Toyohiko Miyazaki

Integrins and reproductive physiology: expression and modulation in fertilization, embryogenesis, and implantation

OBJECTIVE To review the available information regarding the role of integrins in reproductive physiology and to discuss their potential clinical implications. DESIGN Studies that specifically relate to the expression and modulation of integrins in fertilization, embryogenesis, and implantation were identified through the literature and Medline searches. RESULT(S) Integrins are a class of adhesion molecules that participate in cell-to-cell and cell-to-substratum interactions and are present on essentially all human cells. All mammalian eggs express integrins at their surface, and the integrin alpha 6 beta 1 serves as a sperm receptor that mediates sperm-egg binding. In addition, certain integrin moieties appear to be regulated within the cycling endometrium. Specifically, the expression of beta 1 integrins in the early proliferative phase is restricted to the glandular epithelium, whereas stromal cells also express beta 1 integrins in the midsecretory phase. The expression of beta 1 integrins increases at the time of implantation and remains elevated in the decidua during early pregnancy. A disruption of integrin expression is associated with certain types of infertility in women. The apical surface of the mural trophectoderm does indeed possess functional integrins, and trophoblast interactions with extracellular matrix proteins largely depend on the integrin family of adhesion receptors. CONCLUSION(S) Integrins play particularly important roles in both fertilization and embryogenesis, including the process of implantation.

Experimental growth retardation produced by transient period of uteroplacental ischemia in pregnant Sprague-Dawley rats.

OBJECTIVE Introduction of experimental growth retardation, which was based on the hypothesis of uteroplacental postischemic hypoperfusion, was attempted by a transient period of uteroplacental ischemia in dated-pregnant Sprague-Dawley rats. STUDY DESIGN On day 17 of gestation right uterine horn circulation was occluded for 5 to 60 minutes in 35 dams. The fetuses were delivered by cesarean section and studied on day 21 of gestation. For each experiment the fetuses in the right horn served as the ischemia group and those in the left horn were used as the control group. RESULTS Statistical analysis by Wilcoxon signed-rank test demonstrated a significant decrease in the fetal weights and in the liver-to-body weight ratios, in contrast to an increase in the brain-to-body weight ratios in the 60-minute ischemia group, compared with those in the control group. This ischemia resulted in a 14% incidence of fetal deaths. CONCLUSION Ischemia of a single uterine horn circulation in pregnant rat for 60 minutes should readily serve as a suitable model for asymmetric intrauterine growth retardation.

Reduced expression of αvβ3 integrin in the endometrium of unexplained infertility patients with recurrent IVF-ET failures: Improvement by danazol treatment

AbstractPurpose: To determine whether there is any association between the expression of endometrial integrin α v β3 and repeated IVF-ET failure and to examine the effect of danazol treatment on α v β3 expression. Methods: This prospective study was performed using a semiquantitative immunohistochemical analysis on the staining intensity of α v β3 in the mid-secretory endometria derived from 10 fertile women and 57 infertile patients with a history of repeated IVF-ET failures. Nine patients randomly selected from these 22 patients with unexplained infertility were then treated with oral danazol administration for 12 weeks and reexamined at the first mid-secretory phase after the danazol treatment. Result(s): The levels of endometrial α v β3 expression were lower in 22 patients with unexplained infertility than in the fertile control and 35 patients with explained infertility. The 9 patients treated with danazol showed a significant increase in the α v β3 staining. Conclusion(s): The significantly decreased expression of endometrial integrin α v β3 suggested that functional, but not morphological, endometrial defect may be one of the causes for the patients with unexplained infertility. Danazol may have a therapeutic potential in improving endometrial function together with up-regulation of α v β3.

Interactions between insulin-like growth factor-I (IGF-I) and the renin-angiotensin system in follicular growth and ovulation.

