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Rita Cortvrindt

Publications and source records attributed to Rita Cortvrindt.

13 recordsLinked to original sources
PubMed2007

Principal findings from a multicenter trial investigating the safety of follicular-fluid meiosis-activating sterol for in vitro maturation of human cumulus-enclosed oocytes.

OBJECTIVE: To evaluate the safety of applying follicular-fluid meiosis-activating sterol (FF-MAS) in vitro to immature human oocytes. DESIGN: Phase I bicenter, randomized, parallel-group, controlled, partially blinded trial. SETTING: Third-level referral academic centers, including reproductive biology and genetics laboratories. PATIENTS: Endocrinologically normal women with a medical indication for IVF or intracytoplasmic sperm injection, or healthy volunteers. INTERVENTION(S): Subjects were randomized at a ratio 1 to 6 into either conventional GnRH-agonist and recombinant FSH stimulation (IVO) for oocyte retrieval, or minimally stimulated in vitro maturation (IVM) with the use of recombinant FSH. Retrieved immature oocyte cumulus complexes were cultured for 30 or 36 hours in one of six IVM culture conditions containing FF-MAS (range, 0.1-20 microM). Polar body-extruded oocytes from the IVO and IVM groups were processed for chromosomal analysis. MAIN OUTCOME MEASURE(S): The primary endpoint was the incidence of metaphase II stage oocytes with numeric chromosomal abnormalities, using full (spectral karyotyping) or partial (fluorescent in situ hybridization with seven probes) karyotyping or Giemsa count. A secondary objective was to document the frequency of metaphase II oocytes after IVM with FF-MAS supplements. RESULT(S): Oocyte cumulus complexes obtained from the IVO (mean, 8.9) and IVM (mean, 6.2) groups had equal maturation rates. Compared to IVO, exposure of germinal-vesicle oocytes for a maturation period of 30 hours did not increase aneuploidy. An exposure period of 36 hours doubled the aneuploidy rate, but this was significant only for the 20-muM dose of FF-MAS. CONCLUSION: Inclusion of 1-10 microM FF-MAS in a 30-hour IVM protocol is safe.

Adult↗
PubMed2006

In vitro effects of dexamethasone on mouse ovarian function and pre-implantation embryo development.

The effect of dexamethasone (5-80 microg/ml) on ovarian function and embryo development was studied in mice. The follicle bio-assay revealed no effects of DEX up to 40 microg/ml on folliculogenesis and oogenesis, whereas 80 microg/ml hampered follicle differentiation and oocyte maturation. Androgen, estrogen and progestin secretion patterns were strongly impaired at all doses levels. However, the ovulation-induced progesterone increase indicating that the steroid pathway was activated in presence of DEX. Applying the oil-free mouse embryo assay no alteration of DEX on the first cleavage stages were observed whereas blastocyst rate decreased from 20 microg/ml DEX onwards, and hatching capacity was already impaired in presence of 10 microg/ml DEX. In conclusion, steroidogenesis was affected from 5 microg/ml onwards and the minimum effective inhibitory dose was set at 10 microg/ml for early embryo development. Based on these in vitro findings, physiological or therapeutic levels of glucocorticosteroids are unlikely to affect female fertility.

Androgens↗
PubMed2006

Morphological and ultrastructural evaluation of cultured frozen-thawed human fetal ovarian tissue.

OBJECTIVE: To investigate a defined culture condition for the culture of frozen-thawed human ovarian tissue. DESIGN: Prospective laboratory study. SETTING: Reproductive biology laboratories in university hospitals. PATIENT(S): Fetal ovarian tissue from elective termination of pregnancy. INTERVENTION(S): Culture of frozen-thawed fetal ovarian tissue for up to 63 days. MAIN OUTCOME MEASURE(S): Morphology, morphometry, and survival of follicles in relation to culture times. RESULT(S): The proportion of primordial, early primary, and primary follicles in frozen-thawed (day 0) ovarian tissue was 77.5%, 21.7%, and 0.8%, respectively. Pronounced degeneration was found in all cell types, and < or =36% of the follicles had signs of atresia at days 7-14, but this figure improved with culture time to <20% of the total follicular population. After 7-14 and 21-35 days of culture, the relative proportion of the follicles in the different classes remained nearly stable. Morphometric examination of healthy follicles showed a significant increase in both follicle and oocyte diameter compared with control. A few follicles had developed to the early secondary stage. Ultrastructural analysis demonstrated well-preserved morphological integrity of healthy primordial and early primary follicles. Immunohistochemical localization of proliferating cell nuclear antigen was positive in proliferating follicular cells at days 7-14 and 21-35 of culture. CONCLUSION(S): The present culture condition leads to good survival and progressive follicular growth and differentiation that is comparable to the physiological pattern of early folliculogenesis.

Aborted Fetus↗
PubMed2005

Aneuploidy in mouse metaphase II oocytes exposed in vivo and in vitro in preantral follicle culture to nocodazole.

