Autophagy favors survival of corpora lutea during the long-lasting pregnancy of the South American plains vizcacha, Lagostomus maximus (Rodentia, Caviomorpha).

The corpus luteum (CL) is a transient endocrine gland that plays a crucial role in establishing and maintaining pregnancy. Although autophagy and apoptosis have been suggested as cooperative mechanisms, their interaction within the CL of pregnant mammals has not been thoroughly investigated. To understand the collaborative function of autophagy and apoptosis in the CL, we analyzed both mechanisms during pregnancy in the South American plains vizcacha, Lagostomus maximus. This rodent undergoes a decline in progesterone levels during mid-gestation, a reactivation of the hypothalamus-hypophysis-gonadal axis, and the incorporation of new functional secondary CL. Our analysis of autophagy markers BECLIN 1 (BECN1), SEQUESTOSOME1 (SQSTM1), Microtubule-associated protein light chain 3 (LC3B), and lysosomal-associated membrane protein 1 (LAMP1) and anti- and pro-apoptotic markers BCL2 and ACTIVE CASPASE 3 (A-C3) revealed interactive behaviors between both processes. Healthy primary and secondary CL exhibited positive expression of BECN1, SQSTM1, LC3B, and LAMP1, while regressed CL displayed enhanced expression of these autophagy markers along with nuclear A-C3. Transmission electron microscopy revealed a significant formation of autophagic vesicles in regressed CL during full-term pregnancy, whereas healthy CL exhibited a low number of autophagy vesicles. The co-localization between LC3B and SQSTM1 and LC3B with LAMP1 was observed in both healthy and regressed CL during pregnancy, while co-localization of BECN1 and BCL2 was only detected in healthy CL. LC3B and ACTIVE CASPASE 3 co-localization were detected in a subset of luteal cells within the regressing CL. We propose that autophagy could act as a survival mechanism in the CL, allowing the pregnancy to progress until full-term, while also serving as a mechanism to eliminate remnants of regressed CL, thereby providing the necessary space for subsequent follicular maturation.

The key action of estradiol and progesterone enables GnRH delivery during gestation in the South American plains vizcacha, Lagostomus maximus.

The South American plains vizcacha, Lagostomus maximus, is the only mammal described so far that shows expression of estrogen receptors (ERs) and progesterone receptors (PRs) in gonadotropin-releasing hormone (GnRH) neurons. This animal therefore constitutes an exceptional model for the study of the effect of steroid hormones on the modulation of the hypothalamic-pituitary-ovarian (HPO) axis. By using both in vivo and ex vivo approaches, we have found that pharmacological doses of progesterone (P4) and estradiol (E2) produced an inhibition in the expression of hypothalamic GnRH, while physiological doses produced a differential effect on the pulsatile release frequency or genomic expression of GnRH. Our ex vivo experiment indicates that a short-term effect of E2 modulates the frequency of GnRH release pattern that would be associated with membrane ERs. On the other hand, our in vivo approach suggests that a long-term effect of E2, acting through the classical nuclear ERs-PRs pathway, would produce the modification of GnRH mRNA expression during the GnRH pre-ovulatory surge. Particularly, P4 induced a rise in GnRH mRNA expression and protein release with a decrease in its release frequency. These results suggest different levels of action of steroid hormones on GnRH modulation. We conclude that the fine action of E2 and P4 constitute the key factor to enable the hypothalamic activity during the pregnancy of this mammal.

Endoscopy, histology and electron microscopy analysis of foetal membranes in pregnant South American plains vizcacha reveal unusual excrescences on the yolk sac.

The South American hystricognathe Lagostomus maximus is a fossorial rodent whose females show unique reproductive characteristics. They have a 155-day long gestation, show massive polyovulation and a selective process of embryonic resorption in the first half of gestation. In order to explore and perform an in-situ characterization of the reproductive tract, we visualized internal structures through ultrasonography and video-endoscopy in pregnant and non-pregnant females. We describe the finding of protruding structures that lie on the yolk sac and their histological and ultrastructural characterization. The placenta was covered with whitish, small pearl-shaped structures. These structures were also seen on the extra-embryonic space, being the amnion and the umbilical cord free of them. Pearl-shaped structures were composed with loose connective tissue, lacked blood vessels, and showed collagen fibers organized in a spiral form. They were anchored by pedicles to the villous surface of the extraembryonic membrane. We discuss the biological and evolutionary meaning of the pearl-shaped structures that relate L. maximus to the African origin of the South American hystricognathe fauna.

