In vitro morphology, viability and cytokine secretion of uterine telocyte‐activated mouse peritoneal macrophages

Telocytes ( TC s), a distinct interstitial cell population, have been identified in the uterus, oviduct and placenta, with multiple proposed potential biological functions. Their unique structure allows them to form intercellular junctions with various immunocytes, both in normal and diseased tissues, suggesting a potential functional relationship with the local immune response. It has been hypothesized that through direct heterocellular junctions or indirect paracrine effects, TC s influence the activity of local immunocytes that are involved in the inflammatory process and in immune‐mediated reproductive abnormalities. However, no reliable cytological evidence for this hypothesis is currently available. In this study, we cultured primary murine uterine TC s and collected TC conditioned media ( TCM ). Mouse peritoneal macrophages ( pMAC s) were co‐cultured for 48 hrs with TCM or with DMEM /F12 or lipopolysaccharide ( LPS ) as negative and positive controls, respectively. Normal uterine TC s with a typical structure and a CD ‐34‐positive/vimentin‐positive/c‐kit‐negative immunophenotype were observed during culture. Morphologically, TCM ‐treated pMAC s displayed an obvious activation/immunoresponse, in contrast to over‐stimulation and cell death after LPS treatment and no sign of activation in the presence of DMEM /F12. Accordingly, a cell counting kit 8 ( CCK ‐8) assay indicated significant activation of pMAC s by TCM and LPS compared to DMEM /F12, thus supporting the marked morphological differences among these groups of cells. Furthermore, within a panel of macrophage‐derived cytokines/enzymes, interleukin‐6 ( IL ‐6) and inducible nitric oxide synthase were significantly elevated in TCM ‐treated pMAC s; tumour necrosis factor α, IL 1‐R1, and IL ‐10 were slightly, but significantly, up‐regulated; and no changes were observed for transforming growth factor‐β1, IL ‐1β, IL ‐23α and IL ‐18. Our results indicate that TC s are not simply innocent bystanders but are rather functional players in the activation of pMAC s; they trigger and maintain the immune response, likely through indirect paracrine effects. Thus, we provide preliminary in vitro evidence of immunoregulatory and immunosurveillance roles for TCs.