Luisa Coderch

The hair follicle (HF) is a dynamic “mini-organ” which undergoes bi-continuous cycles of growth, destruction and rest. The molecular mechanisms underlying the HF cycle are complex yet not fully understood. Anyhow, it is clear that the epithelial–mesenchymal interactions, and in particular the cross-talk between dermal papilla fibroblast (DPF) and the keratinocytes of the outer root sheath (ORSK) play a pivotal role. Aim of this study is the evaluation of the biological activity of anisotropic osmolyte solutions on the HF cycle. As reported in recent studies, dermal papilla cells deeply modify their gene expression profile when cultured as monolayers, but their transcriptional pattern can be partially restored when they are cultured as 3-dimensional spheroids. This draws our attention to the discovery that the spatial distribution of cells in the growth medium is fundamental in order to produce a verisimilar model. Therefore, we used the hanging drop technology to produce a scaffold-free micro-tissue model applied to a DPF-ORSK co-culture in order to create a µHF 3-dimensional model. As a result, this system was capable of evaluating the efficacy of the anisotropic osmolyte solutions on the progressive increase of the follicle turnover and ‘health’. Moreover, an in silico model was used in order to screen the most promising combination of osmolyte molecules. In vivo objective evaluations were finally carried out on volunteers having hair disorders.

Background: The major in vitro permeation studies are currently performed in Franz-type diffusion cells because of their simplicity, cost effectiveness and because the experimental conditions can be easily controlled. Apart from the skin, Franz-type diffusion cells can be used with synthetic membranes. Nevertheless, they do not emulate the nature of the lipidic matrix, which is responsible for the topical barrier function. Objective: This paper offers two new approaches combining different synthetic membranes (Strat-M^® and Nucleopore^®) with lanolin, which provides lipidic components similar to the lipidic matrix. Methods: The molecular structure of lanolin was studied in membranes by attenuated total reflectance infrared spectroscopy (ATR-IR). The water permeability and absorption of lidocaine, diclofenac sodium and betamethasone dipropionate were also studied and compared against free-lanolin membranes and skin. Results: The results showed an increasing barrier function after lanolin application in both membranes, resulting in a decrease in water permeability. Observing the IR spectra, the lateral packaging of the lipid in the synthetic membranes seems to emulate the orthorhombic disposition from the stratum corneum. Moreover, the three substances applied to the lanolin-containing membranes have a similar absorption to that of the skin. Conclusions: In conclusion, combining synthetic membranes with lanolin may be a useful approach to mimic topical actives’ absorption.

Ceramides are the major lipid constituent of lamellar sheets present in the intercellular spaces of the stratum corneum. These lamellar sheets are thought to provide the barrier property of the epidermis. It is generally accepted that the intercellular lipid domain is composed of approximately equimolar concentrations of free fatty acids, cholesterol, and ceramides. Ceramides are a structurally heterogeneous and complex group of sphingolipids containing derivatives of sphingosine bases in amide linkage with a variety of fatty acids. Differences in chain length, type and extent of hydroxylation, saturation etc. are responsible for the heterogeneity of the epidermal sphingolipids. It is well known that ceramides play an essential role in structuring and maintaining the water permeability barrier function of the skin. In conjunction with the other stratum corneum lipids, they form ordered structures. An essential factor is the physical state of the lipid chains in the nonpolar regions of the bilayers. The stratum corneum intercellular lipid lamellae, the aliphatic chains in the ceramides and the fatty acids are mostly straight long-chain saturated compounds with a high melting point and a small polar head group. This means that at physiological temperatures, the lipid chains are mostly in a solid crystalline or gel state, which exhibits low lateral diffusional properties and is less permeable than the state of liquid crystalline membranes, which are present at higher temperatures. The link between skin disorders and changes in barrier lipid composition, especially in ceramides, is difficult to prove because of the many variables involved. However, most skin disorders that have a diminished barrier function present a decrease in total ceramide content with some differences in the ceramide pattern. Formulations containing lipids identical to those in skin and, in particular, some ceramide supplementation could improve disturbed skin conditions. Incomplete lipid mixtures yield abnormal lamellar body contents, and disorder intercellular lamellae, whereas complete lipid mixtures result in normal lamellar bodies and intercellular bilayers. The utilization of physiological lipids according to these parameters have potential as new forms of topical therapy for dermatoses. An alternative strategy to improving barrier function by topical application of the various mature lipid species is to enhance the natural lipid-synthetic capability of the epidermis through the topical delivery of lipid precursors.

This study sought to obtain internal wool lipid extracts rich in ceramides from different wool types. Extraction methods, i.e., Soxhlet extraction with different organic solvents and supercritical fluid extraction with CO₂ using several polarity modifiers such as MeOH or EtOH, were optimized. The internal wool lipid content varied from 0.2 to 1.9% (based on wool weight) with a ceramide content ranging from 15 to 30% (based on extract weight). The Spanish and Russian Merino wool extracts were the richest in ceramide compounds. TLC‐FID was used to quantify the different internal wool lipid extracts. A new experimental protocol that enabled us to identify most of the different ceramide types is presented. These internal wool lipid extracts, especially the ones with a high ceramide content, may be regarded as an alternative source of animal ceramides, which could be of value in the cosmetic and dermopharmaceutical industries.

Recent studies suggest that supplementing intercellular lipids of the stratum corneum in ageing populations or in people with dry skin can stimulate the functioning of the skin. This work lends support to the reinforcement capacity of two different stratum corneum lipid mixtures (synthetic stratum corneum lipid mixtures, SSCL, and internal wool lipid extracts, IWL) formulated as liposomes on healthy skin of two differently aged groups of individuals. Protection of healthy skin against detergent‐induced dermatitis was evaluated. Transepidermal water loss and capacitance were used to evaluate the effect of these formulations in in vivo long‐term studies. Increase in water‐holding capacity is obtained only when the formulations applied are structured as liposomes. This is slightly more pronounced for aged skin. Subsequent SLS exposure reflected the protection of healthy human skin against detergent‐induced dermatitis. Slightly better results were obtained with IWL containing a mixture of natural ceramides than with SSCL with only one ceramide present in the formulation. All these results support the beneficial effects of skin lipid supplementation given their resemblance to the lipids in the stratum corneum both in composition and in the structuring of the formulation.

The present work deals with the ‘in vivo’ stripping technique to evaluate the percutaneous absorption of sodium fluorescein (NaFl) vehiculized in two different liposome preparations formed by phosphatidylcholine (PC) and lipids mimicking the stratum corneum (SC; ceramides, cholesterol, palmitic acid and cholesteryl sulphate), respectively. Furthermore, the possible effect of these vesicles on the SC lipid alkyl chain conformational order were evaluated at different depths of SC by non-invasive biophysical techniques: Corneometer, Tewameter and especially ATR-FTIR. The results of NaFl percutaneous absorption indicate the highest penetration in the case of incorporation in PC liposomes, which could be related to the increase in SC lipid disorder detected by ATR-FTIR, i.e. a decrease in skin barrier function. On the other hand, SC lipid liposomes have been shown to have a higher affinity for SC owing to the high amount of NaFl found in this layer, suggesting a greater reservoir capacity of SC when similar lipid composition formulation is applied. A lipid order increase is observed by infrared spectroscopy, when these types of liposomes are topically applied, resulting in a strong barrier effect. These results could be useful in designing specific liposomal topical applications.