Summary
There is already evidence that a few components of the haemostatic system exist in
semen. If these comprise a functional system, they may have a role in seminal clotting
and liquefaction processes and ultimately may influence fertility. What might be expected
in semen as collected from fertility clinics i.e., after having both coagulated and
subsequently liquefied is uncertain. It does however still contain significant amounts
of Tissue Factor (TF) although its effect on semen quality remains poorly understood.
The present study analyses semen for Tissue Factor Pathway Inhibitor (TFPI). Measurements
were made in seminal plasma, swim-up sperm and prostasomes and its relationship with
conventional fertility parameters assessed. TFPI antigen levels in seminal plasma
were measured in a total of 176 subjects using an Enzyme-linked immunosorbent assay
(ELISA). These include sub-fertile (n=37), normally fertile (n=40), fertile sperm
donor (n=34), vasectomized subjects (n=65) and in a further group defined by normality
in several parameters derived from the World Health Organization (WHO) fertility criteria
and termed “pooled normal semen parameters” (PNSP). For characterization studies,
both TFPI activity and antigen were measured on whole semen, swim-up sperm and prostasome-rich
fraction (n=5). TFPI levels were significantly higher in normal men as compared to
sub-fertile (P<0.01) or vasectomized subjects (P<0.001). TFPI levels were even higher in the donor quality semen and the PNSP group.
TFPI levels also correlated with semen liquefaction time, normal semen viscosity,
sperm progression, percentage of motile sperm and sperm counts (density). In conclusion,
the present finding substantiates the concept of an active clotting system in human
semen. TFPI could regulate the activity of abundant TF, as it does elsewhere. Given
a functional set of coagulation factors in semen, the TF/TFPI balance might impinge
on its liquefaction and hence on global fertility.
Keywords
Tissue Factor Pathway Inhibitor (TFPI) - human semen - fertility - novel finding