The interactions between insulin-like growth factor-I (IGF-I) and the renin-angiotensin system (RAS) in follicular growth and ovulation were studied with the use of an isolated perfused rabbit ovary preparation. Ovulation failed to occur in either control ovaries or the experimental ovaries perfused with IGF-I in a concentration of 1, 10, or 100 ng/ml in the absence of gonadotropin. Exposure to IGF-I stimulated the secretion rate of angiotensin II-like immunoreactivity (Ang II-IR) in perfused rabbit ovaries in a dose-dependent manner. The percent increase in follicle diameter in ovaries perfused with IGF-I for 12 h was significantly correlated with the secretion rate of Ang II-IR at 12 h after exposure to IGF-I. The addition of IGFBP-3 to the perfusate did not induce ovulation in the absence of gonadotropin, but exposure to IGFBP-3 inhibited hCG-induced ovulation in a dose-dependent manner. In addition, IGFBP-3 significantly reduced the ovarian secretion rate of Ang II-IR and prostaglandins stimulated by hCG administration. Intrafollicular plasminogen activator (PA) activity significantly increased within 4 h after exposure to 100 ng/ml of IGF-I, compared with that in control ovaries perfused with medium alone. The concomitant addition of IGFBP-3 to the perfusate significantly reduced the IGF-I-stimulated PA activity in the preovulatory follicles at 4, 6, and 8 h after exposure to IGF-I. However, IGFBP-3 alone affected neither the ovarian secretion rate of Ang II-IR nor intrafollicular PA activity. Exposure to streptokinase, an exogenous PA, in vitro stimulated both follicular growth and the intrafollicular Ang II-IR content. In conclusion, IGF-I enhances both ovarian Ang II production and follicular development by stimulating intrafollicular PA activity.

Prenatal ultrasound diagnosis of small-bowel torsion

Background We report a case of congenital small-bowel torsion detected by prenatal ultrasonographic examination. Case A 27-year-old primigravida was found to have a fetus with a small-bowel obstruction by ultrasound examination during the third trimester. At 35 weeks of gestation, she complained of absence of fetal activity. A nonstress test showed a nonreactive pattern with reduced baseline variability. Sonographic examination revealed heterogeneous echogenicity within the dilated bowel, and loss of peristalsis. Also noted was a small amount of fetal ascites. After birth, torsion of the dilated small bowel associated with ileal atresia was found at exploratory laparotomy. Conclusion Serial sonographic examinations with special attention to changes in the dilated bowel are useful in the management of prenatally diagnosed small-bowel obstruction.

Role of β1 Integrins in Human Endometrium and Decidua during Implantation

The present study was undertaken to investigate the expression and function of β₁ integrins in human endometrium and decidua. Fluorescence-activated flow cytometry demonstrated the greater expression of the β₁, α₁, α₂, and α₅ subunits of the β₁ integrin family in cultured stromal cells from the midsecretory phase than in those of the early proliferative phase. The addition of estradiol (E₂) and progesterone (P) to cultured stromal cells in the early proliferative phase increased the expression of β₁ integrins in vitro. The immunohistochemical distribution of β₁ integrins demonstrated predominantly glandular epithelial staining in the proliferative phase, and stromal and glandular staining in the midsecretory phase. Flow cytometry also demonstrated the expression of β₁, α₁, α₂, α₃, α₅, and α₆ subunits of β₁ integrin family in cultured decidual cells. Immunohistochemistry confirmed the β₁ integrin cell surface phenotypes in cultured decidual cells observed by flow cytometry. In the subsequent experiment, the effects of antibodies against specific β₁ integrin heterodimers on mouse embryo attachment and spreading were tested to identify the role of β₁ integrins in early implantation. We developed assays for the attachment of mouse embryos and for trophoblastic spreading on cultured human decidual cells. The addition of antibodies directed against β₁ and α integrin subunits to cultured decidual cells did not affect the rates of hatching or attachment of the blastocysts, whereas the outgrowth of embryos on the decidual cells was inhibited by their antibodies in a dose-dependent manner. Thus, β₁ integrin in human endometrium and decidua may be important in mediating the organization of extracellular matrix proteins derived from embryos during the early stage of implantation.

