Cellular Localization of c-JunMessenger Ribonucleic Acid and Protein and Their Relation to the Proliferation Marker Ki-67 in the Human Endometrium1

We studied cellular c-jun messenger RNA (mRNA) expression in the human endometrium during the menstrual cycle (n = 47) and in human decidua during pregnancy (n = 8), by using digoxigenin-labeled RNA probes in in situ hybridization. The same tissue samples were also analyzed for c-Jun protein and the proliferation marker Ki-67. In the proliferative endometrium, strong expression of c-jun was detected in luminal and glandular epithelium as well as in fibroblast-like stromal cells. During the early luteal phase, strong hybridization signals were identified in both epithelial and stromal compartments, with the strongest hybridization in the stromal cells beneath the epithelium. c-jun mRNA was markedly diminished in luminal and glandular epithelia of mid- and late secretory phase endometria, but it remained unchanged in the stroma. Regardless of the phase of the menstrual cycle, significant hybridization was identified in endothelial cells in the endometrium and myometrium, and a low signal was detected in myometrial muscle cells as well. During early gestation, weak expression of c-jun mRNA was observed in glandular epithelial cells and in decidualized stromal cells. In term pregnancy decidua, only low-level hybridization was detected in a few decidual cells. Nuclear immunostaining of c-Jun was detected in luminal and glandular epithelia and in stroma throughout the menstrual cycle. The location of Ki-67 antigen was temporally related to the c-jun mRNA expression in cycling endometrium and pregnancy decidua. From our data we conclude that 1) c-jun mRNA is differentially expressed in endometrial epithelial and stromal cells; 2) c-jun mRNA is cyclically regulated in the human endometrial epithelium; 3) c-jun mRNA expression is temporally related to epithelial proliferation in the endometrium; and 4) c-Jun protein is present in the human endometrium throughout the menstrual cycle.