Comparative effectiveness of low-level laser therapy for adult androgenic alopecia: a system review and meta-analysis of randomized controlled trials

Photobiomodulation CME part II: Clinical applications in dermatology

Photobiomodulation (PBM) is an emerging treatment modality in dermatology with increasing office and home-based use. PBM is the use of various light sources in the red light (620-700 nm) and near-infrared (700-1440 nm) spectrum as a form of light therapy. PBM is often administered through low-level lasers or light-emitting diodes. Studies show that PBM can be used effectively to treat conditions secondary to cancer therapies, alopecia, ulcers, herpes simplex virus, acne, skin rejuvenation, wounds, and scars. PBM offers patients many benefits compared to other treatments. It is noninvasive, cost-effective, convenient for patients, and offers a favorable safety profile. PBM can be used as an alternative or adjuvant to other treatment modalities including pharmacotherapy. It is important for dermatologists to gain a better clinical understanding of PBM for in-office administration and to counsel patients on proper application for home-use devices to best manage safety and expectations as this technology develops. PBM wavelengths can induce varied biological effects in diverse skin types, races, and ethnicities; therefore, it is also important for dermatologists to properly counsel their skin of color patients who undergo PBM treatments. Future clinical trials are necessary to produce standardized recommendations across conditions and skin types.

Physical Treatments and Therapies for Androgenetic Alopecia

Androgenetic alopecia, the most common cause of hair loss affecting both men and women, is typically treated using pharmaceutical options, such as minoxidil and finasteride. While these medications work for many individuals, they are not suitable options for all. To date, the only non-pharmaceutical option that the United States Food and Drug Administration has cleared as a treatment for androgenetic alopecia is low-level laser therapy (LLLT). Numerous clinical trials utilizing LLLT devices of various types are available. However, a myriad of other physical treatments for this form of hair loss have been reported in the literature. This review evaluated the effectiveness of microneedling, pulsed electromagnetic field (PEMF) therapy, low-level laser therapy (LLLT), fractional laser therapy, and nonablative laser therapy for the treatment of androgenetic alopecia (AGA). It also explores the potential of multimodal treatments combining these physical therapies. The majority of evidence in the literature supports LLLT as a physical therapy for androgenetic alopecia. However, other physical treatments, such as nonablative laser treatments, and multimodal approaches, such as PEMF-LLLT, seem to have the potential to be equally or more promising and merit further exploration.

Medical Treatment for Androgenetic Alopecia

Androgenetic alopecia is a common type of hair loss, which is generally influenced by genetic factors and systemic androgens resulting in follicular miniaturization.1 It can cause cosmetic problems leading to psychological distress among affected men and women. Effective standard medical treatments available are topical minoxidil 2 to 5%, oral finasteride, oral dutasteride, and hair transplantation.1 However, some patients do not achieve favorable results with standard treatments. For these reasons, other novel treatments have been developed, including new medications, regenerative medicines (autologous platelet-rich plasma, adipose-derived stem cells, micrograft generation, and exosome), and low-level laser therapy.

A study of the biological effects of low-level light

Low-level light therapy (LLLT), also known as photo biomodulation (PBM), is a type of optical therapy that uses red or near-infrared lasers or light-emitting diodes (LEDs) for medical treatment. The laser wavelengths involved in PBM typically range between 600-700 nm and 780-1100 nm, with power densities ranging between 5 mW/cm2 and 5 W/cm2. PBM is a series of biochemical cascades exhibited by biological tissues after absorbing a certain amount of energy from light. PBM has been widely used in clinical practice in the past 20 years, and numerous clinical trials have demonstrated its biological efficacy. However, the underlying mechanisms have not yet been fully explored. In this paper, we have summarized the research into PBM over the past two decades, to identify the important mechanisms of the biological effects of PBM from the perspective of molecular mechanisms, cellular levels, and tissue changes. We hope our study provide a theoretical basis for future investigations into the underlying mechanisms.

