The immunohistochemical localization of the interferon-gamma and granulocyte colony-stimulating factor receptors during early amelogenesis in rat molars

Previous studies, in which the known janus kinase and signal transducer and activator of transcription (STAT) isoforms were immunohistochemically mapp ed in developing rat molars, implicated a sizeable list of cytokine superfa mily receptor (CSR)/signal-transduction pathway (STP) linkages in the cells of the enamel organ involved in the events leading directly to early amelo genesis. Various combinations of upregulated janus kinases and STATs lire k nown to be linked to single or small groups of CSRs. On the basis of the pr evious observations it was hypothesized that the interferon-gamma receptor (IFN gamma r) and the granulocyte colony-stimulating factor receptor (G-CSF receptor) would be localized in specific sites in the cells of the enamel organ during early amelogenesis. To verify this, whole-head, freeze-dried s ections were here obtained at the level of the mandibular first and second molar from newborn and 5-day-old rats. These sections were not demineralize d or fixed, reducing the possibility of false-negative results. Antibodies to the IFN gamma r and the G-CSF receptor were localized using a modificati on of the avidin-biotin complex method. In the newborn rats, IFN gamma r wa s localized in the preameloblasts in the cervical loop, the proximal and di stal ends of presecretory ameloblasts. the outer enamel epithelium, the den tal lamina, and in bone. In 5-day-old mts, it was confined to the proximal ends of the presecretory and secretory ameloblasts. The G-CSF receptor was observed in the molars of newborn rats in the preameloblasts, the proximal and distal ends of the presecretory ameloblasts, outer enamel epithelium, a nd in bone. In 5-day-old rats, G-CSF receptor was localized in the preamelo blasts. the proximal ends of presecretory and secretory ameloblasts, the st ellate reticulum, the outer enamel epithelium, and in bone. These findings indicate that the IFN gamma r and the C-CSF receptor, and their downstream STP linkages, are upregulated in the cells of the enamel organ and may be i nvolved in the events: leading directly to early enamel formation. (C) 1999 Published by Elsevier Science Ltd. All rights reserved.