Decidual NK cell-derived conditioned medium from miscarriages affects endometrial stromal cell decidualisation: endocannabinoid anandamide and tumour necrosis factor-α crosstalk

STUDY QUESTION: What are the effects of endocannabinoid anandamide (AEA) in uterine natural killer (unK) cells from miscarriage decidua, regarding their cytokine profile and endometrial stromal cell (ESC) crosstalk? SUMMARY ANSWER: uNK-conditioned media from miscarriage samples present high TNF-alpha levels which inhibit ESC decidualisation. WHAT IS KNOWN ALREADY: AEA plasma levels are higher in women who have suffered a miscarriage. Moreover, AEA inhibits ESC proliferation and differentiation, although the levels and impact on the uNK cell cytokine profile at the feto-maternal interface remain elusive. STUDY DESIGN, SIZE, DURATION: This laboratory-based study used human primary uNK cells which were isolated from first-trimester decidua (gestational age, 5-12 weeks) derived from 8 women with elective pregnancy termination and 18 women who suffered a miscarriage. PARTICIPANTS/MATERIALS, SETTING, METHODS: The first-trimester placental tissues were assayed for AEA levels by UPLCMS/MS and respective enzymatic profile by western blot. The uNK cells were isolated and maintained in culture. The expression of angiogenic markers in uNK cells was examined by quantitative PCR (qPCR). The uNK-conditioned medium was analysed for IFN-y, TNF-a and IL-I0 production by enzyme-linked immunosorbent assay, and the impact on ESC differentiation was assessed by measuring decidual markers Pr!, lgfbp- I and Fox degrees I mRNA expression using qPCR. MAIN RESULTS AND THE ROLE OF CHANCE: AEA levels were higher in miscarriage decidua compared with decidua from elective terminations. The uNK cell-conditioned medium from the miscarriage samples exhibited high TNF-alpha levels and interfered with the decidualisation of ESCs. Exacerbated inflammation and elevated TN F-alpha levels at the feto-maternal interface may trigger AEA signalling pathways that, in turn, may impact decidualisation and the angiogenic ability of uNK cells. LARGE-SCALE DATA: N/A. LIMITATIONS, REASONS FOR CAUTION: Primary uNK cell responses are based on a simple in vitro model. Thus, in complex microenvironments, such as the feto-maternal interface, the mechanisms may not be exactly the same. Also, the inflammatory events of miscarriage that, in this study, have happened prior to processing of the samples may cause different responses to that observed. In addition, the magnitude of the inflammatory response, required to trigger the AEA pathways that impact decidualisation and the uNK angiogenic ability in vivo, is still unclear. WIDER IMPLICATIONS OF THE FINDINGS: The endocannabinoid AEA is a modulator of reproductive competence. AEA not only may contribute to neuroendocrine homeostasis but also can take part in uterine changes occurring during early pregnancy.