Male infertility is rising worldwide contributing to nearly 50% of all cases. When clear causes cannot be established, infertility is designated as being of unknown origin (UOMI), including the often-confounded idiopathic (ID) and unexplained male infertility (UMI). The diagnosis of male infertility is essentially based on conventional semen analysis, clearly an obsolete evaluation with poor prognostic value that does not provide adequate information regarding functional sperm. UMI patients, that have normal sperm parameters, are the final proof of this limitation. It is thus reasonable to hypothesize that changes in sperm function, not detected by the conventional analysis, are involved. This highlights the importance to understand the alterations that might be responsible for the infertility state of UOMI patients and raises the questions: Can we distinguish ID and UMI at a functional level? Can an infertility biomarker be found for these patients? We propose to answer this question through a detailed characterization of sperm function, that goes far beyond the conventional analysis. For this purpose, semen samples from ID and UMI patients and from a control group of fertile donors will be collected in 2 fertility clinics with a well-established ongoing collaboration. The starting point of this proposal was the well-known link between sperm nuclear DNA (nDNA) damage and infertility and the fact that this damage is likely to involve oxidative stress and mitochondrial dysfunction. Our first objective is thus to perform a comprehensive evaluation of sperm function assessing parameters such as nDNA integrity, capacitation status, acrosome integrity, calcium signaling and binding/fusion properties, complemented by a bioenergetic evaluation, to determine how and if mitochondrial function is affected in UOMI patients. The second objective is to perform a proteomic analysis of both sperm tail and nucleus, allowing to focus on the main areas of potential damage (mitochondria/nDNA) and from which new proteins may emerge as valuable markers of altered function in these patients. Finally, all obtained data will be correlated with ART outcomes to identify the more reliable indicators of sperm competence and hopefully define a biomarker for UOMI patients. This is will be the first study to bring together multiple aspects of the sperm function of UOMI patients, evaluated through a variety of non-conventional techniques- Raman microspectroscopy, Seahorse Metabolic Flux Analyzer and an innovative subfractionation proteomic analysis- increasing the odds of finding a biomarker, that can be further used to develop new tools that will improve diagnostic and tailored treatments for these patients, and/or to collect information that can be helpful in the hard task of selecting better gametes. Granting this project will definitely allow us to build new knowledge and to contribute to the innovation in the growing reproductive field.
Overall, with our comprehensive multi-level approach, using innovative approaches and relying on an excellent team, we expect to obtain new insights into the mechanisms behind UOMI, that allows us to clearly discriminate ID and UMI infertile men and suggest a reliable biomarker for these patients that could eventually be used to diagnose infertility in these patients and to select better gametes.
PTDC/MEC-AND/28599/2017 ; POCI-01-0145-FEDER-028599