130 Skin ageing: an explorative study based on mechanical properties investigated by Atomic Force Microscopy

Abstract

Skin constitutes a barrier against external injuries and contributes to the maintenance of homeostasis. Dermis with collagen and elastin fibres has a role of support with the extracellular matrix (ECM). During ageing numerous mechanisms induce skin degradation by loss of elasticity, skin thickness and collagen network disorganization. Atomic Force Microscopy (AFM) has been described as a reliable tool to study mechanical properties of various samples. The purpose here is to develop an AFM-based method to quantify nanoscale changes in the biomechanical properties of the different skin layers. Firstly, the global skin explant mechanical properties were measured by AFM Stiffness Tomography (ST), secondly the impact of skin ageing at cellular level was explored (structure and tension between cells, tension between cell and matrix). Three groups from 10 different ages donors were studied (below 30 years old (yo), from 30 to 50 yo and above 50 yo). At the tissue level, a controlled AFM indentation with a spherical tip was applied on fresh tissue sample. Skin explant was maintained by a special device designed to induce an isotropic tension. Mechanical properties were extracted gradually by ST along the skin depth. A global skin elastic modulus evaluation was provided according to the different ages. Then, cryosectionned skin samples were characterized with a sharper AFM tip. The elastic modulus of cell-cell junctions was measured in epidermis and ECM mechanical properties were assessed in the dermis (papillary and reticular). Data showed a general increase of dermis and epidermis elastic modulus across ageing. At the cellular level, epidermic elastic modulus heterogeneity has been showed with an increase of the basal layer skin stiffness. We also observed a bell-curve distribution of the elastic modulus for the papillary dermis and an increase of the reticular dermis rigidity.