Absorption and Metabolism of Topically Applied Testosterone in an Organotypic Skin Culture

Abstract

The Living Skin Equivalent (LSE^TM) is an organotypic coculture of human dermal fibroblasts in a collagen-containing matrix and a stratified epidermis composed of human epidermal keratinocytes. In order to establish the feasibility of using this in vitro system as a model for cutaneous biotransformation, the metabolic fate of topically applied testosterone (T) was monitored in the LSE. After a 24-hour exposure period (37 °C) to radiolabelled T, LSE extracts analyzed by high-performance thin-layer chromatography showed that approximately 50% of the applied T had been metabolized. Identified metabolites included bands which comigrated with polar metabolites and products of T 5Α-reductase. The general distribution of the observed metabolites was similar to that obtained usingbiopsied human skin. The rates of T penetration (32 °C) through the LSE were monitored after application of T in two vehicles (water and petrolatum) and yielded permeability constants (Kps) of 29 and 1.6 × 10^-3 cm/h, respectively. These Kp values were 4- to 6-fold higher than those reported for human abdominal skin, and reflect the vehicle-related shift in penetration seen in human skin. The Kp values for two additional steroids, estradiol and hydrocortisone, and for T were also determined at 22 °C and compared to published Kp values. These Kp values in the LSE were, respectively, 63-, 187-and 35-fold higher than those reported for human skin. The data suggest that compared to human skin the LSE has only a partial barrier function to the passage of test chemicals. The magnitude of the difference in the rates of penetration between the LSE and human skin depends on the test chemical. For specific chemicals, such as T, the LSE simulates certain aspects of skin metabolism and percutaneous absorption.

Synthesis and Characterization of New Ascorbic Derivative: Sodium Isostearyl 2-O-L-Ascorbyl Phosphate

“…Skin penetration of VCP-IS-Na was evaluated using as organotype model of human skin, living skin equivalent-high (LSE-high), namely TESTSKIN TM (28)(29)(30). The time course of permeation amount in the receptor compartment was investigated after 2.5 mL of 2.0% test sample (284.14 mmol as VC, 129.9 mmol as VCP-Na, 98.4 mmol as VCP-IS-Na) solution was applied to a donor cell (Fig.…”

Improvement of the Experimental Setup to Assess Cutaneous Bioavailability on Human Skin Models: Dynamic Protocol

“…Percutaneous absorption studies on human skin models are frequently realized directly in the cell culture insert by manually exchanging the receptor fluid at preselected time intervals (semi-dynamic setup) [4][5][6][7][8]. In addition, in order to limit any possible permeant bypass occurring at the interface between the culture insert side wall and the epidermal tissue, the experiments are performed on the delimited skin surface obtained by gluing a ring onto the epidermis.…”

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“…In spite of the conclusion that most substances Ponec diffuse more rapidly through the reconstructed epidermis than through the native epidermis, this model can be nevertheless used to test the effect of vehicle formulation on the penetration rate of a given compound. It has been shown, for example, that vehiclerelated differences in the penetration rate of testosterone were the same when studied in freshly excised skin and in the living skin equivalent [39]. The finding that the stratum corneum of the reconstructed epidermis shows a significant barrier function offers an opportunity to use it for screening for the cutaneous irritancy of topically applied pharmaceutical or cosmetic products.…”