TAGS: Skin Care
A joint team of researchers from the Biological Science Research Laboratory and the Skin Care Products Research Laboratory of Kao Corporation and Computational Optics Group, University of Tsukuba, led by Prof. Yoshiaki Yasuno, has succeeded in elucidating how the structural changes that occur at various depths in the skin affect wrinkle formation, using JM-OCT that can obtain cross-sectional images of the skin non-invasively.
Wrinkles Influenced by Structural Changes
Further improvement of this method will be helpful for understanding the relationship between wrinkles and the depth of the associated skin structural changes in individuals, and the method could be used for providing an
appropriate skin care approach for each person.
The skin has a multi-layered structure, consisting of the stratum corneum, epidermal cell layer, dermis (papillary and reticular layers), and subcutaneous tissue, from the outer surface inward.
The previous studies have indicated that the process of wrinkle formation is influenced by structural changes in the tissue density and collagen fibers of each of the skin layers due to various deteriorating factors, such as aging and chronic exposure to ultraviolet light. However, the extent to which the structural changes in each tissue layer affect the wrinkle formation had not been determined prior to this research project.
OCT: Non-invasive Intradermal Observation
OCT technology is a method of observing the inside of the skin without damaging it, by irradiating light onto the skin and analyzing the returning light (backscattering light), thereby obtaining cross-sectional images of the skin, from the stratum corneum to the subcutaneous tissue. However, with the conventional OCT technology, it was difficult to quantitatively evaluate the optical properties of the specific depth part of the skin with sufficient accuracy, due to the influence of increased light absorption and scattering with deeper penetration of the light through the skin.
JM-OCT was developed to overcome this shortcoming. JM-OCT uses algorithms for acquiring local data in the skin by dividing up the skin into small sections by depth. The method allows researchers to obtain quantitative local data on the optical properties of the skin at various depths in a single scan sequence, regardless of the light penetration distance (from the surface of the skin inward).
The joint research team used this JM-OCT method to obtain local attenuation coefficient, local birefringence, and local degree of polarization uniformity, and investigate the tissue density and collagen fiber structure at each skin depth, in an attempt to identify local optical properties associated with wrinkle formation.
Degeneration of Collagen Leads to Wrinkle Formation
This study, involving a group of 21 female volunteers in their 70s, measured and calculated the average depth of the wrinkles detected within a 10-mm square of the eye corner area of their eyes, and investigated how the wrinkle data was related to the optical properties of their skin obtained using JM-OCT.
The study found a correlation between the local attenuation coefficients at the depth of 13–19 μm (i.e., stratum corneum and upper epidermis) and the depth of 189–460 μm (i.e., reticular dermis) from the skin surface and the mean wrinkle depth. It suggests that the deeper the wrinkles, the lower the tissue density of those areas.
The study also observed a correlation between the local birefringence at the depth of 88–139 μm from the skin surface (i.e., papillary dermis) and the mean wrinkle depth. It suggests that the deeper the wrinkles, the greater the degeneration of the collagen structure of those areas.
The process of wrinkle formation is affected by multiple factors, such as the density of different tissues and collagen fiber structure. To estimate the degree to which each local optical property affects wrinkle formation, the research team performed a multiple linear regression analysis (stepwise method) using the local attenuation coefficient, local birefringence, and local degree of polarization uniformity measured in each skin depth range as independent variables, and the mean wrinkle depth as an explanatory variable.
The analysis showed that regions showing a correlation between the optical properties and the mean wrinkle depth as described above. It was suggested that alteration of tissue density of the dermal reticular layer and degeneration of collagen fiber structure of the dermal papillary layer are strongly related to wrinkle formation.
Source: Kao