PCOS is a common metabolic disorder in women of reproductive age that affects all physiological, social, and economic aspects of a person’s life. Because of the heterogeneous condition, there are no definite diagnostic criteria for this disorder. But these two signs are required to confirm (1) hyperandrogenism and (2) polycystic ovary [2, 4]. Therefore, biochemical markers and ovarian biopsy are usual evidence for PCOS diagnosis. For this reason, we take into consideration both histological and biochemical evaluations in the present study. We focused on two main features: blood sexual hormone (estrogen), gonadotropins (FSH and LH), and ovarian histology. Obesity is one of the symptoms of PCOS which is observed in rats in this study. Two hundred fifty and 500 mg/kg doses of extracts could prevent weight gain in rats.
There are different methods for the induction of PCOS in the experimental animals. One of the common ways is treatment with estrogen and drugs with estrogenic effects. These compositions induce continuous estrous and cyclic follicles with morphologic effects like what was observed in PCOS women . In this experiment, we tried to induce a PCOS-like phenotype by a single-dose injection of estradiol valerate (2 mg/kg) in Wistar rats.
In normal cases, the ratio of LH/FSH is almost 1:1, but in PCOS women, this ratio is 2 times or 3 times higher (2:1 or 3:1), . The results of our experiment also demonstrated that the ratio of LH/FSH in PCOS rats was 2.5 times more than the control. On the other hand, the estrogen level significantly increased in the PCOS group. On the basis of the previous reports, the dominance of estrogen is the most common cause of ovulatory disorder and even anovulatory. This high level of estrogen finally results in insufficient progesterone, elevated LH, and infertility. Most of the follicles make cystic follicles and arrested to form adult follicles. Also, the reduction of corpora lutea is associated with these changes .
The study of ovaries sections showed a significant increase in the number of cystic follicles in the PCOS group in comparison with the non-injected control group. In contrast, the number of other (preantral, antral, and Graafian) follicles and corpus luteum significantly decreased.
Data of our study indicated a significant decrease in the thickness of the granulosa layer and a significant increase in the thickness of the theca layer in the PCOS group which is consistent with previous studies [16, 17]. Researchers indicated an abnormality in the granulosa cells of cystic follicles. Also, increased staining in the thecal layer may be described by the carbohydrate which is associated with an increased amount of collagen [16, 18].
The Stachys extract caused significant FSH increases and estrogen decrease in comparison with the PCOS group, in the way that the ratio of LH/FSH became close to 1:1 (6.48/5.59) at high doses of extract (500 mg/kg). Therefore, the number of follicles in the different stages and corpora lutea increased significantly. These findings are in agreement with the results of some other useful herbal extract for PCOS treatment [14, 16].
Stachys sylvatica contains iridoids, flavonoids, phenolic acids, sesquiterpenes, and diterpenoids as secondary metabolites . It was reported that flavonoids have an aromatase inhibitory effect . The action of the aromatase enzyme is the biosynthesis of estrogen from the androgen. As it is known, one of the distinct symptoms of PCOS is high levels of androgen which affects follicle development and change of the hypothalamic-pituitary ovarian axis. Chemical aromatase inhibitor drugs like letrazole (prescribed for PCOS patients, off-label usage) can decrease estrogen by preventing androgen to estrogen alteration pathway . It seems that the reduction of estrogen in our experiments after treatment by Stachys extract is due to the flavonoid constituents.
On the other hand, some flavonoids can bind to the benzodiazepine site of GABA (gamma amino butyric acid) receptor and act as GABA receptor agonists. Many documents suggest that GABAergic regulations of GnRH (gonadotropin-releasing hormone) neurons are involved in LH surge alteration. It was reported that the inhibitory effect of GABA on GnRH neurons leads to LH surge [20, 21]. This can justify a decrease in LH/FSH ratio in the PCOS groups treated with high doses of Stachys extract.
Considering the importance of Stachys sylvatica in the Iranian folk medicine for the treatment of some illness, their essential oil compositions were analyzed accurately. β-Caryophellene was the major component, also 9 sesquiterpenes, 13 monoterpenes, δ-cadinene, and bicyclogermacrene were detected . It was demonstrated that sesquiterpenes such as ß-caryophellene and δ-cadinene are responsible for Stachys extract anti-inflammatory, antirheumatic, and diuretic activity .
Studies on PCOS women have shown the ability of some dietary factors like anti-inflammatory materials to improve the metabolic disorder of patients [5, 23]. Women with PCOS have demonstrated a higher level of inflammatory mediators such as tumor necrosis factor, C-reactive protein, and tissue plasminogen activator in their blood which is associated with insulin resistance . Some in vitro experiments have revealed that proinflammatory stimuli can upregulate the steroidogenic enzyme response in the ovarian theca cells in order to produce androgen . Anti-inflammatory factors like flavonoids operate through reducing the synthesis of prostaglandins that have a role in the gonadotropin synthesis. In consequence, Stachys extract could be effective in the PCOS treatment through reducing gonadotropin levels.
Háznagy-Radnai et al. in 2011 investigated the iridoid constituents of Stachys species for the anti-inflammatory properties . The results showed that iridoids are responsible for herb anti-inflammatory effects but other active constituents or their synergism must also be involved.
Hajdari et al., exhibited potent antioxidant activity of Stachys sylvatica . As it is known, oxidative stress can cause hyperinsulinemia and disorder of folliculogenesis . The extract could have some beneficial effects by high degree of materials for extracting free radical scavengers. Moreover, products from arachidonic metabolism (lipoxigenase pathway), including inflammatory prostaglandins seem to play a crucial role in the inflammation . In fact, the Stachys extract by providing potent antioxidant properties has an inhibitory role in this metabolic pathway .