P-111 Spermiogenic maturation in relation to sperm genomic integrity throughout the epididymis
Authors: Souness S , Kocur O , Sung C , Rosenwaks Z , Palermo G.D 
Published: June 2022

Study question

Which portion of the epididymis yields spermatozoa with the highest chromatin integrity and embryo developmental competence?

Summary answer

Spermatozoa retrieved from the distal portion of the epididymis retains the highest chromatin integrity, characterized by higher fertilization, implantation, and clinical pregnancy rates.

What is known already

Surgical sperm retrieval from the proximal male reproductive tract has proven to be an effective treatment for couples with recurrent pregnancy loss due to high DNA fragmentation in the ejaculate. Although spermatozoa retrieved directly from the germinal epithelium displays the highest genomic integrity, epididymal spermatozoa maintain a similar DNA integrity profile but yield higher fertilization and pregnancy rates. Although the caput is the preferred site for sperm aspiration procedures in the epididymis, it is unclear which epididymal region yields the best-quality gametes.

Study design, size, duration

Over a 10-year period, we identified 51 obstructive azoospermic (OA) men who underwent surgical sperm retrieval. These men were grouped according to the different epididymal regions from which their spermatozoa were obtained. Sperm chromatin fragmentation (SCF) was assessed and compared among these groups. The epididymal spermatozoa were then used for ICSI cycles. Fertilization and clinical outcomes were compared among the epididymal regions. All female partners (≤37 years old) had negative infertility workups.

Participants/materials, setting, methods

Epididymal spermatozoa were retrieved from the caput (n = 39), corpus (n = 8), and cauda (n = 4) regions. SCF was assessed by terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay, with a normal threshold of ≤ 15%. Unpaired t and Fisher’s exact tests were used to compare the SCF as well as ICSI and pregnancy outcomes according to the epididymal sperm source. P &lt; 0.05 was considered statistically significant.

Main results and the role of chance

A total of 51 men were categorized based on the site of spermatozoa retrieval: caput, corpus, and cauda. Maternal age was comparable among all three groups (37.9±5, 37.3±4, and 38±3, respectively). Sperm concentration was 23.9±30x106/ml (caput), 24.3±30x106/ml (corpus), and 29.3±36x106/ml (cauda), with 10.8±15% (caput), 14.3±20%(corpus), and 15.2±13% motility (cauda). Average oocytes injected per group was 13.3, 12.3, and 13.2, respectively. Average SCF scores were 19.8%, 9.2% (P &lt; 0.05), and 8.4% (P &lt; 0.05), respectively. The fertilization rates rose from 69.0% in the caput to 78.6% in the corpus and 86.2% (P &lt; 0.05) in the cauda. Implantation rates followed a similar trend: 35.3% in the caput and 44.4% and 50.1% in the corpus and cauda, respectively. In cycles using caput epididymal spermatozoa, there was a 52.9% delivery rate with a 5.5% pregnancy loss rate. Cycles using corpus epididymal sperm showed a 75.0% delivery rate with no pregnancy loss. Finally, cycles using spermatozoa from the cauda resulted in a 100% delivery rate.

Limitations, reasons for caution

Although spermatozoa retrieved from the cauda epididymis has superior genomic integrity and yielded satisfactory clinical outcomes, this approach may be restricted to patients with obstructive azoospermia. While we attempted to control for an eventual confounding female factor, it cannot be entirely ruled out.

Wider implications of the findings

The epididymis plays an important role in sperm maturation; epididymal spermatozoa retain adequate chromatin integrity as demonstrated by the fertilization and pregnancy rates achieved with sperm retrieved from the cauda region. Confirmation of these findings in larger studies may help determine the most favorable site for epididymal sperm retrieval.

Trial registration number

Not applicable