Sperm proteome reflects pregnancy outcome

Abstract

OBJECTIVE: Mapping of the sperm proteome has already revealed the complexity of spermatogenesis and sperm function. Proteins have been identified to be involved in proteosome turnover, transcription, protein synthesis and protein transport. It has been suggested that sperm proteins are essential for normal syngamy and early embryonic development. This study therefore investigated sperm proteomic fingerprints in correlation with infertility and the relationship to reproductive outcome.DESIGN: Proteomic analysis of human sperm.MATERIALS AND METHODS: Infertile couples (n=22) undergoing IVF treatment donated sperm, with consent, following ICSI. The mean maternal and paternal age was 37±3.9 and 39.6±5.4 years respectively. Sperm samples ranged from 12%-74%, mean 54.5±17.4% for motility and 2-181million/ml, mean 65.5±50.6 for concentration. Each washed sperm sample was further diluted to 1 million/ml prior to centrifugation and 2 washes in PBS. The final pellet was resuspended in protein lysis buffer and stored at -80°C until analysis. Samples were processed using surface enhanced laser desorption ionization time-of-flight mass spectrometry to determine a sperm proteomic fingerprint. Implantation outcome was monitored.RESULTS: On average 15.1±6.9 oocytes were retrieved with a fertilization rate of 57.8±19.4%. 14 out of the 22 infertile patients resulted in successful 100% implantation with the remaining 8 infertile patients with 0% implantation. Proteomic fingerprints were generated for each of the 22 sperm samples. Statistical analysis was performed according to implantation outcome and identified a novel set of six sperm proteins across a mass range of 2.9-4.6 kDa that exhibited higher levels of expression with 100% implantation (P < 0.01). Further investigation of these proteins revealed a potential 3.9kDa ID candidate to be hepatocyte growth factor (HGF) activator. HGF is a pleiotropic cytokine that influences mitogenesis, motility and differentiation and has a positive effect on the maintenance of sperm motility.CONCLUSIONS: As proteins are responsible for cellular function, identification and quantification of the sperm proteome will gain new insights into the causes and potential treatment of male infertility. In this study the contribution and expression of a novel set of sperm proteins to the resulting embryo could contribute to reproductive outcome. The ability to diagnostically assay sperm prior to infertility treatment should assist in patient management. OBJECTIVE: Mapping of the sperm proteome has already revealed the complexity of spermatogenesis and sperm function. Proteins have been identified to be involved in proteosome turnover, transcription, protein synthesis and protein transport. It has been suggested that sperm proteins are essential for normal syngamy and early embryonic development. This study therefore investigated sperm proteomic fingerprints in correlation with infertility and the relationship to reproductive outcome. DESIGN: Proteomic analysis of human sperm. MATERIALS AND METHODS: Infertile couples (n=22) undergoing IVF treatment donated sperm, with consent, following ICSI. The mean maternal and paternal age was 37±3.9 and 39.6±5.4 years respectively. Sperm samples ranged from 12%-74%, mean 54.5±17.4% for motility and 2-181million/ml, mean 65.5±50.6 for concentration. Each washed sperm sample was further diluted to 1 million/ml prior to centrifugation and 2 washes in PBS. The final pellet was resuspended in protein lysis buffer and stored at -80°C until analysis. Samples were processed using surface enhanced laser desorption ionization time-of-flight mass spectrometry to determine a sperm proteomic fingerprint. Implantation outcome was monitored. RESULTS: On average 15.1±6.9 oocytes were retrieved with a fertilization rate of 57.8±19.4%. 14 out of the 22 infertile patients resulted in successful 100% implantation with the remaining 8 infertile patients with 0% implantation. Proteomic fingerprints were generated for each of the 22 sperm samples. Statistical analysis was performed according to implantation outcome and identified a novel set of six sperm proteins across a mass range of 2.9-4.6 kDa that exhibited higher levels of expression with 100% implantation (P < 0.01). Further investigation of these proteins revealed a potential 3.9kDa ID candidate to be hepatocyte growth factor (HGF) activator. HGF is a pleiotropic cytokine that influences mitogenesis, motility and differentiation and has a positive effect on the maintenance of sperm motility. CONCLUSIONS: As proteins are responsible for cellular function, identification and quantification of the sperm proteome will gain new insights into the causes and potential treatment of male infertility. In this study the contribution and expression of a novel set of sperm proteins to the resulting embryo could contribute to reproductive outcome. The ability to diagnostically assay sperm prior to infertility treatment should assist in patient management.