Estrogens Regulate Placental Angiogenesis in Horses

A sufficient vascular network within the feto-maternal interface is necessary for placental function. Several pregnancy abnormalities have been associated with abnormal vascular formations in the placenta. We hypothesized that growth and expansion of the placental vascular network in the equine (Equus caballus) placenta is regulated by estrogens (estrogen family hormones), a hormone with a high circulating concentration during equine gestation. Administration of letrozole, a potent and specific inhibitor of aromatase, during the first trimester (D30 to D118), decreased circulatory estrone sulfate concentrations, increased circulatory testosterone and androstenedione concentrations, and tended to reduce the weight of the fetus (p < 0.1). Moreover, the gene expression of CYP17A1 was increased, and the expression of androgen receptor was decreased in the D120 chorioallantois (CA) of letrozole-treated mares in comparison to that of the control mares. We also found that at D120, the number of vessels tended to decrease in the CAs with letrozole treatment (p = 0.07). In addition, expression of a subset of angiogenic genes, such as ANGPT1, VEGF, and NOS2, were altered in the CAs of letrozole-treated mares. We further demonstrated that 17β-estradiol increases the expression of ANGPT1 and VEGF and increases the angiogenic activity of equine endothelial cells in vitro. Our results from the estrogen-suppressed group demonstrated an impaired placental vascular network, suggesting an estrogen-dependent vasculogenesis in the equine CA during the first trimester.

Piper longum (Linn.) restores ovarian function in Letrozole induced PCOS in Rats: Comparison with Metformin and Clomiphene citrate

This study evaluates the prospective use of an herbal plant Piper longum in letrozole induced polycystic ovary syndrome using a rat model. The study used female wistar rats, which were divided into 9 groups, each containing 6 animals. Group I (Control) daily received 1% Carboxy Methyl Cellulose (CMC)as a vehicle control. Letrozole (1mg/kg) was administered by oral route for period of 21days for induction of PCOS in group (II-IX). During experimental period, vaginal smear of all females were collected daily for the estrous cycle determination. During 28 days of letrozole administration, changes in estrous cycle of females were observed and studied. This study showed that PCOS was induced. After Letrozole treatment, 6 animals from group III-IX treated orally with, standard drugs Metformin (300mg/kg/oral route), Clomiphene citrate (100mg/kg/oral route), plant drug Piper longum L. at a concentration of 200mg/kg, 400mg/kg and 800mg/kg, drug interaction groups: Metformin + Piper longum L, 800mg/kg and Clomiphene citrate +Piper lonum L., 800mg/kg body weight and studied for consecutive estrous cycles. Vaginal smear were examined, it showed that hydro alcoholic extract of fruits of Piper longum Linn. group has potential effect on PCOS bringing estrous cycle to normalcy. Also, after Letrozole treatment ovary and reproductive weights of normal rats increased which is normalizes with plant drug treatment. Further studies of hydroalcoholic extract of fruits Piper longum Linn. need to be carried out to check other related parameters of PCOS.

Morphological and morphometric changes and epithelial apoptosis are induced in the rat epididymis by long-term letrozole treatment

The epididymis is an organ that plays a key role in sperm maturation. The aim of this study was to examine the association between the chronic treatment of mature male rats with letrozole and morphological evaluation and morphometric values of epididymis as well as changes in the number of apoptotic cells in epididymal epithelium. Adult rats were treated with letrozole for 6 months and the epididymis weight, morphology, morphometric values and the number of apoptotic cells in the epithelium were examined. Long-term aromatase inhibition resulted in presence of intraepithelial clear vacuoles, hyperplasia of clear cells and a hyperplastic alteration in the epithelium known as a cribriform change. Moreover, changes in diameters of the epididymal duct and the epididymal lumen and changes in the epididymal epithelium height were observed. The number of apoptotic epithelial cells was increased in letrozole-treated group. It can be indicated that chronic treatment with letrozole can affect morphology, morphometric values and apoptosis in the epididymis of adult male rats. Observed changes are similar to that observed in the aging processes and may also be important for patients treated with aromatase inhibitors.

