In vivo confocal fluorescence imaging of skin surface-a novel approach to study effect of products on stratum corneum

Abstract

Various skin imaging techniques are currently available and used to investigate characteristics of skin and the effect of products on skin. Visualization or imaging of skin at the microscopic level requires both enhanced resolution and contrast. The axial and lateral resolution of in vivo confocal microscopy, typically 5 m and 0.5 m respectively, is sufficient to image the different layers of the viable epidermis at the cellular level. However, when imaging the upper layers of the stratum corneum in reflectance the contrast, at best, is good enough to distinguish individual corneocytes, but overall insufficient to determine the cellular morphology of the skin surface. In this presentation we will describe a method based on confocal fluorescence microscopy to image the surface cellular morphology of human skin in vivo. The principle behind the method is that the heterogeneous absorption of a topically applied fluorescent probe, fluorescein, yields a level of contrast, both on an intercellular and an intracellular level, that is superior to that obtained from the variations in refractive index of the different constituents of skin, which is the source of contrast in reflectance microscopy.Depending on skin condition, the surface morphology of human skin in vivo ranges from a highly ordered lattice of regularly shaped corneocytes to disordered patterns where individual corneocytes can no longer be distinguished. We will present an initial attempt at obtaining a surface health scale based on cellular morphology as well as the results of pilot clinical studies that show changes in cellular morphology with various product treatments. Various skin imaging techniques are currently available and used to investigate characteristics of skin and the effect of products on skin. Visualization or imaging of skin at the microscopic level requires both enhanced resolution and contrast. The axial and lateral resolution of in vivo confocal microscopy, typically 5 m and 0.5 m respectively, is sufficient to image the different layers of the viable epidermis at the cellular level. However, when imaging the upper layers of the stratum corneum in reflectance the contrast, at best, is good enough to distinguish individual corneocytes, but overall insufficient to determine the cellular morphology of the skin surface. In this presentation we will describe a method based on confocal fluorescence microscopy to image the surface cellular morphology of human skin in vivo. The principle behind the method is that the heterogeneous absorption of a topically applied fluorescent probe, fluorescein, yields a level of contrast, both on an intercellular and an intracellular level, that is superior to that obtained from the variations in refractive index of the different constituents of skin, which is the source of contrast in reflectance microscopy. Depending on skin condition, the surface morphology of human skin in vivo ranges from a highly ordered lattice of regularly shaped corneocytes to disordered patterns where individual corneocytes can no longer be distinguished. We will present an initial attempt at obtaining a surface health scale based on cellular morphology as well as the results of pilot clinical studies that show changes in cellular morphology with various product treatments.