Sperm regulate expression of inflammatory response genes in the female reproductive tract after coitus in the mouse (#105)
At coitus, seminal fluid acts on epithelial cells lining the female reproductive tract to initiate the immunological adaptations required for pregnancy. Signalling factors in seminal plasma are identified, however recent studies indicate that sperm also play an active role. An early response to insemination is a rapid influx of inflammatory cells which act to induce immune tolerance as well as clear superfluous sperm and microorganisms. We hypothesised that sperm regulate female reproductive tract expression of genes controlling leukocyte recruitment following mating. CBAF1 female mice were mated with intact or vasectomised Balb/c males and sacrificed 8h later, and compared with unmated estrous control mice. RNA was extracted from endometrial tissue and expression profiles were examined by Affymetrix microarray. A total of 685 genes were differentially regulated (>1.5 fold) in intact compared to vasectomised matings. Ingenuity Pathway Analysis of the differentially regulated genes implicated canonical pathways associated with immune recognition and immune tolerance. Analysis of the top functions associated with the inflammatory response showed a particular increase in neutrophil functions. Expression of genes encoding cytokines and chemokines associated with neutrophil recruitment and activation including Csf1, Csf2, Csf3, Cxcl1, Cxcl5, Cxcl7, Csf3r and Il8rb all increased in the presence of sperm compared with seminal plasma alone, and this was confirmed by qRT-PCR. Additionally, immunohistochemical analysis in paraffin sections using the neutrophil-specific antibody RB6 revealed increases in neutrophil numbers in the endometrial tissue of females mated to intact males compared to vasectomised males. We conclude that sperm interact with the female reproductive tract to induce expression of immune regulatory genes that in turn promote recruitment of neutrophils into the endometrial compartment. Future studies will examine the identity of the sperm signals involved in neutrophil recruitment, including the possible contribution of sperm-borne microRNA, and the immune-regulatory role of these neutrophils during the peri-conceptual period.