Effects of tretinoin on photodamaged skin. A histologic study

The histologic effects of topical tretinoin therapy on photodamaged facial skin were investigated in two 24-week, double-blind, randomized, vehicle-controlled studies involving 533 subjects at eight US centers. Three concentrations of tretinoin (0.05%, 0.01%, and 0.001%) in a new emollient cream were studied. Pretherapy and posttherapy biopsy specimens from the periorbital (crow's foot) area were examined by conventional light microscopy and computerized image analysis. Four significant dose-dependent differences from vehicle were found in the tretinoin groups: increased epidermal thickness, increased granular layer thickness, decreased melanin content, and stratum corneum compaction. There was no significant difference between 0.001% tretinoin and the vehicle, and no obvious dermal changes were detected in any group. The four epidermal changes in tretinoin-treated skin establish the biologic activity of the new emollient cream formulation and may partially account for the clinical improvements in photodamage observed in the same group of subjects.     

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.     

Concurrent application of tretinoin (retinoic acid) partially protects against corticosteroid-induced epidermal atrophy

Summary Cutaneous atrophy arising from prolonged use of potent topical corticosteroids has long been a concern. Thus, it would be advantageous to find an agent which protects against atrophy produced by corticosteroids but at the same time does not impair their anti-inflammatory effects. Recent work shows that topical all- trans retinoic acid (tretinoin) prevents skin atrophy in mice treated with topical corticosteroids, but such studies have not been performed in humans. We performed an 8-week clinical, histological and biochemical study to test the ability of tretinoin to enhance efficacy and inhibit atrophogenicity of topical corticosteroids, when used in the treatment of psoriasis. In each of 20 psoriasis patients, one plaque, and its perilesional skin, was treated once daily with betamethasone dipropionate and tretinoin 0·1%, and one plaque, and its perilesional skin, treated with once daily betamethasone dipropionate and tretinoin vehicle. There was no difference in the speed or degree of improvement in plaques treated with either the topical corticosteroid/tretinoin combination or with corticosteroid alone. Light microscopy revealed a 19% reduction in epidermal thickness, in corticosteroid-treated perilesional skin, as compared with a slight (1%) increase in corticosteroid/ tretinoin-treated perilesional areas (P= 0.067). Western blot analysis showed a 55% reduction in procollagen I aminopropeptide in perilesional skin treated with corticosteroid alone, as compared with a 45% reduction in corticosteroid/tretinoin-treated perilesional skin. These data indicate that the addition of tretinoin does not impair the efficacy of a topical corticosteroid, in the treatment of psoriasis, and partially ameliorates epidermal atrophy produced by the topical corticosteroid.     

Studies on the effect of salicylic acid on normal skin

This investigation was prompted by our ignorance of the way in which salicyhc acid aids desquamation. Salicylic acid in aqueous cream or white soft paraffin and in concentrations of 2–12%, was applied to normal skin of twenty-three subjects while the vehicle alone was apphed to the contralateral sites. Biopsies and skin surface biopsies were taken from the test and control sites after 1 week. Histological examination showed that there was less horny layer on the test specimens but that there were no qualitative or quantitative differences in the structure of the viable epidermis. Portions of the biopsies were incubated in the presence of tritiated precursor compounds and subsequent autoradiographic examination showed no difference in the incorporation of thymidine, cytidinc or histidine between test and control preparations. Scanning electron microscopy of skin surface biopsies showed some changes in all specimens—presumably due to hydration—but also showed strking differences between test and control sites and were especially marked with higher concentrations of salicylic acid. It is suggested that salicylic acid causes desquamation by dissolution of intercellular cement material.     

Topical tretinoin (retinoic acid) improves melasma. A vehicle-controlled, clinical trial

Melasma is a common disorder of cutaneous hyperpigmentation predominantly affecting the faces of women. Little is known about the aetiology of melasma, and treatment is frequently disappointing. Topical tretinoin is of benefit in treating other forms of hyperpigmentation, for example liver spots, and we therefore investigated its effectiveness in melasma. Thirty-eight women completed a randomized, vehicle-controlled study, in which they applied 0.1 % tretinoin (n=19) or vehicle cream (n=19) once daily to the face for 40 weeks. At the end of treatment 13 (68%) of 19 tretinoin-treated patients were clinically rated as improved or much improved, compared with 1 (5%) of 19 in the vehicle group (P=0.0006). Significant improvement first occurred after 24 weeks of tretinoin treatment. Colorimetry (an objective measure of skin colour) demonstrated a 0.9 unit lightening of tretinoin-treated melasma and a 0.3 unit darkening with vehicle (P=0.01); these results correlated with clinical lightening (r=0.55, P=0.0005). Histologically, epidermal pigment was reduced 36% following tretinoin treatment, compared with a 50% increase with vehicle (P=0.002). Reduction in epidermal pigment also correlated with clinical lightening (r=0.41, P=0.01). Moderate cutaneous side-effects of erythema and desquamation occurred in 88% of tretinoin-treated and 29% of vehicle-treated patients. Topical 0.1% tretinoin produces significant clinical improvement of melasma, mainly due to reduction in epidermal pigment, but improvement is slow.     

