Defining the mechanism of skin barrier restoration by bacterial lysates

Background: AKT1 controls multiple aspects of skin barrier formation: Ryan O'Shaughnessy has shown that AKT1 knockdown leads defects in both the physical barrier and immune barrier. It prevents filaggrin processing, and inhibits nuclear degradation, a key part of the formation of a tough, protective cornified envelope. AKT1 knockdown keratinocytes have reduced expression of a protease Cathepsin H (CTSH). CTSH is required for filaggrin processing, and control of Th2 cytokines, with Ctsh -/- mice showing increased expression of the Th2 cytokine TSLP.
Effects of bacterial lysates on epidermal barrier: Catherine O'Neill is an expert on the beneficial effects of lactobacillus and bifidobacterial lysates. They enhance tight junctions and promote filaggrin expression, both key components of healthy skin barrier. SB has developed a topical formulation containing one of these bacterial lysates for use in a human study, where they showed reduced transepidermal water loss (an in vivo marker of the barrier) in human volunteers (SB personal communication). The company wishes to understand mechanistically how its lysate is inducing its effects on the barrier. To this end SB developed propriatory techniques to produce lactobacillus lysate fractions and tested them in their bespoke assays.

We hypothesise that these lysates have multiple additional beneficial skin barrier restorative functions related to the processes described above

Overall approach: We will test microbial lysates and fractions thereof developed by SB in barrier deficient and competent keratinocytes and organotypic cultures to understand how they restore or enhance skin barrier. The student will perform proteomics to identify biomarkers of efficacy of the microbial lysates. This work will be critical to SB in their aim of the downstream identification of actives within the microbial preparations, and to skin barrier biology research by improving understanding not only of skin barrier function, but also bacteria-host interaction, currently a "hot-topic" in skin biology research.

Objectives:
1. Testing the ability of bacterial lysates to rescue physical and immune skin barrier function
2. Determining the proteomic profile of keratinocytes treated with bacterial lysates to identify pathways and biomarkers associated with barrier enhancement
3. Fractionation of lysates and assaying biomarkers to identify key actives within the bacterial lysates.

Interdisciplinary aspect and added value: This project combines cell biology, proteomics/bioinformatics , and SB's unique expertise in microbiology and the use of separation techniques to produce lysates with biological activity and to gain new insights into barrier function and bacteria-host interactions in skin.