O-262 Karyotyping of single sperm from non-obstructive azoospermia patients and obstructive azoospermia patients using a combination of micromanipulation and next-generation sequencing
Authors: Sueyoshi S , Hayama T , Ijuin A , Miyakoshi A , Kurumizaka M , Saito M , Tochihara S , Oike Y , Ueno H , Takeshima T , Tanoshima M , Sakakibara H , Yumura Y , Miyagi E , Murase M 
Published: July 2024

Abstract

Study question
Is there a difference in the frequency of aberrant karyotype in sperm when the cause of infertility is non-obstructive azoospermia (NOA) versus obstructive azoospermia (OA)?

Summary answer
Aberrant karyotype was found in 7 of 46 sperm with NOA, none of 26 sperm with OA and none of 28 sperm with control.

What is known already
It is known that aberrant karyotype occurs more frequently in sperm from infertile men than sperm from general population, and that the severity of infertility is proportional to the frequency of sperm chromosomal abnormality. In fact, miscarriage rates are high in cases where TESE-ICSI is performed for azoospermia, and embryonic chromosomal aneuploidy derived from sperm is thought to be one of the causes of miscarriage. Azoospermia is classified into OA and NOA. However, it is unclear whether there is a difference in the frequency of sperm chromosomal abnormality between NOA and OA.

Study design, size, duration
Sperm were picked up individually by micromanipulation for the OA and NOA groups who underwent TESE in clinical practice. For comparison, ejaculated sperm from males who underwent IVF or ICSI for female infertility were picked up. As a quality control, ejaculated sperm from balanced reciprocal translocation (RcT) carriers were also picked up. Each sperm was karyotyped by next-generation sequencing (NGS) to compare the number of normal haploid sperm and aberrant sperm.

Participants/materials, setting, methods
Under the ethical review of Yokohama City University and informed consent with patients, we collected human sperm which were discarded after clinical use. Sperm samples were picked up individually by micromanipulation. Following whole-genome amplification (WGA), karyotyping was performed by NGS. For each sperm, if even one of all chromosomes had abnormality, that sperm was counted as aberrant sperm, and if all chromosomes were haploid, it was counted as haploid sperm.

Main results and the role of chance
We analyzed 10 sperm per patient. Karyotyping analysis was performed on sperm from 2 patients in the RcT group,4 patients in the control group, 4 patients in the OA group, and 5 patients in the NOA group. WGA was successful in 90% (18/20) of RcT carriers group, 95% (38/40) of the control group, 72.5% (29/40) of the OA group, and 92% (46/50) of the NOA group. Acquisition rate of karyotyping was 90% (18/20) of RcT carriers group, 70% (28/40) of the Control group, 65% (26/40) of the OA group, and 95% (46/50) of the NOA group. The results of karyotype analysis showed 28 haploid sperm and no aberrant sperm in the control group, 26 haploid sperm and no aberrant sperm in the OA group, and 39 haploid sperm and 7 aberrant sperm in the NOA group. Karyotyping of sperm from RcT carriers group showed sperm with unbalanced chromosomes derived from translocations of the carriers. The frequency of aberrant karyotype was significantly higher in NOA than control (P = 0.0297). It was also higher in NOA than OA(P = 0.0363).

Limitations, reasons for caution
In our research, micromanipulation was performed manually to isolate sperm, and the number of sperm that could be analyzed was small. Sperm with good morphology are selected using micromanipulation and analyzed by NGS, so the results do not reflect the results of all sperm actually collected by TESE.

Wider implications of the findings
In this study, sperm with good morphology were selected by micromanipulation and analyzed, so it is thought that the karyotype of sperm actually reflects the karyotype used in clinical practice. These results suggest that PGT-A is particularly effective in preventing miscarriages among patients whose azoospermia was caused by NOA.

Trial registration number
not applicable