A comparative study of vascular responsiveness of myometrial and omental small resistance arteries in late-gestation sheep

Enhanced beta-catenin expression and inflammation are associated with human ectopic tubal pregnancy

STUDY QUESTION

Is there a molecular link between Wnt signaling in fallopian tube inflammation and ectopic tubal implantation?

SUMMARY ANSWER

Enhanced beta-catenin expression, reduced E-cadherin expression and glycogen accumulation in the tubal epithelia and hyperplasia in tubal arteries were found in ectopic tubal pregnancy, consistent with the effects induced by Wnt signaling and inflammation.

WHAT IS KNOWN ALREADY

Chronic inflammation caused by infection can alter gene expression in the fallopian tube cells possibly leading to the development of ectopic pregnancy. Knockout mouse models have shown a relationship between Wnt/beta-catenin signaling and predisposition to tubal ectopic pregnancy.

STUDY DESIGN, SIZE, DURATION

Women with ectopic tubal pregnancy (n = 18) were included in the case group, while women with chronic salpingitis (n = 13) and non-pregnant women undergoing sterilization procedures or salpingectomy for benign uterine disease (n = 10) were set as the controls. This study was performed between January 2012 and November 2012.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The ampullary segments of fallopian tubes were collected from patients. Tissues of tubal pregnancy were separated into implantation sites and non-implantation sites. Beta-catenin and E-cadherin expression were determined using immunohistological and immunofluorescence staining. Glycogen production was measured with periodic acid Schiff by staining. The diameter and wall thickness of tubal arteries were evaluated by histological analysis method.

MAIN RESULTS AND THE ROLE OF CHANCE

Immunohistological staining revealed that beta-catenin protein expression was 100% positive in the ectopic pregnant and inflamed tubal tissues, and the staining intensity was significantly higher than in non-pregnant tubal tissues. In contrast, E-cadherin expression was reduced in ectopic pregnant fallopian tubes, possibly as a consequence of increased Wnt signaling. Moreover, glycogen accumulated in the tubal cells, and hyperplasia was observed in the tubal arteries with ectopic pregnancy, which is consistent with the effects induced by Wnt signaling and inflammation. All these changes could create the permissive environment that promotes embryos to ectopically implant into the fallopian tube.

LIMITATIONS, REASONS FOR CAUTION

This finding requires a further confirmation about what activates Wnt signaling in ectopic tubal pregnancies. Also, it is generally recognized that Chlamydia infection is associated with ectopic pregnancy, and disturbs tubal epithelia via the Wnt signaling. However, the infection type in the samples used was salpingitis.

WIDER IMPLICATIONS OF THE FINDINGS

A better understanding of the underlying mechanisms leading to ectopic pregnancies may contribute to our knowledge of the pathogenesis of tubal disorders and infertility and to the prevention of tubal ectopic pregnancy.

In vivo arterial lipoprotein lipase expression augments inflammatory responses and impairs vascular dilatation

OBJECTIVE

Although epidemiologic data suggest that hypertriglyceridemia and elevated plasma levels of fatty acids are toxic to arteries, in vitro correlates have been inconsistent. To investigate whether increased endothelial cell expression of lipoprotein lipase (LpL), the primary enzyme creating free fatty acids from circulating triglycerides (TG), affects vascular function, we created transgenic mice that express human LpL (hLpL) driven by the promoter and enhancer of the Tie2 receptor.

METHODS AND RESULTS

Mice expressing this transgene, denoted EC-hLpL and L for low and H for high expression, had decreased plasma TG levels compared with wild-type mice (WT): 106+/-31 in WT, 37+/-17 (line H), and 63+/-31 mg/dL (line L) because of a reduction in VLDL TG; plasma cholesterol and HDL levels were unaltered. Crossing a high expressing EC-hLpL transgene onto the LpL knockout background allowed for survival of the pups; TG in these mice was approximately equal to that of heterozygous LpL knockout mice. Surprisingly, under control conditions the EC-hLpL transgene did not alter arterial function or endothelial cell gene expression; however, after tumor necrosis factor (TNF)-alpha treatment, arterial vascular cell adhesion molecule-1 (VCAM-1), E-selectin, and endogenous TNF-alpha mRNA levels were increased and arteries had impaired endothelium-dependent vasodilatation. This was associated with reduced eNOS dimers.

CONCLUSIONS

Therefore, we hypothesize that excess vascular wall LpL augments vascular dysfunction in the setting of inflammation.

Oxytocin does not directly affect vascular tone in vessels from nonpregnant and pregnant rats

Recent evidence suggests oxytocin (OT) may regulate vascular tone. OT and its receptor (OTR) have been identified in the rat heart and great vessels. Expression of OT and OTR is increased in some tissues during pregnancy. We hypothesized that the OT/OTR system may be a physiological regulator of vascular tone and mediate the decreased vascular resistance noted during pregnancy. Using a wire myograph system, we measured changes in vascular tone in response to OT in small mesenteric arteries, uterine arcuate arteries, and thoracic aorta from nonpregnant and pregnant rats. Additionally, we used reverse transcriptase-polymerase chain reaction (RT-PCR) to measure mRNA for OTR in these vascular tissues. Although OTR mRNA was identified by RT-PCR, OT did not elicit a vasodilatory effect in any of the vessels studied. High concentrations of OT (>10(-8) M) caused vasoconstriction that was eliminated by a specific vasopressin V(1a) receptor antagonist. Although it may have an indirect effect in regulation of peripheral resistance, we conclude that OT is unlikely to play a direct role in the physiological regulation of vascular tone.