Topical tretinoin decreases healing times of electroepilation-induced wounds.

There is evidence that topical tretinoin promotes wound healing, especially when the wound area is pretreated. In our study, 5 patients were pretreated for 2 weeks with 0.05% tretinoin cream to one groin or axilla, followed by electroepilation to both sides. Electroepilation created small, superficial wounds. Healing was defined as complete re-epithelialization. In all patients the pretreated side showed a significantly decreased healing time as compared to the nonpretreated side. Pretreatment of skin with topical tretinoin may be useful in reducing healing times of patients undergoing electroepilation.     

The effects of an abrasive agent on normal skin and on photoaged skin in comparison with topical tretinoin

Two studies were designed to assess the effect of abrasive preparations on the skin and to test the specificity of the effect of topical tretinoin in the management of chronic photodamage to the skin. In the first study two abrasive preparations (Brasivol fine and Brasivol medium) were compared with white soft paraffin and no treatment in eight volunteer subjects for their effects on the epidermis. The study was conducted over 3 days and measurements were taken of the effects on dansyl chloride-induced fluorescence to assess desquamation, epidermal thickness, and the tritiated thymidine autoradiographic labelling index. The abrasives were found to increase the desquamation rate significantly and to increase epidermal thickness and the epidermal labelling index compared to white soft paraffin and no treatment. In the second study the effect of one of the abrasive preparations (Brasivol medium) was compared with 0.05% tretinoin cream (Retin A) on the photodamaged skin of the dorsal aspects of the forearms of 12 subjects over an 8-week period. Cutaneous blood flow measured by the laser-Doppler flowmeter was found to be significantly increased in the abrasive-treated sites, but there was only a non-significant trend to increased blood flow in the tretinoin-treated sites. Measurements of skin thickness using pulsed A-scan ultrasound demonstrated that both treatments produced significant increases in thickness over the 8-week period but the increase was greater for the abrasive treated site. Measurements of the skin extensibility at the treated sites were made using a uniaxial extensometer. Forces needed for 30% skin extension were increased in the abrasive-treated sites only. Measurements of epidermal thickness and of [3H]-thymidine autoradiographic labelling indices showed greater increases in the abrasive-treated sites than in tretinoin-treated sites compared to untreated sites, but these increases were not statistically significant. No significant inflammation and no changes in the degree of elastosis or the presence of a 'repair zone' were found in any of the post-treatment biopsies. The results indicate that some of the changes produced in the skin by topical tretinoin that are taken to indicate a specific antiphotoageing effect may not in fact be specific and can be achieved by an abrasive preparation.     

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.     

Topical tretinoin and epithelial wound healing

The effects of topical tretinoin on epithelial wound healing were studied using a porcine model. Eight animals were treated with 0.05% tretinoin cream daily for ten days prior to partial-thickness skin wounding. Daily tretinoin treatment was continued after wounding on two of eight animals. Treatment with topical tretinoin before wounding accelerated epithelial wound healing in partial-thickness wounds. Continued tretinoin treatment on the wounds themselves retarded reepithelialization. Biopsy specimens of wounds with continued tretinoin treatment revealed persistent inflammation and fibroplasia in the dermis. The healing epithelium itself displayed areas of spongiosis and intracytoplasmic pale eosinophilic periodic acid-Schiff-positive, diastase-resistant globules. These globules did not stain with alcian blue. These epidermal alterations may be a direct effect of tretinoin or may be secondary to the underlying inflammation. While the dermal inflammation associated with continued tretinoin treatment appears to retard reepithelialization, epithelial cell alterations may also play a role.     

Optimal Fluence and Duration of Low-Level Laser Therapy for Efficient Wound Healing in Mice

BackgroundLow-level laser (light) therapy is a promising technology that stimulates healing, relieves pain and inflammation, and restores function in injured body parts. However, few studies have compared the effects of light-emitting diodes of different fluence levels or different treatment durations.ObjectiveHere, we investigated the effects of various fluence levels and treatment durations on wound closure in mice.MethodsFull-thickness wounds were created on the dorsal skin using an 8-mm diameter punch, and the wounds were irradiated at 1, 4, or 40 J/cm² for 5 consecutive days starting on day 1. To determine the optimal irradiation duration, wounds were irradiated at the most potent fluence of previous study for 5, 10, or 15 days. Photographic documentation, skin biopsies, and wound measurements were performed to compare the effects of different treatment parameters.ResultsThe most effective fluence level was 40 J/cm² at day 5, as determined by monitoring wound closure. There were no statistically significant differences in wound healing with different durations.ConclusionWe have shown that repeated exposure to low levels of light significantly stimulates wound healing in mice and demonstrated more efficient wound closure with certain fluences of 830 nm irradiation.     

