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General and Comparative Endocrinology Oct 2023Although methionine-enkephalin (M-ENK) is implicated in the regulation of reproductive functions in vertebrates, its function in reptiles is little understood. This...
Although methionine-enkephalin (M-ENK) is implicated in the regulation of reproductive functions in vertebrates, its function in reptiles is little understood. This study aims to elucidate the role of M-ENK on seasonal and follicle stimulating hormone (FSH)-induced ovarian recrudescence in the gecko Hemidactylus frenatus. In the first experiment, administration of 5 µg M-ENK did not affect germinal bed activity or follicular developmental stages I, II, and III (previtellogenic) and IV (vitellogenic), but there were no stage V (vitellogenic) follicles in the ovary. However, there was a significant decrease in the mean numbers of oogonia and primary oocytes in the germinal bed associated with the complete absence of stage IV and V follicles in 25 µg M-ENK-treated lizards in contrast to experimental controls. Furthermore, there was a significant decrease in gonadotropin-releasing hormone - immunoreactive (GnRH-ir) content in the median eminence (ME) and pars distalis (PD) of the pituitary gland and sparse labelling of hypothalamic GnRH-ir neurons in 25 µg M-ENK-treated lizards. In the second experiment, treatment with FSH during the regression phase of the ovarian cycle resulted in the appearance of stage IV and V follicles, in contrast to their absence in the initial controls and treatment controls. However, treatment with 25 µg M-ENK + FSH did not result in the appearance of these follicles, indicating the inhibitory effect of M-ENK on FSH-induced ovarian recrudescence. These findings suggest that M-ENK inhibits the germinal bed and vitellogenic follicular growth in a dose-dependent manner, possibly mediated through the suppression of GnRH release in the ME and PD. In addition, M-ENK may also act at the level of the ovary in the gecko.
Topics: Female; Animals; Ovary; Follicle Stimulating Hormone; Analgesics, Opioid; Ovarian Follicle; Enkephalin, Methionine; Seasons; Gonadotropin-Releasing Hormone; Lizards; Methionine
PubMed: 37536461
DOI: 10.1016/j.ygcen.2023.114353 -
Cell Death Discovery Jul 2023A faithful reconstitution of the complete process of oogenesis in vitro is helpful for understanding the molecular mechanisms, genetics, and epigenetic changes related...
A faithful reconstitution of the complete process of oogenesis in vitro is helpful for understanding the molecular mechanisms, genetics, and epigenetic changes related to gametogenesis; it can also be useful for clinical drug screening, disease research, and regenerative medicine. To this end, given the consensus that murine female germ cells initiate meiosis at E13.5, substantial works have reported the successful generation of fertile oocytes using E12.5 female gonads as starting materials. Nevertheless, our data demonstrated that murine germ cells at E12.5 have heterogeneously initiated a meiotic transcriptional program based on a measurement of pre-mRNAs (unspliced) and mature mRNAs (spliced) at a single-cell level. Therefore, to establish a platform that faithfully recapitulates the entire process in vitro (from premeiotic murine germ cells to fully developed oocytes), we here report a novel three-dimensional organoid culture (3-DOC) system, which successfully induced fully developed oocytes from E11.5 premeiotic female germ cells (oogonia). Compared with 2D culture and other 3D culture methods, this new culture system is more cost-effective and can create high-quality oocytes similar to in vivo oocytes. In summary, our new culture platform provides an experimental model for future research in regenerative medicine and reproductive biology.
PubMed: 37518361
DOI: 10.1038/s41420-023-01577-w -
Biology of Reproduction Jul 2023Follicular development is a critical process in reproductive biology that determines the number of oocytes and interacts with various cells within the follicle (such as...
Follicular development is a critical process in reproductive biology that determines the number of oocytes and interacts with various cells within the follicle (such as oocytes, granulosa cells, cumulus cells and theca cells, etc.), and plays a vital role in fertility and reproductive health due to the dogma of a limited number of oogonia. Dysregulation of follicular development can lead to infertility problems and other reproductive disorders. To explore the physiological and pathological mechanisms of follicular development, immunology-based methods, microarrays, and next-generation sequencing have traditionally been used for characterization at the tissue level. However, with the proliferation of single-cell sequencing techniques, research has uncovered unique molecular mechanisms in individual cells that have been masked by previous holistic analyses. In this review, we briefly summarize the achievements and limitations of traditional methods in the study of follicular development. Simultaneously, we focus on how to understand the physiological process of follicular development at the single-cell level and reveal the relevant mechanisms leading to the pathology of follicular development and intervention targets. Moreover, we also summarize the limitations and application prospects of single cell sequencing in follicular development research.
PubMed: 37504504
DOI: 10.1093/biolre/ioad080 -
Tissue & Cell Oct 2023Macrobrachium amazonicum is a species of economic interest with a wide distribution in the Americas and high morphological and reproductive variability. Three phenotypes...
