[Morphology of the interstitial cells of rat polycystic ovaries: an experimental study]

To evaluate the histomorphometry of ovarian interstitial cells, as well as the blood sex steroid concentrations of female rats with polycystic ovaries induced by continuous light.

Twenty female rats were divided into two groups: Control Group - in the estrous phase (CtrlG), and a group of rats with polycystic ovaries induced by continuous illumination (POG). CtrlG animals were maintained on a light period from 07:00 a.m. to 07:00 p.m., and POG animals with continuous illumination (400 Lux) for 60 days. After this period all animals were anesthetized and blood was collected for the determination of serum estradiol (E2), progesterone (P4), and testosterone (T), followed by removal of the ovaries that were fixed in 10% formalin and processed for paraffin embedding. Five-µm histological sections were stained with hematoxylin and eosin and used for histomorphometric analysis. Morphological analyses, cyst count, determination of concentration and of the nuclear volume of interstitial cells were performed with the aid of a light microscope adapted to a high resolution camera (AxioCam), whose images were transmitted to and analyzed by the computer using AxioVision Rel 4.8 software (Carl Zeiss). Data were analyzed statistically by the Student's t-test (p<0.05).

Morphological analysis showed the presence of ovarian cysts in POG animals and corpora lutea in CtrlG animals, as well as evidence of the origin of interstitial cells from the internal theca of these cysts. POG animals presented increased serum estradiol levels (pg/mL) compared to CtrlG animals (POG=124.9 ± 4.2>CtrlG=73.2 ± 6.5, p<0.05), the same occurring with testosterone levels (pg/mL) (POG=116.9 ± 4.6>CtrlG=80.6 ± 3.9, p<0.05). However, progesterone levels (ng/mL) were higher in CtrlG than in POG animals (CtrlG=16.3 ± 2.0>POG=4.2 ± 1.5, p<0.05). Morphometry showed a significant increase in nuclear volume in POG animals (POG=102.1 ± 5.2>CtrlG=63.6 ± 16.5, p<0.05), as well as in the area occupied (%) by interstitial cells (POG=24.4 ± 6.9>CtrlG=6.9 ± 3.2, p<0.05) compared to CtrlG animals.

The interstitial cells of the rat polycystic ovary probably originate from ovarian cysts due to the degeneration of granulosa cells and differentiation of the internal theca cells. The elevations of serum testosterone and estradiol were probably due to the significant increase in cell activity and in the area occupied by interstitial cells.