Coordinated elevation of membrane type 1-matrix metalloproteinase and matrix metalloproteinase-2 expression in rat uterus during postpartum involution

BACKGROUND: The changes occurring in the rodent uterus after parturition can be used as a model of extensive tissue remodeling. As the uterus returns to its prepregnancy state, the involuting uterus undergoes a rapid reduction in size primarily due to the degradation of the extracellular matrix, particularly collagen. Membrane type-I matrix metalloproteinase (MT1-MMP) is one of the major proteinases that degrades collagen and is the most abundant MMP form in the uterus. Matrix metalloproteinase-2(MMP-2) can degrade type I collagen, although its main function is to degrade type IV collagen found in the basement membrane. To understand the expression patterns of matrix metalloproteinases (MMPs) in the rat uterus, we analyzed their activities in postpartum uterine involution. METHODS: We performed gelatin zymography, northern blot analysis and immunohistochemistry to compare the expression levels of MT1-MMP, MMP-2, matrix metalloproteinase-9 (MMP-9) and the tissue inhibitors of MMPs-1 and 2 (TIMP-1 and TIMP-2) in the rat uterus 18 h, 36 h and 5 days after parturition with their expression levels during pregnancy (day 20). RESULTS: We found that both MT1-MMP and MMP-2 localized mainly in the cytoplasm of uterine interstitial cells. The expression levels of MT1-MMP and MMP-2 mRNAs and the catalytic activities of the expressed proteins significantly increased 18 h and 36 h after parturition, but at postpartum day 5, their mRNA expression levels and catalytic activities decreased markedly. The expression levels of MMP-9 increased 18 h and 36 h after parturition as determined by gelatin zymography including the expression levels of TIMP-1 and TIMP-2. CONCLUSION: These expression patterns indicate that MT1-MMP, MMP-2, MMP-9, TIMP-1 and TIMP-2 may play key roles in uterine postpartum involution and subsequent functional regenerative processes

Remarkable features of ovarian morphology and reproductive hormones in insulin-resistant Zucker fatty (fa/fa) rats

<p>Abstract</p> <p>Background</p> <p>Zucker fatty (fa/fa) rats are a well-understood model of obesity and hyperinsulinemia. It is now thought that obesity/hyperinsulinemia is an important cause of endocrinological abnormality, but to date there have been no reports on the changes in ovarian morphology or the ovarian androgen profile in rat models of obesity and insulin resistance.</p> <p>Methods</p> <p>In this study we investigated the effects of obesity and hyperinsulinemia on ovarian morphology and the hormone profile in insulin-resistant Zucker fatty rats (5, 8, 12 and 16 weeks of age, n = 6-7).</p> <p>Results</p> <p>Ovaries from 5-week-old fatty rats had significantly greater total and atretic follicle numbers, and higher atretic-to-total follicle ratios than those from lean rats. Ovaries from 12- and 16-week-old fatty rats showed interstitial cell hyperplasia and numerous cysts with features of advanced follicular atresia. In addition, serum testosterone and androstenedione levels significantly declined in fatty rats from age 8 to 16 weeks, so that fatty rats showed significantly lower levels of serum testosterone (12 and 16 weeks) and androstenedione (all weeks) than lean rats. This may reflect a reduction of androgen synthesis during follicular atresia. Serum adiponectin levels were high in immature fatty rats, and although the levels declined significantly as they matured, it remained significantly higher in fatty rats than in lean rats. On the other hand, levels of ovarian adiponectin and its receptors were significantly lower in mature fatty rats than in lean mature rats or immature fatty rats.</p> <p>Conclusions</p> <p>Our findings indicate that ovarian morphology and hormone profiles are significantly altered by the continuous insulin resistance in Zucker fatty rats. Simultaneously, abrupt reductions in serum and ovarian adiponectin also likely contribute to the infertility seen in fatty rats.</p

Pioglitazone is effective for multiple phenotyepes of the Zucker fa/fa rat with polycystc ovary morphology and insulin resistance