Treatment of Androgenetic Alopecia: Current Guidance and Unmet Needs

Androgenetic alopecia (AGA) is the most common cause of hair loss in men and women. Traditionally, topical minoxidil and oral finasteride have been the standard of care yielding mixed results. New treatments such as Low-Level Laser Therapy (LLLT), microneedling, platelet-rich plasma (PRP), and others have been extensively studied in the literature, and the purpose of this review is to provide a comprehensive discussion of the latest treatment methods and their efficacy in treating AGA. Novel therapies such as oral minoxidil, topical finasteride, topical spironolactone, botulinum toxin, and stem cell therapy offer interesting alternatives to standard of care therapies for patients. In this review, we present data from recent studies on the clinical efficacy of these treatments. Furthermore, as new treatments have emerged, clinicians have tested combination therapies to assess whether there may be a synergistic relationship between multiple modalities. While there has been a great increase in the treatments available for AGA, the quality of evidence varies greatly and there is still a great need for randomized double blinded clinical trials to adequately assess the clinical efficacy of some treatments. While PRP and LLLT have demonstrated encouraging results, standardized treatment protocols are needed to adequately inform clinicians on how to use such therapies. Given the abundance of new therapeutic options, clinicians and patients must weigh the benefits and risks of each treatment option for AGA.

Integrative and Mechanistic Approach to the Hair Growth Cycle and Hair Loss

The hair cycle is composed of four primary phases: anagen, catagen, telogen, and exogen. Anagen is a highly mitotic phase characterized by the production of a hair shaft from the hair follicle, whereas catagen and telogen describe regression and the resting phase of the follicle, respectively, ultimately resulting in hair shedding. While 9% of hair follicles reside in telogen at any time, a variety of factors promote anagen to telogen transition, including inflammation, hormones, stress, nutritional deficiency, poor sleep quality, and cellular division inhibiting medication. Conversely, increased blood flow, direct stimulation of the hair follicle, and growth factors promote telogen to anagen transition and subsequent hair growth. This review seeks to comprehensively describe the hair cycle, anagen and telogen balance, factors that promote anagen to telogen transition and vice versa, and the clinical utility of a variety of lab testing and evaluations. Ultimately, a variety of factors impact the hair cycle, necessitating a holistic approach to hair loss.

The efficacy of LED microneedle patch on hair growth in mice

Light penetration depth in the scalp is a key limitation of low-level light therapy for the treatment of androgenetic alopecia (AGA). A novel light emitting diode (LED) microneedle patch was designed to achieve greater efficacy by enhancing the percutaneous light delivery. The study aimed to investigate the efficacy and safety of this device on hair growth in mice. Thirty-five male C57BL/6 mice which their dorsal skin was split into upper and lower parts to receive either LED irradiation alone or LED irradiation with a microneedle patch. Red (629 nm), green (513 nm), and blue light (465 nm) at an energy dose of 0.2 J/cm² were applied once daily for 28 days. Outcomes were evaluated weekly using digital photographs. Histopathological findings were assessed using a 6 mm punch biopsy. A significant increase in hair growth was observed in the green light, moderate in the red light, and the lowest in the blue light group. The addition of the microneedle patch to LED irradiation enhanced greater and faster anagen entry in all the groups. Histopathology showed an apparent increase in the number of hair follicles, collagen bundles in the dermis, angiogenesis, and mononuclear cell infiltration after treatment with the green-light LED microneedle patches. No serious adverse effects were observed during the experiment. Our study provides evidence that the newly developed green-light LED microneedle patch caused the optimal telogen-to-anagen transition and could lead to new approaches for AGA. Microneedle stimulation may aid percutaneous light delivery to the target hair follicle stem cells.

Single-cell transcriptome analysis of fractional CO2 laser efficiency in treating a mouse model of alopecia

OBJECTIVES

Hair loss, including alopecia, is a common dermatological issue worldwide. At present, the application of fractional carbon dioxide (CO₂ ) laser in the treatment of alopecia has been documented; however, the results vary between reports. These varying results may be due to the limited knowledge of cellular action in laser-irradiated skin. The objective of this study was to investigate the molecular and cellular mechanisms of laser treatment under effective conditions for hair cycle initiation.

