Novel micro-straw for freezing small quantities of human spermatozoa

Abstract

Objective: To evaluate a novel micro-straw as an efficient, simple method for freezing a small number of human spermatozoa for intracytoplasmic sperm injection (ICSI).

Design: Prospective cohort study.

Setting: Sperm bank.

Patient(s): Men with severe oligozoospermia or azoospermia undergoing a total of 143 ICSI cycles at the CITIC-Xiangya Hospital of Reproduction and Genetics from June 1, 2015, to June 31, 2019, and 20 donors at the Hunan Province Human Sperm Bank from 2001 to 2016.

Intervention(s): Analysis of sperm samples and clinical outcomes after sperm use.

Main outcome measure(s): Clinical information, including number of motile sperm before and after freezing, freeze-thaw survival rates, two-pronuclear fertilization rates, clinical pregnancy, and early pregnancy loss rates after sperm use.

Result(s): In the feasibility experiment using the micro-straw, we found a freeze-thaw survival rate of 73% ± 8.3% and no difference in normal sperm morphology, normal acrosome integrity, or DNA fragmentation index between the micro-straw and 1.8-mL cryotubes. The prospective cohort included 1,325 cases, and we collected sperm from testicular, epididymis, and ejaculation sources. We observed motile sperm in 1,294 (97.6%) of 1,325 frozen-thawed samples. Postthaw sperm were available for ICSI in 140 (97.9%) of 143 of cycles. The fertilization, cleavage, and high-quality embryo rates were 1,007 (81.7%) of 1,233; 995 (98.8%) of 1,007; and 537 (53.9%) of 995, respectively. Sixty-nine (49%) clinical pregnancies were achieved, and the miscarriage rate was 6 (8.6%) of 69.

Conclusion(s): The micro-straw is suitable and clinically useful for the cryopreservation of small numbers of spermatozoa.

Keywords: Clinical outcomes; cryopreservation; frozen-thaw survival rate; human sperm; micro-straw.