Skin, reconstructed

Reconstructed Human Epidermis Equivalents Because of the limited availability of human skin, reconstructed human epidermis equivalents are under investigation to serve as membranes in permeation experiments. A summary on these replacement tools has been recently published by Netzlaff et al. [92], First results of a German prevalidation study have shown the suitability of such bioengineered human epidermis equivalents in permeation studies [93],... 

Boelsma, E, Anderson, C., Karlsson, A.M., and Ponec, M., 2000, Microdialysis technique as a method to study the percutaneous penetration of methyl nicotinate through excised human skin, reconstructed epidermis, and human skin in vivo, Pharm. Res., 17, 141-147. 

Scaffold Cellular proliferation Skin reconstruction, blood vessel reconstruction... 

Sheihabeddin L., Berthod F., Damour O., CoUombel C., Characterization of skin reconstructed on a chitosan-collagen-glycosaminoglycan matrix, S nPAarmoco/., 3, 1990, 107—114. 

Quartz cuvette, glass plate. Teflon membrane, Transpore tape, skin (reconstructed or excised), in vivo human volunteer s skin... 

Toriumi, D.M., O Grady, K., Devang, D. and Bagal, A., Use of oclyl-2-cyanoacrylale for skin closure in facial plastic surgery. PLasl. Reconstruct. Surg., 102, 2209-2219 (1998). 

Complete reconstruction of body tissue, rebuilding of normal subcutaneous tissue, and regular regeneration of skin. 

The use of high-strength TCA (65-100%) for acne scarring has proven to be an exciting new application of TCA. In this technique chemical reconstruction of skin scars (CROSS technique) showed significant improvement. Specifically high-concentration TCA is focally apphed to depressed or ice-pick scars and pressed hard with the wooden end of a cotton tip applicator. This induces a localized scar to occur, which over time effaces the depressed scar. Typically this requires five or six courses of treatment spread out over intervals of weeks to months. 

Lee JB, Chung WG, Kwahck H, Lee KH (2002) Focal treatment of acne scars with trichloroacetic acid chemical reconstruction of skin scars method. Dermatol Surg 28 1017-1021... 

The earliest recorded attempts at organ transplant date back thousands of years.1 More than a few apocryphal descriptions exist from ancient Egypt, China, India, and Rome documenting experimentation with transplantation. For example, an Indian text from the second century bc describes a procedure for nasal reconstruction surgery with the use of autografted skin. Also, Roman Catholic lore has saints Damian and Cosmas replacing the gangrenous leg of a man with the leg of a recently deceased man in the third century ad.1... 

We experience heat, visible light, UV and radio waves by the way they interact with our thermometers, our eyes, skin and our radio sets respectively. This is a tremendously important concept. Photons of infrared light are experienced as heat. The photons that cause photochemical changes in the retina at the back of the eye are termed visible . These photochemical reactions in the eye generate electrical signals which the brain encodes to allow the reconstruction of the image in our mind this is why we see a scene only with visible light - indeed this is why we call it visible . 

The following in vitro methods based on reconstructed human skin models are validated (by the ECVAM) for predicting skin corrosion— EPISKIN , EpiDerm , Corrositex —and irritation EPISKEM , EpiDerm , PREDISKIN , SIFT [142], Additionally, the SkinEthic was assessed and... 

A further option to investigate the phototoxic potential of substances is the use of reconstructed human skin models. The evaluation of the cell viability is based on the MTT-assay that is sensitive for the mitochondria activity in cells. Currently, these in vivo substitutes are still under validation and are not approved as full standard test methods for the investigation of the phototoxicity potency of a test chemical. However, several existing models are in use for prevalidation studies and are described elsewhere in more detail [92],... 

K. Meyer, C. Steinhoff, C. Tornier, B. De Wever, and M. Rosdy. Assessment of the skin irritation potential of chemicals by using the SkinEthic reconstructed human epidermal model and the common skin irritation protocol evaluated in the ECVAM skin irritation validation study. Altern. Lab. Anim. 34 393-406 (2006). 

The principle of the human skin model test is that the test material is apphed topically for up to 4h to a three-dimensional human skin model, comprising at least a reconstructed epidermis with a functional stratum comeum (outermost layer of the skin). The human skin models can come from various sources, but they must meet certain criteria. Corrosive materials are identified by their abdity to produce a decrease in cell viabdity (as determined, e.g., by using a dye reduction assay) below defined threshold levels at specified exposure periods. The principle of the test is in accordance with the hypothesis that corrosive chemicals are able to penetrate the stratum comeum (by diffusion or erosion) and are sufficiently cytotoxic to cause cell death in the underlying cell layers. 

We are currently in the process of improving this assay by using gene proflling (Baken et al, unpublished observations). A future extension will be the use of reconstructed skinmodels (RSM). In these models KC spontaneously form the four skin layers. 

Reconstructed Skin a Model for Mimicking Phototoxicity in the Taiget Oigan... 

To overcome the limitations of cells in culture, the use of reconstructed skin models is an interesting alternative. Several studies have reported their capacity to predict... 

Reconstructed skin models may also be used to study photogenotoxicity. In fact, the comet assay was recently adapted to such models, using a specific technique, that is, dissociation and separation ofkeratinocytes after UV exposure of the reconstructed epidermis. Using a mixture of specific enzymes cocktail, it was possible to obtain suspension of cells without damaging them. For instance, the photocomet assay could be successfully performed for lomefioxacin after UVA exposure of reconstmcted epidermis [76], as shown in Figure 19.7. 

Finally, use of more complex models is in progress. For example, Lee et al. [77] studied the phototoxic impact of chemicals on reconstructed skin models that were prepared from cultured keratinocytes and melanocytes on de-epidermized dermis. 

Figure 19.7 Experimental procedure forthe assessment of photocytotoxicity (MTT assay) and photo-genotoxicity (comet assay) on reconstructed epidermis. Drugsorformulationscan be applied on the skin surface (topical route) or provided in the culture medium (systemic route see [76]).

In the future, more accurate in silico methods will hopefully become available in order to orientate chemical synthesis. Moreover, some new approaches should be developed or improved such as the detection of photoallergic potential and the production of more sophisticated industrial reconstructed skin models. 

Schafer-Korting, M., Bock, U Gamer, A., Haherland, A., Haltner-Ukomadu, E., Kaca, M., Kamp, H Kietzmann, M. et al. (2006) Reconstructed human epidermis for skin absorption testing results of the German prevalidation study. Alternatives to Laboratory Animals, 34, 283-294. 

Flamand, N., Marrot, L., Belaidi, J.P., Bourouf L., DouriDe, E., Feltes, M. and Meunier, J.R. (2006) Development of genotoxicity test procedures with Episkin, a reconstructed human skin model towards new tools for in vitro risk assessment of dermally applied compounds Mutation Research, 606, 39-51. 

Fig. 5.2. Cross section of the reconstructed image-guided Raman spectroscopic estimates of bone distribution using (a) backscattered collection using a ring/disk fiber optic probe and (b) transmission measurements using a rectangular array of collection fibers. The contrast between the bone and background from skin and tendons was more than 100-fold greater in the transmission measurements used than in the backscattered measurements (reprinted with permission from [26]. Copyright 2008 Optical Society of America)...

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