Elevated levels of gremlin-1 in eutopic endometrium and peripheral serum in patients with endometriosis

OBJECTIVE: To examine the expression of gremlin-1 (GREM1) on the levels of messenger RNA (mRNA) and protein in eutopic endometrium and its serum level in patients with endometriosis. DESIGN: Prospective, experimental study using reverse-transcription polymerase chain reaction, Western blot, immunofluorescence, and ELISA. SETTING: Gynecological oncology laboratory in a department of obstetrics and gynecology in a medical college in China. PATIENT(S): Thirty-five patients with endometriosis and 23 healthy control women. INTERVENTION(S): During surgery, the eutopic endometria and peripheral serum were obtained from the patients with endometriosis and the control women. MAIN OUTCOME MEASURE(S): The cellular compartment location of GREM1 expression was examined by using immunofluorescent double staining. The expression levels of mRNA and protein for GREM1 were determined by reverse-transcription polymerase chain reaction and Western blot, respectively. The serum level of GREM1 was measured by indirect ELISA. RESULT(S): The expression of GREM1 was defined within endometrial blood vessel endothelium exclusively, with the concomitant expressions of GREM1 and CD146. The expression of GREM1 on the levels of mRNA and protein was significantly higher in eutopic endometria of patients with endometriosis than in those from healthy control women. According to the ELISA established in our laboratory, the concentration of GREM1 in peripheral serum that was collected during the follicular menstrual phase of patients with endometriosis was significantly higher than that in serum from healthy control women. CONCLUSION(S): Gremlin-1 plays a role to some extent in the aberrant angiogenesis of eutopic endometrium in patients with endometriosis. It is possible that the peripheral serum level of GREM1 is a prospective serum biomarker of endometriosis.