We recently described a novel protein in bone marrow of rats, RP59, as a marker for cells with the capacity to differentiate into osteoblasts. In this work, its expression pattern was further investigated to learn about the origin and biological relevance of RP59 expressing marrow cells. As revealed by in situ hybridization and by immunohistochemistry of yolk sac embryos, RP59 was found in the cells of the primitive ectoderm and primitive streak as well as in blood islands and extraembryonal mesoderm. Later, RP59 occurred in fetal liver cells and in circulating blood. From the time around birth, it was found in bone marrow and spleen cells. In addition, in vitro-formed blood vessels contained RP59-positive cells in the lumen. Endothelial cells and the vast majority of cells outside the blood vessels were not labeled. Concerning more mature hematopoietic cell types, RP59 was observed in megakaryocytes and nucleated erythroblasts, but absent from lymphoid cells. In conclusion, RP59 was induced in early mesoderm. It was maintained in the erythroid and megakaryotic lineages and, as earlier described, in young osteoblasts.
We have recently identified a novel RNA sequence in ameloblasts, coding for amelin (Cerny et al., 1996). In the present paper, its expression has been compared with that of amelogenin in developing incisors and molars of rats, by means of in situ hybridization of paraffin sections. The RNAs for both amelin and amelogenin were highly expressed in secretory ameloblasts. The expression of RNA for amelogenin gradually decreased in the post-secretory ameloblasts. In contrast, the RNA expression for amelin remained high in post-secretory ameloblasts up to the stage of fusion between dental and oral epithelia at the time of tooth eruption. We suggest that amelin might be involved in the mineralization of enamel or in the attachment of ameloblasts to the enamel surface. The whole-mount in situ hybridization procedure is described for the first time in dental research. It proved to be a useful method and confirmed the results of the conventional in situ hybridization.
The purpose of this study was to investigate the distribution of epithelial cells and the fate of the basement membrane along the root surface of rat molars during cementogenesis, and to test the hypothesis that the Hertwig's epithelial root sheath (HERS) cells remain on the root surface if mineralization is inhibited. To demonstrate the HERS cells and basement membrane, immunohistochemistry with antibodies against keratin and laminin were used. The dentin matrix mineralization was inhibited by a single injection of 1-hydroxyethylidene-1, 1-bisphosphonate (HEBP). A modified Gomori staining method was used to monitor the inhibition of mineral formation in dentin and cementum. Paraffin sections were stained with haematoxylin-eosin, and freeze-dried sections were used for Gomori and immunohistochemical stainings. We found that the formation of acellular cementum was suppressed above the dentin with inhibited mineralization. Instead, a hyperplastic matrix, different from acellular cementum, covered the dentin. This hyperplastic cementum had keratin- and laminin-positive cells incorporated; such cells were never incorporated in normal acellular cementum. The later formation of cellular cementum correlated, in controls, with the disappearance of HERS cells from the root surface. Treatment with HEBP resulted in a persistent presence of epithelial cells, interpreted as an inhibition of their disappearance. In conclusion, there is evidence that the cells of HERS are involved in the development of both acellular and cellular cementum. The developmental processes of these tissues appear in some way to be influenced by or associated with the initial mineralization of the dentin.
In the present paper, we have investigated early pathophysiological events in graft-versus-host disease (GVHD), a major complication to hematopoietic stem cell transplantation (HSCT). BLLB/c female mice conditioned with busulfan/cyclophosphamide (Bu-Cy) were transplanted with allogeneic male C57BL/6. Control group consisted of syngeneic transplanted Balb/c mice. In allogeneic settings, significant expansion and maturation of donor dendritic cells (DCs) were observed at day +3, while donor T-cells CD8+ were increased at day +5 (230%) compared to syngeneic HSCT. Highest levels of inflammatory cytokines IL-2, IFN-gamma, and TNF-alfa at day +5 matched T-cell activation. Concomitantly naïve T-cells gain effecr-memory phenotype and migrated from spleen to peripheral lymphoid organs. Thus, in the very early phase of GHVD following Bu-Cy conditioning donor, DCs play an important role in the activation of donor T cells. Subsequently, donor naïve T-cells gain effector-memory phenotype and initiate GVHD.
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