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AN ORGAN WHICH CAN BE GROWN |
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A RECONSTRUCTED HUMAN SKIN
The Asselineau model - "Moon children's" skin recreated
The previously described epidermal models are reconstructed on samples of inert dermis or on synthetic support material. In 1986, L'Oral laboratories perfected a real model of human skin where the dermal substrate, inspired from the Bell model, was formed by fibroblasts inserted in a collagen matrix.
 The Asselineau model
To produce a human skin model like Asselineau's, developed at L'Oral, the starting point is the construction of a dermis: a mixture of collagen and fibroblasts is cultured in suitable conditions for three days, enough time for the fibroblasts to "contract" the collagen.
Following this, isolated keratinocytes are deposited on this dermis. They divide for 7 days in a culture medium in the absence of air and then it is all exposed to the air which allows differentiation of the keratinocytes into corneocytes and thus the horny layer is formed. A functional epidermis is thus reconstructed on a "living" dermis: the human skin model has thus taken shape.
Histological section of human skin (A) and reconstructed skin (B). with dermis including fibroblasts (arrows).
L'utilisation de ce modle a permis de confirmer les effets destructeurs des UV-A sur les fibroblastes.
(A) Dermis reconstructed with fibroblast (arrows) (B) destructed 48 heures after UVA irradiation. (C) Preventive treatment with Mexoryl, protect the fibroblasts.
The use of this model has allowed the UVA destructive effects on fibroblasts to be confirmed. The use of appropriate UVA filters makes it possible to limit these harmful effects, only visible in the long term in human, but immediately observable in the laboratory on reconstructed skins.
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"Moon children's" skin recreated
Xeroderma Pigmentosum (XP) is a rare disease caused genetically by an enzymatic deficiency which prevents any repair, even partial, of skin cells damaged by the sun. Children suffering from this disease, commonly known as "Moon children", are excessively sensitive to sunlight, have accelerated cutaneous aging and have a likelihood of developing skin cancers two thousand times higher than normal. A L'Oral team, in collaboration with the CNRS (National Science Research Center), has developed a reconstructed skin model with the characteristics of this deficiency. From keratinocytes and fibroblasts taken from patients with the disease, three models have been built: "Normal dermis / XP epidermis", "XP dermis / normal epidermis" and complete XP skin.
Normal (A) and XP (B) reconstruct skin. XP Stratum corneum (cc) is thinner. Epidermis Invagination in XP dermis
These models have already allowed important observations to be made: the differentiation of the horny layer of the XP epidermis is greatly retarded, the fibroblasts do not have the same orientation in the dermis. In addition, keratinocytes grown on a dermis containing fibroblasts from XP patients show a strong tendency to invaginate into the dermis, a phenomenon found in the early stages of cutaneous cancers. A great many of the results open the way to a better understanding of this disease and of early precancerous phenomena.
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