Cytokeratins 8, 18 and 19 in endometrial epithelial cells during the normal menstrual cycle and in women receiving Norplant

Abstract

Cytokeratins 8, 18 and 19 are members of the cytoskeletal intermediate filament protein family. They are expressed in all simple epithelial tissues, including endometrium, and are recognised as dynamic structures that can be affected by numerous external factors. The Norplant system is a subdermal slow release levonorgestrel implant commonly used as a long-acting progestogen contraceptive. Norplant implants have been shown to have atrophic effects on endometrial epithelial and stromal cells, and cause a range of endometrial bleeding problems among users. The aim of this study is to describe changes in the immunohistochemical expression and distribution of cytokeratins 8, 18 and 19 in endometrial epithelial cells of Norplant implants users and normal menstrual cycle controls. Endometrial biopsies were collected from 65 control normal cycle women and 37 Norplant implants acceptors. The normal menstrual cycle was classified histologically into 9 stages; one menstrual, five proliferative and three secretory. Norplant implants bleeding patterns were categorised into 6 groups according to current World Health Organisation (WHO) definitions; amenorrhoea, frequent bleeding, infrequent bleeding, irregular bleeding, "normal" bleeding, and prolonged bleeding. The tissues were fixed in formalin, embedded in paraffin, and stained immunohistochemically. Semi-quantitative scoring of the staining intensity was performed. Apical versus basal intracellular cytokeratin distribution was also evaluated. The staining intensity was significantly stronger in control endometrial tissue compared to Norplant implants tissue. In control tissues, cytokeratins were predominantly located in the apical region of epithelial cells (52% of biopsies) and in Norplant implants tissues they were predominantly distributed equally between the apical and basal portions of epithelial cells (43% of biopsies). There was no particular cytokeratin distribution pattern associated with the different stages of normal cycle or the different Norplant implants bleeding patterns. It was concluded that long-term exposure to levonorgestrel significantly reduced the cytokeratin expression in endometrial epithelial cells (P < 0.001).

PIP: Researchers compared endometrial tissue data on 37 women, 21-38 years old, in Jakarta, Indonesia, who were using Norplant contraceptive implants for 3-12 months with similar data on 65 women, 19-49 years old, in Melbourne, Australia, who had normal menstrual cycles and were not using any hormonal contraception or an IUD. They aimed to describe changes in the immunohistochemical expression and distribution of cytokeratins 8, 18, and 19 in endometrial epithelial cells of Norplant users and normal menstrual cycle controls. They also wanted to determine whether any levonorgestrel-induced changes in epithelial cytokeratin expression might effect structural fragility of the endometrium and thus contribute to endometrial bleeding. 26 cases experienced some type of prolonged bleeding pattern. There were no differences in cytokeratins 8, 18, and 19 immunostaining intensity between either the different stages of normal menstrual cycle or between different bleeding patterns among Norplant users. On the other hand, the cytokeratins of controls exhibited much greater immunostaining intensity (i.e., more cytokeratins 8, 18, and 19 in the endometrium) than Norplant users (staining score, 2.6 vs. 1.4; p 0.001). This effect may be associated with increased endometrial fragility that could result in increased bleeding. The cytokeratins in the biopsies belonging to the control group were mainly located in the apical region of epithelial cells (52%) while they tended to be evenly distributed in the apical and basal portions of epithelial cells in the Norplant group (43%). 14% of biopsies in the Norplant group did not stain for cytokeratins. No particular cytokeratin distribution pattern emerged with the various stages of the normal menstrual cycle or the various Norplant-related bleeding patterns. These findings show that levonorgestrel exposure decreases expression of cytokeratins 8, 18, and 19 in endometrial cells.