Aspects of interleukin-8 gene expression by gingival and dermal fibroblasts stimulated with interleukin-1beta or tumour necrosis factor alpha.

Fibroblast-derived interleukin (IL)-8 is thought to have an important role in the orchestration of immuno-participant cells infiltrating the skin and gingiva in response to continuously recurring bacterial infection. Therefore, the IL-8 gene expression should be under tight regulatory control and it might be temporally and spatially limited in inflammatory tissue. The purpose of this study was to examine the aspect of the IL-8 gene expression by fibroblasts stimulated with pro-inflammatory cytokines, IL-1beta and TNF-alpha. In situ hybridisation revealed that fibroblasts did not express IL-8 mRNA whereas keratinocytes and endothelial cells did in IL-1beta- or TNF-alpha-injected mice skin. However, cultured mouse dermal fibroblasts expressed not only IL-8 but also IL-1beta mRNA without stimulation by exogenous IL-1beta and TNF-alpha, and the expression was not enhanced by the exogenous cytokines. A similar result was obtained in late-passage human gingival fibroblasts. These results suggest that fibroblasts remain insensitive to IL-1beta and TNF-alpha so as to induce the IL-8 gene expression in non-inflammatory mice skin. Mouse dermal and late-passage human gingival fibroblasts in vitro are likely to be altered in phenotype into IL-8-producing cells along with the production of IL-1beta. In skin inflammation and periodontal diseases, fibroblasts may express the IL-8 gene even without an exogenous cytokine, IL-1beta or TNF-alpha, during their proliferation similar to the situation in our culture system.

Cooperative Activation of HoxD Homeobox Genes by Factors from the Polarizing Region and the Apical Ridge in Chick Limb Morphogenesis: (chick limb bud/HoxD homeobox genes/ZPA factor/AER factor/in situ hybridization).

When a mouse zone of polarizing activity (ZPA) at the posterior margin of the limb bud was grafted into the anterior margin of the chick limb bud, the expressions of the chick homeobox genes HoxD12 and D13 were induced prior to the formation of chick extra digits. This induction was observed in a restricted domain close to both the grafted mouse ZPA and the chick apical ectodermal ridge (AER). When the posterior half of the AER was removed, the normal expression was diminished in the distaloposterior region. Thus, it is likely that at least two distinct factors, one from the ZPA and the other from the AER, act cooperatively to provide positional information to induce the sequential expression of the HoxD genes.

Retinoic Acid Treatment Induces the Ectopic Exporession of Retinoic Acid Receptor ß Gene and Excessive Cell Death in the Embryonic Mouse Face.

Maternal treatment with 100 mg/kg of retinoic acid (RA) on day 9 of gestation in mice caused craniofacial abnormalities of the mandibulofacial dysostosis type. The abnormal morphology was attributed to the excessive cell death in the dorsal aspects of the maxillary and mandibular prominences of the first pharyngeal arch and in the proximal region of the mandibular prominence. To investigate the expression of the RA receptor (RAR) genes in abnormal face morphogenesis, in situ hybridization was performed. The distribution patterns of RAR α and γ transcripts were not altered in the treated embryos. By contrast, the teratogenic dose of RA increased the level of RAR ß transcripts, as early as 3 hr after RA-treatment, in the regions where the RAR ß expression is at a low level in normal development. The increase of RAR ß transcripts was detected by 12 hr, and declined to the low level within 24 hr after the treatment. The regions where ectopic expression of RAR ß gene was observed included the areas where the excessive cell death occurred 9-12 hr after RA-treatment. These results suggest that ectopic induction of RAR ß by RA may lead to the excessive cell death, threfore may cause abnormal morphogenesis.