The objectives of this program focus on the cellular, molecular and biochemical characterization of the underlying pathologic events in infectious and autoimmune diseases, with the long-term intent to develop novel approaches to therapeutic intervention. Nonhealing mucosal and cutaneous lesions due to infection, inflammation or neoplasia can become chronic and debilitating. Despite the profound health effects that chronic wound healing problems and excessive scarring pose, the mechanisms underlying normal and pathologic healing are little understood. Moreover, mucosal epithelial healing is typically more rapid and nearly scarless, prompting a comparison of cutaneous and oral mucosal wound repair to identify controlling factors which may be of benefit in clinical delayed healing responses. In recent studies, not only were the kinetics, cellular composition, and outcome of the healing response found to be substantially altered between cutaneous and oral wounds, but secretory leukocyte protease inhibitor (SLPI) was identified as a pivotal regulatory factor in oral wounds. Age, hormones and immune deficiency play a significant role in inflammatory lesion repair, both in terms of rate of healing and the degree of scarring incurred, attributed in part, to altered inflammatory responses in the aged, with a predominance of neutrophils, excess elastase and a delay in monocyte influx. The delayed cutaneous healing response can be mimicked in animal models including ovariectomized rodents and SLPI knockout mice. Using these pre-clinical models, delayed healing can be reversed by the topical application of TNF antagonists (TNFalpha antibody, thalidomide), recombinant SLPI and synthetic fibronectin peptides, which block downstream inflammatory events and disrupt signal transduction pathways to ameliorate the overzealous leukocyte recruitment and promote matrix degradation. Based on the successful topical delivery of these and other agents in reversing nonhealing wounds, additional novel approaches for inhibiting the persistent leukocyte recruitment and overabundant elastase released at the inflammatory site are being evaluated for their efficacy in facilitating the healing process. Tissue injury in the oral mucosa of humans also activates a cascade of transcriptional events important during the healing process that are not yet clearly defined. To characterize these events and identify potential gene targets for future studies, we used cDNA expression arrays in a clinical model of tissue injury. Mucosal biopsies were taken before 3rd molar extraction, 2-4 hours post-operatively, or at 48 hours. Hybridization patterns were analyzed and validated using real-time PCR. Prior to extraction, the biopsied mucosal tissues were characterized by a panoply of genes that were constitutively expressed. After injury, analysis revealed differential expression of genes involved in transcription, inflammation and remodeling. At 2-4 hours after injury, genes such as Fos, Jun and early growth response protein were upregulated, while genes responsible for inter-cellular adhesion were downregulated. At 48 hours after injury, the gene profile had shifted towards tissue remodeling. In these new studies, we identify genes constitutively expressed in normal oral mucosa and transcriptional events following mucosal tissue injury, which may be useful in identifying new therapeutic targets. In clinically-derived chronic inflammatory lesions, perpetuated by bacteria and/or their products (periodontal tissues, etc.), viruses (HIV-1), other pathogens, or autoimmune responses (Sjogren's Syndrome), characterization of the systemic immune response, as well as the lesion cellular constituents using laser capture microdissection, and proteome and transcriptome responses (cDNA expression array), offers new insight into targets for amelioration of tissue degradation and delayed repair.
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