Human Sperm Cryopreservation: Update on Techniques, Effect on DNA Integrity, and Implications for ART

Abstract

Cryopreservation of human spermatozoa—introduced in the 1960's—has been recognized as an efficient procedure for management of male fertility before therapy for malignant diseases, vasectomy or surgical infertility treatments, to store donor and partner spermatozoa before assisted reproduction treatments and to ensure the recovery of a small number of spermatozoa in severe male factor infertility. Despite the usefulness of it, cryopreservation may lead to deleterious changes of sperm structure and function: while the effects of cryopreservation on cells are well documented, to date there is no agreement in the literature on whether or not cryopreservation affects sperm chromatin integrity or on the use of a unique and functional protocol for the freezing-thawing procedure. Therefore, sperm cryopreservation is an important component of fertility management and much of its successful application seems to affect the reproductive outcome of assisted reproduction technologies (ART): appropriate use of cryoprotectants before and sperm selection technologies after cryopreservation seem to have the greatest impact on preventing DNA fragmentation, thus improving sperm cryosurvival rates.

Effect of sperm storage and selection techniques on sperm parameters

“…This can be done using fast freezing or slow freezing methods or with a programmable freezer. With all three methods, a low molecular weight cryoprotectant is added to a processed semen sample to prevent ice formation in sperm cells [Di Santo et al 2012]. These chemicals optimize osmotic pressure and pH, provide extracellular energy to sperm, and prevent bacterial contamination (they include antibiotics) [Anger et al 2003].…”

“…This mixture protects sperm cell membranes and prevents osmotic stress within the cells [Anger et al, 2003]. However, glycerol can alter the acrosomal membrane and change the mitochondrial environment [Di Santo et al 2012].…”

Cryopreservation triggers DNA fragmentation and ultrastructural damage in spermatozoa of oligoasthenoteratozoospermic men

“…It has also been shown that cryopreservation reduces the antioxidant activities of the spermatozoa, making them more sensitive to reactive oxygen injuries [16]. Elevated concentrations of reactive oxygen species and decreases of antioxidant enzymes cause cell death after cryopreservation [17,18]. It has been reported that normospermic samples have higher levels of polyunsaturated fatty acids than do oligospermic and asthenospermic samples and that the total antioxidant capacity was higher in normospermic samples than the oligospermic and oligoastenospermic groups before freezing.…”

Pregnancy Outcome of Intracytoplasmic Sperm Injection in Relation to Duration of Cryopreservation of Spermatozoa Obtained through Testicular Sperm Extraction

“…Routine use of sperm storage started in the 60's for patients who undergo gonadotoxic treatment [18]. More recently, sperm storage has also been proposed to patients presenting a very low sperm count or suspected at high risk of rapid decrease in the sperm count (possibly linked to several genetic origins of the oligozoospermia) and asking for Assisted Reproductive Techniques [19].…”