Researchers have used an original proteomic strategy to identify a biomarker for residual spermatogenesis in the semen of patients with nonobstructive azoospermia (NOA).
In a study of 40 men, the technique revealed that the expression of lectin galactose-binding, soluble 3 binding protein (LGALS3BP) was significantly higher in patients who had post-meiotic germ cells present in their semen than in those who did not.
The biomarker could be used to predict the success of testicular sperm extraction (TESE) in men with NOA before treating infertile couples with intracytoplasmic sperm injection (ICSI), suggest Thomas Freour (University Hospital of Nantes, France) and colleagues.
"There is currently no powerful and accurate clinical or biological predictor of successful TESE, even if scores associating various clinical and hormonal parameters appear to be promising," remarks the team. "A specific biomarker that could predict residual spermatogenesis would obviously be of interest before performing TESE."
The researchers used an isotope-coded protein label (ICPL)-based proteomic screening approach, which combines stable isotopic labeling of free amino acid groups with mass spectrometry, to compare the abundance of different peptides in the men's semen.
As reported in Andrology, they found 12 proteins that were differentially expressed according to the presence or absence of spermatogenesis among the samples. The mean concentration of LGALS3BP in particular was significantly higher among individuals with evidence of spermatogenesis than in those without, at 345 ng/mL versus 207 ng/mL.
In addition, a seminal plasma LGAS3BP level above the threshold of 153 ng/mL was associated with a favorable TESE outcome, reports the team. "This cut-off could thus be evaluated as an exclusion criteria, limiting the number of patients undergoing TESE with very few or no chance of successful sperm retrieval."
Currently, whether or not physicians propose ICSI to an infertile couple in the case of NOA depends on spermatogenesis, testicular histology, and the potential for retrieving live spermatozoa. "Unfortunately this favorable outcome is only obtained in 30-50% of testicular sperm extraction," note Freour and colleagues.
The researchers say future studies should be carried out to improve the technical performance of proteomic analysis and to identify other clinically useful candidate biomarkers.
"External validation in a larger population will be essential to confirm the relevance of this strategy," they conclude.
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