Relevance and reliability of the PREDISAFE assay in the COLIPA eye irritation validation program (phase 1).

The 6th Amendment of the European Directive on Cosmetics induces a potential ban on animal testing for cosmetic ingredients and finished products. In this new context, COLIPA (The European Cosmetic Toiletry and Perfumery Association) has initiated an international multicentric study with the main goal of validating available alternatives to in vitro methods for assessing the eye irritation potential of cosmetic raw materials and formulations. In order to test undiluted and hydrophobic ingredients and formulations, a cytotoxicity test named PREDISAFE was incorporated into our internal battery of in vitro tests for 3 years. This cell culture test based on the neutral red release procedure was prevalidated with several cosmetic formulations and used systematically by comparison with internal benchmarks. In this article, the defined prediction model and the protocol used in the COLIPA eye irritation program are described, and furthermore the PREDISAFE assay results obtained during Phase I of the above mentioned study are presented and discussed in detail. The statistical analysis proves clearly a great interest in the PREDISAFE test for the prediction of eye irritation potential of cosmetic formulations. Its strong compatibility for a wide category of finished products associated with its ease of use offer relevant advantages for a routine use in the ocular irritancy screening in the cosmetics industry. This paper also explains the reasons for false negative and false positive in vitro tests results and describes possible technical modifications to avoid these wrong predictions. At the end, some recommendations for the Phase II of the COLIPA study are considered with the main objective to prove that a multivariable analysis could be useful to find the best battery of in vitro assays for acceptance by the regulators for the replacement of the Draize eye irritation test.

Advantage of the presence of living dermal fibroblasts within in vitro reconstructed skin for grafting in humans.

Methods for serial cultivation of human keratinocytes can provide large quantities of epidermal cells, which have the potential of restoring the vital barrier function of the epidermis in extensive skin defects such as burns. To investigate the value of combining an epidermis with a dermal component, fibroblasts originated from the superficial dermis were used to seed a collagen lattice as described by E. Bell (dermal equivalent). Beginning in 1981, we grafted 18 patients (burns and giant nevi) using 35 grafts 10 x 10 cm in size. In the course of this work, the original technique was modified and improved as experience was gained. We began by using small skin biopsy samples as a source of keratinocytes cultured on a dermal equivalent before grafting in a one-step procedure, but this gave poor cosmetic results, because of a nonhomogeneous epidermalization. We then chose to cover the graft bed using a two-step procedure. The first step consisted of grafting a dermal equivalent to provide a dermal fibroblast-seeded substrate for subsequent in vivo epidermalization by cultured epidermal sheets. Whatever the epidermalization technique used, a living dermal equivalent applied to the graft bed was found to reduce pain, to provide good hemostasis, and to improve the mechanical and cosmetic properties of the graft. A normal undulating dermal-epidermal junction reappeared by 3 to 4 months after grafting and elastic fibers were detectable 6 to 9 months after grafting. As a result of the biosynthesis of these products, the suppleness (e.g., elasticity) of the grafts was closer to that of normal skin than the cicatricial skin usually obtained with epidermal sheets grafted without the presence of living dermal cells. This rapid improvement of the mechanical properties of the graft could be attributed to the presence of fibroblasts cultured from the dermis and seeded into the collagen matrix.

Biafine applied on human epidermal wounds is chemotactic for macrophages and increases the IL-1/IL-6 ratio.

Using a model of pure epidermal wounds in normal human volunteers, we have studied the effects of Biafine emulsion firstly on inflammatory cell migration, vascular permeability and cytokine release during the first 24 h, and secondly on epidermal wound healing by measuring transepidermal water loss from day 1 to day 7. Under these conditions, Biafine does not improve epidermal healing, in contrast to what is observed with bleeding dermoepidermal wounds. Our results suggest that the effects of Biafine are essentially at the dermis level. The analysis of epidermal wound exudates leads to the same conclusion. As a matter of fact, we demonstrated that Biafine is chemotactic for macrophages and increases the IL-1/IL-6 ratio, chiefly by reducing the secretion of IL-6. This study permits to progressively clarify the mode of action of Biafine, that seems to be located at the level of granulation tissue formation and not at the epidermal level.

