FR2982152A1 - Non-therapeutic cosmetic method, useful for improving barrier function of skin and/or for hydrating skin using sulfated polysaccharide with rhamnose pattern, comprises applying a composition comprising sulfated polysaccharide on skin - Google Patents

Abstract

Non-therapeutic cosmetic method to improve barrier function of skin and/or to hydrate the skin, comprises applying a composition comprising 2-60 wt.% of a sulfated polysaccharide with rhamnose pattern on the skin.

Description

The present invention relates to a cosmetic skin moisturizing method using a sulfated polysaccharide with a particular rhamnose pattern. The skin is a tissue whose cells are contiguous and integral with each other. The cutaneous tissue forms an outer covering comprising sebaceous or sweat glands, and hair follicles. The skin, and especially the scalp, are epithelia with continual renewal. Renewal, or desquamation, is a coordinated and finely regulated process resulting in the elimination of surface cells, insensitively and nonvisibly.

Human skin consists of two compartments, namely a superficial compartment, the epidermis, and a deep compartment, the dermis. The epidermis is conventionally divided into a basal layer of keratinocytes constituting the germinal layer of the epidermis, a so-called spinous layer consisting of several layers of polyhedral cells arranged on the germinal layers, one to three so-called granular layers consisting of flattened cells containing distinct cytoplasmic inclusions, keratohyalin grains and finally, a set of upper layers called corneal layers (or stratum corneum), consisting of keratinocytes at the terminal stage of their differentiation called corneocytes. Corneocytes are anucleate cells consisting primarily of a fibrous material containing cytokeratins, surrounded by a horny envelope. There is a permanent production of new keratinocytes to compensate for the continuous loss of epidermal cells in the stratum corneum by a mechanism called desquamation. However, an imbalance between cell production at the basal level and the desquamation rate can lead to scale formation on the skin surface. Similarly, a terminal differentiation deficit of stratum corneum cells, for various reasons, can lead to the formation of large, thick, visible to the naked eye cells called "dander", or in d other situations, thinning of the stratum corneum. Disorders of this terminal differentiation can lead to fragility, even a lack of barrier properties of the epidermis, chronic dehydration of the stratum corneum, loss of mechanical elasticity, tightness, and lack of radiance and transparency of the skin. As an example of factors promoting this deterioration of the surface quality of the skin, mention may be made of stress, the winter period, an excess of sebum, a lack of hydration. These disorders also appear in the case of dry skin of elderly subjects.

Thus, an alteration of the skin barrier can occur in the presence of external irritants (detergents, acids, bases, oxidants, reducing agents, concentrated solvents, noxious gases or fumes), mechanical stresses (friction, shock, abrasion, tearing). surface, dust, particles, shaving or epilating), thermal or climatic imbalances (cold, dryness, radiation), xenobiotics (undesirable micro-organisms, allergens) or internal stress-type stressors . One of the critical steps in the process of terminal differentiation of stratum coronum is the crosslinking of protein precursors to the horny envelope (EC). This phenomenon plays an essential role in the development and maintenance of cutaneous cohesion, the physical properties of the skin as barrier function, and is a crucial step in the process of terminal differentiation. The horny envelope is an essential component of corneocytes. In healthy subjects, impaired barrier function, particularly of the face, may be associated with the presence of immature and fragile corneal envelopes in the stratum corneum (Hirao T et al. 2002; 6 (2): 103-109). The maturation of the horny envelope from the deep layers to the superficial layers of the stratum corneum can be characterized by morpholocal and biophysical or mechanical parameters. The moisturizing active ingredients conventionally used, such as humectants, moisturizing polymers, fatty substances such as petrolatum, transiently modify the superficial properties of the skin. These active agents can lead to a mechanical relaxation of the stratum corneum, an increase in its state of hydration, an improvement of the micro-relief of the skin by formation of a film on the surface of the skin. Generally, these effects are not persistent in time and last only a few hours. In addition, after cleaning the skin, these active ingredients are eliminated and the effect of mechanical relaxation of the skin, the improvement of the texture of the skin or its optical properties disappear. Moreover, the use of film-forming agents on the skin, in particular the use of humectant polysaccharides such as carrageenan, often leads to a "tensor" effect on the skin, an increase in the elastic modulus of the skin and this surface stiffening results in discomfort of the skin.

