The clinical and biological effects of the use of probiotic VSL#3 in patients with oral lichen planus

Oral lichen planus (OLP) is an inflammatory - autoimmune disease of the oral cavity with unknown aetiology. This disease account for almost 40% of the visits yearly to the Eastman Dental Hospital. Currently there is no curative therapy and the management is aimed at reducing painful symptoms, which is typically achieved through healing of mucosal erosion and ulceration. A novel therapeutic approach could be the poly-biotic VSL#3 that is known to have anti-inflammatory and wound healing properties in diseases of the gastrointestinal tract. In this thesis, we hypothesise that the poly-biotic VSL#3 might have a potential therapeutic effect on oral lichen planus (OLP) lesion. In vitro experiments were focused on isolating, identifying, and characterizing the single species contained in VSL#3 and comparing their immunomodulatory properties to the whole mixture. I used both the human monocytic cell line THP-1 and the human oral epithelial line MOE1a to gain an understanding of how probiotics bacterial influence the immune response to pro- inflammatory stimuli such as E. coli and interferon-γ. I developed an oral epithelial wound healing assay to determine the effects of VSL#3 on the speed of healing and cell morphology. In vivo studies were performed to A. Profile the cytokine levels and neutrophil reactive oxygen species (ROS) generation in patients with OLP and compare between different disease phenotypes (n=80) and healthy control (HC) subjects (n=44). B. Setup and ran the first ever double-blind, randomized, placebo-controlled, feasibility two arm study on the treatment of OLP patients (n=30) with VSL#3. In the clinical trial I quantified a range of clinical and mechanistic parameters such as pain score, oral disease severity score, quality of life, serum and saliva cytokines level, metagenomics changes, and most importantly the safety, tolerability, and acceptance of the participants toward the highly concentrated poly biotic VSL#3. The initial in vitro results provide assurance that at a cellular level VSL#3 was non-toxic and unable to eliciting a strong immunological response in THP-1 or MOE-1a cells. In fact, VSL#3 and the isolated single species were all capable of reducing the immune response of both THP-1 and MOE-1a cells upon E coli and IFN-γ stimulation. A beneficial effect of VSL#3 on wound healing was also observed and provided encouragement for the therapeutic potential of this probiotic in OLP. Cytokine profiling of OLP patients revealed an elevation in pro- inflammatory cytokines, which differed depending on disease phenotype. The release of CXCL10 and IFN-γ was higher in erosive OLP, which is the most aggressive form of the disease. The clinical trial was successfully completed and analysed within the study period. The pilot data demonstrated the safety and acceptability of the VSL#3 in the OLP patients (compliance 100 %). The overall trend was highly suggestive of a beneficial effect of VSL#3 on OLP with a trend for a reduction in mean site score, CXCL10/IFN- γ levels in saliva and an improvement in quality-of-life score. Taken together, this study supports the use of VSL#3 and may be probiotics in general as an adjunct therapy for OLP.