The importance of the junctional zone of the endometrium in human reproduction.

Junctional zone endometrium (JZE) thickness and contractility seem to determine gamete and embryo transportation and implantation. Proper function depends on concentration levels, mode and timing of oestrogen and progesterone production. Most probably, the remodelling of spiral arteries, and the development of endometrium and decidua are also highly dependent on JZE activity. Fibroids that are adjacent to JZE affect JZE contractility contributing to abnormal or failed implantation. Disruption of the JZE continuity provokes adenomyosis, a condition that causes chronic inflammation and fibrosis, which negatively affects the normal function of JZE. Imaging by magnetic resonance imaging and three-dimensional sonography can diagnose JZE abnormal appearance, alterations in thickening and contractility frequency, usually in the advanced stage of the disease. Failures of assisted reproduction, and adverse early pregnancy outcomes have also been associated with abnormal JZE. Altered uterine contractions due to JZE changes are strongly associated with poor reproductive outcome and early pregnancy loss. Endometriosis and adenomyosis prevalently co-exist, with clear relation and negative effects on the JZE. The presence of endometriosis should alert to the possibility of coexisting adenomyosis. Co-existence of endometriosis may mask the extent of the negative impact of adenomyosis in infertility.

Junctional Zone Endometrium Morphological Characteristics and Functionality: Review of the Literature.

The junctional zone endometrium (JZE) is a compacted layer of smooth muscle cells with little extracellular matrix. The innermost myometrium adjacent to the endometrium, JZE is best visualized and evaluated on T2-weighted magnetic resonance imaging (MRI) and two-dimensional/three-dimensional transvaginal ultrasound (TVUS) scanning. Increased thickness of JZE >12 mm on MRI images has been associated with myometrial and subendometrial pathologic conditions, such as, adenomyosis, and is considered a poor prognostic factor for implantation. Gonadotrophin-releasing hormone analogue (GnRHa) has been proposed as a treatment for adenomyosis and fibroids larger than 7 cm, and overall improvement in symptoms and disease progression were attributed to JZE thinning after GnRHa treatment. JZE contractility and frequency of contractions are affected by ovarian hormone cyclic activity and pathologic changes adjacent to JZE, such as fibroids and polyps. However, JZE contractility is not evaluated by TVUS during gynecological examinations because guidelines do not exist and the process is time consuming. The present data indicate that JZE is an important part of the nongravid uterus anatomy, structure, and functionality. When more evidence is available, the morphologic features, thickness, and contractility of JZE may potentially be used as markers for diagnosis and prognosis of normal and abnormal uterine function, for early stages of pregnancy, and possibly for early detection of endometrial cancer. A new tool for JZE measurements should be further investigated to fill this clinical gap. Key Message: JZE is an important component of the nongravid uterus anatomy, structure, and functionality. The thickness and contractility of JZE could potentially be used as markers for diagnosis and prognosis of normal and abnormal uterine function, early stages of pregnancy, and early detection of endometrial cancer. A new tool for JZE measurements should be further investigated.

Junctional zone endometrium alterations in gynecological and obstetrical disorders and impact on diagnosis, prognosis and treatment.

PURPOSE OF REVIEW: To investigate the JZE alterations in gynecological and obstetrical disorders and impact on diagnosis, prognosis and treatment. RECENT FINDINGS: JZE was found to be significantly extended in patients with endometriosis, leading to the conclusion that endometriosis is a primary disease of the uterus, much like adenomyosis. Statistical correlation was then demonstrated between the severity of endometriosis and the depth of the adenomyosis infiltrates, hence the thickening of the JZE. Stem cells, predominantly found in the JZE were also found in histological sections of leiomyoma, suggested to be the origin of leiomyoma. This reservoir of JZE stem cells is influenced by different stressors leading to their differentiation into leiomyoma, endometriosis, adenomyosis or endometrial cancer, according to the stressor. The variability in presentation was hypothesized to be connected to genetic and epigenetic factors. JZE was also suggested to act as a barrier, stopping endometrial carcinoma cells invasion and metastasis. In addition, JZE plays a major role in conception, pregnancy and postpartum. SUMMARY: JZE is an important anatomical landmark of the uterus contributing to normal uterine function under the influence of ovarian hormones. Alterations of the JZE thickness and contractility can be used as pathognomonic clinical markers in infertility and chronic pelvic pain, for subendometrial and myometrial disorders, for example, adenomyosis and fibroids. Prospective randomized control trials will clarify the diagnostic steps, imaging modalities to follow and probably triage the patients between medical and surgical treatments.