A.T. Dobson

Effect of in vitro fertilization on gene expression and development of mouse preimplantation embryos

In vitro culture (IVC) of preimplantation mouse embryos is associated with changes in gene expression. It is however, not known if the method of fertilization affects the global pattern of gene expression. We compared gene expression and development of mouse blastocysts produced by in vitro fertilization (IVF) versus blastocysts fertilized in vivo and cultured in vitro from the zygote stage (IVC) versus control blastocysts flushed out of the uterus on post coital day 3.5. The global pattern of gene expression was assessed using the Affymetrix 430 2.0 chip. It appears that each method of fertilization has a unique pattern of gene expression and development. Embryos cultured in vitro had a reduction in the number of trophoblastic cells (IVF 33.5 cells, IVC 39.9 cells, and 49.6 cells in the in vivo group) and, to a lesser degree, of inner cell mass cells (12.8, 11.7, and 13.8 respectively). The inner cell mass nuclei were larger after culture in vitro (140 microm(2), 113 microm(2), and 86 microm(2) respectively). Although a high number of genes (1912) was statistically different in the IVF cohort when compared with the in vivo control embryos, the magnitude of the changes in gene expression were low and only a minority of genes (29 genes) was changed more than fourfold. Surprisingly, IVF embryos were different from IVC embryos (3058 genes were statistically different, but only three changed more than fourfold). Proliferation, apoptosis, and morphogenetic pathways are the most common pathways altered after IVC. Overall, IVF and embryo culture have a profound effect on gene expression pattern and phenotype of mouse preimplantation embryos.

A quantitative assessment of follicle size on oocyte developmental competence

OBJECTIVE To quantitatively assess the impact of follicle size on oocyte maturation, fertilization, and embryo quality. DESIGN Prospective study. SETTING Academic medical center. PATIENT(S) Couples undergoing ovarian stimulation and in vitro fertilization (IVF). INTERVENTION(S) A total of 235 cycles were monitored prospectively, and 2934 oocytes were collected from five groups of follicle size. Repeated measures multivariate analyses were used to compare the smaller follicle sizes with the lead follicle. MAIN OUTCOME MEASURE(S) Oocyte maturation, fertilization, and embryo quality. RESULT(S) Compared with the lead follicular group (>18 mm), the odds of a mature oocyte from a 16 to 18 mm size follicle were 37% and declined progressively with each size. The odds of fertilization of oocytes from follicles 16 to 18 mm in size was 28% less than the lead group and decreased with each size. The rate of polyspermy with conventional insemination was increased for the smaller follicular groups (adjusted odds ratio = 2.37). Follicle size did not predict embryo cell number, but embryos from smaller follicles had a statistically significantly higher fragmentation compared with the lead group. CONCLUSION(S) The lead follicular group was most likely to have a mature oocyte that was capable of fertilization and best suited for development into a high-quality embryo. The smaller follicles were capable of producing metaphase II oocytes that could fertilize, but at rates approaching only 60% that of the lead follicular group.

The effect of follicular fluid hormones on oocyte recovery after ovarian stimulation: FSH level predicts oocyte recovery

BackgroundOvarian stimulation for assisted reproductive technology (ART) overcomes the physiologic process to develop a single dominant follicle. However, following stimulation, egg recovery rates are not 100%. The objective of this study is to determine if the follicular fluid hormonal environment is associated with oocyte recovery.MethodsThis is a prospective study involving patients undergoing ART by standard ovarian stimulation protocols at an urban academic medical center. A total of 143 follicular fluid aspirates were collected from 80 patients. Concentrations of FSH, hCG, estradiol, progesterone, testosterone and prolactin were determined. A multivariable regression analysis was used to investigate the relationship between the follicular fluid hormones and oocyte recovery.ResultsIntrafollicular FSH was significantly associated with oocyte recovery after adjustment for hCG (Adjusted odds ratio (AOR) = 1.21, 95%CI 1.03–1.42). The hCG concentration alone, in the range tested, did not impact the odds of oocyte recovery (AOR = 0.99, 95%CI 0.93–1.07). Estradiol was significantly associated with oocyte recovery (AOR = 0.98, 95% CI 0.96–0.99). After adjustment for progesterone, the strength of association between FSH and oocyte recovery increased (AOR = 1.84, 95%CI 1.45–2.34).ConclusionThe relationship between FSH and oocyte recovery is significant and appears to work through mechanisms independent of the sex hormones. FSH may be important for the physiologic event of separation of the cumulus-oocyte complex from the follicle wall, thereby influencing oocyte recovery. Current methods for inducing the final stages of oocyte maturation, with hCG administration alone, may not be optimal. Modifications of treatment protocols utilizing additional FSH may enhance oocyte recovery.