METHODS

A fractional CO₂ laser was applied and optimized to initiate the hair cycle in a mouse model of alopecia. Several cellular markers were analyzed in the irradiated skin using immunofluorescence staining. Cellular populations and their comprehensive gene expression were analyzed using single-cell RNA sequencing and bioinformatics.

RESULTS

The effective irradiation condition for initiating the hair cycle was found to be 15 mJ energy/spot, which generates approximately 500 μm depth columns, but does not penetrate the dermis, only reaching approximately 1 spot/mm² . The proportion of macrophage clusters significantly increased upon irradiation, whereas the proportion of fibroblast clusters decreased. The macrophages strongly expressed C-C chemokine receptor type 2 (Ccr2), which is known to be a key signal for injury-induced hair growth.

CONCLUSIONS

We found that fractional CO₂ laser irradiation recruited Ccr2 positive macrophages, and induced hair regrowth in a mouse alopecia model. These findings may contribute to the development of stable and effective fractional laser irradiation conditions for human alopecia treatment.

Efficacy comparison of monotherapies and combination therapies for androgenetic alopecia: A Bayesian network meta-analysis

Even though a variety of treatments for androgenetic alopecia (AGA) currently have been using in clinical, satisfactory therapeutic methods are still lacking. We aimed to compare and rank these treatments for AGA according to their differences in efficacy via Bayesian network meta-analysis, suggesting the optimal therapy for clinical utility to refer. A systematic search of PubMed, Embase, Web of Science, and Cochrane Library database was performed and we included eligible randomized controlled trials. We compared differences in treatment effects of monotherapies and combination therapies using the Bayesian network model. The average difference in alteration from baseline of hair density and hair diameter, and variation value (mean ± SD) between the pre- and post-intervention was selected for main outcome measure and secondary outcome measure. Total 49 RCTs involving 3133 patients and six interventions were included. Regardless of based on hair density or hair diameter, topical/systemic combined with adjunctive therapeutics had the best treatment efficacy among all interventions (MD: 40.11; 95% CrI 25.65-54.59), followed by topical combined with systemic medical therapeutics (MD: 36.41; 95% CrI 17.54-55.24). In addition, in terms of hair density, treatment efficacy had significant difference sequentially among topical medical therapeutics (MD: 22.15; 95% CrI 12.88-31.42), systemic medical therapeutics (MD: 19.91; 95% CrI 6.504-33.22), and adjunctive therapeutics (MD: 18.60; 95% CrI 8.020-29.10) compared to placebo. In recent years, combination therapies are showing significant promise as potential therapies. Taken together with the outcomes of this study, despite the specific mechanism of the effect of combination therapies was not clear and further studies are needed, it may be the best treatment for AGA.

Hair Growth Promoting Effects of 650 nm Red Light Stimulation on Human Hair Follicles and Study of Its Mechanisms via RNA Sequencing Transcriptome Analysis

Background

Androgenetic alopecia (AGA) leads to thinning of scalp hair and affects 60%~70% of the adult population worldwide. Developing more effective treatments and studying its mechanism are of great significance. Previous clinical studies have revealed that hair growth is stimulated by 650-nm red light.

Objective

This study aimed to explore the effect and mechanism of 650-nm red light on the treatment of AGA by using ex vivo hair follicle culture.

Methods

Human hair follicles were obtained from hair transplant patients with AGA. Hair follicles were cultured in Williams E medium and treated with or without 650-nm red light. Real-time RT-PCR and immunofluorescence staining were used to detect the expression level of genes and proteins in hair follicles, respectively. RNA-sequencing analysis was carried out to reveal the distinct gene signatures upon 650 nm treatment.

Results

Low-level 650 nm red light promoted the proliferation of human hair follicles in the experimental cultured-tissue model. Consistently, 650 nm red light significantly delayed the transition of hair cycle from anagen to catagen in vitro. RNA-seq analysis and gene clustering for the differentially expressed genes suggests that leukocyte transendothelial migration, metabolism, adherens junction and other biological process maybe involved in stimulation of hair follicles by 650-nm red light treatment.

Conclusion

The effect of 650-nm red light on ex vivo hair follicles and the transcriptome set which implicates the role of red light in promoting hair growth and reversing of miniaturization process of AGA were identified.

