Novel methods for generating fractional epidermal micrografts.

BACKGROUND: Epidermal suction blister grafts are an effective treatment for chronic wounds or vitiligo, but this treatment is time consuming and limited to small areas. OBJECTIVES: To compare two novel strategies to create fractional epidermal grafts. METHODS: Epidermal blisters were raised from fresh human skin ex vivo at 38-40 °C, with suction of 380-510 mmHg. In Strategy 1, a 1-cm blister was micromeshed into approximately 500 pieces, transferred to elastic adhesive dressing, then pneumatically expanded to approximately nine times the original blister area. In Strategy 2, a 25-cm(2) array of 100 small blisters was raised, simultaneously harvested and captured directly onto an adhesive dressing. Measurements were taken for the pneumatic expansion limit, the release of microblisters upon hydration of the dressing adhesive, light microscopy, epidermal cell viability and positive L-3,4 dihydroxyphenylalanine melanocyte presence in blisters. RESULTS: Both strategies yielded viable fractional epidermal microblister arrays, carried on a dressing for transfer to graft recipient sites. The microblisters were gradually released upon hydration of the dressing adhesive. Strategy 2 has major advantages as only small blisters are made at the donor site, skilful dissection and physical expansion are not required and the strategy can be scaled to create large-area grafts. CONCLUSIONS: Strategy 2 is the more practical method for fractional epidermal micrografting to treat larger lesions with less donor-site trauma and has recently been commercialized.

Enhanced uptake and photoactivation of topical methyl aminolevulinate after fractional CO2 laser pretreatment.

BACKGROUND AND OBJECTIVES: Photodynamic therapy (PDT) of thick skin lesions is limited by topical drug uptake. Ablative fractional resurfacing (AFR) creates vertical channels that may facilitate topical PDT drug penetration and improve PDT-response in deep skin layers. The purpose of this study was to evaluate whether pre-treating the skin with AFR before topically applied methyl aminolevulinate (MAL) could enable a deep PDT-response. MATERIALS AND METHODS: Yorkshire swine were treated under general anesthesia with a fractional CO(2) laser using stacked single pulses of 3 milliseconds, 91.6 mJ per pulse and subsequent topical MAL application for 3 hours (Metvix®). Red light (LED arrays) was then delivered at fluences of 37 and 200 J/cm(2). Fluorescent photography and microscopy was used to quantify MAL-induced porphyrin distribution and PDT-induced photobleaching at the skin surface and five specific depths down to 1,800 µm. RESULTS: Laser-ablated channels were approximately 1,850 µm deep, which significantly increased topical MAL-induced porphyrin fluorescence (hair follicles, dermis, P < 0.0001) and PDT response, both superficially and deep, versus topical MAL application alone. The fraction of porphyrin fluorescence lost by photobleaching was slightly less after 37 J/cm(2) than after 200 J/cm(2) (overall median values 67-90%; 37 vs. 200 J/cm(2), P > 0.05 for all but one comparison). Photobleaching was steady throughout skin layers and did not vary significantly with skin depth at either LED fluence (P > 0.05). CONCLUSIONS: AFR greatly facilitates topical MAL-induced porphyrins and the fraction of photobleached porphyrins is similar for superficial and deep skin. These observations are consistent with AFR-enhanced uptake of MAL, increased porphyrin synthesis, and photodynamic activation of deep porphyrins even at the lower fluence of 37 J/cm(2), widely used in clinical practice. AFR appears to be a clinically practical means for improving PDT deep into the skin. Clinical studies are suggested to evaluate selectivity in targeting dysplastic cell types.

Thermal relaxation of port-wine stain vessels probed in vivo: the need for 1-10-millisecond laser pulse treatment.

Although thermal relaxation times of cutaneous port-wine stain microvessels have been calculated and used to formulate laser selective photothermolysis, they have never been measured. A scheme to do so was devised by measuring the skin response to pairs of 585-nm dye laser pulses (250-360 microseconds each) as a function of the time interval between the two pulses, in five volunteers with port-wine stains. After a pump pulse delivering 80% of the fluence necessary for causing purpura, the fluence of a second probe pulse necessary to cause purpura was determined and was found to increase with the interval between the two pulses, in a manner consistent with thermal diffusion theory. Biopsy specimens were obtained from four of the five subjects to examine the nature and extent of vessel damage and to measure the port-wine stain vessel diameters. Using diffusion theory, the thermal relaxation time was calculated based on the measured vessel diameters. These calculated values are consistent with the increase in radiant exposure (fluence) of the probe pulse necessary to induce purpura for longer time delays. Two simple models for thermal relaxation of port-wine stain vessels are presented and compared with the data. The data and histologic assessment of the vessel injury strongly suggest that pulse durations for ideal laser treatment are in the 1-10-millisecond region and depend on vessel diameter. No dermatologic lasers presently used for port-wine stain treatment operate in this pulse width domain.

