Transforming growth factor-β (TGFβ) in porcine seminal plasma

Bioactive factors in seminal plasma induce cellular and molecular changes in the female reproductive tract after coitus. An active constituent of seminal plasma in mice and humans is the potent immune-modulating cytokine transforming growth factor-β (TGFβ). To investigate whether TGFβ is present in boar seminal plasma, TGFβ(1) and TGFβ(2) were measured by immunoassay. High levels of TGFβ(1) and TGFβ(2) were detected in 100% of seminal fluid samples from 73 boars. Both were predominantly in the active, not latent form. Interferon-γ (IFNγ) and lipopolysaccharide (LPS), agents that interact with TGFβ signalling, were detectable in 5% and 100% of samples, respectively. TGFβ(1) and TGFβ(2) concentrations varied widely between boars, but correlated with each other and with sperm density, and remained relatively constant within individual boars over a 6-month period. Frequent semen collection substantially diminished the concentration of both TGFβ isoforms. Using retrospective breeding data for 44 boars, no correlation between TGFβ content and boar reproductive performance by artificial insemination (AI) with diluted semen was found. It is concluded that TGFβ is abundant in boar seminal plasma, leading to the speculation that, in pigs, TGFβ may be a male-female signalling agent involved in immune changes in the female reproductive tract elicited by seminal fluid.