Aneuploidy tests are important in evaluating genetic hazards especially when chemical exposures are suspected to affect the fidelity of chromosome segregation in oocytes and embryos. In the current study, a newly established method, mouse preantral follicle culture, was employed to grow oocytes in vitro within follicles. The sensitivity of in vitro grown follicle enclosed oocytes was compared with oocytes maturing in vivo in the ovary. In both the cases, oocytes were exposed to the cytostatic chemical, nocodazole, from the time of hormonally stimulated resumption of meiosis. The in vivo study revealed a significant decrease in the number of ovulated mouse oocytes and an increase in meiosis I-arrested and hyperploid metaphase II oocytes at a single i.p. dose of 70 mg/kg body weight of nocodazole. A significant increase was also observed in the number of meiosis I-arrested and hyperploid mouse oocytes from preantral follicle culture, when they were cultured in the presence of >or=30 nM nocodazole during the final stages of maturation. This concentration is slightly lower than that previously shown to induce nondisjunction in denuded mouse oocytes or in cultured human lymphocytes. The higher sensitivity of the in vitro matured oocytes from preantral follicle culture than that of denuded oocytes may be related to a synergistic adverse influence of nocodazole on the oocyte, on somatic cell integrity and on cell-cell communication, which possibly also affects ovulation in vivo. When expressed in molarity relative to the mouse weight, the effective dose of the acute exposure in vivo is 3-4 orders of magnitude higher than the lowest effective concentration employed continuously in vitro. Reduced bioavailability of nocodazole to the target cells due to its poor water solubility may contribute to this difference. Preantral follicle culture can be helpful in analysing mechanisms in chemically induced aneuploidy in mammalian oogenesis, and in predicting the consequences of chemical exposures in vivo.

Aneuploidy↗
PubMed2004

A reproducible two-step culture system for isolated primary mouse ovarian follicles as single functional units.

A reproducible two-step culture system for isolated mouse ovarian follicles smaller than 100 microm (type 3a follicles) was designed. First, isolated follicles were grown in single droplets of alpha-minimal essential medium (MEM) without (deoxy)ribonucleosides at a lower concentration of fetal bovine serum (FBS; 1%) for 6 days with mechanical prohibition of thecal cell attachment. Growing follicles reaching at least 100 microm were transferred to alpha-MEM medium enriched with a higher concentration (5%) of FBS to allow attachment and were cultured subsequently for an additional 12 days. Overall, more than 85% of the follicles survived the first culture step, and oocyte growth and granulosa cell proliferation had increased by 25% (P < 0.05). Follicle survival at Day 18 was related to initial follicle diameters at isolation. Average meiotic maturation rates and estrogen secretion were lower compared to those of cultures starting with early preantral follicles of 100-130 microm. Although reverse transcription-polymerase chain reaction analysis revealed the presence of LH-receptor mRNA in thecal cells, an exogenous androstenedione replacement resulted in an increase of estrogen production, suggesting substrate insufficiency. The time needed to grow from early preantral stages to in vitro ovulation is strongly dependent on the initial follicle diameter at isolation. Morphological characteristics of cultured follicles were suggestive for combined transforming growth factor beta deficiencies during in vitro culture.

Animals↗
PubMed2004

Number of ovarian follicles in human fetuses with the 45,X karyotype.

OBJECTIVE: To evaluate the numbers of ovarian follicles during fetal life in the gonads of human female fetuses with the 45,X karyotype (Turner syndrome, TS) and to compare them with those from age-matched 46,XX fetuses. DESIGN: Retrospective study. SETTING: An academic hospital. PATIENT(S): Ovarian samples from TS fetuses (aged 17-37 weeks), mainly obtained after induced abortion, and ovaries from eight control fetuses (matching gestational ages). INTERVENTION(S): Embedded blocks of ovaries were collected from anatomy-pathology departments of three university hospitals and were sectioned and stained with hematoxylin-eosin. MAIN OUTCOME MEASURE(S): Observation of primordial and growing follicles. RESULT(S): In the fetal ovaries of controls, numerous oogonia were observed at 18 weeks. Primordial follicles were present in all ovaries from 20 weeks' gestation onward, whereas preantral and antral follicles were observed from 26 weeks onwards. In ovaries from 45,X TS fetuses, oogonia were observed in some ovaries, but no primordial, preantral, or antral follicles were found, even in ovaries from the third trimester of gestation. CONCLUSION(S): Follicle formation and growth are severely reduced in ovaries from aborted 45,X TS fetuses.

Abortion, Induced↗
PubMed2004

Preantral follicle culture as a novel in vitro assay in reproductive toxicology testing in mammalian oocytes.