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.     

Wound healing in Behçet's syndrome

Background Because there is an increased inflammatory response to trauma, particularly of the skin, in patients with Behçet's syndrome (BS), an alteration in wound healing in BS is expected. The aim of this study was to investigate the healing features of punch biopsy wounds in BS and acne vulgaris (AV) patients used as controls.
Method Full-thickness skin punch biopsies (4 mm) were taken from the hairless sites of the non-dominant forearms in 20 BS and 20 AV patients. Each patient was examined on days 1, 2, 3, 4, 5, 8, and 10, and the biopsy wound area and induration were marked on sterile glass slides. Other inflammatory changes, such as suppuration and pain, were also recorded. No antiseptic solutions or ointment, except saline, were used.
Results The wound area healed similarly in both groups ( p > 0.05). Thirteen (65%) BS patients had erythematous haloes around the wound on the first day. The number of patients presenting inflammatory changes reached 18 (90%) on the second day in the BS group. The area of erythema around the wound in BS patients was significantly greater than that in AV patients (5; 25%). It gradually decreased day by day. Purulent changes were observed in four BS patients on day 1, and induration around the biopsy wound in six patients on day 2. Only one patient with AV had suppuration, which appeared on the second day, while no AV patient displayed induration.
Conclusion Biopsy-induced trauma may cause increased inflammation in BS, but wound healing is not altered.     

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.     

Faster healing and less pain in skin biopsy sites treated with an occlusive dressing

We prospectively studied 174 patients on whom 226 unsutured parallel incisional (shave) and 3-mm punch skin biopsies were performed. Two wound-care programs, occlusive dressing therapy and conventional therapy, were compared. The biopsy sites were evaluated after 1 or 2 weeks for healing, pain, and infection. We found that healing was unrelated to the indication for biopsy or the patients' age, gender, or race. Occlusive dressing therapy-treated shave biopsy sites were 3.83 times more likely to be healed than those treated with conventional therapy. Regardless of the treatment method, a facial shave biopsy site was 3.6 times more likely to be healed than a biopsy site in other locations. No punch biopsy site had healed after 1 week. At 2 weeks, only 7% and 36% of conventional therapy- and occlusive dressing therapy-treated punch biopsy sites, respectively, had healed. Pain at the biopsy site was six times more common in both shave and punch biopsy sites treated with conventional therapy. The absence of pain with occlusive dressing therapy was significant for both types of biopsy. One punch biopsy site treated with conventional therapy became infected, and one treated with occlusive dressing therapy was suspected of being infected. Forty patients, who had biopsy sites treated with both therapies, preferred occlusive dressing therapy over conventional therapy by a ratio of 3:1 because of ease of wound care and lack of pain. We conclude that occlusive dressing therapy may be the wound management of choice for shave biopsy sites. Since punch biopsy sites do not heal readily, it may be more appropriate to suture them, at least until therapies are developed that more effectively speed their healing.     

Autologous full-thickness skin substitute for healing chronic wounds

BACKGROUND: Chronic wounds represent a major problem to our society. Therefore, advanced wound-healing strategies for the treatment of these wounds are expanding into the field of tissue engineering. OBJECTIVES: To develop a novel tissue-engineered, autologous, full-thickness skin substitute of entirely human origin and to determine its ability to heal chronic wounds. METHODS: Skin substitutes (fully differentiated epidermis on fibroblast-populated human dermis) were constructed from 3-mm punch biopsies isolated from patients to be treated. Acellular allodermis was used as a dermal matrix. After a prior 5-day vacuum-assisted closure therapy to prepare the wound bed, skin substitutes were applied in a simple one-step surgical procedure to 19 long-standing recalcitrant leg ulcers (14 patients; ulcer duration 0.5-50 years). RESULTS: The success rate in culturing biopsies was 97%. The skin substitute visibly resembled an autograft. Eleven of the 19 ulcers (size 1-10 cm2) healed within 8 weeks after a single application of the skin substitute. The other eight larger (60-150 cm2) and/or complicated ulcers healed completely (n = 5) or continued to decrease substantially in size (n = 3) after the 8-week follow-up period. Wound healing occurred by direct take of the skin substitute (n = 12) and/or stimulation of granulation tissue/epithelialization (n = 7). Skin substitutes were very well tolerated and pain relief was immediate after application. CONCLUSIONS: Application of this novel skin substitute provides a promising new therapy for healing chronic wounds resistant to conventional therapies.     