Non-ablative Er:YAG laser is an effective tool in the treatment arsenal of androgenetic alopecia

Background

Up to 70% of the adult population worldwide is affected by androgenetic alopecia (AGA) hair loss. Laser therapy offers an addition or alternative to pharmaceutical and surgical treatment of hair regrowth, with non‐ablative lasers being preferred over ablative lasers in terms of safety and downtime. Combining laser therapy with different topical agents may result in better hair regrowth.

Objective

The aim was to evaluate the effectiveness and safety of non‐ablative Er:YAG laser used in clinical practice, alone or in combination with other treatment modalities, in patients with both early and advanced stages of AGA.

Methods and patients

Sixteen patients (7 male and 9 female) with active AGA in different stages were treated with the non‐ablative Er:YAG laser (SMOOTH^TM mode, 7 mm spot size, 7.00 J/cm² pulse fluence, 3.3 Hz frequency) as a monotherapy or in combination with injections of platelet‐rich plasma (PRP) to the scalp, topical minoxidil, and oral supplements for the promotion and support of hair growth. Efficacy was assessed with clinical assessment of AGA grade (Ludwig scale for female / Norwood‐Hamilton scale for male) and with blind evaluation of hair quality in global photographs before and after treatment. Patients subjectively rated their satisfaction with the laser treatment on a scale from 0–3 and pain on a VAS scale from 0–10.

Results

AGA grade after treatment was lower compared to baseline (p = 0.015 and p = 0.125 in female and male patients, respectively). Blind evaluation indicated an improvement in hair quality in 93% of patients, either being described as much better (14%) or as better (79%), which was not correlated with age or AGA grade. The median satisfaction score was 3, and the median VAS score for pain was 2. The positive effect of the treatment on the hair quality is ongoing. No adverse reactions were reported.

Conclusions

The treatment was effective in treating AGA, confirmed by a decrease in AGA grade and by blinded evaluation of global photographs. Although the possible additive or complementary effect of topical minoxidil or nutraceuticals cannot be excluded, our results suggest that the non‐ablative Er:YAG laser SMOOTH^™ mode as a monotherapy, or in combination with PRP, is an efficient and safe treatment for AGA—with a high satisfaction rate among patients regardless of patient age, AGA duration, or AGA stage.

Photobiomodulation: The Clinical Applications of Low-Level Light Therapy

BACKGROUND

Low-level light therapy (LLLT) is a recent addition to the pantheon of light-based therapeutic interventions. The absorption of red/near-infrared light energy, a process termed "photobiomodulation," enhances mitochondrial ATP production, cell signaling, and growth factor synthesis, and attenuates oxidative stress. Photobiomodulation is now highly commercialized with devices marketed directly to the consumer. In the gray area between the commercial and therapeutic sectors, harnessing the clinical potential in reproducible and scientifically measurable ways remains challenging.

OBJECTIVES

The aim of this article was to summarize the clinical evidence for photobiomodulation and discuss the regulatory framework for this therapy.

METHODS

A review of the clinical literature pertaining to the use of LLLT for skin rejuvenation (facial rhytids and dyschromias), acne vulgaris, wound healing, body contouring, and androgenic alopecia was performed.

RESULTS

A reasonable body of clinical trial evidence exists to support the role of low-energy red/near-infrared light as a safe and effective method of skin rejuvenation, treatment of acne vulgaris and alopecia, and, especially, body contouring. Methodologic flaws, small patient cohorts, and industry funding mean there is ample scope to improve the quality of evidence. It remains unclear if light-emitting diode sources induce physiologic effects of compararable nature and magnitude to those of the laser-based systems used in most of the higher-quality studies.

CONCLUSIONS

LLLT is here to stay. However, its ubiquity and commercial success have outpaced empirical approaches on which solid clinical evidence is established. Thus, the challenge is to prove its therapeutic utility in retrospect. Well-designed, adequately powered, independent clinical trials will help us answer some of the unresolved questions and enable the potential of this therapy to be realized.