Topical retinoic acid for treatment of solar damage

Twenty patients with chronic solar damage of the skin were entered in a double-blind, within-patient trial to compare the effect of 0.05% tretinoin cream with a placebo applied once daily for 12 weeks. Sixteen completed the study. Clinical assessment of the individual signs of solar damage were recorded on separate visual analogue scales. After 12 weeks, there were significant improvements in fine wrinkling around the eyes, crease lines around the mouth and cheeks, wrinkling on the dorsum of the hands and yellow discoloration. Overall, 14 of the tretinoin-treated sides were judged to have improved compared to only two of the placebo-treated sides (P = 0.011). Measurement of skin thickness by pulsed A-scan ultrasound revealed that the sides treated with tretinoin were significantly thicker than the placebo-treated sides (P = 0.019). Skin biopsies taken before and after treatment showed an increase in mean epidermal thickness with tretinoin treatment (P = 0.019). The clinical signs of improvement persisted at the follow-up assessment performed 4 weeks after cessation of therapy.     

Cell cycle analysis by flow cytometry of non-exposed, sun-exposed, and tretinoin-treated skin

The percentage of keratinocytes in the proliferative phase of the cell cycle (S + G2 + M) was measured by DNA flow cytometry in sun-exposed, non-exposed, and tretinoin-treated skin. Before tretinoin treatment, the percentage of keratinocytes actively cycling was higher in sun-exposed than in non-sun-exposed skin (p = .002) and was correlated with clinically assessed photodamage (p = .007). Subsequently, tretinoin-treated sun-exposed skin was compared to the pre-treatment sun-exposed skin. Overall, there was no statistically significant change. However, there was a trend toward a decrease in the percentage of keratinocytes in the S + G2 + M phases immediately after four months of tretinoin use that was limited to the most severely damaged patients. This effect was no longer evident two months after discontinuing treatment. This is the first study, to our knowledge, utilizing flow cytometry to investigate the effects of tretinoin in patients with varying degrees of photodamage.     

HISTOLOGICAL EVALUATION OF THE EFFECT OF 0.05% TRETINOIN IN THE TREATMENT OF PHOTO DAMAGED SKIN

In a randomised double-blind vehicle controlled trial of 0.05% tretinoin cream in the treatment of photodamaged skin, the histological results of paired biopsies from 28 individuals who applied tretinoin for 26 weeks are compared with 28 paired biopsies from a control group applying vehicle alone. There was a significant increase in epidermal thickness in the tretinoin-treated group (P.001). Epidermal atrophy was reversed in ten patients applying tretinoin cream. Baseline biopsies obtained from participants in Melbourne, Victoria (38° latitude) showed significantly less elastosis than those in Sydney (34° latitude) and Newcastle in N.S.W., although the two groups did not show significant differences in age or sex, and the differences could not be correlated with skin type. Tretinoin cream had no effect on the degree of solar elastosis after 26 weeks application. Tretinoin cream appears effective in reversing epidermal atrophy and clinically diminishes fine wrinkling, mottled hyperpigmentation and skin roughness. Tretinoin cream may not offer a solution to the gross solar damage seen in the Australian population who have marked solar elastosis as a principal, clinical and histologie finding. However it is possible that dermal repair and reversal of solar elastosis may require topical application of tretinoin cream for a longer period than the six months used in this trial.     

