A Review: Biomechanical Aspects of the Fallopian Tube Relevant to its Function in Fertility

The fallopian tube (FT) plays a crucial role in the reproductive process by providing an ideal biomechanical and biochemical environment for fertilization and early embryo development. Despite its importance, the biomechanical functions of the FT that originate from its morphological aspects, and ultrastructural aspects, as well as the mechanical properties of FT, have not been studied nor used sufficiently, which limits the understanding of fertilization, mechanotrasduction, and mechanobiology during embryo development, as well as the replication of the FT in laboratory settings for infertility treatments. This paper reviews and revives valuable information on human FT reported in medical literature in the past five decades relevant to the biomechanical aspects of FT. In this review, we summarized the current state of knowledge concerning the morphological, ultrastructural aspects, and mechanical properties of the human FT. We also investigate the potential arising from a thorough consideration of the biomechanical functions and exploring often neglected mechanical aspects. Our investigation encompasses both macroscopic measurements (such as length, diameter, and thickness) and microscopic measurements (including the height of epithelial cells, the percentage of ciliated cells, cilia structure, and ciliary beat frequency). Our primary focus has been on healthy women of reproductive age. We have examined various measurement techniques, encompassing conventional metrology, 2D histological data as well as new spatial measurement techniques such as micro-CT.

Trophoblastic infiltration of tubal pregnancy may have an association with chronic inflammation of the fallopian tube

OBJECTIVE

To explore the factors associated with trophoblastic infiltration in ampullary pregnancy from the perspective of clinical and pathologic characteristics.

METHODS

A single-center, retrospective, clinicopathologic cohort study was conducted in women who were diagnosed with tubal pregnancy and underwent salpingectomy in the International Peace Maternal and Child Health Care Hospital from January 2018 to June 2021.

RESULTS

A total of 333 eligible women diagnosed with ampullary pregnancy were included in the analysis. Multivariate logistic analysis showed that preoperative β-human chorionic gonadotropin greater than 3000 IU/L (adjusted odds ratio [aOR] 3.77, 95% confidence interval [CI] 2.02-7.03), and vascular remodeling phenomenon (aOR 4.34, 95% CI 2.41-7.83) were positively correlated with the infiltration of extravillous trophoblasts into serosa, while presence of chronic inflammation of the fallopian tube was a negatively corellated factor (aOR 0.49, 95% CI 0.29-0.85).

CONCLUSION

The depth of trophoblastic infiltration in tubal pregnancy may be related to the presence of chronic inflammation in the fallopian tube. A tubal pregnancy in a tube with chronic salpingitis is more likely to develop into an abortive ectopic pregnancy; whereas in a fallopian tube without chronic inflammation, the risk of it developing into a ruptured ectopic pregnancy increases. Hence, early identification is needed to properly address this dangerous pregnancy situation.

Emergency Contraception: Access and Challenges at Times of Uncertainty

BACKGROUND

The UN Commission on Life-Saving Commodities for Women's and Children's Health identified emergency contraceptive pills as 1 of the 13 essential underused, low-cost, and high-impact commodities that could save the lives of millions of women and children worldwide. In the US, 2 emergency contraceptive regimens are currently approved, and their most plausible mechanism of action involves delaying and/or inhibiting ovulation.

AREAS OF UNCERTAINTY

Abortion and contraception are recognized as essential components of reproductive health care. In the US, in the wake of the Dobbs v. Jackson Women's Health Organization Supreme Court decision on June 24, 2022, 26 states began to or are expected to severely restrict abortion. It is anticipated that these restrictions will increase the demand for emergency contraception (EC). Several obstacles to EC access have been described, and these include cost, hurdles to over-the-counter purchase, low awareness, myths about their mechanisms of action, widespread misinformation, and barriers that special populations face in accessing them. The politicization of EC is a major factor limiting access. Improving sex education and health literacy, along with eHealth literacy, are important initiatives to improve EC uptake and access.

DATA SOURCES

PubMed, The Guttmacher Institute, Society of Family Planning, American College of Obstetrician and Gynecologists, the World Health Organization, The United Nations.