Efficacy of Minoxidil Combined With Photobiomodulation for the Treatment of Male Androgenetic Alopecia. A Double-Blind Half-Head Controlled Trial

BACKGROUND

Androgenetic alopecia (AGA) is a hair loss disorder that frequently affects the male population. Conventional treatment modalities are limited to minoxidil, 5α reductase inhibitors, and hair transplantation procedures. The efficacy of low-level laser therapy (LLLT), also known as photobiomodulation, in the treatment of AGA has been reported, yet little is known about the outcomes of combining photobiomodulation with other conventional therapies.

OBJECTIVE

To evaluate hair growth improvement in males with AGA, during the administration of minoxidil with and without photobiomodulation, using a half-head model.

STUDY DESIGN/MATERIALS AND METHODS

Twenty-one men with AGA agreed to undergo 12 minutes of low-level laser irradiation (using a modified Capellux®), followed by topical minoxidil application (1 ml of 5% solution), to the affected scalp two times per day for 6 months. The photobiomodulation devices were modified such that the left half emitted light, and the right half did not. Efficacy was assessed by blinded analyses of clinical photos and automated phototrichograms (Trichoscan®) taken before treatment and after 3 and 6 months of therapy.

RESULTS

None of the study participants experienced any adverse events. All patients showed improvements in hair coverage on both sides of the scalp at 3 and 6 months. On the side with combined treatments, the number of total hairs was significantly increased after 3 (P < 0.001) and 6 months (P = 0.001). A similar increase was also observed on the minoxidil-only side, at both 3 (P < 0.001) and 6 months (P < 0.001). No statistically significant differences were detected between sides (P > 0.05).

CONCLUSION

Additional improvement was not observed with the association of photobiomodulation to topical minoxidil in male AGA. Differences from previous studies that might have influenced our result include non-collimated light source, higher dosimetry, and a cohort with darker skin phototype and more severe alopecia. Lasers Surg. Med. 2021. © 2021 Wiley Periodicals LLC.

Hair Loss and Hair Restoration in Women

Hair restoration in women involves mastering both the medical and the surgical treatment. Preoperatively, women should be thoroughly evaluated for biochemical causes of hair loss along with a complete history and physical examination taken. The physician must recognize the clinical presentation of scarring alopecias and maintain a low threshold for biopsy to rule out this condition. Postoperative hair shock loss is a common feature following hair transplant in women, and the surgeon should understand the preoperative counseling and preventative measures needed, the intraoperative methods to reduce the incidence, and the postoperative strategies to handle the situation.

Factors influencing the effect of photobiomodulation in the treatment of androgenetic alopecia: A systematic review and analyses of summary-level data

Low-level laser therapy (LLLT) is used to treat androgenetic alopecia (AGA). The therapeutic effect of LLLT on AGA has been evaluated; however, there is a paucity of studies that investigated device- and usage-related factors that may influence the effect of LLLT on hair regrowth. The literature was systematically searched to identify eligible studies; PubMed, Scopus, EMBASE and clinicaltrials.gov databases were searched on 30 April 2020. Eligible studies were randomized trials that investigated the effect of LLLT on hair density in AGA. Robust linear regressions were used to make comparisons. An increase in the per-session energy fluence by 1 J/cm² is significantly associated with an increase in hair density by 0.23 hairs/cm² (95% CI: 0.21 hairs/cm² , 0.25 hairs/cm² ). The number of laser or light-emitting diodes is not significantly associated with change in hair density. Increasing the total duration of exposure to treatment is associated with a significant increase in hair density (β = .53, P < .05). Switching from continuous to pulse irradiation was associated with a significant increase in hair density (β = 10.11, P < .01). Energy fluence, irradiation session duration, and light pulsing have a significant therapeutic effect on AGA, while the number of diodes does not.

Low-level light therapy using a helmet-type device for the treatment of androgenetic alopecia: A 16-week, multicenter, randomized, double-blind, sham device-controlled trial

INTRODUCTION

Androgenetic alopecia is the most common form of hair loss in both sexes. In recent studies, low-level light therapy (LLLT) has been established as an effective treatment for alopecia. The purpose of this study was to evaluate the safety and efficacy of LLLT using a new helmet-type device for the treatment of androgenetic alopecia.