An evaluation of the effectiveness of azelaic acid as a depigmenting and chemotherapeutic agent.

In the past five years, it has been reported that certain dicarboxylic acids (C8-C13) and azelaic acid (C9) (AZA), in particular, have a remarkable effect in the management of lentigo maligna, human malignant melanoma, and certain disorders of hyperpigmentation. Preclinical trials, therefore, were undertaken in order to evaluate the effectiveness of AZA as a depigmenting agent and as a chemotherapeutic agent. Twenty-seven uniformly black pigmented guinea pigs were given topical applications of various concentrations (3, 5, 10, 15, and 20%) of AZA preparations for 8 weeks, and their effects on the melanocytes of epilated skin of the backs and the nonepilated ears of guinea pigs were compared to the effects of well-known depigmenting agents. Whereas 4-isopropylcatechol, monobenzylether of hydroquinone, monoethylether of hydroquinone, hydroquinone, and 4-hydroxyanisole were found to be selectively cytotoxic to melanocytes in black-skinned guinea pigs, AZA has little or no visually recognizable effect on melanocytes in these animals. The therapeutic effect of local s.c. injections of various concentrations of AZA preparations on the development of s.c. implanted B-16 melanoma tumor was evaluated in 96 C57BL/6J mice. In addition, 31 BDF1 mice, implanted i.p. with B-16 melanoma tumor, were used to assess the effect of 100-500 mg/kg concentrations of AZA administered i.p. In both studies, AZA revealed no significant tumoristatic or tumoricidal effect on the size, color, and growth of melanoma. The effect of AZA was also evaluated on S-91A (melanotic or pigmented) and S-91B (amelanotic) human melanoma cells in culture. Low concentrations (10(-5) and 10(-3) M) of AZA had no inhibitory effect on the growth of these cells. Only at higher concentrations (greater than 10(-3) M) was a cytotoxic effect on cell viability observed. These observations indicate AZA is not selectively cytotoxic to normal and proliferative melanocytes and has no apparent inhibitory effect on the formative process of melanin pigmentation.

Hair growth cycle affects hair follicle destruction by ruby laser pulses.

It has been shown that normal mode ruby laser pulses (694 nm) are effective in selectively destroying brown or black pigmented hair follicles in adult Caucasians. This study investigated how the various stages of the hair follicle growth cycle influence follicle destruction by ruby laser treatment, using a model of predictable synchronous hair growth cycles in the infantile and adolescent mice. A range of ruby laser pulse fluences was delivered during different stages of the hair growth cycle, followed by histologic and gross observations of the injury and regrowth of hair. Actively growing and pigmented anagen stage hair follicles were sensitive to hair removal by normal mode ruby laser exposure, whereas catagen and telogen stage hair follicles were resistant to laser irradiation. Selective thermal injury to follicles was observed histologically, and hair regrowth was fluence dependent. In animals exposed during anagen, intermediate fluences induced nonscarring alopecia, whereas high fluences induced scarring alopecia. The findings of this study suggest treatment strategies for optimal laser hair removal.

Permanent hair removal by normal-mode ruby laser.

OBJECTIVE: To assess the permanence of hair removal by normal-mode ruby laser treatment. METHODS: Hair removal was measured for 2 years after a single treatment with normal-mode ruby laser pulses (694 nm, 270 microseconds, 6-mm beam diameter). OBSERVATIONS: Six test areas on the thighs or backs of 13 volunteers were exposed to normal-mode ruby laser pulses at fluences of 30 to 60 J/cm2 delivered to both shaved and wax-epilated skin. In addition, there was a shaved and wax-epilated control site. Terminal hairs were manually counted before and after laser exposure. Transient alopecia occurred in all 13 participants after laser exposure, consistent with induction of telogen. Two years after laser exposure, 4 participants still had obvious, significant hair loss at all laser-treated sites compared with the unexposed shaved and wax-epilated control sites. In all 4 participants, there was no significant change in hair counts 6 months, 1 year, and 2 years after laser exposure. Laser-induced alopecia correlated histologically with miniaturized, velluslike hair follicles. No scarring and no permanent pigmentary changes were observed. CONCLUSIONS: Permanent, nonscarring alopecia can be induced by a single treatment with high-fluence ruby laser pulses. Miniaturization of the terminal hair follicles seems to account for this response.

Reduction of regrowing hair shaft size and pigmentation after ruby and diode laser treatment.

