Binucleate human oocytes from large follicles

Development of in vitro maturation techniques for clinical applications

In vitro maturation (IVM) refers to maturation in culture of immature oocytes at different stages that may or may not have been exposed to short courses of gonadotropins. The source of immature oocytes is an important feature for subsequent embryonic development, pregnancy, and healthy live births. IVM is an effective treatment that has already achieved significant outcomes of acceptable pregnancy and implantation rates and has led to the births of several thousand healthy babies. As the development of IVM treatment continues, an attractive possibility for improving the already successful outcome is to combine a natural-cycle in vitro fertilization (IVF) treatment with immature-oocyte retrieval followed by IVM of those immature oocytes. If the treatment processes can be simplified for immature-oocyte retrieval, different types of infertile women may be able to take advantage of these treatments. Mild-stimulation IVF combined with IVM treatment may represent a viable alternative to the standard treatment. Although IVM treatment is still considered to be experimental, it is now time to reconsider the IVM technology and its development. Mild-stimulation IVF combined with IVM may prove to be not just alternatives to standard treatments, but potentially first-line treatment choices.

Nuclear degeneration and meiotic aberrations observed in human oocytes matured in vitro: analysis by light microscopy

OBJECTIVE

To apply an improved air-dry procedure for the light microscopic identification of both degenerate and aberrant meiotic configurations in cultured human oocytes. MATERIAL AND DESIGN: Meiotically immature, normal appearing human oocytes retrieved after oophorectomy were placed into culture for 9 to 46 hours. Subsequently, oocytes were assessed morphologically and then air dried for light microscopic examination of chromatin configurations.

MAIN OUTCOME MEASURES

Oocyte chromatin configurations were identified as normal, degenerate, or aberrant and then classified according to meiotic stage. Retrospective analyses were conducted to determine if [1] normal meiotic configurations were associated with morphologically viable oocytes and [2] degenerate or aberrant meiotic configurations were always associated with degenerate oocytes. In addition, for each meiotic stage, the proportion of oocytes exhibiting either degenerate or aberrant chromatin configurations was calculated.

RESULTS

Of 101 oocyte chromatin configurations analyzed, 71.3% were normal, 11.9% were degenerate, and 16.8% displayed meiotic aberrations. Retrospective analyses revealed that the majority of both normal and aberrant chromatin configurations were associated with morphologically viable oocytes (93.1% and 88.2%, respectively), whereas all of the degenerate chromatin configurations were associated with morphologically degenerate oocytes. When assessed by stage, nuclear degeneration was observed exclusively at the germinal vesicle and diakinesis stages, whereas meiotic aberrations occurred most frequently after chromosome condensation. These aberrations were manifested either as clumped metaphase I configurations or as two distinct groups of bivalents that appeared to result from bivalent migration along the meiotic spindle without homologue segregation.

CONCLUSIONS

Slightly > 25% of human oocytes recovered after oophorectomy were incapable of undergoing normal meiotic maturation in culture. The majority of these abnormal oocytes appeared morphologically normal and yet possessed meiotic aberrations. These observations indicate that caution should be taken when using oocytes matured in vitro for application in assisted reproductive technology programs.

Recovery of a preovulatory binucleate oocyte in a patient following induction of ovulation for in vitro fertilization

A preovulatory oocyte with two germinal vesicles was recovered. This oocyte underwent germinal vesicle breakdown but did not form a polar body.

Frequent occurrence of multiovular follicles and multinuclear oocytes in the adult human ovary

A study of 117 ovaries of adult women showed that multiovular follicles and multinuclear oocytes are found in 98% of 18- to 52-year-old women. The relative frequency of these follicles was not age-dependent and varied between 0.06% and 2.44% of the total follicular population of the ovary. Their frequency was unaffected by gonadotropic hormones, oral contraceptives, pregnancy, or day of the menstrual cycle. Young women with benign cystic teratomas did not have more multinuclear oocytes and multiovular follicles than did other patients. The probability that such follicles will ovulate is very low; therefore they could not be a significant cause of the birth of dizygotic twins or the appearance of triploidy.