The most common genetic disorder in humans, trisomy, is caused predominantly by errors in chromosome segregation during oogenesis. Isolated mouse oocytes resuming meiosis and progressing to metaphase II in vitro have recently been used to assess targets, aneugenic potential and sensitivity of oocytes to chemical exposures. In order to extend in vitro maturation tests to earlier stages of oogenesis, an in vitro assay with mouse preantral follicle cultures has been established. It permits the identification of direct and also indirect effects of environmental chemicals on the somatic compartment, the follicle and theca cells, that may lead to disturbances of oocyte growth, maturation and chromosome segregation. Early preantral follicles from prepubertal female mice are cultured in microdroplets for 12 days under strictly controlled conditions. The follicle-enclosed oocytes resume maturation, develop to metaphase II and become in vitro ovulated within 16 h after a physiological ovulatory stimulus with recombinant human gonadotrophins and epidermal growth factor. These oocytes grown and matured in vitro possess normal barrel-shaped spindles with well-aligned chromosomes. Their chromosomes segregate with high fidelity during anaphase I. The model aneugen colchicine induced a meiotic arrest and aneuploidy in these in vitro grown, follicle-enclosed oocytes in a dose-dependent manner, comparable to in vivo tests. Therefore, preantral follicle culture appears to provide an effective and reliable method to assess the influences of environmental mutagens, pharmaceutical agents and potentially endocrine disrupting chemicals on the fidelity of female meiosis.

Aneugens↗
PubMed2003

Effects of chilling on structural aspects of early preantral mouse follicles.

Chilling injury is one of the major limiting factors for achieving optimal cryopreservation of gametes. This study aimed to determine potential chilling-induced damage on several structural aspects of early preantral mouse follicles. Mechanically isolated intact early preantral follicles (type 3b-4) were exposed to 0 degrees C for 1, 5, 10, or 30 min. Control and chilled follicles were analyzed by confocal microscopy after staining for tubulin, F-actin, and chromatin, and by electron microscopy. Chilling for only 1 min was sufficient to cause depolymerization of microtubules in the oocyte and the surrounding granulosa cell layer as evidenced by a substantial decrease in fluorescence intensity after antitubulin labeling. Cooling for longer periods caused alterations in microtubule organization in the follicle-enclosed oocyte. These alterations included the loss of interphase microtubules, concomitant with the formation of perinuclear or cortical microtubule asters and sometimes a complete disappearance of microtubules. The extent of microtubule modification was related to the time of chilling, but was fully reversible after rewarming follicles at 37 degrees C for 1 h. Chilling had only minor effects on the actin-containing elements located predominantly in the oocyte cortex and the transzonal projections. Ultrastructural analysis confirmed that oocyte-somatic cell interactions were present. There was no influence on the chromatin configuration within the follicle-enclosed oocyte. These results indicate that mouse follicles are relatively tolerant to direct chilling injury and, as a consequence, are able to withstand the cooling-warming steps during conventional cryopreservation procedures.

Actin Cytoskeleton↗
PubMed2003

Human oocytes reversibly arrested in prophase I by phosphodiesterase type 3 inhibitor in vitro.

This study addresses the role of cAMP hydrolytic isoenzyme phosphodiesterase type 3 (PDE 3) modulation on human oocyte maturation in vitro. Presence of phosphodiesterase type 3 A (PDE 3A) mRNA was confirmed in human germinal vesicle-stage (GV) oocytes. Making use of a selective PDE 3 inhibitor, Org 9935 (10 microM), oocytes retrieved from immature follicles were arrested in prophase I with a high efficiency for up to 72 h. Cumulus oocyte complexes (COCs) were retrieved in the follicular phase of the cycle before or after exposure to endogenous LH or hCG administration in vivo and randomly distributed into maturation medium with or without the PDE 3 inhibitor. Previous exposure of small follicles to LH activity in vivo had no influence on the arresting capacity of the PDE 3 inhibitor. Reversal from pharmacological arrest leads to a progression through meiosis in a normal time frame with formation of a well-aligned metaphase plate. Ultrastructure analysis of COC derived from follicles between 8 and 12 mm showed that the induced extension of prophase I arrest in vitro resulted in cytoplasm changes but not in apparent nuclear changes during culture.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMedDate not supplied

Ovarian follicle bioassay reveals adverse effects of diazepam exposure upon follicle development and oocyte quality.

A mouse ovarian follicle bioassay was used to study folliculogenesis and oocyte quality in vitro. Diazepam (DZ) was chosen as test compound to evaluate the system for its ability to detect possible effects of chemicals on reproduction. The bioassay is suitable to analyze the influence of DZ on each of the follicular components at any stage of development. A dose finding study revealed that follicle growth, differentiation and steroidogenesis were significantly disturbed by > or =5 microg/ml DZ. A transient exposure procedure was used to examine stage-specific sensitivities of oogenesis to DZ. The oocyte appeared to be most vulnerable during its growth process within the follicle. Resumption of meiosis was disturbed dose-dependently with reduced oocyte quality after chronic exposure to > or =2.5 microg/ml DZ. The bioassay is a highly efficient and informative tool to assess the hazards of chemical compounds for female fertility and to elucidate their mechanisms of action.

Animals↗