Pretreatment of photoaged forearm skin with topical tretinoin accelerates healing of full-thickness wounds

Pretreatment of skin with all-trans retinoic acid (tretinoin) has been shown to enhance wound healing. Previous studies have mainly used animal models to demonstrate this effect. We wanted to determine whether pretreatment could promote wound healing in severely photoaged dorsal forearm skin. Four elderly men with severely actinically damaged forearms were treated daily for 16 weeks. One arm was treated with 0.05-0.1% tretinoin cream (Retin A®, Ortho), and the other with Purpose® cream (Ortho) as a vehicle control. Four-millimetre punch biopsies were taken from both dorsal forearms prior to treatment. After 16 weeks, full-thickness 2-mm punch biopsies were taken from both sides. Serial photographs were taken, and healing of the wounds quantitatively assessed by image analysis. On the 11th day, the wounds were excised using a 4-mm biopsy punch. Biopsies were processed for light microscopy. After 16 weeks, the tretinoin-treated Forearms showed moderate erythema and scaling. Polarized tight photographs revealed multiple, red, vascularized foci and/or a diffuse network of small vessels. The histological effects were typical for tretinoin, i.e. compaction of the stratum corneum, epidermal acanthosis with correction of atypia, an increase in small vessels, and increased cellularity in the upper dermis. Purpose® cream had no effect, either clinically or historically. On the tretinoin-treated side, the wound areas were 35-37% smaller on days 1 and 4, and 47-50% smaller on days 6, 8, 11, compared with the controls. Clinically and histologically. reepithelialization occurred more rapidly. Thus tretinoin dramatically accelerated wound healing in photodamaged skin.     

Topical tretinoin for treatment of photodamaged skin. A multicenter study

The clinical and histologic effects of a new emollient cream formulation of topical tretinoin at concentrations of 0.05% and 0.01% were examined in 251 subjects with mild to moderate photodamaged facial skin in a randomized, double-blind, vehicle-controlled, multicenter study. Seventy-nine percent of the subjects who received 0.05% tretinoin for 24 weeks showed overall improvement in photodamaged skin compared with improvement in 48% of the vehicle-treated control subjects. Significant reductions were found in fine wrinkling, mottled hyperpigmentation, roughness, and laxity after 0.05% tretinoin therapy when compared with controls. In addition, histologic changes of increased epidermal thickness, decreased melanin content, and stratum corneum compaction provide independent evidence supporting clinical improvement. Side effects of erythema, peeling, and stinging were usually mild and well tolerated.     

Ultrastructural effects of topical tretinoin on dermo-epidermal junction and papillary dermis in photodamaged skin. A controlled study

Abstract We examined the effects of daily topical application of 0.05% tretinoin cream on photodamaged Caucasian facial skin by electron microscopy. Specimens obtained pretreatment, after 6 and 12 months of tretinoin therapy (20 patients), and after 6 months of vehicle treatment (5 patients) were compared in a blinded fashion, with special attention to the dermoepidermal junction and papillary dermis. Baseline specimens disclosed various degrees of damage including reduplication of basal lamina, smudging and sparsity of collagen fibers, and nodular arrangement of degenerated microfibrils in the papillary dermis. No significant changes were observed at 6 months in the papillary dermis of either tretinoin-treated or vehicle-treated patients. After 12 months of tretinoin treatment, however, disorganized collagen fibers, which were conspicuous in 11 patients at baseline, were replaced by new well-organized collagen fibers in a wavy pattern in 6 patients. In addition, the amount of nodularly degenerated microfibrillar material decreased in 15 of 18 patients with this finding at baseline. In contrast, no significant change was noted in the number of anchoring fibrils per unit length of the lamina densa. These observations provide further evidence that topical treatment with 0.05% tretinoin produces papillary dermal reconstruction, for which more than 6 months of application were required.     

Lifetime topical application of tretinoin to hairless mice.

The discovery that topical tretinoin can reverse some of the effects of photodamage may lead to its chronic application. Examination of long-term effects was of interest. Three groups of hairless mice (age 6-8 weeks) were treated dorsally with 1) tretinoin (0.025%), 2) cream vehicle, 3) sham treatment. Applications were 3 times weekly and continued for up to 2 years until all mice were sacrificed or had died. Biweekly examinations showed no sign of retinoid toxicity, with growth and longevity similar in all groups. Tretinoin-treated skin was smooth and pink, resembling that of younger mice. Controls had yellowed, irregularly thickened skin. Histologically, tretinoin-treated skin had a hyperplastic epidermis consisting of plump, cytologically normal cells. Control skin had 3-4 compressed cell layers. Foci of new normally staining collagen were present in the subepidermal dermis of tretinoin-treated skin; fibroblasts were large and abundant in these areas. These foci were absent in controls. Mice treated with tretinoin also appeared to have increased amounts of elastic fibers and glycosaminoglycans.     