TOPICAL TRETINOIN IMPROVES THE APPEARANCE OF PHOTO DAMAGED SKIN

A multicentre clinical trial has been conducted to assess the efficacy and safety of tretinoin 0.05% cream (Retin-A®) in the treatment of photodamaged Australian skin. Subjects with cutaneous facial photodamage were randomised to treatment with tretinoin (62) or vehicle (63) cream. After an initial two week run-in, all subjects applied the cream to the face, neck and left forearm/hand, once nightly for 24 weeks. Changes in clinical signs of photodamage and parameters of cutaneous irritation were assessed by investigators using a 7 point scale, whilst changes in signs of photodamage were rated by subjects using a 5 point scale. Changes in skin biopsies and silicone skin surface replicas were also assessed. Significant improvements in skin wrinkles, mottled hyperpigmentation, laxity, lentigines and roughness of tretinoin treated subjects were noted by investigators. Subjects receiving tretinoin noted significant improvements in skin wrinkles, tightness, colour and pores. Improvement in overall severity of photodamage was significantly greater for tretinoin treated subjects and was progressive over the study period. Histological findings included a significant increase in mean epidermal thickness. Significant topographical changes were not detected in skin surface replica sets. Cutaneous irritation, the most common side effect, was usually mild and transient. We conclude that tretinoin 0.05% cream significantly improved the appearance of photodamaged skin.     

Adapalene 0·1% gel and adapalene 0·1% cream stimulate retinoic acid receptor mediated gene transcription without significant irritative effects in the skin of healthy human volunteers

A randomized, investigator masked, intra individual comparative study was conducted in 30 healthy volunteers to compare the cutaneous effects of adapalene 0·1% gel and adapalene 0·1% cream with their respective vehicles, using tretinoin 0·05% cream ( n  = 21) or tretinoin 0·1% cream ( n  = 9) and a tretinoin cream vehicle ( n  = 30) as controls. The products were applied to hip/buttock skin for 4 days under occlusive conditions. Cytosolic retinoic acid binding protein-II (CRABP-II) mRNA levels were measured using the RT-PCR technique in punch biopsies taken from 10 subjects. Epidermal thickness was assessed using image analysis of haematoxylin and eosin stained sections from another 11 subjects. Erythema was assessed in all subjects both by a visual scoring system and by chromameter.
  Adapalene 0·1% gel and adapalene 0·1% cream produced similar significant increases in CRABP-II mRNA levels compared to their vehicles ( P < 0·01). The two tretinoin formulations also resulted in similar significant increases in CRABP-II compared to the cream vehicle ( P < 0·001). However, only the two tretinoin formulations resulted in an increase in epidermal thickness and only the tretinoin 0·1% cream resulted in significant erythema.
  Adapalene 0·1% gel and adapalene 0·1% cream induce RAR-mediated gene expression to a similar degree in this model, without the irritant effects of tretinoin.     

Reduced wound contraction and scar formation in punch biopsy wounds. Native collagen dermal substitutes. A clinical study

