Aging Collagen in the Human Papillary Dermis: Comparison of Non Invasive in vivo Methods
Podium 56
Presented by: Gunja Springmann
Introduction
With a share of 90%, collagen is the most abundant protein in the dermis. It forms a fine network of fibers and is largely responsible for the skin's resistance and elasticity. With increasing age, collagen degrades and fibers become cross-linked. Skin elasticity decreases and wrinkles form. A major cause of collagen loss is sun exposure. UV-A rays penetrate into the dermis and generate free radicals. The skin reacts e.g. with the formation of metalloproteinnases, enzymes that cut collagen fibers, and the collagen degradates.
Imaging of the collagen network with invasive methods using punch biopsies and histological staining is established for a long time. However, in cosmetic research, noninvasive methods should be used whenever possible. A number of imaging techniques that can be applied directly to living skin are available. These include skin ultrasound imaging, two photon microscopy, confocal reflectance microscopy, and Line Confocal Optical Coherence Tomography (LC-OCT). Furthermore, there exists an indirect method to measure collagen density in vivo and depth-resolved with confocal Raman spectroscopy by quantification of the dermal water content. Due to different resolution and different measurement principles, the age-related degradation of collagen in the papillary dermis presents differently with the different methods.
The aim of this work was to compare the age-related collagen degradation as presented by LC-OCT with the methods reported in the literature. In a clinical study, images of papillary collagen were acquired in subjects of different ages using LC-OCT. The suitability of LC-OCT for in vivo collagen imaging, its advantages and disadvantages are discussed based on our own study, and the current literature on existing techniques.
Methods
In twelve male and female subjects aged 7-70 years with fair skin and no signs of pronounced photoaging, images of papillary collagen were obtained with LC-OCT. Images were taken on the inner, sunlight-protected forearm and on the sun-exposed dorsal forearm respectively. In a visual evaluation, two independent raters assessed the status of the collagen using a scoring system. Main criteria were the density and reflectiveness of the collagen structure.
Results
Visual assessment of LC-OCT images revealed an age-related decrease in density and reflectiveness of the collagen. Aged collagen was more fibrous and increasingly embedded in dark non reflective structues. Intraindividual differences between dorsal and volar collagen pattern gradually became larger with increasing age, as the dorsal collagen change started earlier at age and developed quicker.
In some of the literature documented methods, aging collagen presents differently from LC-OCT images. Different contrasting methods and magnifications are the main reasons for that. The greatest similarity of the LC-OCT results was found with confocal reflectance microscopy imaging.
Discussion and Conclusion
The LC-OCT method as a non-invasive in vivo method was found to be well suited to visualize signs of aging of collagen in the papillary dermis. The results observed complement the literature documented collagen imaging and measurement. Advantageous is the fast image acquisition and the spatial resolution of about 1 µm, which is excellent for confocal systems. However, the collagen of the deeper reticular dermis cannot be evaluated with this method, since the images clearly lose sharpness and contrast from a depth of about 200 µm on. For an evaluation of the collagen in the papillary dermis, the method is well suited.
With a share of 90%, collagen is the most abundant protein in the dermis. It forms a fine network of fibers and is largely responsible for the skin's resistance and elasticity. With increasing age, collagen degrades and fibers become cross-linked. Skin elasticity decreases and wrinkles form. A major cause of collagen loss is sun exposure. UV-A rays penetrate into the dermis and generate free radicals. The skin reacts e.g. with the formation of metalloproteinnases, enzymes that cut collagen fibers, and the collagen degradates.
Imaging of the collagen network with invasive methods using punch biopsies and histological staining is established for a long time. However, in cosmetic research, noninvasive methods should be used whenever possible. A number of imaging techniques that can be applied directly to living skin are available. These include skin ultrasound imaging, two photon microscopy, confocal reflectance microscopy, and Line Confocal Optical Coherence Tomography (LC-OCT). Furthermore, there exists an indirect method to measure collagen density in vivo and depth-resolved with confocal Raman spectroscopy by quantification of the dermal water content. Due to different resolution and different measurement principles, the age-related degradation of collagen in the papillary dermis presents differently with the different methods.
The aim of this work was to compare the age-related collagen degradation as presented by LC-OCT with the methods reported in the literature. In a clinical study, images of papillary collagen were acquired in subjects of different ages using LC-OCT. The suitability of LC-OCT for in vivo collagen imaging, its advantages and disadvantages are discussed based on our own study, and the current literature on existing techniques.
Methods
In twelve male and female subjects aged 7-70 years with fair skin and no signs of pronounced photoaging, images of papillary collagen were obtained with LC-OCT. Images were taken on the inner, sunlight-protected forearm and on the sun-exposed dorsal forearm respectively. In a visual evaluation, two independent raters assessed the status of the collagen using a scoring system. Main criteria were the density and reflectiveness of the collagen structure.
Results
Visual assessment of LC-OCT images revealed an age-related decrease in density and reflectiveness of the collagen. Aged collagen was more fibrous and increasingly embedded in dark non reflective structues. Intraindividual differences between dorsal and volar collagen pattern gradually became larger with increasing age, as the dorsal collagen change started earlier at age and developed quicker.
In some of the literature documented methods, aging collagen presents differently from LC-OCT images. Different contrasting methods and magnifications are the main reasons for that. The greatest similarity of the LC-OCT results was found with confocal reflectance microscopy imaging.
Discussion and Conclusion
The LC-OCT method as a non-invasive in vivo method was found to be well suited to visualize signs of aging of collagen in the papillary dermis. The results observed complement the literature documented collagen imaging and measurement. Advantageous is the fast image acquisition and the spatial resolution of about 1 µm, which is excellent for confocal systems. However, the collagen of the deeper reticular dermis cannot be evaluated with this method, since the images clearly lose sharpness and contrast from a depth of about 200 µm on. For an evaluation of the collagen in the papillary dermis, the method is well suited.