Colour Doppler indices of follicular blood flow as predictors of pregnancy after in-vitro fertilization and embryo transfer

Utility of color Doppler indices of dominant follicular blood flow for prediction of clinical factors in in vitro fertilization-embryo transfer cycles

OBJECTIVE

To investigate the relationship between color Doppler indices of dominant follicular blood flow and clinical factors in in vitro fertilization-embryo transfer cycles.

SUBJECTS AND METHODS

This was a prospective study involving 26 patients completing a total of 33 in vitro fertilization cycles. Dominant follicular blood flow indices, peak systolic velocities, the resistance index and the pulsatility index were evaluated using transvaginal color Doppler. The indices were compared to the clinical outcomes of in vitro fertilization-embryo transfer.

RESULTS

There was a significant correlation between dominant follicular peak systolic velocities and the number of oocytes retrieved, as well as the number of mature oocytes obtained. There was no significant correlation between dominant follicular resistance index or pulsatility index and the number of follicles > 10 mm in diameter, the number of oocytes retrieved or the number of mature oocytes. There were no significant differences between dominant follicular peak systolic velocities, resistance index or pulsatility index, and fertilization rate or the ratio of good quality embryos. However, significant differences were found between the number of oocytes retrieved, as well as the number of mature oocytes for those patients in which the peak systolic velocity was below 25 cm/s.

CONCLUSIONS

Doppler assessment of dominant follicle blood flow alone is useful for predicting the number of retrievable oocytes. However, morphological quality of the embryo produced or the pregnancy rate cannot be predicted by this method.

Differential effects of repeated ovarian stimulation on cytoplasmic and spindle organization in metaphase II mouse oocytes matured in vivo and in vitro

The effects of four rounds of ovarian stimulation spaced 1-6 weeks apart on the normality of metaphase II (MII) spindle formation, chromosomal alignment and cytoplasmic organization were examined in intact ovulated mouse oocytes and at MII for oocytes obtained at the germinal vesicle stage from the same ovaries and matured in vitro. The terminal deoxynucleotidyl transferase-mediated dUDP nick-end labelling assay was used to identify DNA strand breaks in chromosomes, and histological studies of ovaries between and at each round of ovarian stimulation were performed. The results demonstrate a progressive and significant increase in the frequency of spindle defects with each round of ovarian stimulation, including those spaced weeks apart. Oocytes with spindle defects were also characterized by the occurrence of detached chromosomes and cytoplasmic asters. In contrast, in-vitro matured oocytes derived from the same ovaries were normal. No evidence of DNA strand breaks with repeated rounds of ovarian stimulation was detected in ovulated or in-vitro matured oocytes. The development and persistence of nodules of hypertrophied granulosa in regions where follicular growth occurs suggest that a progressively increasing proportion of oocytes in the ovulatory pathway may experience an intrafollicular milieu that has negative consequences for competence. The results are discussed with respect to ovarian and oocyte biological ageing and possible adverse implications for human oocyte competence with repeated hyperstimulation.

Angiogenesis in ovarian follicular and luteal development

Angiogenesis is the process of new capillary formation from previously existing mature vessels. The adult ovary exhibits dramatic growth and regression of capillary networks on a cyclic basis. Ovarian follicles and the corpus luteum contain and produce endothelial cell-specific factors, which may act alone or in concert to regulate the process of angiogenesis. These factors are ultimately controlled by endocrine, paracrine and autocrine regulation, as well as by metabolic cellular signals such as intracellular oxygen content and ageing. Aberrant production of these angiogenic factors may be the cause of vascular dysfunction and the development of ovarian disorders. Recent technological advances for monitoring blood flow and measuring angiogenic factors could assist in accurately diagnosing ovarian disorders. Further elucidation of specific physiological role(s) of factors involved in angiogenesis of the pre-ovulatory follicle and developing corpus luteum may be useful in addressing issues of infertility in women.

Differential mitochondrial distribution in human pronuclear embryos leads to disproportionate inheritance between blastomeres: relationship to microtubular organization, ATP content and competence

It has been suggested that mitochondrial DNA defects that effect metabolic capacity may be a proximal cause of failures in oocyte maturation, fertilization, or early embryonic development. Here, the distribution of mitochondria was examined by scanning laser confocal microscopy in living human pronuclear oocytes and cleavage stage embryos, followed either by measurements of the net ATP content of individual blastomeres or anti-tubulin immunofluorescence to determine the relationship between mitochondrial distribution and microtubular organization. The results indicate that specific patterns of perinuclear mitochondrial aggregation and microtubular organization are related, and that asymmetrical mitochondrial distributions at the pronuclear stage can result in some proportion of blastomeres with reduced mitochondrial inheritance and diminished ATP generating capacity. While the inability to divide appears to be a development consequence for an affected blastomere, for the embryo, reduced competence may occur during cleavage if several blastomeres inherit a mitochondrial complement inadequate to support normal cellular functions. The findings provide a possible epigenetic explanation for the variable developmental ability expressed within cohorts of morphologically normal early cleavage stage human embryos obtained by in-vitro fertilization.