Abstract
Post-thawed sperm quality parameters vary across different species after cryopreservation. To date, the molecular mechanism of sperm cryoinjury, freeze-tolerance and other influential factors are largely unknown. In this study, significantly dysregulated microRNAs (miRNAs) and mRNAs in boar and giant panda sperm with different cryo-resistance capacity were evaluated. From the result of miRNA profile of fresh and frozen-thawed giant panda sperm, a total of 899 mature, novel miRNAs were identified, and 284 miRNAs were found to be significantly dysregulated (195 up-regulated and 89 down-regulated). Combined analysis of miRNA profiling of giant panda sperm and our previously published data on boar sperm, 46, 21 and 4 differentially expressed (DE) mRNAs in boar sperm were believed to be related to apoptosis, glycolysis and oxidative phosphorylation, respectively. Meanwhile, 87, 17 and 7 DE mRNAs in giant panda were associated with apoptosis, glycolysis and oxidative phosphorylation, respectively. Gene ontology (GO) analysis of the targets of DE miRNAs showed that they were mainly distributed on membrane related pathway in giant panda sperm, while cell components and cell processes were tied to the targets of DE miRNAs in boar sperm. Finally, Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis of DE mRNAs indicated that most of these DE mRNAs were distributed in membrane signal transduction-related pathways in giant panda sperm, while those in boar sperm were mainly distributed in the cytokine-cytokine receptor interaction pathway and inflammatory related pathways. In conclusion, although the different freezing extenders and programs were used, the DE miRNAs and mRNAs involved in apoptosis, energy metabolism, olfactory transduction pathway, inflammatory response and cytokine-cytokine interactions, could be the possible molecular mechanism of sperm cryoinjury and freeze tolerance.
Highlights
Cryopreservation, as an important part of artificial insemination (AI), is the most efficient method for long-term preservation of valuable genetic material from livestock, especially in endangered wild animals [1,2]
Giant panda sperm appears to be strongly cryo-resistant and is capable of surviving repeated cycles of freeze-thawing [15]. Spindler and his colleagues reported that the functional capacitation of plasma membrane of giant panda sperm [16] and sperm head morphometry [15] were not be affected by the rapid rates of thawing in cryopreservation protocol, neither was the decondensation of sperm, a key step of fertilization [17]
Along with our previously published miRNA and mRNA profiles of boar sperm, we aimed to explore the differences in miRNA and mRNA expression pattern between boar and giant panda sperm, which is believed to be influenced by freezing procedures and high resistance to repeated freezing, respectively
Summary
Cryopreservation, as an important part of artificial insemination (AI), is the most efficient method for long-term preservation of valuable genetic material from livestock, especially in endangered wild animals [1,2]. The composition (i.e., P1 only in boar, bull, and ram sperm; P1 and P2 in human, stallion, and mouse sperm) and the ratio of P1 to P2 in different species could potentially affect the resilience of the chromatin structure to freeze-thawing procedures [6]. Giant panda sperm appears to be strongly cryo-resistant and is capable of surviving repeated cycles of freeze-thawing [15]. Spindler and his colleagues reported that the functional capacitation of plasma membrane of giant panda sperm [16] and sperm head morphometry [15] were not be affected by the rapid rates of thawing in cryopreservation protocol, neither was the decondensation of sperm, a key step of fertilization [17]. The conception and reproductive success rate of AI using frozen-thawed giant panda sperm were still unsatisfactory [17]
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