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Background: Hyaluronic acid (HA) formulations are used for aesthetic applications. Different cross-linking technologies result in HA dermal fillers with specific characteristic visco-elastic properties. Objective: Bio-integration of three CE-marked HA dermal fillers, a cohesive (monophasic) polydensified, a cohesive (monophasic) monodensified and a non-cohesive (biphasic) filler, was analysed with a follow-up of 114 days after injection. Our aim was to study the tolerability and inflammatory response of these fillers, their patterns of distribution in the dermis, and influence on tissue integrity. Methods: Three HA formulations were injected intradermally into the iliac crest region in 15 subjects. Tissue samples were analysed after 8 and 114 days by histology and immunohistochemistry, and visualized using optical and transmission electron microscopy. Results: Histological results demonstrated that the tested HA fillers showed specific characteristic bio-integration patterns in the reticular dermis. Observations under the optical and electron microscopes revealed morphological conservation of cutaneous structures. Immunohistochemical results confirmed absence of inflammation, immune response and granuloma. Conclusion: The three tested dermal fillers show an excellent tolerability and preservation of the dermal cells and matrix components. Their tissue integration was dependent on their visco-elastic properties. The cohesive polydensified filler showed the most homogeneous integration with an optimal spreading within the reticular dermis, which is achieved by filling even the smallest spaces between collagen bundles and elastin fibrils, while preserving the structural integrity of the latter. Absence of adverse reactions confirms safety of the tested HA dermal fillers.

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To assess whether the expression of connexins (Cx) by keratinocytes is altered under conditions of abnormal epidermal differentiation, we have compared Cx26, Cx32, Cx37, Cx40, and Cx43 in the epidermis of 11 psoriatic patients who had not been treated for at least 1 mo and of seven healthy individuals. In all samples of fully mature psoriatic plaques, we have observed a massive expression of Cx26, as judged at both the transcript level (northern blot) and the protein level (immunofluorescence). This protein became consistently detected between keratinocytes of the basal and granular layers at the periphery of psoriatic plaques and in all layers of fully developed psoriatic epidermis, except in regions of parakeratosis. None or a minimal amount of Cx26 was observed in both control and nonlesional regions of psoriatic epidermis. Psoriatic plaques also contained Cx43, the prominent gap junction protein in the interfollicular epidermis of normal human skin. The levels of this protein appeared to be slightly higher in psoriatic than in control skin, as judged at both the transcript level (northern blot) and the protein level (immunofluorescence). Three other connexins (Cx32, Cx37, and Cx40), which are not observed in control interfollicular epidermis, were not induced in either nonlesional or lesional regions of psoriatic skin. The data indicate that selective changes in the normal expression of connexins by keratinocytes are associated with the changes in the proliferation and differentiation program that these cells undergo in psoriasis.