METHOD

A randomized, sham device-controlled, double-blind clinical trial was conducted at 2 institutions. Sixty participants diagnosed with androgenetic alopecia aged from 19 to 65 years were recruited. LLLT was performed through a helmet-type device that emitted light with a mean output power of 2.36 mW/cm at a wavelength of 655 nm. Participants were divided into 2 groups, which respectively used the experimental device and a sham device. After tattooing at the central point of the vertex, phototrichograms at that point were obtained at 0, 8, and 16 weeks. The primary endpoint of the study was the difference in the rate of change of hair density between the test group and the control group.

RESULTS

Comparing the results at baseline and week 16, the experimental group showed an increase in hair density of 41.90 hairs/cm and an increase in hair thickness of 7.50 μm, whereas the control group showed an increase of 0.72 hairs/cm and a decrease of 15.03 μm, respectively (P < .001). No adverse events or side effects occurred.

CONCLUSION

LLLT showed a significant effect on increasing hair density in patients with androgenetic alopecia. LLLT could be a safe and effective treatment for androgenetic alopecia in both sexes.

Immune cell regulation of the hair cycle

The ability to manipulate the mammalian hair cycle will lead to novel therapies and strategies to combat all forms of alopecia. Thus, in addition to the epithelial-mesenchymal interactions in the hair follicle, niche and microenvironmental signals that accompany the phases of growth, regression and rest need to be scrutinized. Immune cells are well described in skin homeostasis and wound healing and have recently been shown to play an important role in the mammalian hair cycle. In this review, we will summarize our current knowledge of the role of immune cells in hair cycle control and discuss their relevance to human hair cycling disorders. Increased attention to this aspect of the hair cycle will provide new avenues to manipulate hair regeneration in humans and provide better insight into developing better ex vivo models of hair growth.

Female Androgenetic Alopecia: An Update on Diagnosis and Management

Female androgenetic alopecia (FAGA) is a common cause of non-scarring alopecia in women. The onset may be at any age following puberty and the frequency increases with age. Clinically, it shows a diffuse hair thinning over the central scalp, while the frontal hairline is usually retained. FAGA can have a significant psychological impact, leading to anxiety and depression. For this reason, early diagnosis is very important to stop the progression of the disease. The sex hormonal milieu is the main pathogenetic mechanism studied in FAGA. The role of androgens is not clearly defined and only one-third of women with FAGA show abnormal androgen levels. Endocrinological diseases with hyperandrogenism associated with FAGA comprise polycystic ovarian syndrome (PCOS), hyperprolactinemia, adrenal hyperplasia and, rarely, ovarian and adrenal tumours. Usually the diagnosis of FAGA is made clinically. A complete clinical examination and a blood examination can reveal other signs of hyperandrogenism. Trichoscopy shows the typical hair miniaturization. A scalp biopsy can be useful when the clinical evaluation does not provide a definitive diagnosis or when cicatricial alopecias with hair loss in the distribution of FAGA or alopecia areata are suspected. FAGA is a slowly progressive disease. The goal of therapy is to stop the progression and to induce a cosmetically acceptable hair regrowth. The most important drugs are topical minoxidil and oral anti-androgens. The purpose of this review is to provide an update on FAGA and to create a guideline on diagnosis and management of this frequent hair disease, not always easily recognizable from cicatricial alopecias with a similar distribution.

Photobiomodulation for the management of alopecia: mechanisms of action, patient selection and perspectives

Photobiomodulation (PBM) or low-level laser therapy was discovered over 50 years ago, when Mester in Hungary observed regrowth of hair in mice when irradiated with a ruby laser. At the present time, several different PBM devices are marketed to assist with hair regrowth in alopecia patients. This review covers the three main types of alopecia (androgenetic, areata, and chemotherapy-induced), and discusses the mechanism of action of PBM for each disease. The different devices used (mostly low powered red laser diodes), dosimetry, animal models, and clinical trials are summarized. Criteria for patient selection are outlined. Finally a perspectives section looks forward to the future.