Abstract
BackgroundAlthough sperm cryopreservation has been widely used in human reproductive medicine as an integral infertility management in infertility clinics and for banking sperm in sperm banks, the freezing/thawing protocols are not optimal. The freezing and thawing processes result in changes at both structural and molecular levels, some even detrimental, in human sperm when compared with fresh sperm. The change of sperm proteins after cryopreservation may play negative roles for fertilization and early embryo development. Conventionally, cryostraws (CS) and cryovials (CV) are the most widely used cryopreservation carriers (CPCs) for human sperm cryopreservation accompanied with the use of egg yolk free commercial media. However, the influence of cryopreservation on the proteomic profile of human sperm preserved with the two CPCs is unknown. Therefore the purpose of the present study was to compare the frozen-thawed motility, investigate the proteomic profile of human sperm cryopreserved with the two types of CPCs, and identify the susceptible proteins that play key roles for sperm function and fertility.MethodsThe present study compared the cryosurvival of human sperm frozen with the two different CPCs and identified the sperm proteomic changes by using the isobaric tags for relative and absolute quantification labeling technique coupled with 2D LC–MS/MS analysis after freezing and thawing.ResultsOur results indicated that sperm cryopreserved with CV showed higher values for percentage of motile sperm and forward activity rate than those with CS. Compared to fresh sperm, 434 and 432 proteins were differentially identified in human sperm cryopreserved with CS and CV, respectively.ConclusionThe proteomic profiles of human sperm are greatly affected by cryopreservation with either type of CPC. GO analysis revealed that most of the differentially identified sperm proteins enriched in the extracellular membrane-bounded organelles, cytoplasm and cytosol. In addition, 106 susceptible proteins having known identities related to sperm functions were identified. In general, cryovial seems to be the preferred CPC for human sperm cryopreservation based on the post-thaw motility parameters and the effect on sperm proteomic profiles. These results are beneficial for the insight into the understanding of the cryoinjury mechanism of sperm and the development of human sperm cryopreservation strategies.
Highlights
Sperm cryopreservation has been widely used in human reproductive medicine as an integral infertility management in infertility clinics and for banking sperm in sperm banks, the freezing/thawing protocols are not optimal
The aims of this study were to (1) compare two different cryopreservation carriers (CPCs): cryostraw (CS) and cryovial (CV) on the cryosurvival of human sperm frozen with a chemically defined medium, (2) investigate the proteomic profiles of human sperm cryopreserved with CS and CV, which were evaluated by using isobaric tags for relative and absolute quantification (iTRAQ) techniques, and (3) identify the susceptible proteins that play key roles in sperm function and fertility
The results showed that after freezing and thawing, the sperm cryopreserved with either cryostraw or cryovial (CS or CV group) presented a large number of changes in sperm proteins compared to those from the non-frozen control group (C group)
Summary
Sperm cryopreservation has been widely used in human reproductive medicine as an integral infertility management in infertility clinics and for banking sperm in sperm banks, the freezing/thawing protocols are not optimal. The freezing and thawing processes result in changes at both structural and molecular levels, some even detrimental, in human sperm when compared with fresh sperm. The purpose of the present study was to compare the frozen-thawed motility, investigate the proteomic profile of human sperm cryopreserved with the two types of CPCs, and identify the susceptible proteins that play key roles for sperm function and fertility. Current sperm freezing protocols are not optimal and the freezing and thawing process results in inevitable changes, both at structural and molecular levels, most of them are detrimental to sperm and cryopreserved sperm have shown decreased frozen-thawed motility, cell viability and fertilizing ability compared to fresh sperm [3]. The monitoring of proteinic alteration at the proteomics level in human sperm will benefit our understanding of the mechanism of cryoinjuries resulted from the sperm freezing and thawing process. The method used for the quantification of proteins has developed into a combination of isobaric tags for relative and absolute quantification (iTRAQ) and LC–MS/MS [21]
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