In full-thickness skin wounds dermal regeneration usually fails, resulting in scar formation and wound contraction. We studied dermal regeneration by implantation of collagenous matrices in a human punch biopsy wound model. Matrices were made of native bovine collagen 1 fibres, and either hyaluronic acid, fibronectin, or elastin was added. Matrices were placed in 6-mm punch biopsy holes in seven patients (biopsies were used for the grafting of leg ulcers), and covered with a protective semi-permeable polyether urethane membrane. Histology, wound contraction and dermal architecture were studied. Dermal architecture was evaluated using a recently developed laser scatter technique. All collagen matrices showed a tendency to reduce wound contraction, compared with control wounds; elastin- and fibronectin-treated matrices showed significantly less contraction than control wounds. Only the addition of elastin had a clear beneficial effect on dermal architecture; collagen bundles were more randomly organized, compared with control wounds, and wounds treated with collagen matrices coated with fibronectin or hyaluronic acid, or without coating. We conclude that the punch biopsy wound model provides important information on dermal regeneration in humans. Native collagen matrices with elastin contributed to dermal regeneration and reduced wound contraction, in contrast with matrices coated with fibronectin or hyaluronic acid, or without coating. Future clinical studies of large-area, full-thickness wounds will be required to establish their clinical relevance for leg ulcer and burn treatment.     

Intracutaneous injection of the macrophage-activating lipopeptide-2 (MALP-2) which accelerates wound healing in mice--a phase I trial in 12 patients

Chronic skin ulcers, such as leg ulcers, pressure sores and diabetic foot ulcers, are a challenge to physicians and medical personnel and a cause of tremendous discomfort and ensuing loss of quality of life to the patients. Wound healing involves production and action of various growth factors. A novel approach, distinct from the application of single growth factors, is the administration of the macrophage stimulator macrophage-activating lipopeptide-2 (MALP-2). The rationale is based on the finding that macrophages are the main source of several growth factors required for wound healing, which are sequentially released during this process. MALP-2 has previously been shown to be effective in an established animal model with diabetic mice. The purpose of the present phase I study was to establish tolerability of MALP-2 when applied into small cutaneous wounds in human beings. Twelve patients (six females and six males; mean age 66.8 years; range 52-87 years) with different diagnoses were enrolled into the study. An artificial wound was created with a 2-mm diameter skin biopsy punch and a volume of 30 microl MALP-2 (0.125-1 microg) or vehicle control, respectively, was injected intracutaneously into the wound and closed with a water-resistant transparent adhesive. Photos were taken daily from every patient up to 6 days, and skin biopsies were performed after 1 week from six patients. We could show in the present study for the first time that MALP-2 caused a transient erythema and was tolerated without any systemic side effects up to a dose of 1 microg per wound in human beings. In healthy as well as in diabetic patients, MALP-2 induced local inflammation that faded after 48 h. The effectiveness of MALP-2 in the healing of chronic wounds in humans, e.g. in chronic skin ulcers, such as leg ulcers, pressure sores and diabetic foot ulcers, could now be addressed in further studies.     

Wound healing assessment using 20 MHz ultrasound and photography

Background/aims To compare two non-invasive techniques of assessing wound healing, photography and high resolution ultrasound (HRUS) scanning, in experimentally induced full-thickness human skin wounds.
Methods Punch biopsy wounds, 4 mm in diameter, were made aseptically through locally anaesthetised skin on the anterior (volar) surface of the non-dominant forearm, 3 cm below the base of the cubital fossa, of 20 human participants. The wounds were treated with a topical antibiotic and covered for 3 days with Mepore sterile dressings. Wound healing was assessed on post-operative days 3, 7, 14 and 21 from photographs and HRUS B-scans. All photographs were taken of the wound site and adjacent intact skin under standardised conditions. The prints obtained were examined visually and digitised. Digital HRUS B-scans were taken through the centre of the wound bed and the adjacent intact skin parallel to the epidermis. Using the scanner's calibrated linear measurement capability, the wound width was measured adjacent to the deep surface of the scab, at the base of the wound, and midway between these two levels.
Results The wound margins were more clearly defined in the HRUS scans than in the photographs of the wounds; in some of the latter the scab masked the wound margins. Changes in the surface width of the wound were affected by the time of scab dehiscence, which varied between volunteers. There was less individual variation in the width of the base of the wound, as measured from the HRUS scans.
Conclusions In contrast to photography, which allows recording of changes in the superficial aspect of the wound only, HRUS scanning permits the quantitative assessment of structural changes deep within the wound. Temporal changes in the width of the base of the wound can be used as an indication of the progress of repair.     

