Onychomycosis is an infection caused by the presence of fungi (the most relevant is Trichophyton rubrum) that affects the lamina of the nails, hands and feet and involves 2-10% of the adult population. The use of topical products that act directly at the level of the lamina and the nail bed has obvious advantages for this local pathology: reduction of systemic exposure to drugs, greater therapeutic efficacy, reduced dose of active.
In dermatology, many nail disorders such as onychomycosis are treated topically to be more efficient and to avoid side effects and interactions of systemic treatments. To be efficient, such treatments have to penetrate through the thick and dense nail plate and reach the infection site.
At the pre-clinical stage, the challenges and critical factors are twofold: from one side to have information about ungual absorption properties of actives and from the other side to develop a pre-clinical model which takes into account the contribution to the infection of both skin and nail even if exclusively on the nail the infection produces visible damage.
The use of formulation solutions (such as enamels and dispensers) that allow the application/localization of the ingredient to the site of interest represents an interesting approach for the pre-clinical development of products for the treatment of onychomycosis. For the development of an in vitro pre-clinical model, it is not possible to use only the nail but, to ensure the fungal attachment, it is necessary to create a water rich and metabolically active environment.
Therefore, VitroScreen has developped and in vitro experimental model that closely mimick the real biological system composed of epidermis + nail: VitroScreen model is based on reconstructed epidermis model (RHE) infected with the fungus that acts as a support for a nail obtained from bovine donors. The model has been shown to be suitable to evaluate the efficacy of market references in healing the infected nail and cuticula based on GMS staining.
GMS (black) STAINING on RHE
After RHE infection by Trichophyton rubrum for 5 days, conidia and hyphae were found in higher concentration in the stratum corneum and diffused in the whole viable epidermis.