THERAPEUTIC ADVANCES

A randomized noninferiority trial showed that the 52 mg levonorgestrel intrauterine device was noninferior to the copper intrauterine device when used as an EC method in the first 5 days after unprotected intercourse. This is a promising and highly effective emergency contraceptive option, particularly for overweight and obese patients, and a contraceptive option with a different bleeding profile than the copper intrauterine device.

CONCLUSIONS

EC represents an important facet of medicine and public health. The 2 medical regimens currently approved in the US are very effective, have virtually no medical contraindications, and novel formulations are actively being investigated to make them more convenient and effective for all patient populations. Barriers to accessing EC, including the widespread presence of contraception deserts, threaten to broaden and accentuate the already existing inequities and disparities in society, at a time when they have reached the dimensions of a public health crisis.

The role of SK3 in progesterone-induced inhibition of human fallopian tubal contraction

BACKGROUND

Normal motor activity of the fallopian tube is critical for human reproduction, and abnormal tubal activity may lead to ectopic pregnancy (EP) or infertility. Progesterone has an inhibitory effect on tubal contraction; however, the underlying mechanisms remain unclear. Small-conductance calcium-activated K⁺ channel 3 (SK3) is abundantly expressed in platelet-derived growth factor receptor α positive (PDGFRα+) cells and was reported to be important for the relaxation of smooth muscle. The present study aims to explore the expression of SK3 in the human fallopian tube and its role in progesterone-induced inhibition of tubal contraction.

METHODS

We collected specimens of fallopian tubes from patients treated by salpingectomy for EP (EP group) and other benign gynecological diseases (Non-EP group). The expression of SK3 was detected by quantitative real-time polymerase chain reaction, western blot, immunocytochemistry, and immunohistochemistry analyses. Isometric tension experiments were performed to investigate the role of SK3 in progesterone-induced inhibition of tubal contraction.

RESULTS

The baseline amplitude and frequency of human fallopian tube contraction were both statistically lower in the EP group compared with the non-EP group. The expression levels of SK3 in different portions of fallopian tubes from the non-EP group were significantly higher than in those from the EP group. Progesterone had an inhibitory effect on tubal contraction, mainly on the amplitude, in both groups, and SK3 as well as other calcium-activated K⁺ channels may be involved. SK3-expressing PDGFRα (+) cells were detected in the human fallopian tube.

CONCLUSIONS

The expression of SK3 is lower in the EP group, and SK3 is involved in the progesterone-induced inhibition of human fallopian tube contraction.

The association between mitochondrial DNA copy number, telomere length, and tubal pregnancy

Growing evidence has demonstrated association between the occurrence of tubal ectopic pregnancy (TP) and oxidative stress (OS) status, in which mitochondria and telomeres play important roles. However, little is known about the underlying correlation between TP and the mitochondrial DNA copy number (mtDNAcn) or telomere length (TL) abnormalities. In this study, we found OS level was elevated in TP patients. We hierarchically detected the relative mtDNAcn and TL of villi from normal pregnancy (NP) and TP samples according to different gestational age, fetal sex, maternal age, and BMI. The results revealed that the relative mtDNAcn was significantly lower in the villi in the TP group compared with the NP cohort, which was negatively correlated with OS status. In the NP group, the mtDNAcn in the female subgroup was apparently lower than that in the male subgroup, while no statistical difference was found in the mtDNAcn in the TP group between the female and male subgroups. Moreover, the relative TL in the TP group was at a similar level to the NP group, and no statistical correlation was observed between relative TL and OS level. In summary, our findings indicate that the abnormal level of mtDNAcn rather than TL is correlated with TP, which provides new insights into the mechanism of TP.