Macrobrachium amazonicum is a species of economic interest with a wide distribution in the Americas and high morphological and reproductive variability. Three phenotypes can be observed in this species: i) large-size amphidromous, ii) large-size and iii) small-size hololimnetic prawns. In the present work, the morphological, histochemical and ultrastructural aspects of ovarian development in the three phenotypes were comparatively analyzed. In addition, the interaction between the ovary and the hepatopancreas was investigated in these phenotypes through the use of gonadosomatic (GSI) and hepatosomatic (HSI) indices. Despite the morphological differences and different reproductive strategies adopted by the females, the macroscopic, histochemical and ultrastructural patterns of ovarian development showed no differences between the phenotypes. The ovaries were macroscopically classified into five stages of development (I to V). In early stages (I and II), the ovaries are full of oogonia, previtellogenic oocytes and oocytes in primary or endogenous vitellogenesis. At these stages, the rough endoplasmic reticulum (RER) produces a granular electron-dense material and sends it to the Golgi apparatus, where it will be modified, compacted and transformed into immature yolk granules. From stage III, secondary or exogenous vitellogenesis begins (with no interruption of endogenous vitellogenesis), where follicular cells nourish the oocytes and extracellular material is absorbed by endocytic vesicles, which fuse with immature yolk granules (forming mature granules) or with existing mature yolk granules. In stages IV and V, secondary vitellogenesis continues and mature yolk granules progressively occupy the cytoplasm. In M. amazonicum, the patterns of increase in oocyte diameter are quite similar between phenotypes, being greater in the small-size phenotype. This is related to the formation of larger oocytes/eggs and the production of large lipid reserves for their larvae. Changes in GSI and HSI during ovarian development show strong similarity between phenotypes, supporting the results obtained by histology and ultrastructure. Females in stages III and IV mobilize hepatopancreas reserves for ovarian maturation, which justifies the higher HSI values recorded in these stages. On the other hand, females in stage V show higher GSI and lower HSI values, indicating a mobilization of resources for the end of ovarian development as the females are ready to spawn.
Topics: Animals; Female; Palaemonidae; Oocytes; Ovary; Oogonia; Phenotype
PubMed: 37499319
DOI: 10.1016/j.tice.2023.102166 -
BMC Zoology Jul 2023The precise mechanisms of hormone action responsible for the full course of events modulating folliculogenesis in crocodilian have not been determined, although...
BACKGROUND
The precise mechanisms of hormone action responsible for the full course of events modulating folliculogenesis in crocodilian have not been determined, although histological features have been identified.
RESULTS
The Alligator sinensis ovarian morphological characteristics observed at 1, 15, 30, 60, 90, and 300 days post hatching(dph) revealed that the dynamic changes in germ cells varied in different meiotic and developmental stages, confirming that the processes of folliculogenesis were protracted and asynchronous. The presence of endogenous follicle-stimulating hormone(FSH) mRNA and protein expression within the cerebrum at 1 dph, in parallel with the increase in germ cells within the germ cell nests(Nest) from 1 dph to 15 dph, suggested that endocrine regulation of the pituitary-gonad axis is an early event in oogonia division. Furthermore, the endogenous expression of FSH showed a trend of negative feedback augmentation accompanied by the exhaustion of maternal yolk E observed at 15 dph. Such significant elevation of endogenous FSH levels was observed to be related to pivotal events in the transition from mitosis to meiosis, as reflected by the proportion of oogonia during premeiosis interphase, with endogenous FSH levels reaching a peak at the earliest time step of 1 dph. In addition, the simultaneous upregulation of premeiotic marker STRA8 mRNA expression and the increase in endogenous FSH further verified the above speculation. The strongly FSHr-positive label in the oocytes within Pre-previtellogenic follicles was synchronized with the significant elevation of ovarian cAMP detected at 300 dph, which suggested that diplotene arrest maintenance during early vitellogenesis might be FSH dependent. In addition, preferential selection in asynchronous meiotic initiation has been supposed to act on somatic supportive cells and not directly on germ cells via regulation of FSH that in turn affects downstream estrogen levels. This suggestion was verified by the reciprocal stimulating effect of FSH and E on the accelerated meiotic marker SYCP3 and by the inhibited cell apoptosis demonstrated in ovarian cell culture in vitro.
CONCLUSION
The corresponding results contribute an expansion of the understanding of physiological processes and shed some light on the specific factors responsible for gonadotropin function in the early folliculogenesis of crocodilians.
PubMed: 37403129
DOI: 10.1186/s40850-023-00170-z -
Reproductive Sciences (Thousand Oaks,... Nov 2023The regulation of protein turnover by the unique deubiquitinating enzyme ubiquitin C-terminal hydrolase L1 (UCHL1) is only seen in oocytes, spermatogonia, and neurons....
The regulation of protein turnover by the unique deubiquitinating enzyme ubiquitin C-terminal hydrolase L1 (UCHL1) is only seen in oocytes, spermatogonia, and neurons. Our objective was to investigate variation in expression of UCHL1 across fetal maturation of oocytes that result in lifelong ovarian reserve. We performed a retrospective cohort study of 25 fetal autopsy specimens from 21 to 36 weeks. This was an IRB-approved protocol with parental permission for use of tissues for research purposes. Tissues were stained for expression of the oocyte-specific protein UCHL1, and expression levels were evaluated using quantitative immunofluorescence across gestational ages after correction for the area and background absorbance. Corrected total cell fluorescence (CTCF) for expression of UCHL1 within human oocytes was compared across fetal gestational ages and oocyte size. Trends were analyzed using a locally weighted scatterplot smoothing algorithm. Local expression of UCHL1 increases in oocytes across ovarian development reaching a plateau at 27 weeks with the maintenance of elevated levels through 36 weeks gestational age. This maturation trend is also evidenced by the increase in protein expression as oocyte area increases (r = 0.5530, p ≤ 0.001) with the largest rise occurring as oocytes are enveloped into primordial follicles. The increase in expression as oocytes transition from oogonia into oocytes in primordial follicles and beyond may be part of the preparation of both oocytes and the surrounding somatic cells for the long-term maintenance of the ovarian reserve.
Topics: Female; Humans; Ubiquitin Thiolesterase; Ovarian Reserve; Retrospective Studies; Oocytes; Ovarian Follicle
PubMed: 37277688
DOI: 10.1007/s43032-023-01275-z