The enigmatic uterine junctional zone: the missing link between reproductive disorders and major obstetrical disorders?

Abstract

While there is a growing realization that the origins of major obstetrical complications associated with defective deep placentation, such as pre-term labour, fetal growth restriction and pre-eclampsia, may lie in the very early pregnancy events, the underlying mechanisms are not understood. Impaired deep placentation is foremost a vascular pathology, characterized by a lack of endovascular trophoblast invasion and remodelling of a segment of the spiral arteries embedded within the inner myometrium of the uterus. Outside pregnancy, the inner myometrium represents a highly specialized, hormone-dependent structure, termed the junctional zone (JZ), which plays an integral part in the implantation process. The JZ changes with age and is disrupted in several reproductive disorders, such as endometriosis and adenomyosis, which in turn may account for the increased risk of adverse pregnancy outcome. Unlike the endometrium, the myometrial JZ is not readily accessible to biochemical or molecular studies, yet its structure and function can be assessed using imaging techniques, such as high-resolution ultrasound and magnetic resonance imaging. Thus, non-invasive assessment of the JZ prior to conception may turn out to be useful in identifying those women at risk of major obstetrical complications.

Complications and outcomes of pregnant women with adenomyosis in Japan

“…22 As the thickening and disruption of the junctional zone appearance is strongly associated with uterine adenomyosis, adenomyosis might be related to placental insufficiency and poor placental perfusion, resulting into PIH. 4 Our results also showed that the incidence of FGR (11.8%; 31/262) was higher than that reported in the general population (5%-10%). 23 FGR cases of adenomyosis-complicated pregnancy with poor placental blood flow were reported.…”

“…During pregnancy, the invasion of trophoblasts into the endometrium and the myometrial junctional zone causes decidualization and unique vascular changes. 4 The thickening and disruption of the junctional zone in women with adenomyosis might be associated with placental insufficiency and complications of pregnancy. In addition, the type of adenomyosis is considered to be an important factor affecting decidualization and placentation.…”

“…4 The impaired decidualization of the myometrial spiral arteries is a predisposing factor for failed intravascular trophoblast invasion. 21 Defective deep placentation has been reported to be associated with a spectrum of obstetric complications, including late miscarriage, preterm labor, FGR, and pre-eclampsia.…”

Imaging for the evaluation of endometriosis and adenomyosis

“…Pelvic endometriosis, especially in severe stages, is also strongly associated with junctional zone thickening [73,74,83,84]. Observational studies suggest that perturbations in junctional zone structure or functions before conception predispose towards a spectrum of fertility and obstetrical complications [85].…”

Dysmenorrhea, Adenomyosis, Endometriosis, Tumor Process: Causation

“…Процессу инвагинации эндометри-альной ткани способствуют нарушения регуляции молеку-лярных механизмов апоптоза, пролиферации, неоангио-генеза и экспрессии матриксных металлопротеиназ [13]. Данные трансмиссионной электронной микроскопии, иммуногистохимического окрашивания для Cadherin, иммунофлюоресценции для CD45 и CD68 подтверждают, что ультрамикротравма в зоне эндомиометриального перехода (junctional zone) является одним из ключевых звеньев патогенеза аденомиоза [14].…”