There is therefore a need for active agents improving the hydration state of the skin, especially dry or aged skin, avoiding tugging and feelings of discomfort when applied to the skin.

Maintaining or restoring a properly matured horny shell is essential to maintaining a good quality barrier function that provides protection from external aggressions and lasting hydration of the skin, especially the skin. Surprisingly, it has been found that these goals can be achieved by using sulfated polysaccharides with particular rhamnose patterns that promote the maturation of corneal envelopes of corneocytes; this induction of differentiation allows a lasting improvement of the surface quality of the skin, in particular the state of hydration of the skin. The inventors have discovered that certain rhamnose-pattern polysaccharides described below are good agents for improving the barrier function of the skin. These polysaccharides are therefore good moisturizing agents of the skin, in particular dry skin. In addition, these polysaccharides during application to the skin do not present a sensation of discomfort, tightness of the skin.

Thus, the subject of the present invention is a non-therapeutic cosmetic method for improving the skin barrier function and / or moisturizing the skin, comprising the application to the skin of a composition comprising, in a physiologically acceptable medium, a sulfated polysaccharide comprising from 2% to 60% by weight, based on the total weight of the polymer, of rhamnose unit. The cosmetic process is suitable for the treatment of dry skin. The invention further relates to the cosmetic use of a sulphated polysaccharide rhamnose pattern as described above as a moisturizing agent of the skin.

The sulphated polysaccharides with rhamnose units used according to the invention may be chosen from ulvans and sulphated exopolysaccharides with a rhamnose pattern. The rhamnose is present in these polysaccharides in a content ranging from 2% to 60% by weight, relative to the total weight of the polysaccharide, and preferably ranging from 5% to 40% by weight. Preferably, this rhamnose content can range from 5% to 30% by weight, relative to the total weight of the polysaccharide. Advantageously, the sulfation rate of the polysaccharides can range from 1% to 30% by weight, relative to the weight of the polysaccharide. Preferably this sulfation rate can range from 2% to 20% by weight.

The polysaccharide may be optionally acetylated. The degree of acetylation can range from 0 to 10% by weight (weight ratio of acetyl units relative to the total weight of the polymer). The polysaccharide used according to the invention preferably has a weight average molecular weight of between 1000 and 10.106 Daltons, preferably between 5000 and 2.106 Da, preferably between 10,000 and 1.5.106 Da and more preferably between 100 000 and 1200. 000 Da. The sulfated polysaccharides with rhamnose units used according to the invention may be chosen from ulvans. Ulvans are sulfated polysaccharide extracts containing rhamnose obtained from green algae belonging to the order of the ulvals. Ulvans are water soluble sulphated anionic polysaccharides which are localized at the level of the cell in the cell wall. Ulvans are particularly extracted from ulvae or enteromorphs. These green algae are part of the phyllum chlorophytes and order ulvals characterized by a thallus tube (enteromorph) or double layer cell (ulva). These ulvan extracts can be obtained from numerous ulva species among which mention may be made of Ulva lactuca, Ulva rigida, Ulva armoricana, Ulva rotundata and UI-varia obscura, as well as several species of enteromorphs such as in particular Enteromorpha compressa, Enteromorpha intestinalis and Enteromorpha ramulosa. Ulvans account for 8 to 29% of the dry weight of algae. They consist mainly of rhamnose, glucuronic acid, glucose, galactose and xylose and also include sulfate groups. They may also include varying amounts of galacturonic acid, iduronic acid and mannose. Rhamnose is generally sulphated at position 3. Xylose may also be partially sulphated. Most of the constituent sugars are distributed according to repetitive sequences. The two major ones are disaccharide sequences, one called ulvanobiuronic acid with 3 sulphates called type A (A3s) comprising rhamnose 3-sulphate linked to glucuronic acid by a link of type 1-4, the other denominated 3-type ulvanobiuronic acid type B (B3s) comprising rhamnose 3-sulfate bound to Iduronic acid by a type 1-4 bond. The relative proportion of sugars varies according to the place of harvest of the ulva, the species and also the time of harvest in the year. To obtain ulvans by extraction from ulva, reference can be made to the extraction methods described in Carbohydrate Research 274 (1995) 251-261 or Hydrobiologia 326/327, 473-480, 1996. In general, the extracts used according to the invention are advantageously prepared by extraction in aqueous medium of ulva and / or enteromorphs, the extraction step being advantageously followed by an ultrafiltration step. For example, the extraction of ulvans can be carried out either from dried algae, or preferably from fresh algae frozen at -30 ° C.

