Endometrial Stromal Cells Circulate in the Bloodstream of Women with Endometriosis: A Pilot Study

Abstract

Endometriosis is characterized by the presence of endometrial tissue outside the uterus. While endometriotic tissue is commonly localized in the pelvic cavity, it can also be found in distant sites, including the brain. The origin and pathophysiology of tissue migration is poorly understood; retrograde menstruation is thought to be the cause, although the presence of endometrium at distant sites is not explained by this hypothesis. To determine whether dissemination occurs via the bloodstream in women with endometriosis, we analyzed circulating blood for the presence of endometrial cells. Circulating endometrial stromal cells were identified only in women with endometriosis but not in controls, while endometrial epithelial cells were not identified in the circulation of either group. Our results support the hypothesis that endometrial stromal cells may migrate through circulation and promote the pathophysiology of endometriosis. The detection of these cells in circulation creates avenues for the development of less invasive diagnostic tools for the disease, and opens possibilities for further study of the origin of endometriosis.

Keywords: CD10; circulating endometrial cells; diagnostics; endometriosis; liquid biopsy; stromal cells.

Figure 1

Immunofluorescence of CD10 in endometriosis patients. This figure shows an example of the CD10 positive cells found in circulating blood of endometriosis patients. The patient ID is showed in the second column and the number of CD10 positive cells in the third column. Nuclear staining (DAPI, blue), CD10 positive cells (Alexa555, Red) and merge pictures are shown for each patient. The field was taken at ×40 magnification. A manual amplification of a CD10 positive cell in each case is shown in the figure.

Figure 2

Hormonal treatments. (A) Antagonist protocol: After menses, rFSH is administrated for around 10–12 days. When the follicles reach around 12mm, the antagonist (GnRHAn) is administrated. At the end of the stimulation cycle, hCG is injected before the oocyte retrieval. (B) HRT protocol: After menses, valerate estradiol at oral dosages (6–8 mg/day) for 10–12 days is administrated. Then, 800 mg/day of natural micronized progesterone vaginally are added to the estradiol treatment for 15 more days. (C) GnRH downregulation protocol + HRT: in luteal phase, one injection of triptorelin 3.75 (GnRHa) is administrated and subsequently for two more months. rFSH: recombinant follicle stimulating hormone; GnRHa: gonadotropin releasing hormone agonist; GnRHAn: gonadotropin releasing hormone antagonist; HRT: hormonal replacement treatment; hCG: human chorionic gonadotropin.

Figure 3

ScreenCell^®Cyto Technology process. First, blood is collected and mixed with dilution buffer (Incubation). After, there is a filtration process, washing and fixation with PFA 4%. Then, IF can be performed on the filter. After mounting, the IF is visualized by a fluorescence microscope. PBS: phosphate buffered saline; PFA: paraformaldehyde; IF: immunofluorescence.