Evaluation of the radiologic findings on hysterosalpingography by selective hydrotubation with flexible hysterofiberscope.

PurposeThe objective of this study was to assess further the significance and accuracy of hysterosalpingography (HSG) by comparing the radiologic findings on HSG to selective hydrotubation (SHT) using a hysterofiberscope in 106 women with tubal occlusion.ResultsPatency was successfully observed by SHT in 72 of 134 tubes and 62 of 106 patients. Proximal obstruction was divided into three groups according to the shape of cornual obstruction (sharp, dull, defect) on HSG. The success rate for SHT in unilateral obstruction (64%) were significantly higher than those in bilateral obstruction (39%). In the three groups of proximal obstruction, the success rates for SHT were 24, 75, and 30% in sharp, dull, and defect, respectively. The group of dull had significantly higher success rate than the groups of sharp and defect. Thirteen of 62 patients who successfully recanalized became pregnant at 9-month follow-up interval.ConclusionCareful evaluation of the cornual obstruction in radiologic findings on HSG may be important for the decision on further treatment. Furthermore, SHT using a hysterofiberscope is an effective method for evaluating tubal obstruction and for managing it in a selected group of patients with tubal obstruction.

Prediction of smallness for gestational age by maternal serum human chorionic gonadotropin levels and by uterine artery Doppler study

Objectives: To compare the utility of maternal serum human chorionic gonadotropin (MShCG) levels with that of uterine artery Doppler study in predicting small for gestational age (SGA) birth and pregnancy-induced hypertension (PIH). Methods: MShCG assay and uterine artery Doppler study were performed in 359 consecutive pregnant women with singleton pregnancies. MShCG levels ≧2.0 multiples of the median at 15–18 weeks’ gestation were considered to be elevated. An abnormal uterine artery Doppler velocimetry at 21–24 weeks’ gestation was defined as a mean pulsatility index above the 95th percentile or the presence of an early diastolic notch in either uterine artery. The predictive values of MShCG levels and uterine artery Doppler velocimetry were evaluated for the risk of SGA birth and PIH. Results: Forty-one subjects gave birth to SGA infants, and 20 developed PIH. Patients with MShCG elevation or abnormal uterine artery Doppler velocimetry showed a significantly higher incidence of SGA infants than the controls. The sensitivity and specificity of MShCG elevation for SGA birth were 17.1 and 93.4%, respectively, compared with abnormal uterine artery Doppler velocimetry, which had 24.4 and 94.3%, respectively. There was no significant difference between these methods. Elevated levels of MShCG and abnormal uterine artery Doppler velocimetry were not associated with PIH. Conclusion: Elevated levels of second-trimester MShCG were as sensitive and specific in predicting SGA births as abnormal uterine artery Doppler velocimetry.

A New Hysteroscopic Tubal Embryo Transfer Catheter : Development and Clinical Application

Objective: Development and clinical application of a new hysteroscopic tubal embryo transfer catheter.

The effects of gonadotropin-releasing hormone agonist on androstenedione production and follicular development during controlled ovarian hyperstimulation.

Purpose:We performed a prospective randomized study to assess the effects of a GnRH agonist (GnRH-a) onfollicular development and steroidogenesis during controlled ovarian hyperstimulation (COH).Methods:Patients undergoing in vitro fertilization (IVF)for tubal infertility received human menopausal gonadotropin (hMG) stimulation with or without the GnRH-a, buserelin, beginning in the midluteal phase of the prior cycle. We analyzed serum hormone levels, follicular development, and outcome of IVF.Results:The mean number of retrieved oocytes was significantly greater, and the implantation rate per embryo was significantly higher, in the GnRH-a/hMG group (n = 101) than in the hMG-only group (n = 97). The concentration of androstenedione (A) and the A/estradiol ratio in the serum were significantly lower in the GnRH-a treatment group throughout the follicular phase.Conclusions:The concomitant use of GnRH-a during COH prevents atretic change of the follicles and enhances follicular development by reducing androgen accumulation, resulting in a higher developmental competence of the oocytes.