The algae are thawed and then crushed roughly into pieces of about 0.5 cm and macerated in 0.05 M sodium oxalate for 2 hours, with constant stirring, at 85-90 ° C. The suspension is then filtered on canvas and then on Buchner, after addition of 2% of filtering ground (Celatom® Diatomite, Eagle-Picher). The filtrate is then concentrated by ultrafiltration (10 kDa membrane, Millipore) and diafiltered against 5 volumes of ultrapure water. After freezing, the extract is lyophilized and kept dry.

Analyzes carried out on extracts of ulvan: The dry matter, the mineral matter, the organic matter, as well as the sulphate and protein contents of the extracted ulvans were measured according to the following methods: The content of dry matter (DM) corresponds the weight obtained after drying 24h at 103 ° C; The contents of organic matter (OM) and mineral (MM) were quantified gravimetrically after 12 hours at 550 ° C; The sulfate (SO4) content was quantified according to Quemener et al. (1997) ; Protein content was estimated from N Kjelhdahl x 6.25 N assay; The total content of uronic acids was determined by colorimetric method, using m-phenyl phenol (Thibault, 1979), using D-glucuronic acid as a state. The profile of the sugars (neutral and uronic) was realized. after acid methanolysis and reverse phase HPLC chromatography (Absorbosphere RP18, 5 μm, 4 × 250 mm), Quemener et al. 2000; The molar mass distribution profile of ulvan was determined by size exclusion HPLC (Shodex SB-806M HQ column, injection volume: 50 μL, mobile phase: 0.05 M NaNO 3 + 0.02% NaN 3 flow rate: 0.5 mL / min, pressure: 20 bar, detectors: refractive index and UV multi-wavelength).

The following references describe the methods of assays used: - Quemener, B., Lahaye, M., Bobin-Dubigeon, C. (1997) Sugar determination in a chemical-enzymatic method coupled with high performance anion exchange chromatogra phy. Journal of Applied Phycology, 9, 179-188. Thibault J.-F. 1979. Automation of the dosage of pectic substances by the meta-hydroxydiphenyl method. Lebensm-Wiss. Technol., 12, pp. 247-251. Quemener B., Marot C., Mouillet L., Da Rice V., Diris J. (2000). Quantitative analysis of hydrocolloids in food systems by methanolysis coupled to reverse HPLC. Food Hydrocolloids, 14, pp. 9-17. As particular examples of ulvans, those having the following characteristics (in percentages by weight) can be used: Ulvane UR (extracted from the alga Ulva rotunda according to the protocol described previously, evaluated in Examples 1 and 2) MS (% MB) = 94.9% MO (% MS) = 75.9% MM (% MS) = 24.1% Na (% MS) = 5.74% 50 Proteins (N x 6.25) (% MS) = 7.40% Rhamnose% = 25.30% Glucuronic acid = 17.40% Iduronic acid% = 3.20% Xylose% = 3.4% 55 Galactose% = 1.80% 35 40 Glucose% = 0.70% Sulphate content = 15.70% Mw (eq pullulan g / mol) HP-SEC = biopopulate 1 062 300 Da (54%) 123 200 Da (46%) The sulphated polysaccharides with rhamnose patterns used according to the invention may be selected from sulfated exopolysaccharides having a rhamnose pattern.

Exopolysaccharides (abbreviated as EPS) are, in a known manner, polysaccharides excreted by various strains of marine bacteria. The majority of these polysaccharides consist of glucose, galactose, rhamnose, and optionally glucuronic acid and galacturonic acid.

These sulphated exopolysaccharides can be obtained from bacterial strains of cyanobacterial or Alteromonas type. Such exopolysaccharides are for example described in the thesis of Olivier Roger: Study of bioactive oligosaccharides from bacterial exopolysaccharides: obtaining, characterization and structure / function relationship (Université Paris 13) published on 29.11.2002. (Http://archimer.ifremer.fr/doc/2002/these-622.pdf). The sulphated exopolysaccharides used according to the invention contain sulphated inorganic substituents, as for example described on page 18 of the thesis cited above.