Pretreatment with topical all-trans-retinoic acid is beneficial for wound healing in genetically diabetic mice

Abstract Objective: Topical pretreatment with all-trans-retinoic acid (atRA) is known to improve healing of cutaneous wounds. We tested the effect of atRA on wound healing of genetically diabetic db/db mice. It is known that cutaneous wounds of db/db mice show delayed wound healing due to impaired wound contraction, delayed granulation tissue formation and underexpression of keratinocyte growth factor (KGF). Methods: 0.1% atRA in 100 mg aqueous gel was applied to the back skin of db/db mice as well as to their normal heterozygous littermates, db/+ mice, for five consecutive days, and 2 days after completion of the atRA treatment, two round excisional wounds were created down the panniculus carnosus with a 6-mm punch biopsy on the back skin of each mouse. Results: After 5 days treatment with 0.1% atRA, significant hypertrophy of the epidermis and dermis, neovascularization, and inflammatory cell invasion were seen in the skin of the db/db mice, but these effects were seen only weakly in db/+ mice. Wounds in atRA-treated db/db mice closed more rapidly than those in vehicle-treated db/db mice. KGF mRNA expression, which is usually significantly lower in db/db mice than in normal mice, in wounds of atRA-treated db/db mice on day 1 of treatment was as strong as in db/+ mice. Conclusion: Pretreatment with atRA reversed the impaired wound healing in db/db mice. Received: 9 March 2001 / Revised: 3 July 2001 / Accepted: 16 September 2001     

Comparison of the effects of tretinoin, adapalene and collagenase in an experimental model of wound healing

Adapalene is a new naphthoic acid derivative with strong retinoid agonistic pharmacological properties. We propose that adapalene might contribute to the wound repairing process as is detected with retinoids. In this controlled study, the effects of topical adapalene, tretinoin and collagenase on full-thickness wound healing were compared in an animal model. Thirty-two adult male Wistar-Albino rats were used in the study. Two circular, full-thickness wounds were made for each animal with a standard 8-mm punch biopsy, on both sides of the midline on the back. No treatment was given to Group I rats (n:8) which comprised the control group. Tretinoin cream (0.1%) was applied topically in Group II (n:8), adapalene gel (0.1%) in Group III (n:8), and collagenase ointment in Group IV (n:8) once daily. On day 7, the wounds were photographed to measure the wound surface area. The wounds on the left side of each animal were excised on day 7, for histopathologic and biochemical examination. The treatments were continued for the right side wounds up to 14 days when the same procedure was repeated. In Group II, a significant decrease in hydroxylproline (HP) levels was detected at day 7 (p = 0.018), and an increase at day 14 (p = 0.002) compared to the control group. HP results revealed no difference either in Group III nor in Group IV versus control at day 7 or 14. However, findings of improved healing were more prominent in Groups II and III than the other groups in histopathologic examination. In conclusion, tretinoin and adapalene contributed to the wound healing process resulting in an enhancement of collagen production, angiogenesis and granulation tissue formation.     

Short-contact topical tretinoin therapy to stimulate granulation tissue in chronic wounds

BACKGROUND: The use of retinoids in wound healing is increasing. It has been shown that retinoic acid reverses the inhibitory effects of glucocorticoids on wound healing and accelerates the formation of healthy granulation tissue. Pretreatment with tretinoin before epidermal injury such as chemical peeling and dermabrasion has shown accelerated wound healing. Enhanced healing of full-thickness skin wounds has also been demonstrated in early wound healing studies. However, tretinoin therapy can be quite irritating. OBJECTIVE: Our purpose was to observe the clinical and histologic effects of topical tretinoin solution 0.05% applied directly to the wound beds of chronic leg ulcerations. METHODS: We report on the cases of 5 patients with long-standing leg ulcerations. All were treated with topical tretinoin solution 0.05% applied directly to the wound bed. The tretinoin solution was left in contact with the ulcer bed for a maximum of 10 minutes daily and then rinsed with normal saline. Punch biopsy specimens were obtained from the wound beds at baseline and mid therapy. Standard wound care was continued throughout the study. RESULTS: In this study we found that as early as 1 week after treatment with topical tretinoin solution 0.05%, there was increased granulation tissue first noted at the wound's edge. After 4 weeks of therapy with tretinoin, there was further stimulation of granulation tissue, new vascular tissue, and new collagen formation. CONCLUSION: Short-contact tretinoin therapy is a novel modality in which to treat chronic ulcers and stimulate the formation of granulation tissue.     

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.     

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.