Characterization of sperm protein SP22 as a biomarker of fertility in men

Abstract

Infertility affects about 15% of couples of reproductive age, and men are responsible for nearly half of the cases. Decrease of male fertility is due several conditions that include congenital malformations, genetic and endocrine disorders, infectious and inflammatory diseases and exposure to environmental toxicants. In recent years, considerable effort has been made by several researchers to identify and characterize sperm proteins that are functionally important to the process of fertilization. Several sperm proteins, as well as epididymal fluid and seminal plasma proteins, have been associated with the fertile potential and the sperm protein SP22 (Sperm Protein, 22KDa) has been demonstrated to be a biomarker of male fertility. In rats, it is well established that SP22 levels in sperm extracts from the cauda epididymis correlated with the fertility of these sperm. This protein was also described in other animal species, such as equine, bovine, caprine, avian and humans. However, to incorporate this biomarker into epidemiology and clinical studies, quantitative human data are needed. Thus, this study aims to standardize the technique for quantifying the SP22 protein on human sperm and assessing the potential of this protein as a biomarker of fertility in humans. A prospective clinic case-control study will be performed on semen samples from 100 men attending the fertilization in vitro service (FIV) of the School of Medicine of Federal University of São Paulo, already excluded those in which the couple is inflicted with female factor infertility, for example, endometriosis. These men will be grouped according to the results of the FIV (pregnancy or not after the assisted reproduction procedure). The semen analysis will be carried out as recommended by the World Health Organization (2010), evaluating the concentration, motility, sperm morphology and seminal volume. In addition, functional analysis of semen will be conducted to investigate DNA fragmentation, mitochondrial activity, acrosome integrity and levels of SP22. The correlation among these parameters will be investigated. SP22 localization will be assessed by immunocytochemistry and quantification by ELISA (sperm extracts). This study will receive Institutional Review Board approval from the São Paulo Federal University Research Ethics Committee and included individuals provide written consent. The main goal is to identify the levels of SP22 that can contribute for the design of diagnostic of the fertility/infertility male human to be used in clinic and epidemiology study. It is also desirable to strength research collaborations with other laboratories in Brazil and abroad, as well as the formation of qualified human resources in Biology and Toxicology of Reproduction. The results that will be obtained will be submitted for publication in international journals and indexed impact, as well published in scientific events in this area.