Eh. Luque et al., ROLE OF RELAXIN AND ESTROGEN IN THE CONTROL OF EOSINOPHILIC INVASION AND COLLAGEN REMODELING IN RAT CERVICAL TISSUE AT TERM, Biology of reproduction, 59(4), 1998, pp. 795-800
Ripening and dilation of the rat cervix at term involves a widespread
reduction in the density and organization of collagen fibers following
a polymorphonuclear eosinophilic invasion. These are hormonally regul
ated events; however, the correlation between hormonal milieu and thes
e morphological changes is not well understood. To investigate the rol
e of preparturient relaxin and estradiol-17 beta (E-2) in cervical col
lagen remodeling and eosinophilic infiltration, pregnant rats were eit
her sham-ovariectomized (group C) or ovariectomized in the morning of
Day 22. Ovariectomized rats were treated with E-2 (group OE), relaxin
(group OR), E-2 plus relaxin (group OER), or hormone vehicles (group O
). There were 4 or 5 animals per group. Cervices were taken from anima
ls killed approximately 1 h before expected parturition. Five-micromet
er serial sections of paraffin-embedded cervices were stained with eit
her Sirius Red in alkaline solution to measure eosinophil infiltration
or in Picrosirius to measure collagen birefringence. Ovariectomized r
ats treated with E-2 (group OE or OER) showed high levels of eosinophi
lic infiltration that did not differ from those in group C intact cont
rols. However, the values of eosinophilic infiltration in ovariectomiz
ed rats treated with relaxin or hormone vehicles (groups OR and O) wer
e low and far below (p < 0.01) those of groups OE and C. In ovariectom
ized rats treated with E-2 alone (group OE), the widespread reduction
in collagen organization that occurred in group C controls was not obs
erved. It was only in ovariectomized rats treated with relaxin or E-2
+ relaxin (groups OR and OER) that the values of birefringence were lo
w, and they were as low as in control group C. In conclusion, this stu
dy indicates that eosinophilic infiltration and collagen remodeling in
the rat cervix at term are under the control of different hormones: E
-2 stimulates eosinophilic invasion, and relaxin promotes a widespread
reorganization of collagen fibers.