Role of interferon-gamma on the in vivo expression of functional interleukin-2 receptors by murine macrophages.

Interferon-gamma activates both in vitro and in vivo macrophage functions. Injection of rat recombinant interferon-gamma (rR-IFN-gamma) induced the expression of interleukin-2 receptors (IL-2R) by peritoneal macrophages from normal BALB/c and MRL-+/+ mice. Moreover, rR-IFN-gamma stimulated in a dose-dependent manner the oxidative burst of cells as revealed by luminol-dependent chemiluminescene (LDCL). Resident peritoneal macrophages from MRL-lpr/lpr (mice that develop a systemic lupus-like syndrome) showed a higher PMA-triggered LDCL response. This enhanced activity was accompanied by an increase in IL-2R expression (30% vs. less than 1%). The "activated" macrophages from rR-IFN-gamma-treated normal mice as well as MRL-lpr/lpr mice did not respond to the addition of recombinant interleukin-2 (rHu-IL-2) by an increase in LDCL. However, rHu-IL-2 triggering became efficient when cells enriched in IL-2R-bearing macrophages were preincubated overnight with rHu-IL-2R. This response may point out a functional role for IL-2R and provide a role for IL-2 in certain macrophage functions.

Activation of human dermal fibroblasts by fibroblast growth factors (FGFs) and/or interleukin-1 beta (IL-1 beta).

Human dermal fibroblast proliferation was dependent of growth factors such as interleukin-1 (IL-1) and fibroblast growth factors (FGFs). These mediators, which induce proliferation of the cells in culture, were able to synergize when added in combination. This synergistic effect seems to be restricted to the mitogenic activity since IL-1-induced PGE2 release and interferon-beta 1 (IFN-beta 1) production by fibroblasts was inhibited in the presence of FGFs, which by themselves were unable to stimulate the production of IFN-beta 1 and the release of arachidonate metabolites from the fibroblasts even at high concentration.

Opposite effect of Interferon-gamma on PGE2 release from Interleukin-1-stimulated human monocytes or fibroblasts.

Stimulated monocytes produce prostaglandins (PGE2) in response to lipopolysaccharide (LPS), Muramyl dipeptide (MDP) or Interleukin-1 (IL-1). This response could be modulated in different ways by Interferon-gamma (IFN-gamma). This lymphokine, known to potentiate IL-1 production by LPS- or MDP-stimulated monocytes, suppressed different Il-1 activities such as PGE2 release by the same cells. By contrast, an impairement of suppression by IFN-gamma was evidenced in rIL-1 beta-induced PGE2 release from human dermal fibroblasts. Salmon calcitonin (sCT), another inhibitor of IL-1-induced bone resorption, was able to prime monocytes to potentiate PGE2 elaboration by LPS, but failed to modulate PGE2 liberation from either rIL-1 beta-stimulated monocytes or fibroblasts.

Differential effect of D-penicillamine on the cell kinetic parameters of various normal and transformed cellular types.

The cell-growth-inhibitory and phase-specific effects of D-penicillamine on cell-cycle progression were investigated using cell-proliferation patterns, quantitative cell-cycle analysis by flow cytometry, and determination of the mitotic index and binucleate cell fraction of normal (rabbit articular chondrocytes, L 809, rabbit fibroblasts) and transformed (HeLa, L 929) cells. D-penicillamine treatment resulted in an inhibition of growth within a dose range of 5 x 10(-4) M to 7.5 x 10(-3) M. Examination of DNA by flow cytometric analysis revealed that rabbit articular chondrocytes were preferentially arrested in the G0/1 phase of the cell cycle, whereas the other cell lines were blocked in the G2 + M phase; the increase in the proportion of cells with G2 + M DNA content was partially due to an enhancement of binucleate cells, resulting in a cytokinesis perturbation for HeLa and L 929 cells. These results showed that D-penicillamine affects cell proliferation through different events according to cell type.