Anchoring fibrils constituted primarily of type VII collagen and anchoring filaments composed of kalinin are essential structural elements of the dermal-epidermal junction and critical for its stability. The role of fibroblasts in the production of these structural elements and the formation of the dermal-epidermal junction was studied by using a living skin equivalent model. This model had been modified such that keratinocytes and fibroblasts were allowed direct contact. After 2 weeks, immunohistochemical studies showed the linear deposition of type VII collagen and kalinin, as well as type IV collagen and alpha6 integrin at the dermal-epidermal junction. By electron microscopy, anchoring fibrils, a continuous lamina densa, and numerous hemidesmosomes were noted. Reverse transcriptase-polymerase chain reaction analysis showed an increased expression of both type VII collagen and kalinin genes in keratinocytes when they were in direct contact with fibroblasts. These results suggest that fibroblasts synthesize an extracellular matrix which favors keratinocyte adhesion and the formation of a dermal-epidermal junction by increasing the production and the further arrangement of dermal-epidermal junction components.

Journal Article↗

PubMedDate not supplied

Use of dermal equivalent and skin equivalent models for identifying phototoxic compounds in vitro.

Phototoxicity inducing in vivo photoirritation, a reversible inflammatory reaction of the skin after chemical contact and UVA radiation exposure, is increasingly observed as a side effect associated with the use of both cosmetics and systemic drugs. In order to systematically screen for the phototoxic potential of new compounds, we propose two three-dimensional models suitable for in vitro testing: a dermal equivalent (DE) and a skin equivalent (SE) model. The DE model includes a collagen-glycosaminoglycans-chitosan porous matrix populated by normal human fibroblasts. The SE model is made by seeding normal human keratinocytes onto the DE, leading to a fully differentiated epidermis. The objectives of this pilot study are: 1) to compare the deleterious effects of UVA radiation on the two models and 2) to evaluate to what extent the in vitro results can predict the in vivo phototoxicity caused by well-known photoirritant compounds, included in the COLIPA validation phototoxicity reference chemical list. Dilutions of thiourea, sulisobenzone, promethazine, chlorpromazine and tetracycline were applied (20 microliters) onto DEs and SEs (n = 6) and incubated for 1 h (or 15 h) at 37 degrees C. Irradiated samples received 3 J/cm2 UVA. The 24 h post-irradiation residual cellular viability was measured using the MTT test on treated and untreated tissues and IL-1 alpha release measurement in collected SE culture media. A concordance in terms of photoirritant/non-photoirritant was obtained between the in vivo data and the in vitro results, suggesting that the DE and the SE models could be integrated, after a complete validation study, into a protocol for in vitro testing of the photoirritant potential of new molecules.

Anti-Allergic Agents↗

PubMedDate not supplied