Letrozole Protects Against Cadmium-induced Inhibition of Spermatogenesis via LHCGR and Hsd3b6 to Activate Testosterone Synthesis in Mice

The heavy metal cadmium is believed to be one of the environmental endocrine disruptors of spermatogenesis. Cadmium-induced inhibition of spermatogenesis is associated with hormone secretion disorder. Letrozole is an aromatase inhibitor that can raise peripheral androgen levels and stimulate spermatogenesis. However, the potential protective effects of letrozole against cadmium-induced reproductive toxicity remain to be elucidated. In this study, male mice were administered CdCl2 (4 mg/kg BW) orally by gavage alone or in combination with letrozole (0.25 mg/kg BW) for 30 days. Cd exposure caused a significant decrease in body weight, sperm count, motility, vitality and plasma testosterone levels. Histopathological changes revealed extensive vacuolization and decreased spermatozoa in the lumen. However, in the Cd+letrozole group, letrozole treatment compensated for deficits in sperm parameters (count, motility, and vitality) induced by Cd. Letrozole treatment significantly increased serum testosterone levels, which were reduced by Cd. Histopathological studies revealed a systematic array of all germ cells, a preserved basement membrane and relatively less vacuolization. For mechanistic exploration, RNA-seq was used to profile alterations in gene expression in response to letrozole. Compared with that in the Cd-treated group, RNA-Seq analysis showed that 214 genes were differentially expressed in the presence of letrozole. Gene ontology (GO) enrichment analysis and KEGG signaling pathway analysis showed that steroid biosynthetic processes were the processes most affected by letrozole treatment. Furthermore, we found that the expression of the testosterone synthesis-related genes LHCGR (luteinizing hormone/choriogonadotropin receptor) and Hsd3b6 (3 beta- and steroid delta-isomerase 6) was significantly downregulated in Cd‐induced testes, but in letrozole-treated testes, these genes maintained similar expression levels as the control group. However, the transcription levels of inflammatory cytokines, such as IL-1β and IL-6, and oxidative stress-related genes (Nrf2, Nqo1, and Ho-1) showed no changes. The present study suggests that the protective potential of letrozole against Cd-induced reproductive toxicity might be due to upregulation of LHCGR and Hsd3b6, which could beneficially increase testosterone synthesis to achieve optimum protection in sperm quality and spermatogenesis.

Severe hemoperitoneum resulting from restart of letrozole after oocyte retrieval procedure: a case report

Background In the field of oncofertility, patients with breast cancer are often administered letrozole as an adjuvant drug before and after oocyte retrieval to prevent an increase in circulating estradiol. Case presentation We report a case of abdominal hemorrhage due to an ovarian rupture in a 29-year-old Japanese patient who restarted letrozole 2 days after an oocyte retrieval procedure in which 14 mature oocytes were retrieved. The patient had sought embryo cryopreservation as a fertility preservation option before undergoing treatment for recurrent breast cancer. A day after restarting letrozole treatment, the patient unexpectedly developed severe abdominal pain. Laparoscopic hemostasis was performed to manage the ovarian swelling and hemorrhage. Conclusions The ovaries can be restimulated by restart letrozole after an oocyte retrieval procedure. Therefore, reproductive-medicine practitioners should understand the potential complications of letrozole administration in such cases and take steps to ensure that they are minimized.

Maternal aromatase inhibition via letrozole altered RFamide-related peptide-3 and gonadotropin releasing hormone expression in pubertal female rat

Despite the prevalence of polycystic ovary syndrome (PCOS) among childbearing women and the development of many animal models for this syndrome, information on its etiology is still scarce. Intrauterine hyperandrogenic environment may underlie changes at the levels of hypothalamus, pituitary and ovary organization in female offspring, and PCOS later in life. Letrozole, has been shown to mimic reproductive and metabolic characteristics of PCOS in adult rodent models. Therefore, the aim of this research was to assess the condition in a prenatal letrozole-treated rat model. Twenty-eight female rats from dams receiving letrozole at certain doses during late pregnancy were used in the trial. Pregnant Sprague-Dawley rats (n = 21) received letrozole treatment on days 16–18 gestation at doses 1.25, 1.0, 0.75, 0.5, and 0.25 mg/kg body weight (BW). Prenatal letrozole-treatment delayed parturition time and reduced the litter size in pregnant dams (P < 0.0001). Late puberty onset, irregular ovarian cyclicity, increased anogenital distance (AGD), body weight gain, and serum testosterone concentration and reduced estradiol levels (P < 0.0001) were observed in the female offspring of dams receiving 1.25 and 1 mg/kg BW letrozole. Furthermore, Letrozole at 1.25 and 1 mg/kg BW showed increased Rfrp and decreased Gnrh mRNA expression (P < 0.0001). Letrozole treatment at doses 1 mg/kg BW and lower was not feto-toxic. It was concluded that 1 mg/kg BW letrozole may be suggested for prenatal PCOS induction.