Local production of neurostradiol affects gonadotropin-releasing hormone (GnRH) secretion at mid-gestation in Lagostomus maximus (Rodentia, Caviomorpha).

Females of the South American plains vizcacha, Lagostomus maximus, show peculiar reproductive features such as massive polyovulation up to 800 oocytes per estrous cycle and an ovulatory process around mid-gestation arising from the reactivation of the hypothalamic-hypophyseal-ovary (H.H.O.) axis. Estradiol (E2) regulates gonadotropin-releasing hormone (GnRH) expression. Biosynthesis of estrogens results from the aromatization of androgens by aromatase, which mainly occurs in the gonads, but has also been described in the hypothalamus. The recently described correlation between GnRH and ERα expression patterns in the hypothalamus of the vizcacha during pregnancy, with coexpression in the same neurons of the medial preoptic area, suggests that hypothalamic synthesis of E2 may affect GnRH neurons and contribute with systemic E2 to modulate GnRH delivery during the gestation. To elucidate this hypothesis, hypothalamic expression and the action of aromatase on GnRH release were evaluated in female vizcachas throughout pregnancy. Aromatase and GnRH expression was increased significantly in mid-pregnant and term-pregnant vizcachas compared to early-pregnant and nonpregnant females. In addition, aromatase and GnRH were colocalized in neurons of the medial preoptic area of the hypothalamus throughout gestation. The blockage of the negative feedback of E2 induced by the inhibition of aromatase resulted in a significant increment of GnRH-secreted mass by hypothalamic explants. E2 produced in the same neurons as GnRH may drive intracellular E2 to higher levels than those obtained from systemic circulation alone. This may trigger for a prompt GnRH availability enabling H.H.O. activity at mid-gestation with ovulation and formation of accessory corpora lutea with steroidogenic activity that produce the necessary progesterone to maintain gestation to term and guarantee the reproductive success.

Methylene blue prevents retinal damage in an experimental model of ischemic proliferative retinopathy.

Perinatal asphyxia induces retinal lesions, generating ischemic proliferative retinopathy, which may result in blindness. Previously, we showed that the nitrergic system was involved in the physiopathology of perinatal asphyxia. Here we analyze the application of methylene blue, a well-known soluble guanylate cyclase inhibitor, as a therapeutic strategy to prevent retinopathy. Male rats (n = 28 per group) were treated in different ways: 1) control group comprised born-to-term animals; 2) methylene blue group comprised animals born from pregnant rats treated with methylene blue (2 mg/kg) 30 and 5 min before delivery; 3) perinatal asphyxia (PA) group comprised rats exposed to perinatal asphyxia (20 min at 37°C); and 4) methylene blue-PA group comprised animals born from pregnant rats treated with methylene blue (2 mg/kg) 30 and 5 min before delivery, and then the pups were subjected to PA as above. For molecular studies, mRNA was obtained at different times after asphyxia, and tissue was collected at 30 days for morphological and biochemical analysis. Perinatal asphyxia produced significant gliosis, angiogenesis, and thickening of the inner retina. Methylene blue treatment reduced these parameters. Perinatal asphyxia resulted in a significant elevation of the nitrergic system as shown by NO synthase (NOS) activity assays, Western blotting, and (immuno)histochemistry for the neuronal isoform of NOS and NADPH-diaphorase activity. All these parameters were also normalized by the treatment. In addition, methylene blue induced the upregulation of the anti-angiogenic peptide, pigment epithelium-derived factor. Application of methylene blue reduced morphological and biochemical parameters of retinopathy. This finding suggests the use of methylene blue as a new treatment to prevent or decrease retinal damage in the context of ischemic proliferative retinopathy.