الفهرس 
• Histology of the SkinOnly 14 pages are availabe for public view
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Abstract
Skin is the outer organ of the human organism, which represents a barrier to the environment and protects the human body from water loss and penetration of environmental compounds into skin, such as hazardous substances and bacteria. Additionally, the skin barrier protects the living cells from mechanical damage. Dermatopathology is the combination of the clinical diagnosis and microscopic pathology of the skin, and this not only of direct benefit to individual patients but also has led to the recognition of many new skin lesions and increase our understanding of mechanisms of skin diseases.
Traditionally, skin is evaluated either visually by the experienced eye of the dermatologist, or possibly by utilizing a magnifying, or if the diagnosis is equivocal, the removal of a skin biopsy becomes necessary, which can be worked up histologically by different staining and fixation processes. However, the removal of biopsies remains a strong invasive process, which might be hardly warrantable in basic research to determine the penetration kinetics of certain substances, require a high number of biopsies to be taken, alter the original morphology, non-repeatable on the same site and always requires an iatrogenic trauma. Another limitation of histology is that in vitro conditions are not always comparable to in vivo conditions, e.g., as shown for the SC thickness.
Due to the serious complications and drawbacks of skin biopsies, new noninvasive approaches have been developed over the years to provide objective evaluation of the skin both in health and in disease. The advent of computers, lasers and photonics, made it possible to develop additional techniques that were impossible a few years ago. These approaches provide dermatologist with sensitive tools to measure the skin’s condition in terms of physiologic parameters (color, erythema, pigmentation and SC lipids as a barrier function, etc…).
These techniques help dermatologists to evaluate the skin lesions in noninvasive pattern that does not penetrate mechanically, nor break the skin, i.e., it doesn’t require an invasive incision into the skin or removal of biological tissue. Those noninvasive techniques divided into two big classes, the first class depends mainly on the optical properties of the skin and the second class depends on the genetics.
The rapid development of optical and spectroscopic techniques has induced the deployment of analytical systems, which can be used to evaluate the skin properties and parameters noninvasively. The analysis of skin properties with optical and spectroscopic methods is of interest, both in field of cosmetology as well as in the area of diagnostics and therapy control of skin diseases.
Optical properties of the skin come from the reality that the skin is comprised of many different structures that cause scattering events with respect to light source that enter the surface and then escape back out of skin. These scattering events are wavelength dependent and also depend on different kinds of chromophores, absorbers and scatterers present in skin structures. Skin scattering is caused by lipids, water and proteins like collagen. Skin absorbing is caused by hemoglobin, melanin, betacarotene and bilirubin which are very strong absorbers. So that optical imaging and spectroscopic techniques are developed.
The first one of optical noninvasive dermatological techniques is dermoscopy which opens up new dimensions on clinical morphology of skin lesions through its digital follow-up examinations and computer-aided diagnosis. It is functionally similar to a magnifying lens, but with added of an inbuilt illuminating system. Higher magnification can adjust the ability to assess structures as deep as in the reticular dermis. Johann Saphier was the first one that described dermoscopy in 1920, and then it was further developed in United States until become a routine technique in Europe and is gaining acceptance in other countries. Its use has been shown significantly improve diagnostic accuracy as it is a rapid method and decreases number of excised benign lesions.
The second one of optical noninvasive dermatological techniques is CSLM which firstly invented by Marvin Minsky in 1955. It constitutes a visualization of tissue architecture with resolution more than that of light microscopy. Confocal imaging enables in vivo measurements of surface and subsurface skin microstructures. Skin annexes, as well as cutaneous cells from different epidermal layers, can be easily distinguished; their change in morphology from skin surface to the papillary dermis can be observed.
CSLM possesses a high potential for diagnostical purposes and dermatological research. The aspect of normal skin in contrast to the pathogenic state can be exposed. It used in morphological analysis of healthy human skin and for imaging a number of clinically relevant inflammatory and neoplastic skin disorders. It has ability to produce high-resolution histoimages of normal and pathological epidermis. Changes in keratinocyte size, shape, and morphology can also be detected.
