Investigation of the link between the human skin relief and the dermal fibers network by coupling topographic analysis and LC-OCT imaging before and during folding tests

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Knowing the evolution of the skin’s response to mechanical solicitations and understanding its origin is important in medicine, surgery, and cosmetics. Studies performed in vitro and ex vivo show that links exist between the topographic skin properties and the collagen and elastin fibers network in the dermis. But, to our knowledge, no in vivo study shows this link. In this study we propose a combination of experimental tests to demonstrate the link between the topographic skin properties and the fibers network in the dermis in vivo. The first method consists in analyzing the skin relief images. The second method uses a recently developed imaging technique of human skin in vivo with a high spatial resolution: Line-field Confocal Optical Coherence Tomography (LC-OCT). This technology provides two types of images modalities: vertical and horizontal section images. The skin relief images and its internal layers are carried out for the skin at rest and during a folding test. The latter is performed using a folding system developed in this study. From these images, we calculate the density of the skin lines printed on the skin surface and their orientations. Thanks to the two modalities of LC-OCT, we obtain the full 3D image of the skin volume. From these images we extract the fibers density and their orientation in the plans parallel and perpendicular to the outer skin surface. The study is carried out on 42 volunteers aged from 20 to 55 years-old. Skin relief analysis and LC-OCT images are performed on the skin of the forearm and thigh. The results show similar distributions of the skin lines on the surface and of its fibers in the volume. We could observe a correlation between the skin lines at the surface and the structure in depth of its layers in the volume (0.40 < rSpearman < 0.73).