Endometrial pinopodes indicate a shift in the window of receptivity in IVF cycles

Detection of endometrial pinopodes by light microscopy

OBJECTIVE

To study the value of light microscopy (LM) in the assessment of endometrial pinopodes.

DESIGN

Comparative histologic study.

SETTING

Outpatient infertility clinic in an academic teaching institution.

PATIENT(S)

Eighteen oocyte donors undergoing controlled ovarian hyperstimulation.

INTERVENTION(S)

Endometrial biopsies on days 14-24 of the cycle.

MAIN OUTCOME MEASURE(S)

Assessment of pinopodes by scanning electron microscopy (SEM) and of endometrial surface projections by LM.

RESULT(S)

The luminal surface was identified by LM in 36 of 38 endometrial specimens obtained. Although apical projections could be recognized in all, they were few, moderate, and abundant in 20, 12, and 4 cases, respectively. Pinopodes were detected by SEM in all 4 samples with abundant projections, but in only 14 of 32 samples with lesser quantities of these surface features. No predictive value could be ascribed to apical projections viewed by LM for the developmental stage of pinopodes as defined by SEM.

CONCLUSION(S)

The LM of routine endometrial specimens can serve as a preliminary tool in the evaluation of surface morphology. Although abundant apical projections by LM are compatible with the presence of pinopodes by SEM, the latter modality remains as the definitive method in cases with few or moderate projections and for the evaluation of the stage of pinopode development.

In vitro models of human blastocyst implantation

This paper reviews different in vitro models used for the study of blastocyst implantation in animals and the human. Furthermore, results from human blastocyst-endometrial interactions in vitro, investigated by scanning electron microscopy (SEM), light microscopy (LM) and transmission electron microscopy (TEM), are presented. SEM demonstrates the preference of human blastocysts to adhere to pinopode-presenting areas on endometrial cell cultures. LM and TEM show that the first morphological sign of cell contact, defined as junction formation, is present at the apical-to-lateral border of endometrial epithelial cells, whereas trophoblast attachment to apical endometrial epithelial plasma membranes was not observed. More advanced stages illustrate that the human blastocyst penetrates the epithelial lining by the intrusive penetration mechanism.

Modulation of endometrial transformation in gonadotrophin-stimulated and unstimulated pseudo-pregnant rabbits: studies with the progesterone receptor antagonist, onapristone

Advanced endometrial transformation often occurs in IVF and embryo transfer therapy after ovarian stimulation with gonadotrophins. One reason is probably the early rise in peripheral progesterone concentration after ovulation induction. Consequently, we studied in a rabbit model, whether the post-ovulatory application of the progesterone receptor antagonist, onapristone, could prevent such an advancement of endometrial transformation after stimulation with different gonadotrophin preparations. The inhibitory effect of onapristone on the endometrium is dependent upon the strength of ovarian stimulation. In unstimulated animals or animals treated with recombinant LH (nine corpora lutea/animal in both groups), secretory differentiation and proliferation of the endometrium was strongly inhibited by onapristone. After weak ovarian stimulation with a 3:1 mixture of FSH and LH (22 corpora lutea/animal), secretory differentiation was strongly inhibited, while proliferation was enhanced. After strong stimulation with either a 1:1 mixture of FSH and LH, or human menopausal gonadotrophin (HMG; >40 corpora lutea/animal), only limited inhibitory effects of onapristone on secretory transformation or proliferation could be detected. In conclusion, these graded effects of onapristone after stimulation with gonadotrophins, resemble the basic observations from which a therapeutic strategy emerges, to modulate the advanced endometrial transformation which occurs in many IVF patients after ovarian stimulation.

Surface morphology of the human endometrium. Basic and clinical aspects

The human endometrium is an extremely sensitive target for steroid hormones. During the menstrual cycle, this tissue undergoes dynamic changes that are reflected on the surface morphology of the epithelium and that can be followed by scanning electron microscopy. The morphologic changes peak at the midsecretory phase, with the formation of the so-called pinopodes. Increasing evidence suggests that these pinopodes are accurate markers for endometrial receptivity, and their detection may be of high clinical utility in the preparation of endometrium before embryo transfer. This article recapitulates published figures of endometrial ultrastructure and presents some unpublished data from ongoing studies.

Cellular and molecular events surrounding blastocyst implantation: report on a NICHD meeting, Bethesda, MD, USA, 15-16 November 1999

This meeting, supported by the Reproductive Sciences Branch, Center for Population Research, National Institute of Child Health and Human Development (NICHD), NIH, was held to achieve dual purposes: (1) the evaluation of the ongoing National Cooperative Program on Markers of Uterine Receptivity for Blastocyst Implantation and (2) to update our knowledge of blastocyst implantation research. The Cooperative Program was evaluated as being highly successful, with good productivity, rapid exchange of information, and remarkable progress. Our knowledge of many molecules that concern interactions between blastocyst and maternal tissues was also updated as a result of the meeting.

The effects of the early uterine environment on the subsequent development of embryo and fetus

Synchrony between the embryo and the uterine endometrium is essential for the establishment of pregnancy and birth in people and livestock. When asynchronous conditions occur a variety of complication result that include failure of the embryo to implant, early embryonic mortality, retarded development and growth, and accelerated development and growth. These complications all appear to be induced within the first week of embryo development and not withstanding the immediate endpoint of large or small size at birth, may alter the course of development throughout the life of the animal. Progesterone appears to play a causative role in establishing the abnormal growth of the fetus by decelerating or accelerating embryonic development. This may act through increasing the transport of blood born growth factors into the uterine lumen or by stimulating the release of growth factors from the endometrium directly. It can not be ruled out that progesterone mediated abundance of, or absence of, appropriate nutrition may bring about the same lifelong outcome. In vitro culture situations that include serum and/or co-culture can also bring about these abnormalities of growth. It is hypothesized that exposure to growth factors "out of phase" may result in an irreversible induction of abnormal development. The described abnormalities that occur in sheep and cattle have not yet been described for children resulting from IVF.