Histomorphometrics and quantitative unbiased stereology in canine uteri treated with medroxyprogesterone acetate

This article describes the effects of MPA use on the canine uterus using stereological methods. Entire reproductive tracts were removed from normal healthy canine bitches (Canis lupus familiaris) and grouped as: nulliparous (n = 11), multiparous (n = 11) and MPA-treated (n = 11; nulliparous; two treatments; 5 mg/kg). 1 cm samples were cut from the corpus, horn and uterine tube and fixed in 10% formaldehyde. Sections of each were mounted on slides and stained with hematoxylin-eosin. We assessed the fraction area for components of endometrium and myometrium and V_V (volume density) and S_V (surface density) of the gland and stroma using the M₃₆ test system provided by the STEPanizer Stereological Tool. No gross histological differences were observed between study groups in the uterine tube, uterine corpus and horn. The wall of the uterine corpus and horn in MPA-treated bitches was characterized as being thicker than in the other groups. A cross-section of the uterine corpus revealed no differences between components of uterine wall in the corpus and horn; however, differences were observed in the volume density [V_V; %] in variables such as: V_{V[str.vasc/uterus]} (nulliparous vs. multiparous; p = 0.0019) and V_{V[str.supravasc/uterus]} (multiparous vs. nulliparous and MPA; p = 0.0035). In the endometrial gland, differences were detected in S_{V[gland/endom]} (multiparous vs. MPA, p = 0.0442). In the uterine horn, differences were only observed in the variable V_{V[lumen.gland/endom]} (multiparous vs. MPA; p = 0.0019). This study shows quantitative changes in the architecture of the endometrium and myometrium in all the uterine segments, mainly morphological endometrial gland changes of the uterine corpus, increasing the surface area per unit of volume; however, these changes usually do not differ quantitatively from those observed in the uterus of multiparous bitches.