As examples of sulphated exopolysaccharides with a rhamnose motif, mention may be made of spirulans. Spirulanes are polysaccharide extracts obtained from Spirulina which is both a microalga and a cyanobacterium (formerly known as "blue algae" then cyanophyceae). Spirulina is a unicellular blue planktonic algae also known as Arthrospira platensis. Spirulina is composed of vegetable proteins (55% to 70% of its weight) and polysaccharides (about 20% of its weight), including specific sulphated polysaccharides called spirulans. Spirulans are mainly composed of rhamnose, ribose, mannose, fructose, galactose, xylose, glucose, glucuronic acid and galacturonic acid and also include sulphate groups. Methyl sugars may also be present such as 3-O-methylrhamnose (acofriose), 2,3-di-O-methylrhamnose, 3-O-methylxylose. These spirulan extracts can be obtained from various species of spirulina among which Arthrospira spirulina or Spirulina platensis and Spirulina maxima can be mentioned. As particular examples of spirulans, one can be used having the following characteristics: Spirulane (extracted from the alga Spirulina sp, evaluated in Examples 1 and 2): MS (% MB) = 100% MO (% MS) = 89.2% MM (% DM) = 10.8% Na (% DM) = 2.90% Proteins (N x 6.25) (% DM) = 51.31% Rhamnose = 6.60% Glucose = 3 , 30% Galactose = 3.00% Xylose = 1.30% Glucuronic acid = 1.40% Sulphate content = 2.20% Mw (eq pullulan g / mol) HP-SEC = 263280 Da.

The sulphated polysaccharides with a rhamnose pattern may be present in the cosmetic compositions in contents ranging from 0.01% to 20%, preferably from 0.01% to 15%, and still more preferably from 0.1% to 10% by weight. relative to the total weight of the cosmetic composition.

The compositions used according to the invention contain a physiologically acceptable medium, that is to say, compatible with cutaneous tissues such as the skin and the scalp. This physiologically acceptable medium may more particularly consist of water and optionally of a physiologically acceptable organic solvent chosen, for example, from lower alcohols containing from 1 to 8 carbon atoms and in particular from 1 to 6 carbon atoms, such as ethanol, isopropanol, propanol, butanol; polyethylene glycols having from 6 to 80 ethylene oxide units and polyols such as propylene glycol, isoprene glycol, butylene glycol, glycerine and sorbitol.

The compositions according to the invention may be in any of the galenic forms conventionally used for topical application and especially in the form of aqueous, hydroalcoholic solutions, oil-in-water (O / W) or water-in-oil emulsions ( E / H) or multiple (triple: W / H / E or H / E / H), aqueous gels, or dispersions of a fatty phase in an aqueous phase using spherules, these spherules being polymeric nanoparticles such as nanospheres and nanocapsules or lipid vesicles of ionic and / or nonionic type (liposomes, niosomes, oleosomes). These compositions are prepared according to the usual methods. In addition, the compositions used according to the invention may be more or less fluid and have the appearance of a white or colored cream, an ointment, a milk, a lotion, a serum, a paste or foam. They may optionally be applied to the skin in the form of an aerosol. They may also be in solid form, for example in the form of a stick.

The composition used according to the invention comprises adjuvants usually used in the cosmetics field, and especially chosen from water; the oils ; waxes, pigments, fillers, dyes, surfactants, emulsifiers; cosmetic actives, UV filters, polymers, thickeners, film-forming polymers, preservatives, perfumes, bactericides, odor absorbers, antioxidants.

The amounts of these various adjuvants are those conventionally used in the field in question, and for example from 0.01 to 20% of the total weight of the composition. The following examples illustrate the invention without limiting its scope.

EXAMPLE 1 Evaluation of the Hydration Potential In vivo, it has been demonstrated that a lack of hydration of the skin and a defect in the skin barrier function are correlated with an increase in the rate of immature corneal envelopes. . A reconstructed skin in vitro assay was conducted to determine the influence of several rhamnose sulfated polysaccharides on the immature corneal envelope rate. Episkin® reconstructed epidermis was used to evaluate the moisturizing activity of several rhamnose sulfated polysaccharides.

Episkin J7 were cultured with rhamnose sulfated polysaccharides evaluated for 7 days. After isolating the stratum, the horny envelopes were extracted. Three types of horny, mature, intermediate and immature envelopes are identified and counted by specifically developed image analysis software. Treatments: The Episkin® kits were received at 7 days (J7) of culture. The transport agar is changed in favor of the differentiation medium. Each sample was treated with 30 μl of water or sulfated polysaccharide to be evaluated in solution in water. The kits thus treated were cultured in a humid oven at 37 ° C. under CO2. This procedure (change of culture medium and treatment) was applied on D7, D9, D10 and D13.

