Microscopic sacs, known as exosomes, present in semen may shed light on previously unexplained cases of male infertility.
Unexplained male infertility refers to a diagnosis of males who have undergone routine semen analysis which had not identified any abnormalities. In the UK, around 25 percent of cases of male infertility are unexplained.
At the recent annual meeting of the European Society of Human Reproduction and Embryology (ESHRE) Hadis Gholipour, a PhD student at the Iran University of Medical Sciences involved in the work, told the conference 'They're a challenging group to treat', New Scientist reported.
Exosomes are formed within a cell and typically contain cellular protein, DNA and RNA, which can be transferred to other cells as a form of cellular communication. Importantly, exosomes are present within seminal fluid and are known to bind to sperm and promote maturation. It has previously been shown that exosomes present in the semen of males with fertility problems differ from those found in the semen of males without fertility issues.
The new research presented at ESHRE as an abstract which was published in the Journal of Human Reproduction, has shown that exosomes in the semen of infertile males may negatively influence the receptivity of the uterus lining to embryo implantation.
The research team isolated exosomes from semen samples of ten males undergoing infertility treatment and ten sperm donor males without fertility problems. Cells from the uterus lining, known as the endometrium, were collected from six women during the follicular phase of the menstrual cycle, also known as the proliferative phase as the endometrium thickens during this time. These endometrial epithelial cells were cultured and incubated with the exosomes for six or 24 hours before the team analysed gene expression patterns.
'The incubated exosomes bind to the endometrial cells and can be found inside the cells. Once inside the cells, the exosomes can deliver diverse signals,' said Gholipour.
Genes known to promote uterus receptivity were found to be significantly downregulated following incubation with the exosomes of males diagnosed with unexplained infertility. The research team have speculated that the exosomes of infertile males can reduce uterus receptivity by altering gene expression patterns and may be a cause of their infertility.
The results presented at ESHRE represent only preliminary findings and further evaluation of a larger sample size will be undertaken soon. Moreover, the research team intend to assess the exosomal composition of fertile and infertile males to build upon their understanding of the role of exosomes in conception.