Effect of zinc pyrithione on mitotic activity in normal human skin

Summary Two concentrations (0.02% and 0.002%) of zinc pyrithione (ZPT) in water and a water control were applied to normal forearms—both on normal skin (six subjects) and also where the skin had been stripped to the glistening layer (six subjects) with adhesive tape. Measurements of labelling index (LI), mean epidermal thickness (MET), mean stratumcorneum thickness (MSCT), total epidermal thickness (TET) and basal/granular cell ratio (B/G) showed no significant differences between the three treatments on normal skin or the parameters studied in stripped skin. It is concluded that ZPT has no effect on epidermal renewal in normal skin in vivo.     

The new topical ascomycin derivative SDZ ASM 981 does not induce skin atrophy when applied to normal skin for 4 weeks: a randomized, double-blind controlled study

BACKGROUND: SDZ ASM 981 is a selective inhibitor of inflammatory cytokines released from T lymphocytes and mast cells, which has been developed for the treatment of inflammatory skin diseases. OBJECTIVES: In the present study, the atrophogenic potential of SDZ ASM 981 1% cream in humans was compared with that of medium and highly potent topical steroids, and vehicle. METHODS: Four different preparations, SDZ ASM 981 1% cream, the corresponding vehicle of SDZ ASM 981 1% cream, betamethasone-17-valerate 0.1% cream and triamcinolone acetonide 0.1% cream, were applied to the volar aspect of the forearms of 16 healthy volunteers, twice daily, 6 days a week, for 4 weeks. Skin thickness was evaluated by ultrasound examination, clinical signs of atrophy by stereomicroscopy, and epidermal thickness was assessed by histology. RESULTS: Both topical corticosteroids induced a significant reduction in skin thickness, as compared with SDZ ASM 981 1% cream and vehicle, which were shown to be equivalent. The difference in skin thickness (measured by ultrasound examination) between patients treated with SDZ ASM 981 1% cream and those receiving either of the two topical steroids was significant from day 8 onwards. Histological analysis performed at day 29 showed significant epidermal thinning with topical steroids compared with SDZ ASM 981 1% cream or the vehicle. Conclusion The lack of atrophogenic properties of SDZ ASM 981 1% cream in this short-term study demonstrates its potential as long-term treatment for inflammatory skin diseases, thus overcoming a major drawback of topical steroids. This may also be important for the treatment of children, and sensitive areas of skin, such as the face and skin-folds.     

Changes in photo-aged human skin following topical application of all-trans retinoic acid.

Although topical applications of retinoids on rodents and humans have been shown to cause epidermal hyperplasia, a detailed study of the influence of retinoids on epidermal differentiation in vivo has not been performed. In order to assess the pharmacologic effects of chronic topical tretinoin application used to improve the appearance of patients with photoaged skin, cutaneous biopsies from 25 patients in a controlled clinical study were examined histologically and immunocytochemically. Chronic application of tretinoin causes epidermal thickening (25 of 25 samples), stratum granulosum thickening (15 of 25), parakeratosis (13 of 25), a marked increase in the number of cell layers expressing epidermal transglutaminase (13 of 25), and focal expression of two keratins, K6 (12 of 25) and K13 (8 of 25), not normally expressed in the epidermis. The morphologic changes correlated with immunohistochemical abnormalities; neither of these correlated with the subjective cosmetic response. Three major epidermal differentiation products, keratins K1, K10, and K14 were not altered, within the limits of the methods used. Thus, chronic topical tretinoin reprograms some, but not all, aspects of human epidermal differentiation in vivo.     

Site variation in anthralin inflammation on forearm skin

The effect of application site on anthralin inflammation was measured at 10 clinically normal volar skin sites on each forearm of 31 subjects as the increase in skin thickness at 48 h using Harpenden calipers. Pre-treatment and increase in skin thickness were significantly related to application site. Pre-treatment thickness increased distally and laterally by an amount depending on sex, and to a lesser extent other factors, whilst the increase in skin thickness values was greater proximally, laterally and on the right arm but was not affected by age, sex or skin type. When increases in skin thickness values were adjusted for pre-treatment thickness, the difference between proximal and distal sites was lost but there was still a significant difference between the medial and lateral aspect and the right and left arms. The absolute differences were small but demonstrate the need to use symmetrical forearm skin sites and randomized treatment sides when comparing the effects of topical agents on anthralin inflammation.     

