Characterization of fibroblastic cell plasticity in the lamina propria of the rat uterine cervix at term

Different organs contain fibroblasts with specific features and functions, indicating the complexity of fibroblast biology. in the rat cervical stroma , fibroblasts are preferentially located in the fibrous ring that surrounds the mucous layer. The purpose of this study was to investigate the morphol ogical features and immunophenotype of fibroblastic cells of the uterine ce rvix in cycling, pregnant, and postpartum rats. Expression of the cytoskele tal proteins desmin, vimentin, and alpha -smooth muscle actin (alpha -SMA) were studied by immunohistochemistry. The optical density of immunohistoche mical staining was quantified by image analysis. The ultrastructural featur es of fibroblastic cells were observed under transmission electron microsco py. Cervical fibroblastic cells always expressed vimentin and desmin but ne ver alpha -SMA. During the first half of pregnancy (Day 5 [D5] to D14), des min intensity values were similar to those of cycling and postpartum fibrob lasts. In contrast, a strong expression of desmin was found from D15 to D22 , with maximal expression at term (D23). Immunohistochemical expression for vimentin was constant throughout pregnancy and showed no differences with cycling and postpartum uterine cervices. Stromal cells from cycling and ear ly pregnant rats displayed ultrastructural features characteristic of typic al fibroblasts. In contrast, at the end of pregnancy, fibroblasts different iated and showed increased secretory characteristics, reaching the ultrastr uctural features of a myofibroblast. Based on the differential expression o f desmin and the electron microscopic observations, the foregoing results s howed a modulation of the fibroblastic phenotype in the uterine cervix duri ng pregnancy. To our knowledge, this is the first report that addresses the presence of myofibroblasts derived from resident fibroblasts in the fibrou s ring of the rat uterine cervix. Fibroblastic-myofibroblastic cell plastic ity may have implications in the physiological changes displayed in the ute rine cervix during pregnancy, parturition, and postpartum involution.