The scarring processes in mucosal tissues after immune injury

Impaired leukocyte trafficking and skin inflammatory responses in hamsters lacking a functional circadian system

The immune system is under strong circadian control, and circadian desynchrony is a risk factor for metabolic disorders, inflammatory responses and cancer. Signaling pathways that maintain circadian rhythms (CRs) in immune function in vivo, and the mechanisms by which circadian desynchrony impairs immune function, remain to be fully identified. These experiments tested the hypothesis that the hypothalamic circadian pacemaker in the suprachiasmatic nucleus (SCN) drives CRs in the immune system, using a non-invasive model of SCN circadian arrhythmia. Robust CRs in blood leukocyte trafficking, with a peak during the early light phase (ZT4) and nadir in the early dark phase (ZT18), were absent in arrhythmic hamsters, as were CRs in spleen clock gene (per1, bmal1) expression, indicating that a functional pacemaker in the SCN is required for the generation of CRs in leukocyte trafficking and for driving peripheral clocks in secondary lymphoid organs. Pinealectomy was without effect on CRs in leukocyte trafficking, but abolished CRs in spleen clock gene expression, indicating that nocturnal melatonin secretion is necessary for communicating circadian time information to the spleen. CRs in trafficking of antigen presenting cells (CD11c(+) dendritic cells) in the skin were abolished, and antigen-specific delayed-type hypersensitivity skin inflammatory responses were markedly impaired in arrhythmic hamsters. The SCN drives robust CRs in leukocyte trafficking and lymphoid clock gene expression; the latter of which is not expressed in the absence of melatonin. Robust entrainment of the circadian pacemaker provides a signal critical to diurnal rhythms in immunosurveilliance and optimal memory T-cell dependent immune responses.

Molecular cloning of wound inducible transcript (wit 3.0) differentially expressed in edentulous oral mucosa undergoing tooth extraction wound-healing

Tooth extraction is the most commonly prescribed ablation surgery in dentistry and results in the formation of edentulous mucosa. Although the edentulous mucosa serves as the critical interfacial tissue for removable and implant-assisted prostheses, the structure and physiology of this wound-induced tissue are largely uninvestigated. We addressed the hypothesis that tooth extraction activates the expression of a unique set of genes in healing edentulous mucosa. Using the Differential Display Polymerase Chain Reaction and 5' Rapid Amplification of cDNA Ends protocols, we isolated overlapping cDNAs encoding a 3.0-kb-long mRNA, Wound Inducible Transcript, 3.0 (wit 3.0). In situ hybridization demonstrated that wit 3.0 was primarily expressed by the fibroblasts associated with tooth extraction wound-healing. Appearing to generate from the wit 3.0 gene, two alternative transcripts presented, encoding 215-(wit 3.0 alpha) and 253-(wit 3.0 beta) amino-acid-long peptides with the characteristics of an intracellular molecule. Analysis of these data may provide new clues to the molecular mechanism of edentulous mucosa formation.