Abstract Background Hyperandrogenism and insulin resistance may be related to the etiology of PCOS. Zucker fa/fa rats with polycystic ovary are obese, have insulin resistance without diabetes mellitus or hyperandrogenism and can be utilized as PCOS model rats without effects of hyperandrogenemia. PCOS patients are reported to have elevated levels of serum anti-Mullerian hormone (AMH), which has an inhibitory action on folliculogenesis, and low levels of serum adiponectin, which blocks apoptosis and induces biological effects in some tissues. Pioglitazone, an insulin sensitizer, is administered to PCOS patients with insulin resistance to induce ovulation but the mechanisms by which this occurs have not been elucidated. Methods We purchased 4-week-old female fatty Zucker fa/fa rats as well as lean Zucker +/+ rats for use as control rats with normal insulin sensitivity. The Zucker fa/fa rats were administered pioglitazone (2.5 mg/kg body weight/day) or a vehicle every day for 14 days in separate groups. The Zucker +/+ rats were also administered the vehicle. After 2 weeks of treatment, they were euthanized and we obtained serum samples and both ovaries and determined the body weight, ovarian weight, and serum AMH, adiponectin, testosterone, and androstenedione levels. We also examined ovarian histology to check follicle numbers by using hematoxylin-eosin staining, and the number of atretic follicles using Tdt-mediated dUTP nick end labeling (TUNEL) methods. Results The Zucker fa/fa rats used as PCO model rats and Pioglitazone treated PCO model rats were significantly heavier than the Zucker +/+ control rats (p < 0.05) at 15 day old. Pioglitazone treatment did not influence body weight or ovarian weight in either group. However, the total number of follicles was significantly larger in the PCO model rats than in the control rats (P < 0.05). Although pioglitazone treatment appeared to decrease the total number of follicles in the PCO model rats, the decrease was not statistically significant. However, pioglitazone treatment significantly decreased the total number of atretic follicles and the rate of atreteic follicles in the PCO model rats (P < 0.05). The serum AMH level was significantly higher in the PCO model rats than in the control rats. Pioglitazone treatment significantly decreased the serum AMH level and significantly increased the serum adiponectin level in the PCO model rats (P < 0.05). Serum testosterone and androstenedione levels were quite low or undetectable in the 3 groups of rats, and were not influenced by pioglitazone treatment. Conclusion In this study, pioglitazone treatment reduced the serum AMH level and increased the serum adiponectin level in PCO model rats. These effects are related to reduction of the total number of atretic follicles and rate of atretic follicles. This proves that pioglitazone treatment improves healthy follicle growth in these PCO model rats with insulin resistance

Pioglitazone suppresses excessive follicular development in murine preantral follicles

Abstract Polycystic ovary syndrome (PCOS) is an endocrine disease that is common in women in their reproductive period. Patients with this disease suffer from anovulation and hyperandrogenism. Ovulation induction with exogenous gonadotropin often causes ovarian hyperstimulation syndrome because many small antral follicles pause in their growth. Treatment with insulin sensitizers is reportedly effective for both anovulation associated with PCOS, and suppression of excessive follicular growth; however, the underlying mechanism of action remains unknown. Although pioglitazone is known as an insulin sensitizer, it also has a potent modulator of cell growth and apoptosis irrespective of insulin resistance. To clarify the effect of pioglitazone on follicular growth, we performed in vitro culture of murine preantral follicles. Secondary follicles (100-160 μm in diameter) isolated from 6-week-old ICR mice were individually cultured for 13 days. Culture conditions were as follows: 1) follicle-stimulating hormone (FSH; 33 mIU/mL; control), 2) FSH plus dihydrotestosterone (DHT; 500 ng/mL), 3) FSH plus pioglitazone (5 ng/mL), and 4) FSH plus DHT/pioglitazone. Survival rate and follicle diameter were evaluated, and concentrations of estradiol (E2) and vascular endothelial growth factor (VEGF) in culture media were measured. mRNA expression of various growth-promoting factors and Vegf within follicles were also assessed. Although no significant differences were observed with regard to survival rate, follicle diameters on day 13 were significantly different. Compared with the control group, the DHT group showed enhanced growth, while groups administered pioglitazone showed stagnation of the accelerated growth induced by DHT. Although DHT treatment enhanced the expression of bone morphogenetic protein 2 (Bmp2) mRNA, pioglitazone exposure suppressed induction of Bmp2 mRNA by DHT. Vegf mRNA and protein expression were also significantly reduced when pioglitazone was added to culture media containing DHT. Administration of pioglitazone negatively affected follicular growth and VEGF levels, which may suppress excessive follicular growth and prevent ovarian hyperstimulation syndrome

Androgen potentiates the expression of FSH receptor and supports preantral follicle development in mice

Abstract Hyperandrogenism is one of the cardinal symptoms in polycystic ovary syndrome and plays a key role in the pathogenesis of polycystic ovary syndrome. However, the precise effects and mechanisms of excess androgen during follicular development are still unclear. Here we investigated the effects of androgen on mouse follicle development in vitro. Androgen did not affect the growth of follicles smaller than 160–180 μm in the presence of follicle-stimulating hormone (FSH). However, in the presence of low FSH, androgen supported the growth of follicles larger than 160–180 μm, a size at which growing follicles acquire FSH-dependency. Androgen did not change the mRNA expression of various growth-promoting factors but did increase mRNA expression of the FSH receptor. We suggest that androgen has a positive impact on follicle development by augmentation of the actions of FSH. Therefore, FSH-responsive but FSH-independent follicles grow in the presence of a certain level of FSH or androgen, and androgen compensates for FSH deficiency in FSH-dependent follicles