Quantification of nucleolar channel systems: uniform presence throughout the upper endometrial cavity

Abstract

Objective: To determine the prevalence of nucleolar channel systems (NCSs) by uterine region, applying continuous quantification.

Design: Prospective clinical study.

Setting: Tertiary care academic medical center.

Patient(s): Forty-two naturally cycling women who underwent hysterectomy for benign indications.

Intervention(s): NCS presence was quantified by a novel method in six uterine regions-fundus, left cornu, right cornu, anterior body, posterior body, and lower uterine segment (LUS)-with the use of indirect immunofluorescence.

Main outcome measure(s): Percentage of endometrial epithelial cells (EECs) with NCSs per uterine region.

Result(s): NCS quantification was observer independent (intraclass correlation coefficient 0.96) and its intrasample variability low (coefficient of variation 0.06). Eleven of 42 hysterectomy specimens were midluteal, ten of which were analyzable with nine containing >5% EECs with NCSs in at least one region. The percentage of EECs with NCSs varied significantly between the LUS (6.1%; interquartile range [IQR] 3.0-9.9) and the upper five regions (16.9%; IQR 12.7-23.4), with fewer NCSs in the basal layer of the endometrium (17 ± 6%) versus the middle (46 ± 9%) and luminal layers (38 ± 9%) of all six regions.

Conclusion(s): NCS quantification during the midluteal phase demonstrates uniform presence throughout the endometrial cavity, excluding the LUS, with a preference for the functional luminal layers. Our quantitative NCS evaluation provides a benchmark for future studies and further supports NCS presence as a potential marker for the window of implantation.

Figure 1

(A) Endometrial gland: indirect immunofluorescence of nuclear pore complex proteins that are highly enriched in NCSs (one is highlighted by an arrow) on one of the ten random optical fields analyzed for the anterior body region of one uterus (red in B). A maximum projection of 22 0.3μm-thick optical sections is shown. Inset: twofold magnification of a single optical section from the boxed area above; note, in that optical plane only two of the three NCSs seen in the maximum projection are visible (i.e., the NCS in the lower right corner is situated on a different plane), and note the outline of the nuclear boundary by the individual pore complexes. (B) Regional prevalence of NCSs in the uterus. % EECs with NCSs in six regions of 9 uteri (colors correspond to the following numbers in Table 2: blue = 1, light green = 2, purple =3, light blue = 4, orange = 5, red = 6, brown = 7, green = 8, yellow = 9). The medians ± interquartile range (IQR) are indicated for each region, as is the significant difference between the lower uterine segment and the other five regions (p = 0.008, Wilcoxon signed ranks test). (C) Prevalence of NCSs in the endometrial layers. The distribution of NCSs (left) and Glands (right) between three equal layers (basal, middle, and luminal) of the endometrium of one uterus (yellow in B) is indicated for all regions together (first column each) and for each individual region (abbreviations as in B). The numbers correspond to 100% of each column. Note the reduced amount of NCSs in the basal layer compared to the middle and luminal ones.