Histological investigation of picosecond laser-toning and fractional laser therapy

Abstract

Background and aims: Rejuvenation therapy using picosecond pulse laser and picosecond pulsed fractional therapy with a fractional lens have been performed with clinical effects evaluated. However, no histological analysis of effects on photoaged skin exists. In this study, influence of laser-toning and fractional therapy using picosecond pulse laser on photoaging was histologically investigated.

Subjects and methods: The flexor side forearm of a male, age 61, with photoaging was divided into three 20 cm² areas and irradiated with approximately 400 shots of 10-Hz laser, 8 mm spot size, and nine passes at an output of 0.7, 0.9, and 1.1 J/cm² using picosecond laser-toning therapy six times, every two weeks. Two weeks post final irradiation, 2 mm punch biopsies were taken from the irradiation fields. Fractional therapy using Micro Lens Array (MLA) attached picosecond fractional therapy was applied to the medial crural skin with marked photoaging of a male, age 63. Irradiation was applied at 0.5 and 0.7 J/cm² through two passes, with 3 mm punch biopsies taken from each irradiation field immediately after and again two months post-irradiation. Samples were subjected to hematoxylin and eosin (HE) and Elastica van Gieson staining and compared.

Results: In the picosecond laser-toning therapy sample, photoaging-induced dermis reconstruction occurred. The picosecond fractional therapy sample showed both epidermis and dermis reconstruction, with intrinsic aging and photoaging improvements.

Conclusions: Recovery of dermal and epidermal age related atrophy by picosecond laser-toning and picosecond fractional therapy was histologically confirmed. Picosecond fractional therapy demonstrated superior improvement.

Keywords: Picosecond pulsed fractional therapy; Picosecond pulsed laser-toning therapy; Rejuvenation; intrinsic aging; photoaging.

Fig. 1:

a: Fine wrinkles are seen at the forearm b: Clinical findings shows the remarkable improvement in texture and tightening at the forearm of irradiation site as laser intensity increased.

Fig. 2:

Hematoxylin-Eosin stain (HE stain) a: Dispersed collagen fibers are seen at the whole dermis. b: Narrow continuous collagen are recognized in the upper dermis and collagen bundles are appeared in the reticular dermis. c: In the upper dermis, cleared collagen fibers recognized and increased in thickness. d: Collagen fibers and bundles increased prominently.

Fig. 3:

Elastica van Gieson stain (EV stain) Elastica van Gieson staining stain elastin fibers. Normally, elastic fibers in the papillary dermis are present either as bundles of microfibrils oxytalan fibers,or as cross-linked elastin and elong to epidermis. In the reticular dermis elastin appear to be fragmented in sections(a,b). Elastin appeares in the papillary layer in the region irradiated at 0.9 J/cm² (c). Elastin fibers obviously synthesized dendritically are observed in specimen(d).

Fig. 4:

a: Base line shows crepe-like wrinkles on the medial side of the crus.Area cutanea does not recognize. b: I mmediately after irradiation using MLA. Spot-like intradermal bleeding is more frequent on the right. Biopsy sites are seen. c: 2 months after irradiation using MLA. Wrinkles are disappeared and area cutanea has been recovered. Biopsy sites are still red.

Fig. 5:

a: B aseline. HE staining: The epidermis is thin and epidermal rete ridges are lost. The dermal components have markedly decreased and capillary blood vessels are dilated, showing marked telangiectasia with an increase in the number and diameter of small blood vessels. b: Baseline. Elastin is stained black by EV staining. Reduction of the volume is observed. c: HE staining: immediately after picosecond fractional therapy. LIOB is present in the deep layer of the dermis (arrows). d: HE staining: 2 months after irradiation at 0.5 J/cm². Thickening of the epidermis and regeneration of epidermal reteridges are noted. Dermal collagen fibers increase in number. Capillary blood vessels are also observed in the deep layer of the dermis. e, f: EV staining: 2 months after irradiation. Elastin markedly increases compared with that at the baseline (b). In the region irradiated at 0.7 J/cm², dendritically extending fibers and those extending toward the epidermis are noted in the dermis. In addition, many capillary blood vessels are present in the superficial to middle layers of the dermis.