Proposed mechanisms of low-level light therapy in the treatment of androgenetic alopecia

Light exposure and its applications in human health

Light exposure has been proven to have a significant impact on human health. As a result, researchers are increasingly exploring its potential benefits and drawbacks. With advancements in understanding light and the manufacturing of light sources, modern health lighting has become widely utilized in daily life and plays a critical role in the prevention and treatment of various illnesses. The use of light in healthcare is a global trend, with many countries actively promoting the development and application of relevant scientific research and medical technology. This field has gained worldwide attention and support from scientists and doctors alike. In this review, we examine the application of lighting in human health and recent breakthroughs in light exposure related to pathology, therapeutic strategies, molecular changes, and more. Finally, we also discuss potential future developments and areas of application.

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.

Dissolving microneedles for alopecia treatment

Alopecia is a treatable benign disease, however, approximately 15-30% of women and 50% of men suffer from alopecia, which greatly affects patient's self-esteem and quality of life. Currently, commercial products for alopecia treatment include topical minoxidil solution, oral finasteride tablets and oral baricitinib tablets. However, the barrier of stratum corneum, systemic adverse effects and poor cure rate limit the application of commercial products. Therefore, researchers investigated the mechanism of alopecia, and developed new drugs that could target lactate dehydrogenase-related pathways, remove excessive reactive oxygen in hair follicles, and reduce the escape of hair follicle stem cells, thus injecting new strength into the treatment of alopecia. Moreover, starting from improving drug stratum corneum penetration and reducing side effects, researchers have developed hair loss treatment strategies based on dissolved microneedles (MNs), such as drug powders/microparticles, nanoparticles, biomimetic cell membranes, phototherapy and magnetically responsive soluble microneedles, which show exciting alopecia treatment effects. However, there are still some challenges in the practical application of the current alopecia treatment strategy with soluble microneedles, and further studies are needed to accelerate its clinical translation.

Photobiomodulation at molecular, cellular, and systemic levels

Since the reporting of Endre Mester's results, researchers have investigated the biological effects induced by non-ionizing radiation emitted from low-power lasers. Recently, owing to the use of light-emitting diodes (LEDs), the term photobiomodulation (PBM) has been used. However, the molecular, cellular, and systemic effects involved in PBM are still under investigation, and a better understanding of these effects could improve clinical safety and efficacy. Our aim was to review the molecular, cellular, and systemic effects involved in PBM to elucidate the levels of biological complexity. PBM occurs as a consequence of photon-photoacceptor interactions, which lead to the production of trigger molecules capable of inducing signaling, effector molecules, and transcription factors, which feature it at the molecular level. These molecules and factors are responsible for cellular effects, such as cell proliferation, migration, differentiation, and apoptosis, which feature PBM at the cellular level. Finally, molecular and cellular effects are responsible for systemic effects, such as modulation of the inflammatory process, promotion of tissue repair and wound healing, reduction of edema and pain, and improvement of muscle performance, which features PBM at the systemic level.

A transient photoactivation of epidermal stem cells by femtosecond laser promotes skin wound healing

Wound healing is a long-term complex process, in which epidermal stem cells (EPSCs) in epidermis of skin have been found to play an essential role in it. We develop a noninvasive method to activate EPSCs in skin in vivo to promote wound healing, based on a microscopic system to enable a sequential frame-by-frame scanning of a femtosecond laser at 800 nm to the predefined skin region for a single time for 16 seconds. The laser is tightly focused on a submicron spot and localized in the epidermis, and scans point by point to activate EPSCs there. The density and stemness of EPSCs are significantly enhanced for at least 60 hours after the single-time transient photoactivation. We demonstrate this method works in a skin wound mouse model. Our results provide an optical method for in vivo EPSC activation and hold good potential in wound healing.

Application of lncRNA-miRNA-mRNA ceRNA network analysis in the treatment of androgenic alopecia

BACKGROUND

Long noncoding RNAs (lncRNAs) can be used as competitive endogenous RNAs (ceRNAs) to bind to microRNAs (miRNAs) to regulate gene expression. Previous studies have demonstrated that ceRNAs play an important role in the development of tumors. However, it is not clear whether the lncRNA-miRNA-mRNA ceRNA network plays a role in androgenic alopecia (AGA).

