M. Reichart et al., In vivo and in vitro impairment of human and ram sperm nuclear chromatin integrity by sexually transmitted Ureaplasma urealyticum infection, BIOL REPROD, 63(4), 2000, pp. 1041-1048
The incidence of Ureaplasma urealyticum infection in the semen of infertile
men is variable (7%-42%). Evidence has accumulated through routine semen a
nalysis to suggest that this infection can cause embryo loss without necess
arily affecting sperm quality. The aim of this study was to specifically in
vestigate the effects of U. urealyticum infection on sperm chromatin stabil
ity and DNA integrity, which are known to be correlated to pregnancy outcom
e. Sperm cells isolated from human semen infected in vivo with U. urealytic
um exhibited a low percentage of stable chromatin as determined by nuclear
chromatin decondensation assay (42% +/- 4.8%, n = 8) and a high percent of
denatured DNA as determined by sperm chromatin structure assay (60.9% +/- 9
.1%, n = 7). After doxycyclin treatment, a significant improvement in both
parameters was observed (73.7% +/- 3.6%, P < 0.001 and 30.1% +/- 3.5%, P <
0.008, respectively). Sperm cells infected in vitro exhibited higher rates
of viability and motility than uninfected cells. In contradistinction, U. u
realyticum caused significant dose- and time-dependent chromatin decondensa
tion and DNA damage. The percentage of human sperm cells with denatured DNA
increased significantly by 54.9% +/- 23.9% and 47.9% +/- 12.1%, after 30 m
in infection with serotypes 8 and 3, respectively, at a multiplicity of inf
ection of 100 ureaplasmas per sperm compared with uninfected control cells.
The damage to DNA was significantly more pronounced in infected ram sperm
(180.9% +/- 21.5%). These results indicate that preserved sperm activity po
st U, urealyticum infection resulted in damage to paternal DNA, although a
high fertilization rate was maintained, and embryonic development may, ther
efore, be impaired.