TRPV4 is involved in levonorgestrel-induced reduction in oviduct ciliary beating

Previous studies revealed the increasing risk of tubal pregnancy following failure of levonorgestrel (LNG)‐induced emergency contraception, which was attributed to the reduced ciliary motility in response to LNG. However, understanding of the mechanism of LNG‐induced reduction in the ciliary beat frequency (CBF) is limited. The transient receptor potential vanilloid (TRPV) 4 channel is located widely in the female reproductive tract and generates an influx of Ca²⁺ following its activation under normal physiological conditions, which regulates the CBF. The present study aimed to explore whether LNG reduced the CBF in the Fallopian tubes by modulating TRPV4 channels, leading to embryo retention in the Fallopian tubes and subsequent tubal pregnancy. The study provided evidence that the expression of TRPV4 was downregulated in the Fallopian tubes among patients with tubal pregnancy and negatively correlated with the serum level of progesterone. LNG downregulated the expression of TRPV4, limiting the calcium influx to reduce the CBF in mouse oviducts. Furthermore, the distribution of ciliated cells and the morphology of cilia did not change following the administration of LNG. LNG‐induced reduction in the CBF and embryo retention in the Fallopian tubes and in mouse oviducts were partially reversed by the progesterone receptor antagonist RU486 or the TRPV4 agonist 4α‐phorbol 12,13‐didecanoate (4α‐PDD). The results indicated that LNG could downregulate the expression of TRPV4 to reduce the CBF in both humans and mice, suggesting the possible mechanism of tubal pregnancy. © 2019 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Left-Right Asymmetry of Tubal Pregnancy: A 12-Year Retrospective Hospital-Based Study

STUDY OBJECTIVE

To investigate whether there are left-right asymmetries, factors affecting lateral dominance, and clinical feature differences in the left and right sides of tubal pregnancy (TP).

DESIGN

Retrospective study (Canadian Task Force classification II-2).

SETTING

International Peace Maternity and Child Health Hospital, School of Medicine, Shanghai Jiao Tong University.

PATIENTS

Patients (n = 6186) with TP treated surgically.

INTERVENTIONS

We used data from the digital medical records system of the hospital. Women diagnosed with ectopic pregnancy(EP) between January 2005 and December 2016 in the inpatient department of gynecology were included. All data from the medical files were obtained retrospectively, including demographic characteristics; reproductive, gynecologic, and surgical history; clinical features; and treatment. Patients who were previously treated by salpingectomy or nonsurgical management and those with unknown-site EP or non-TPs were excluded.

MEASUREMENTS AND MAIN RESULTS

The overall frequency of right-sided TP was 54.48% (3370/6186), which is significantly higher than 50% (p < .001, binominal test). The proportion of right-sided TPs decreased with age (p for trend = .007) and from the proximal (interstitial) end to the distal (fimbrial) end of the tube (p for trend = .017). Of the TP patients with a corpus luteum, we found the corpus luteum was more frequently located in the right ovary (p < .001) and in the contralateral ovary to the TP side in 41.38% of cases. However, tubal rupture was more frequent in left TP than the in right TP (p = .005).

CONCLUSION

The left-right asymmetries of TP include right-side dominance and the clinical feature differences between the 2sides of TP.

Progesterone Receptor Isoforms, Nuclear Corepressor-1 and Steroid Receptor Coactivator-1 and B-Cell Lymphoma 2 and Akt and Akt Phosphorylation Status in Uterine Myomas after Ulipristal Acetate Treatment: A Systematic Immunohistochemical Evaluation

OBJECTIVE

To investigate whether ulipristal acetate (UPA) treatment modifies the expression of progesterone receptor (PR), its nuclear cofactors steroid receptor coactivator-1 (SRC1) and nuclear corepressor-1 (NCoR1), prosurvival factor B-cell lymphoma 2 (Bcl-2), and Akt in uterine myomas.

PATIENTS

Prospective study of 59 women with symptomatic myomas undergoing myomectomy. Forty-two patients were treated preoperatively with UPA; the remaining 17 were not and they served as controls.

METHOD

Tissue microarrays were obtained from surgical specimens and immunohistochemistry was performed. Blinded quantification of expression of PR (PR-A vs. PR-B), coactivator SRC1 and corepressor NCoR1, and prosurvival factor Bcl-2, and Akt and evaluation of Akt phosphorylation levels.

RESULTS

Compared with the control group, UPA does not alter PR protein levels or expression patterns in myomas, and the PR-A/PR-B ratio was similar, as well as cytoplasmic or nuclear expression of cofactors SRC1 and NCoR1. Bcl-2 was heterogeneously expressed throughout the samples and no significant modification in expression was evidenced. No significant difference was found in Akt expression and phosphorylation between treated and untreated myomas.

CONCLUSION

This study did not find any significant change in the expression of the studied factors in myomas after UPA exposure. In conclusion, various theories on myomas cells proposed on the basis of in vitro studies are not supported in vivo.