A double-blinded, randomized, vehicle-controlled, multicenter, parallel-group study to assess the safety and efficacy of tretinoin gel microsphere 0.04% in the treatment of acne vulgaris in adults

This double-blinded, randomized, vehicle-controlled, multicenter, parallel-group, 12-week, phase 4 study was conducted in adults with mild to moderate acne vulgaris. Of 178 subjects randomized to be treated, 88 subjects (49%) were treated with tretinoin gel microsphere 0.04% and 90 subjects (51%) were treated with vehicle. Inflammatory lesion counts were statistically significantly reduced at 2 weeks in tretinoin-treated subjects (P = .0110), and reductions in total lesion counts also were noted. The reduction in total lesion counts reached statistical significance at week 4 (P = .0305); at week 12, mean total, inflammatory, and noninflammatory lesion counts were statistically significantly lower in the tretinoin treatment group versus vehicle group (P < .05), and mean percentage reductions in lesion counts were significantly greater in the subjects with noninflammatory lesions treated with tretinoin compared with vehicle (P < .05). Mean percentage reductions in total, inflammatory, and noninflammatory lesion counts were 35.5%, 38.2%, and 33.6%, respectively, at week 12 for the tretinoin treatment group compared with 20.9%, 19.2%, and 20.4%, respectively, for the vehicle group (all P < .05). All adverse events were of mild or moderate intensity with the exception of severe skin irritation in one tretinoin-treated subject. At week 12, there were no statistically significant differences between treatment groups for any measured tolerability parameter.     

Actinic keratoses and the epidermis on which they arise

The appearance of the epidermis and epidermal autoradiographic labelling indices were compared in actinic keratoses and paralcsional skin in seventeen patients after injection of tritiated thymidine. The skin of the buttock area was also studied as a ‘non-sun exposed’ control. Labelling indices obtained from skin removed after i h were as follows: actinic keratoses 17.4%; paralesional skin 11.2%; buttock skin 5.4%. Many of the epidermal cells in the keratoses that incorporated tritiated thymidine were bizarre and not restricted to the basal or suprabasal regions but were scattered through the thickness of the epidermis. Paralesional skin also showed epidermal thickening and cytological abnormalities including the formation of multinucleate epidermal cells. These findings suggest that the development of actinic keratoses takes place in epidermis that is itself abnormal. The changes suggest that there is a gradual stepwise progression of sun damaged epidermis via the clinically obvious keratosis to squamous cell epithelioma.     

Topical tretinoin increases dermal mast cells,induces epidermal mast cell growth factor (c-kit ligand) and modulates its distribution in hairless mice

In previous studies we have noted that mast cells are increased in tretinoin-treated photoaged hairless mouse skin. Because UV radiation is known to increase mast cell numbers, we were interested in whether tretinoin alone would modulate the mast cell population in unirradiated mice. Animals were treated topically with 0.05% tretinoin, 5 days a week, for 2, 4, 6, 8 and 10 weeks. Untreated and vehicle controls were included. Biopsies were processed for light microscopy and stained with toluidine blue. Mast cells in the upper and lower dermis were scored separately under high magnification. After 2 weeks of tretinoin, mast cells in the upper dermis were significantly increased, as indicated by the appearance of small, moderately metachromatically granulated cells near the dermal-epidermal junction. Mast cells in the lower dermis, the site of a granulomatous reaction, were large, densely granular and significantly increased after 6 weeks of treatment. Immunohistochemical evaluation for mast cell growth factor (MGF) revealed a marked increase in keratinocyte cytoplasmic staining by week 2. After 4–6 weeks, membrane-associated or intercellular staining was evident. Cells in the upper dermis also showed membrane reactivity for MGF. By 8–10 weeks, epidermal MGF reactivity had dissipated in the more basal keratinocytes. These findings show that topical tretinoin can induce epidermal MGF along with an associated mast cell hyperplasia. It is suggested that the two populations of dermal mast cells may have different functions.     

EFFECT OF TOPICAL TRETINOIN ON EPIDERMAL LANGERHANS'CELLS IN PHOTODAMAGED SKIN

Background. Topical tretinoin has been successfully applied to treat photoaging; however, a decrease in the number of Langerhans’cells (LC) has been reported after its topical application in Macaque skin. A study was performed to evaluate the possible effect of topical tretinoin on the number of LC in human beings. Methods. Eight patients were studied. Topical tretinoin was applied in progressively increasing concentrations: 0.025% for 1 month, 0.05% for one month and 0.1% for 4 months. A skin biopsy from the malar area was taken before this therapy and 6 months later. To study LC, 4 p frozen sections were stained with the anti-CD1 antibody. Results. The number of CD1+ cells did not change when they were counted per unit of epidermal length, but they decreased when they were counted per unit of epidermal surface. Conclusions. These results indicate that topical tretinoin might damage epidermal Langerhans’cells, when it is applied for long periods of time; future studies are necessary to clarify this point.