Binovular follicles in the adult human ovary

The human ovary may contain binovular or polyovular follicles at birth, but they are unusual later in life. Binbovular follicles were found in bilateral ovarian biopsies from a patient with primary amenorrhea who had been treated with exogenous gonadotropins. The fine structural morphology of these follicles has shown that both oocytes were in the resting meiotic prophase, that their respective vitelline bodies faced each other across the intervening plasma membranes, and that the adjacent oocytes made mutual contacts similar to those found between granulosa cells and oocytes. From the appearance of the multivesicular bodies in nearby stromal fibroblasts it is suggested that these follicles had formed by fusion of two adjacent primordial follicles by a mechanism similar to the depolymerization of the ground substance in the apex of the Graafian follicle that leads to ovulation.

The incidence and significance of polynuclear follicles

In the treatment of pelvic disorders, ovarian tissue was surgically removed from 165 patients (divided into four age groups) and examined microscopically. This article presents the incidence of polynuclear follicles and discusses potential signficance of these structures in the histogenesis of the ovarian teratoma.

Human follicular oocytes and their maturation in vitro

To study the maturation of follicular oocytes, germ cells were flushed from visible follicles in the ovaries of 145 oophorectomized patients 17 to 65 years of age. The number of oocytes recovered decreased (P less than 0.05) as patient age increased. More oocytes (P less than 0.05) were recovered from ovaries removed during the proliferative stage of the menstrual cycle than during the secretory stage. Of 776 oocytes obtained, 132 (17%) were examined without incubation. Two had matured in vivo and another possessed two vesicular nuclei. Of 124 oocytes incubated in tissue culture Medium 199 or Ham's F10 supplemented with 10% fetal calf serum, 52 (42%) displayed germinal vesicle breakdown and 39 (31%) progressed to metaphase of the second meiotic division within 42 hours. Neither the stage of the cycle at which ovaries were removed nor the addition of progesterone to the medium had a significant effect on maturation. The rate of maturation peaked with oocytes from women 34 to 39 years of age. Even though more oocytes were recovered from patients 17 to 33 years of age than from patients 34 to 39 years, fewer oocytes obtained from the younger patients appeared to be viable, perhaps because of a greater incidence of ovarian follicle pathology in the youngest group.

[Oocytes from polycystic human ovaries (author's transl)]

Little is known whether oocytes of polycystic ovaries, espacially those of the Stein-Leventhal-syndrome, are able to perform complete maturation. Therefore the maturation capacity of ova derived from biopsies of two patients with polycystic ovaries was investigated using the culture technique with subsequent meiotic preparations. A remarkably high number of 42 and 54 oocytes have been found. The degeneration rates were 76.20% in the polycystic and 85.20% in the Stein-Leventhal-ovaries. The degenerative changes mainly appeared as shrinkage of the ooplasm and partial or total loss of corona cells. 14.28 and 7.40% resp. showed no or incomplete maturation, whether ova remained in dictyotene stage or were found arrested shortly after resuming meiosis. Four oocytes from each of the two patients underwent normal meiosis. A biovular follicle, observed in the Stein-Leventhal-ovary, is particularly mentioned. It may be concluded, that the majority of the oocytes of polycystic ovaries is degenerate, but there are a few ova able to mature in vitro.

Anomalous patterns of mammalian oocyte maturation and fertilization

This report illustrates some of the errors that may occur during in vivo and in vitro maturation and fertilization of mammalian ova, considers the possible mechanisms accounting for their occurrence, and discusses their functional consequences. Included in the description are anomalies of oocyte and follicular development, i.e., multinucleated oocytes, polyovular follicles, and aberrations of zona pellucida formation. Also considered are deviations from the normal process of oocyte maturation such as chromosomal anomalies, development of abnormal nuclear structures (subnuclei), inhibition of polar body formation and abberations of polar body structure. Anomalies of the process of fertilization such as polyspermia, sperm penetration into polar bodies, and development of multinucleated blastomers in two-cell embryos are also described.