Cryopreservation of single-sperm: where are we today?

Abstract

Background: Patients with severe oligospermia and nonobstructive azoospermia have very limited numbers of viable sperm in their epididymal and testicular samples. Thus, cryopreservation of their sperm is performed to avoid repeated sperm retrievals and to preserve their sperm from any side effects of any treatment regimens. Main body: The development of intracytoplasmic sperm injection technology has extended the therapeutic capacity of assisted reproductive technology for men with azoospermia via the surgical or percutaneous isolation of sperm from the testis/epididymis. The conventional cryopreservation techniques are inadequate for preserving individually selected sperm. The technique for freezing single sperm was first developed in 1997 and has been explored from the perspective of frozen carriers, freezing programs, and cryoprotectant formulations. Among these methods, advances in frozen carriers have directly improved single-sperm freezing technology. In this review, we evaluate the different technologies for the cryopreservation of single sperm by discussing the advantages and disadvantages of different freezing methods, their clinical applications, and the outcomes for a range of frozen carriers. Conclusion: Our review article describes the latest and current technologies implemented for the cryopreservation of single sperm that could potentially benefit patients with severe oligospermia and who rarely have any sperm in their ejaculate. This review provides a platform to understand the process and pitfalls of single-sperm cryopreservation to ensure further improvements in the cryopreservation technology in future studies.

A decellularized oocyte‐derived scaffold provides a “sperm safe” to preserve mammalian spermatozoa

“…This method is only relevant for special cases where there is a specific need to store and recover extremely limited numbers of spermatozoa and is not intended to be superior to or replace standard sperm freezing methods. Given the need to be able to store small numbers of spermatozoa, there have historically been numerous attempts to come up with suitable strategies, including microdrops, cryoloops, ICSI needles, alginate beads, algae spheres, hyaluronan microcapsules, micro‐straws, and high security straws 11,35‐43 . However, these methods have failed to become widespread clinically likely because they are technically challenging, not scalable or robust, or not feasible within a clinical setting.…”

Sperm Selection Procedures for Optimizing the Outcome of ICSI in Patients with NOA

“…Limited numbers of studies with NOA cases have reported healthy pregnancies in ICSI cycles using testicular spermatozoa frozen by vitrification [ 151 , 163 , 164 ]. For this purpose, specially designed tools have been developed that can allow freezing of a small number of spermatozoa [ 165 ]. Spis et al compared the results of TESE spermatozoa cryopreserved by conventional freezing with those frozen using cryoprotectant and cryoprotectant-free vitrification methods [ 163 ].…”

“…For this purpose, loading a small number of spermatozoa on a cryoloop in a 50:50 mixture of test yolk buffer with glycerol and modified human tubal fluid medium supplemented with 6% Plasmanate was shown to preserve sperm viability and function [ 182 ]. Various protectant mixtures have been investigated to reduce the concentration of compounds in order to ensure their maximum efficiency without reaching toxic levels [ 165 ].…”

Male Infertility in Cryptozoospermia or Severe Oligozoospermia is sperm Useful Cryopreservation

“…However, the spermatozoa found in a section of semen samples using a microscopic directly, but cannot be included due to low con- (Ketabchi, 2016) [7,8].…”