Another one of technologies which have been used for the early detection of cancer and biochemical changes in cells and tissues causing cancer is spectroscopic technique. RS has attracted considerable attention for medical diagnosis as it provides detailed information about molecular structure of normal and diseased tissues. Raman scattered light occurs at wavelengths that are shifted from the incident light by the energies of molecular vibrations. CRS used in dermatological studies, including a method for determining the thickness of the SC, and to a method for quantifying the effectiveness of a skin care composition. The methods of the invention carried in vivo directly on the human skin of a person.
OCT is the promising method for dermatological applications as the analysis of different skin parameters like dryness and oiliness of the skin, the barrier function and the structure of furrows and wrinkles. Images of human skin show a strong scattering from tissue; its resolution enables the visualization of architectural changes but not of single cells. The epidermis distinguished from the dermis, adnexal structures and blood vessels. Skin tumors show a homogenous signal distribution and in some cases, tumor borders to healthy skin are detectable. Inflammatory skin diseases lead to changes of OCT image, such as thickening of epidermis and reduction of the light attenuation in dermis. A quantification of treatment effects, such as swelling of the horny layer due to application of a moisturizer, is possible. Repeated measurements allow a monitoring of the changes over time.
Additionally the homogeneity of distribution of topically applied creams, as well as their penetration into the skin was investigated, this method is highly valuable in dermatology for diagnostic and therapy control and for basic research, for instance in the field of structure analysis of hair follicles and sweat glands. The vertical images of the tissue produced by OCT are easily compared with histological sections. Unfortunately, the resolution of the OCT technique not high enough to carry out measurements on a cellular level, as is possible by FSLM which has the advantage that it can be used for the investigation of penetration and storage processes of topically applied substances especially if the substances have fluorescent properties or if they are fluorescent- labelled.
In line-up of the developed optical non-invasive techniques, DRS is the most closely related to visual observations. In physiological studies of superficial tissue, DRS is often referred to as an in vivo optical biopsy technique because its ability to identify and quantify molecular structures in the sample, based on the analysis of the reradiated or absorbed light by tissue chromophores. DRS can be used to detect individual absorption features due to specific chemical bonds or substances in the investigated tissue, a feature that makes the method suitable for tissue physiology and viability studies. The technique’s inherent shortcoming of single-point probing is addressed by the ongoing evolutionary step of spectroscopic modalities. This allowed the detection of specific viability markers (e.g. tissue oxygen delivery and consumption), their relative concentrations and spatial extent and finally the alterations of the named parameters over the given period of time.
NIRS is promising technique for the screening of skin lesions. In vivo of skin neoplasms were collected by placing a fiber optic probe on the skin, whether significant spectral differences existed and whether spectra classified according to lesion type where significant differences were found between the lesion groups. NIRS used for the continuous monitoring of tissue oxygen delivery, as it detects light absorbance of Hb chromophores to determine tissue oxygen saturation. As skin colour is also determined by the presence of chromophores, NIRS signal quality may be affected by skin pigmentation. It has been shown that the NIR imaging method is capable of detecting changes in skin hydration induced by skin moisturizers and cleansers. The imaging is rapid and non-contact.
Taking into consideration the rapid development of optical systems and their miniaturization, it can be expected that in the near future low-cost optical systems will be available on market, which will be frequently applied in the fields of dermatology and cosmetology.
The second class of dermatological noninvasive techniques is the microarrays. They used in biomedical research and dramatically increased during the past years. In the present review; we provide an overview on the basic types of microarrays technologies and advantages of each type. A focus is then put on their applications in dermatological research. In recent years, a series of gene expression studies have been performed for various dermatological diseases as MM, psoriasis and LE. However, further functional studies will be needed for more complete understanding of the pathogenesis of these diseases.
This may be performed by means of the recently developed RNA interference technology. Besides its role in large-scale gene expression studies, microarrays technologyies have proved to be a valuable tool for genomic screens, e.g. single nucleotide polymorphisms. These play role in tumor development and progression, and also function as genetic markers for disease susceptibility. Microarrays technologies open enormous perspectives for dermatologists. It may help us understand the complex pathogenesis of a variety of dermatologic diseases and identify their genetic background.
These new lines of investigation will help both dermatologists and patients. They will make the pathological diagnosis easily, help also in early treatment, non destructive or disfiguring to the patient, also help in follow-up of cases. But there techniques are very expensive, not available in developed countries and need special experience.