At day 14, the samples were punched (cutting discs - punch - diameter 4 mm). The punches were reserved for histological sections (Haematoxylin Eosin Saffron staining). The remaining epidermis was recovered and the stratum corneum was isolated by trypsic digestion (contacting for 1 hour at room temperature - AT = 25 ° C - solution of bovine trypsin of pancreas at 10% (marketed by Sigma-Aldrich under the reference Trypsin from bovine pancreas (ref: T9201) - powder,> 7,500 BAEE units / mg solid) in Tris-HCl buffer at pH 8). The stratum corneum was rinsed in 3 successive baths of ultrapure water. Then they were dried for 24 hours in a drying box (in the presence of silica gel pellets Chameleon® C 1-3 mm sold by the company WWR desiccant). The stratum corneum was then punched (punch diameter 4mm) for the preparation of corneal envelopes (EC). A cell viability test (MTT) is performed.

Extraction of the horny envelopes: The punches were placed in 2 ml microtubes and immersed in 1.5 ml of denaturation buffer (100 mM Tris-HCl pH 8.5, 20mM Dithiothreitol, 2% sodium lauryl sulfate, 5mM1 EDTA). The samples were heated to 100 ° C in a dry bath for 10 minutes without shaking. They were centrifuged (3000 rpm, 10 min, 20 ° C). The pellets have been recovered. The denaturation phase was applied 3 times. The final pellets were taken up in 0.5 ml of PBS (Phosphate Buffered Saline) buffer without Ca 2+ and Mg 2+ and vortexed.

The cell suspensions were deposited on functionalized slides (SuperFrost Gold Plus at 100 μl in a 15 × 16 mm well (GeneFrame), dried at room temperature and protected from dust for 24 hours) The slides were fixed with methanol at -20 ° C for 10 minutes, then dried in a hood.

Quantification of the different types of corneal envelopes (mature, intermediate and immature): Immunolabelling and lipid counterstaining: Protocol: The immunolabeled slides were viewed under a microscope (Leica DM6000B) according to 2 observation modes: phase contrast and fluorescence . The phase contrast provides a gray level image allowing us to visualize all the cells present in the field. The fluorescence mode (filter cube set) was used to visualize the fluorochromes attached to the sample: Nile Red is a fluorescent probe for locating the hydrophobic zones, more particularly the lipids. It is highlighted by the N2.1 filter. This marker highlights mature cells. - Alexa Fluor® 488 is a fluorochrome with no specific specificity. It is coupled to a secondary antibody. This specifically recognizes the primary antibody, specific for involucrine. The visualization was carried out thanks to the L5 filter. This marker highlights immature cells. Filtercube Correlation Fluoro- Excitation Excitation Dichromatic Supression Filter chrome / filtercube Range Filter Mirror N2.1 Nile Red Green BP 560515-580 LP 590 L5 Alexa Fluor 488 Blue BP 480/40 505 BP 527/30 - Hydration of slides in DPBS (Dulbecco's PBS ) 10 min at RT Saturation in DPBS / BSA (Bovine Serum Albumin) at 5% 20 min at RT Saturation in DPBS / BSA at 0.2% 10 min at RT - Deposition of 100 μl of primary antibody ([Monoclonal anti- involucrine Clone SY5] at 1 / 100th) 1h in the dark in humid medium with light agitation o Rinses X3 in DPBS (3 times 5 min) with stirring Deposition of 100p1 anti-secondary body ([Alexa Fluor® 488 goat anti-mouse IgG (H + L) 2 mg / ml - A11001 Invitrogen] 1 / 100th) 1 hour in the dark in a humid medium with gentle stirring 3 rinses in DPBS (3 times 5 min) with stirring Nile Red staining in an aqueous solution at 75% glycerol for 10min at RT o 3 Rinsing with DPBS (3 times 5 min) with stirring o Rinse Acetone Fast Fitting Citifluor AF1 The various types of horny envelopes (Nile Red labeled, highlighted by the Alexa Fluor® 488) are counted on the images acquired under a microscope with the help of Image analysis (Image J) using a counting macro. The number of mature cells and the number of immature cells are then known for each sample, compared to the controls on which only the solvent has been applied. Percentage increase of mature horny envelopes with respect to water control was determined.