METHODS

The hair follicles of three AGA patients and three healthy individuals were collected for high-throughput whole transcriptome sequencing to screen for differentially expressed lncRNAs. Differentially expressed lncRNA target genes were subjected to databases to predict miRNA-mRNA and lncRNA-miRNA relationship pairs, and a ceRNA network was constructed using Cytoscape software. Relative expression was verified by real-time quantitative reverse transcription-polymerase chain reaction (qRT-PCR).

RESULTS

84 lncRNAs were significantly differentially expressed between the hair follicles of AGA patients and those of healthy individuals; 30 were upregulated, and 54 were downregulated. The top 10 upregulated lncRNAs were ENST00000501520, ENST00000448179, ENST00000318291, ENST00000568280, ENST00000561121, ENST00000376609, ENST00000602414, ENST00000573866, ENST00000513358, and ENST00000564194. The top 10 downregulated lncRNAs were ENST00000566804, ENST00000561973, ENST00000587680, ENST00000569927, ENST00000340444, ENST00000424345, ENST00000589787, NR_024344, NR_073026, and NR_110001. The qRT-PCR validation results and receiver-operating characteristic curve analysis indicated that one upregulated lncRNA, LOXL1-AS1 (ENST00000564194), had the most significant clinical diagnostic potential. After further analysis, it was concluded that LOXL1-AS1 could be used as a sponge to target hsa-miR-5193, thereby regulating TP53 expression.

CONCLUSION

The ceRNA network-regulating AGA was constructed through high-throughput sequencing. Our study also identified a key lncRNA that is possibly related to the AGA pathological process.

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.

Low-level laser treatment promotes skin wound healing by activating hair follicle stem cells in female mice

The aim of the study was to explore the effect and mechanism of a low-level laser on hair follicle stem cells in full-thickness skin wound healing in mice. Full-thickness skin defects were generated by a 5-mm punch biopsy tool on the backs of depilated C57/BL6N mice, which were randomly divided thereafter into a low-dose laser treatment group (LLLT-Low), a high-dose laser treatment group (LLLT-High), and a control group (control). From the day of modeling to the day before the skin samples were taken, the wound area and wound edge of the mice in the LLLT-Low and LLLT-High groups were irradiated with a laser comb every 24 h, and the energy density was 1 J/cm2 and 10 J/cm2, respectively. The control group was irradiated with an ordinary fluorescent lamp. At 0, 3, 5, 10, and 14 days after modeling, pictures of each wound were taken, and the percent wound closure was analyzed. At 3, 5, 10, and 14 days after modeling, the samples were observed by hematoxylin and eosin (HE) and immunofluorescence (IF) staining. Whole transcriptome sequencing (RNA-Seq) was performed on the samples on day 10. Gene Ontology (GO) analysis was performed, and the results were validated by Western blot analysis and enzyme-linked immunosorbent assay (ELISA). The analysis of the percent of wound closure showed that healing was accelerated (significantly from 5 to 10 days) in the LLLT-Low group, but there was no clear change in the LLLT-High group. HE staining showed that the LLLT-Low group had an increasing number of hair follicles and a tendency to migrate to the center of the wound. There was no significant increase in the number of hair follicles and no obvious migration in the LLLT-High group. Immunofluorescence staining showed that the total number of CK15 + hair follicle stem cells in the LLLT-Low group was higher than that in the control group and LLLT-High group at all time points. The number and farthest migration distance of CK15 + hair follicle stem cells increased significantly with time, and after 5 days, they were significantly higher than those in the control group and LLLT-High group. RNA-Seq and Western blot analysis showed that the expression of related genes in hair follicle stem cells, including CK15, in the LLLT-Low group was upregulated. GO analysis and ELISA showed that the expression of many cytokines, represented by IL34, in the LLLT-Low group was upregulated. Low-level laser treatment can promote the proliferation, differentiation, and migration of CK15 + hair follicle stem cells by upregulating the cytokine IL34, thereby promoting skin wound healing in mice.

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.