Progesterone-mediated angiogenic activity of endothelial progenitor cell and angiogenesis in traumatic brain injury rats were antagonized by progesterone receptor antagonist

OBJECTIVES

Progesterone (P4) has the potential therapeutic effects for traumatic brain injury (TBI) whose recovery depended on the enhanced angiogenesis. Endothelial progenitor cell (EPC) plays an essential role in vascular biology. We previously demonstrated that P4 administration improved circulating EPC level and neurological recovery of rat with TBI. Here, we hypothesized that P4 augmented angiogenic potential of EPC and the angiogenesis-related neurorestoration after TBI through classical progesterone receptor (PR).

MATERIALS AND METHODS

EPC derived from rats were stimulated with graded concentrations (0, 10^-10 , 10^-9 , 5 × 10^-9 , 10^-8 , 10^-7  mol/L) of P4 or 10^-6  mol/L ulipristal acetate (UPA, a PR antagonist). Male rats were subjected to cortical impact injury and treated with (i) DMSO (dimethyl sulfoxide), (ii) P4 and (iii) P4 and UPA.

RESULTS

It showed that P4 improved the angiogenic potential of EPC, including tube formation, adhesion, migration and vascular endothelial growth factor secretion, in a dose-dependent fashion with the maximal effect achieved at 10^-9  mol/L P4. High concentration (10^-7  mol/L) of P4 impaired the angiogenic potential of EPC. Notably, 10^-6  mol/L UPA antagonized the stimulatory effects of 10^-9  mol/L P4. After administrating P4, a significant improvement of neurological function and the restoration of the leaked blood-brain barrier were observed as well as a reduction of the brain water content. Both vessel density and expression of occludin of vessels were increased. When UPA was administered with P4, the neural restoration and angiogenesis were all reversed. Western blot showed that 10^-9  mol/L P4 increased the content of PRA and PRB of EPC, while 10^-7  mol/L P4 reduced the content of both PR isoforms, but there was no change found in the TBI rats.

CONCLUSIONS

It may suggest that P4-mediated angiogenic activity of EPC and angiogenesis in TBI rats were antagonized by PR antagonist.

Pregnancy Outcomes Following Ulipristal Acetate Emergency Contraception Failure: A Report of Five Cases

INTRODUCTION

The emergency contraceptive ulipristal acetate (UPA) 30 mg is increasingly used by women, but there is no published data on UPA exposure in pregnancy.

CASE REPORT

Here we describe five cases of unintended pregnancies following the use of UPA for emergency contraception. Of five pregnant women exposed to UPA, one decided to terminate the pregnancy for personal reasons. Two of them experienced premature rupture of membranes and the babies were born large for gestational age (LGA). The other two women experienced gestational diabetes, and one of them also delivered a LGA baby. The blood glucose levels of the mothers were normal after delivery and at six weeks postpartum. No birth defects and no growth or developmental abnormalities for the infants were reported during 6 months follow-up.

CONCLUSION

Pregnant women inadvertently exposed to UPA should be monitored carefully, unless further data are available.

Mechanism of Action of Ulipristal Acetate for Emergency Contraception: A Systematic Review

Ulipristal acetate (UPA) is now recommended as first choice hormonal emergency contraception (EC), due to its higher efficacy and similar safety compared to Levonorgestrel - EC. Even though all trials demonstrated that the first mechanism of action is inhibition of ovulation, some authors still postulate that a post fertilization effect is also possible, raising the alert on medication and fostering the ethical debate. A Medline database search was performed in order to find recent articles related to UPA's effects on ovulation, on fallopian tube and on endometrium. We also analyzed the effects on sperm function and pregnancy. All studies conclude that UPA is effective in inhibition of ovulation even when administered shortly before LH peak. The effects on fallopian tube are unclear: according to some authors UPA inhibits ciliar beat through an agonistic effect on progesterone receptors, according to others it antagonizes the progesterone-induced ciliar beat decrease. Concerning the action on endometrium and on embryo implantation most of the studies concluded that low dose UPA used for EC has no significant effect on the decrease of endometrial thickness and on embryo's attachment, but these results are still matter of debate. Finally recent evidence suggests that UPA modulates human sperm functions while it has no effect on established pregnancy. To date the majority of the evidence concurs in excluding a post-fertilization effect of UPA, even though more studies are needed to clarify its mechanism of action.