Laser pulses which selectively damage pigmented hair follicles are a useful treatment for hypertrichosis. Clinically, regrowing hairs are often thinner and lighter after treatment. In this study, hair shaft diameter and optical transmission (700 nm) were measured before and after ruby (694 nm) and diode (800 nm) laser irradiation. Hair was collected from 47 and 41 subjects treated with ruby (0.3 ms and 3 ms) and diode (10-20 ms) lasers, respectively. "Responders" were defined as subjects with significant long-term hair loss as determined by hair counts at 9 and/or 12 months after treatment. In ruby laser responders (34/47), regrowing hairs were significantly both thinner (decreased diameter) and lighter (increased transmission). In "nonresponders" (13/47), regrowing hairs were lighter, but not thinner. The regrowing hair shaft absorption coefficient (as calculated assuming Beer's law) was significantly decreased by 0.3 ms ruby laser treatment, but was not changed by 3 ms ruby laser or diode laser treatment. After diode laser treatment, 38 of the 41 subjects were responders and regrowing hairs were both thinner and lighter. These results show that laser treatments can affect structural recovery (size of hair), follicular pigmentation (hair absorption coefficient), or both. Regrowth of thinner hair (decreased shaft diameter) occurs in conjunction with actual loss of hair. After long pulses (3 ms ruby; diode), regrowing hair was thinner and also lighter to an extent related to the decrease in hair diameter. In contrast, short ruby laser pulses (0.3 ms) appeared to be capable of inhibiting follicular pigmentation per se, in addition to affecting the hair diameter. This may account for the complete regrowth of lighter hair in "nonresponders" treated with 0.3 ms pulses. Laser-induced reduction in hair diameter and/or pigmentation are both long-term responses which confer cosmetic benefits in addition to actual hair loss.

Microsecond-long flash photography of laser-induced ablation of biliary and urinary calculi.

High-speed flash photographs of laser-induced fragmentation of biliary and renal calculi under water were obtained using one-microsecond-long dye-laser pulses for both illumination and ablation. The photographs show the presence of a bubble with irregularities on the surface that suggest the early presence of debris or microbubbles. Fragmentation occurs before the bubble collapses, suggesting that fragmentation is due to laser-induced acoustic transients rather than to collapse of a laser-induced cavitation bubble.

Ruby laser hair removal: evaluation of long-term efficacy and side effects.

BACKGROUND AND OBJECTIVE: Although several studies on laser-assisted hair removal have been published, data on long-term follow-up are few. The present study investigated the long-term efficacy and safety of normal-mode ruby laser pulses on hair removal. STUDY DESIGN/MATERIALS AND METHODS: The normal-mode ruby laser (Epilaser; 694 nm, 3 msec) was used to treat a wide range of body sites in 51 volunteers. The mean follow-up after the last treatment was 8.37 months. RESULTS: Sixty-three percent of the patients had sparse regrowth. The mean fluence used was 46.5 J/cm(2) in patients who had sparse hair regrowth and 39.3 J/cm(2) in patients who had moderate hair regrowth (P = 0.0127). Transient pigmentary changes occurred most frequently in patients with skin type 4. CONCLUSION: The normal-mode ruby laser is an efficient and safe method for long-term hair reduction, especially in fair-skinned individuals with dark hair. Higher fluences produce greater long-term efficacy. Adverse effects are minimal and transient.

Hair removal with an 800-nm pulsed diode laser.

BACKGROUND AND OBJECTIVE: Laser hair removal is a relatively new procedure. Our purpose was to study the efficacy and safety of a high-power, pulsed diode laser array for removing unwanted hair. METHODS: A total of 38 subjects were treated with a prototype of the 800-nm diode laser system. Fluences ranging from 10 to 40 J/cm(2) (mean, 33.4 J/cm(2)) were used and 1 to 4 treatments (mean, 2.7) were performed. Evaluation of hair loss was performed at least 4 months after the last treatment (mean, 8.7 months) by a blinded assessment of clinical photographs. RESULTS: A total of 59% of the subjects had only sparse hair regrowth at the final follow-up. Higher fluences and multiple treatments produced greater long-term efficacy. Transient pigmentary changes occurred in 29% of the subjects and were more common in darker skin types IV to VI (P =. 047). CONCLUSION: The 800-nm diode laser is an efficient and safe technique for hair reduction. Adverse pigmentary effects occur, but are transient.

Selective vascular coagulation of rabbit colon using a flashlamp-excited dye laser operating at 577 nanometers.

Previous studies have demonstrated that brief pulses of selectively absorbed optical radiation can be used to confine thermal injury to pigmented targets within tissues. We performed studies in rabbits to assess the usefulness of this technique for selectively coagulating the colonic vasculature. By measuring the optical absorbance of rabbit colon with a spectrophotometer, it was determined that hemoglobin exhibits strong absorption relative to the rabbit colon at a wavelength of 577 nm. Because light must be absorbed to affect tissue, it was hypothesized that laser pulses of this wavelength would selectively damage blood vessels. This hypothesis was tested by examining the effect of 300-microseconds-long 577-nm laser pulses on rabbit colon in vivo. For delivered radiant exposures between 4 and 8 J/cm2, selective coagulation of the colonic vasculature could be produced without damage to the surrounding colon. At greater radiant exposures, vessel hemorrhage was occasionally noted but no transmural thermal injury was produced with delivered radiant exposures as high as 22 J/cm2. This technique may form the basis of a safe and simple treatment of vascular lesions of the colon such as angiodysplasia.