Non-invasive evaluation of topical calcipotriol versus clobetasol in the treatment of psoriasis.

Topical treatment of psoriasis with calcipotriol has been proven effective. The efficacy of calcipotriol has been compared to that of topical corticoids in a number of studies using subjective visual scoring systems such as the PASI index. The purpose of this study was to compare, with objective data, the efficacy of calcipotriol and clobetasol propionate 0.05% in the treatment of plaque type psoriasis. Transepidermal water loss (TEWL) and laser Doppler velocimetry (LDV) were used to monitor restoration of water barrier and normalization of blood flow, respectively, in psoriatic plaques of the limbs of 24 male patients during 3 weeks of treatment. Data were compared to subjective evaluation using the PASI index of the same areas. Significant differences were recorded during treatment in both groups. The results correlated well with the PASI score. Clobetasol was faster in restoring barrier function than calcipotriol. However, no significant differences were detected between the two groups. The use of vitamin analogues may be effective in the topical treatment of psoriasis by normalizing skin biophysical parameters and minimizing the risks of side-effects induced by potent topical corticoids.

In vivo transcutaneous penetration of nicotinates and sensitive skin.

Proclivity to develop irritant reactions and transcutaneous penetration of nicotinates has been investigated in 20 subjects of both sexes, divided into reactors and nonreactors on the basis of the responses to irritant stimuli. 1% sodium lauryl sulphate (patch application for 24 h) and 5% lactic acid in aqueous solutions were used to detect chemical and sensory (subjective) irritation. The vasodilatation induced was measured using a chromameter for 1 h after topical application of the chemical. The area-under-the-curve response and the peak response was used to assess the in vivo penetration of methyl nicotinate (10 mM in aqueous solution). Significant differences were found between reactors and non-reactors. Non-reactors showed a significantly decreased area-under-the-curve response and peak response to methyl nicotinate compared to reactors. Nicotinate-induced vasodilatation has been used as a model to study transcutaneous penetration of chemicals; the correlation between increased penetration of nicotinates and skin hyperreactivity to irritant substances may suggest an increased transcutaneous penetration of water-soluble chemicals in individuals with sensitive skin.

Skin bioengineering in the noninvasive assessment of cutaneous aging.

Cutaneous changes induced by aging can be quantified and monitored noninvasively by means of bioengineering tools. Skin elasticity, hydration, skin blood flow and skin surface pattern show age-related changes reflecting the damage of cutaneous structures involved. Impairment and degeneration of elastic and collagen networks are responsible for the progressive decrease in skin elasticity recorded during aging. Reduction in blood flow and water supply with probably defective stratum corneum binding result in reduced stratum corneum water content and transepidermal water loss. Morphological changes such as increased skin roughness, pigmentation and alteration of skin surface pattern appearing from the age of 30 years onwards may be investigated at a subclinical level allowing the detection of early signs of aging.

In vivo tretinoin-induced changes in skin mechanical properties.

Topical tretinoin has been reported as having anti-aging effects on photodamaged skin. The purpose of this study was to evaluate tretinoin-induced changes in the mechanical properties of the skin of 18 patients (aged 39 +/- 8 years) after 4 months of treatment with topical 0.05% tretinoin on one forearm and a placebo base cream on the other. The biomechanical skin parameters investigated were elasticity, extensibility and hysteresis and data were normalized for skin thickness. A slight but non-significant increase of skin elasticity was detected in the tretinoin-treated sites using low-stressing forces (1.2 X 10(4) Nm-2) and at higher loads (3.8 X 10(4) Nm-2), the increase in skin elasticity was significant (P less than 0.01). This improved skin elasticity was dependent on the increased collagen resulting from topical tretinoin and the replacement of elastotic material. However, topical tretinoin treatment did not improve the responses mediated by elastic fibres.

Skin extensibility time in women. Changes in relation to sex hormones.

The influence of female sex hormones on mechanical properties of the skin has been assessed in an in vivo extensometric study. Twenty young (20 +/- 4 years) and 12 middle-aged healthy women (42 +/- 3 years) entered the study. Measurements were carried out on the volar surface of the left forearm on the 10th and 25th day of the menstrual cycle. A significantly decreased skin extensibility time in the pre-menstrual phase was found (25th day) when compared with the 10th day in the young group, while the older one did not reveal significant changes. The data are compatible with an increased water content of the skin noticeable in the pre-menstrual phase and more relevant in young women. In studies on mechanical properties of the skin, changes relative to sex hormones and menstrual cycle need to be taken into account.