An investigation of the action of cytokines on human endometrial and endometriotic colony forming units

Abstract

Cyclic proliferation and differentiation occur in the human endometrium in each menstrual cycle. Aside from the precise regulation of estrogen and progesterone, the physiology of the human endometrium is also tightly regulated by cytokines. It is therefore not surprising that imbalance of cytokine expression could be observed when women suffer from gynecological disease such as endometriosis, a common gynecological disease associated with altered cytokine profile and chronic inflammatory response. Although the etiology of endometriosis is not yet well elucidated, a commonly accepted Sampson theory suggests reflux of endometrial tissue to other parts of the reproductive tract would be one of the causes. As recent findings demonstrate the presence of somatic stem cells residing in human endometrium and endometriotic cyst, the hypothesis of the thesis was that cytokines confer a regulatory role in the proliferation and self-renewal of the endometrial and endometriotic stem/progenitor cells.

In this project the following objectives were studied: 1) To investigate the effect of cytokines interleukin (IL) - 1β, IL-8, IL-10, IL-13, tumor necrosis factor (TNF) – α and interferon (IFN) – γ on the clonogenic ability of endometrial and endometriotic colony forming units (CFUs); 2) To determine the effect of IL-1β and IL-13 on the self-renewal and proliferative potential of the CFUs; 3) To elucidate the expression patterns of IL-1 and IL-13 receptors in endometrial and endometriotic sections and CFUs.

Clonogenic analysis of endometrial and endometriotic stem cells showed an increase in clonogenicity in endometrial epithelial cells when treated with IL-1β. Treatment of IL-13 led to a drop in clonogenicity in endometrial epithelial and stromal cells while IFN-γ treatment resulted in a decreased clonogenicity in endometrial epithelial, stromal and endometriotic stromal cells. Other cytokines (IL-8, IL-10, TNF-α) displayed no effect on the clonogenicity of endometrial and endometriotic cells.

Functional study by replating IL-1β and IL-13 treated endometrial and endometriotic CFUs revealed that these cytokines did not affect the self-renewal ability of endometrial and endometriotic CFUs. The proliferative potential of CFUs was determined by total cell output assay. The results suggested that IL-1β up-regulated the proliferative potential of the endometriotic stromal CFUs but not the endometrial epithelial and stromal CFUs, while IL-13 did not alter the proliferative potentials of endometrial and endometriotic CFUs. Comparative analysis on the effect of IL-1β and IL-13 between endometrial and endometriotic stromal CFUs demonstrated that IL-1β would preferentially promote the proliferative potential of ectopic stromal CFUs while IL-13 selectively increases that of normal stromal CFUs.

Receptor expression analysis by immunostaining demonstrated the presence of IL-1 receptor and IL-13 receptors protein in the glandular epithelium of endometrial tissue. Their expression was more diffuse in the endometriotic tissues. Using reverse transcription–polymerase chain reaction, IL-1RI, IL-13Rα1, IL-13Rα2 mRNA was detected in endometrial and endometriotic stromal cells, while only in endometrial epithelial cells express IL-1RII mRNA as well as IL-1RI, IL-13RαI and IL-13Rα2 mRNA. The present study suggests a role of cytokines on endometrial and endometriotic stem/progenitor cells and further investigation of actions of cytokines would be constructive on the development of endometriosis.