In vitro investigation of corneodesmosin deficiency and development of a pathogenesis-based therapy for Peeling skin disease

• Applicant: Privatdozent Dr. Vinzenz Oji
• Subject Area: Dermatology ; Human Genetics
• Term: from 2015 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 279483194

The generalized Peeling skin disease (PSD) is an autosomal recessive form of congenital ichthyosis caused by nonsense-mutations in the gene of corneodesmosin (CDSN). The clinical and therapeutic situation of the disease is extremely unsatisfying requiring the development of a targeted therapy. CDSN is located in the intercellular space of the corneodesmosomes of the epidermis and reinforces the adhesion within and under the stratum corneum (SC). The primary CDSN form of 52-56 kDa is gradually processed by the serin-proteases of the SC. Patients with PSD harbor a striking lack of the protein. The following project aims to understand, whether the application of a recombinant human CDSN (rhCDSN) on skin models of patients with PSD can lead to a repair of the impaired epidermal adhesion. From the basic scientific point of view the project expends the understanding of the skin barrier by analyzing compensatory mechanisms (tight junctions) and inflammatory components (cytokine expression study).In the first part of the project the in vitro testing system and the read out strategy becomes standardized. In the pre-studies of the project we have established 3D skin equivalents, which are generated from primary keratinocytes and fibroblasts of the affected patients having a genetic lack of CDSN. The analyses primarily focus on immunohistochemical and ultrastructural investigations (cooperation partners in Heidelberg and Lyon) as well as on the examination of the epidermal barrier function. In addition, the novel technique of 5D intravital tomography (5D IVT) will be introduced, which offers a non-invasive method for the visualization of corneodesmosin in the skin (by fluorescence lifetime imaging). Part two of the project concerns the development of the study substance. After piloting expression analyses with a prokaryotic expression system, which showed a degradation of the recombinant protein, and because of the glycolization pattern of CDSN we have changed to the Baculovirus expression system. Preliminary expressions with Spodoptera frugiperda (Sf9) cells show promising results. In order to avoid preterm proteolysis of rhCDSN in the SC but to promote protein uptake of the SC, a liposomal packing of the protein is planned (cooperation partner in Berlin). Finally, after standardization of the testing system and the production of liposomal rhCDSN the vehicle-controlled in vitro protein substitution on 3D skin equivalents will be performed representing the third part of the project.The strategy of protein substitution with liposomal rhCDSN should be further developed in a follow-up DFG application and lead into a translational project for the affected patients.

• DFG Programme: Research Grants
• Co-Investigators: Professorin Dr. Eva Liebau; Professor Dr. Heiko Traupe