperm recovery with improved chromatin integrity can be achieved if the epididymis is bypassed, has led researchers to explore the use of testicular sperm for assisted reproductive treatments. Because of the relevance of the clinical decision to resort to the use of testicular sperm for ICSI, especially because of the inherent risks and clinical implications of such an intervention, the potential benefit of testicular sperm for ICSI needs to be clarified in these cases and, thus, to determine the potential improvement that it could allow.

Our most recent work led us to examine the available evidence regarding ICSI outcomes with testicular sperm (Testi-ICSI) and ejaculated sperm (Ejac-ICSI) among non-azoospermic infertile men with confirmed post-testicular damage through a systematic review and meta-analysis of the available information, where we compared: 1) ICSI outcomes of Testi-ICSI and Ejac-ICSI among infertile men with high SDF (as defined in each study) in the ejaculate; and 2) SDF rates among testicular sperm and ejaculates of infertile men regardless of whether or not ICSI data were provided. Taking into account: 1) study population (history of ICSI failure versus no prior history of ICSI failure); 2) semen analysis profile of participants (oligozoospermia vs. normozoospermia); 3) method of SDF testing; and 4) method of sperm retrieval, and finding conflicting evidence regarding the use of Testi-ICSI in nonazoospermic men and the inherent risks of complications after sperm retrieval, it is necessary to clarify whether any particular male infertility population may derive benefit from this intervention.