The following results were obtained: Sulphated polysaccharide tested Content tested (as% Change in maturation weight) of the horny envelopes (% relative to the water control) Ulvane UR 3 + 12 Spirulane 3 + 66 These results show that the 2 sulphated polysaccharides studied induced a large increase in the rate of mature envelopes after treatment. This very significant increase in the maturation of the horny envelope has a favorable impact on the barrier function of the stratum corneum, its hydration and its resistance to drying and changes in external humidity. Example 2 Evaluation of the mechanical relaxation of the stratum corneum and ease of application A DMA (Dynamic Mechanical Analysis) apparatus sold under the reference ElectroForce® 3100 was used by the company Bose.

This technique makes it possible to study the viscoelastic properties of the stratum corneum. The material is sinusoidally stressed and its deformation is measured. We can then determine the conservation modulus (E ') of the stratum corneum, which characterizes it mechanically. This size is directly related to the elastic properties of the stratum corneum. The impact of several sulfated polysaccharides on this storage module has been studied. Sample Preparation and Protocol: The surface area of the Stratum Corneum sample to be tested is 2 cm2 (1 cm X 2 cm). The samples were preconditioned at 75% relative humidity for a minimum of 12 hours, and the measurement was also carried out at 75% relative humidity. Solutions of 1% sulfated polysaccharide (dry extract) in water were prepared. 10 μl / cm 2 of test solution was applied to the stratum sample. The solution was spread on the stratum corneum so as to cover the entire surface.

The dynamic amplitude of stress was set at 40 μm, which corresponds to a deformation in the elastic domain of Stratum Corneum (0.2% deformation). Each sample was solicited at the frequency of 1 Hz, according to the greatest length. Stratum corneum from the same donor was always used.

Carrageenan (sulfated polysaccharide without rhamnose motif) sold under the name Satiagum UTC 10 by Cargill was also evaluated for comparison. For each evaluated sulphated polysaccharide, the variation of the elastic modulus measured with each treated sample was calculated during the first two hours of treatment (E2h) relative to that of the same untreated sample at t = 0 (E0). AE = E2h / E0 The following results were obtained: Polysaccharide tested AE Ulvane UR 1,2 Spirulane 1,4 Carrageenan 2.7 The results obtained show that the application of sulphated polysaccharides with rhamnose pattern of the Ulvane type, Spirulane on the human stratum corneum causes a small increase in elastic modulus (varaiation less than 1.5), or even zero during the first two hours of drying, unlike other types of sulphated carrageenan or porphyridium polysaccharides. The sulfated polysaccharides with rhamnose patterns thus lead after application to the skin to a comfort effect (no tugging) significantly higher during the first minutes and hours of application, that of carrageenan. EXAMPLE 3 Evaluation of the Persistence of Hydration and the Remanence of the Barrier Function The evolution of the hardness of mature and immature corneocytes was measured as a function of different ambient humidity levels. Varnish strippings were made in extreme and deep areas on skin qualified normal type by a dermatologist. Extracellular samples allow a supply of mature corneocytes (rigid envelope). Depth sampling (ie at the junction with the epidermis) allows a mature supply of corneocytes (with a fragile envelope). Isolated corneocytes were removed from these strippings. The corneocytes are obtained after direct stirring of the stripping and centrifugation in Tris-HCl and Triton X 100 buffer.

The state of maturation of these rigid and fragile envelope corneocytes was characterized by the same types of labeling as those described in Example 1. It was thus validated that there was a population of corneocytes with an envelope. mature and immature envelope corneocyte population. The tests were carried out on these two types of corneocyte population.

The nanoindentation technique was used by using the MTS Nanoindentor XP apparatus. The measurements were carried out in a chamber thermostatically controlled at 30 ° C. and with controlled hygrometry at different humidity (relative humidity) levels of 20%, 50% and 20% respectively. 70%. At 30 ° C.

By applying a normal force on the surface of the corneocyte, using a coil / magnet system and by measuring the displacement of a non-deformable diamond punch using a capacitive sensor, the technique of instrumented nanoduracy makes it possible to determine the mechanical quantities such as the hardness of the corneocyte tested at a given depth. The nano-indentation tests were performed at an imposed strain rate (P '/ P = 3.10-2 5-1, P is the applied load and P' is the derivative of this load) and at a maximum load of 1 mN. The amplitude of the sinusoidal component of the signal is 7 nm and the working frequency is 32 Hz. An indent was made on each corneocyte.

The analysis of the results is based on the quantitative values of the mechanical quantities of hardness, between 10 nm and the maximum depression, ie between 50 nm and 100 nm. Thus, the evolution of the hardness as a function of the plastic penetration in the material has been demonstrated as a function of the hygrometry rate.

The following results were obtained: Hardness Hv (MPa) Hygrometry HR Hygrometry HR Hygrometry HR 20% 50% 70% Cornecocyte maize 158 135 99 ture Cornecocyte im-155 It was thus found that the hardness of immature corneocytes decreased considerably. strongly when the hygrometry rate increases (74.8% decrease between hardness at 20% RH and 70% RH). While the hardness of mature corneocytes decreases much less (37.3% decrease between hardness at 20% RH and 70% RH). This important modification of the hardness of the immature corneocytes is due to a greater sensitivity to water of these immature corneocytes. On the other hand, mature corneocytes are much less sensitive to water and more resistant to variations in hygrometry: the hydrophobic and strongly organized bound lipidic envelope plays an osmo-protective role. This maintenance of the hardness of the mature corneocytes with respect to the extreme conditions of hygrometry (great dryness) is the guarantee of a maintenance of the physical properties of the skin under conditions of extreme drought or extreme humidity or strong variations of external conditions (air conditioning, etc ...). The water contained in the cell is therefore maintained when the corneocyte is mature. Sulphated polysaccharides promote the maturation of the corneocyte. The mature corneocyte has mechanical properties that are maintained at different hygrometries, unlike the immature corneocyte.

In conclusion, the sulphated polysaccharides previously tested therefore have a beneficial effect on the remanence of the cell's barrier function and therefore on the stratum corneum, and on the persistence of the hydration of the cell and therefore of the stratum corneum. EXAMPLE 4 Moisturizing Gel of the Skin A moisturizing skin care composition comprising the following ingredients is prepared. Crosslinked Acrylic Acid (CARBOPOL 941) 0.3% - Ulvarane UR 0.5% - Preservatives qs - Water qs 100, 0% The gel applied to the skin gives the skin a good moisturizing effect without tugging.

Claims (10)

REVENDICATIONS1. A non-therapeutic cosmetic method for improving the barrier function of the skin and / or for moisturizing the skin comprising applying to the skin a composition comprising, in a physiologically acceptable medium, a sulfated polysaccharide comprising from 2% to 60% by weight, based on the total weight of the polymer, of a rhamnose unit. 2. Method according to the preceding claim, characterized in that the sulfated polysaccharide comprises from 5 to 40% by weight, based on the total weight of the polymer, rhamnose pattern. 3. Method according to the preceding claim, characterized in that the sulfated polysaccharide comprises a polysaccharide sulfation rate ranging from 1% to 30% by weight, relative to the weight of the polysaccharide. 4. Process according to any one of the preceding claims, characterized in that the sulphated polysaccharide is chosen from ulvans and the sulphated exopolysaccharides with a rhamnose pattern. 5. Method according to any one of the preceding claims, characterized in that the sulphated polysaccharide is chosen from ulvans. 6. Process according to any one of the preceding claims, characterized in that the sulphated polysaccharide is chosen from spirulans. 7. Process according to any one of the preceding claims, characterized in that the sulphated polysaccharide is chosen from sulphated exopolysaccharides containing a rhamnose motif consisting of glucose, galactose, rhamnose, and optionally glucuronic acid and galacturonic acid. . 8. Process according to any one of the preceding claims, characterized in that the sulphated polysaccharide is present in the composition in a content ranging from 0.01% to 20% by weight, relative to the total weight of the composition. 9. Method according to any one of the preceding claims, characterized in that the composition comprises a cosmetic adjuvant selected from water, oils, waxes, pigments, fillers, dyes, surfactants, emulsifiers; cosmetic active agents, UV filters, polymers, thickeners, film-forming polymers, preservatives, perfumes, bactericides, odor absorbers, antioxidants. 10. Cosmetic use of a sulfated polysaccharide rhamnose according to any one of claims 1 to 7 as a moisturizing agent of the skin.