Effects of CO2 fractional laser on hair growth in C57BL/6 mice and potential underlying mechanisms

Progress of clinical research on fractional laser treatment of androgenetic alopecia: A review article

BACKGROUND

Androgenetic alopecia (AGA) is a prevalent form of hair loss that affects both men and women, severely impacting patients' quality of life. Traditional treatments include oral medications, topical medications, and hair transplantation, but these methods have certain side effects and limitations. How to safely effectively and maximally promote hair growth has been a key issue in the treatment of AGA. In recent years, fractionated laser therapy, as a noninvasive method, has gradually gained attention due to its minimally invasive and highly effective nature.

AIMS

In this paper, we summarized the studies related to fractional laser treatment of AGA in the past 15 years, and discussed its therapeutic mechanism, clinical effect, future development direction, and advantages and disadvantages compared with traditional treatment methods in the treatment of AGA.

METHODS

An extensive literature search was conducted using PubMed, Google, Google Scholar, Embase, and Scopus. All available articles studying fractional laser treatment of AGA were compiled in March 2024. Titles and abstracts were then screened for relevance and thoroughly examined for patient clinical outcomes. Prospective clinical trials, retrospective chart reviews, case series, and individual case reports were included in the literature review.

CONCLUSIONS

Fractional laser treatment of AGA showed remarkable efficacy and high safety. Compared with traditional treatments, fractional laser has the advantages of minimally invasive, quick recovery, fewer side effects, and a wide range of population applicability, providing an effective treatment option for AGA patients. Further large-scale clinical studies will help optimize the laser parameters and treatment settings to improve the therapeutic effect.

Carbon Dioxide Fractional Laser Treatment Induces Lgr5+ Stem Cell Activation and Hair Regrowth Through the Canonical Wnt/β-Catenin Pathway

BACKGROUND

Different types of alopecia have negative impacts on patients. Recently, some kinds of laser or light therapies have been reported to effectively alleviate hair loss. Carbon dioxide fractional laser (CO2FL) treatment is one of the most effective laser treatments, but its beneficial effects and exact mechanism in hair regrowth have not been reported in detail. The purpose of this study was to investigate the effect and molecular mechanism further.

METHODS

C57 and Lgr5-Cre: Rosa-mTmG mouse models of hair regrowth were established by CO2FL treatment, and the parameters that induced the best effect were determined. Tissues were harvested on the day prior to the treatment day and on days 3, 5, 7, 10 and 14 after CO2FL. H&E and immunofluorescence staining, RNA sequencing (RNA-seq), quantitative real-time polymerase chain reaction (qPCR), Western blotting (WB) and related inhibitor were used to determine the molecular mechanism underlying the effect of CO2FL treatment on the hair cycle and hair regrowth. In clinical trial, five participants were treated three sessions at 1-month intervals to obverse the effects.

RESULTS

Hair regrew and covered the treatment area on the tenth day after CO2FL treatment with the best parameters, while the control group showed signs of hair growth on the 14th day. H&E and immunofluorescence staining showed that the transition of hair follicles (HFs) from telogen to anagen was accelerated, and the rapid activation and proliferation of Lgr5+ hair follicle stem cells (HFSCs) were observed in the treatment group. The RNA-seq, qPCR and WB results indicated that the Wnt pathway was significantly activated after CO2FL treatment. Improvement achieved with CO2FL treatment in clinical trial.

CONCLUSIONS

The results of this study suggest that CO2FL treatment can promote hair regrowth by activating Lgr5+ HFSCs and upregulating the Wnt/β-catenin pathway. Clinical trial results demonstrated that CO2FL treatment will be a promising therapeutic regimen for alopecia.

NO LEVEL ASSIGNED

This journal requires that authors assign a level of evidence to each submission to which Evidence-Based Medicine rankings are applicable. This excludes Review Articles, Book Reviews, and manuscripts that concern Basic Science, Animal Studies, Cadaver Studies, and Experimental Studies. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

What Do We Know About Hair Growth Induced by Wounding and Its Therapeutic Applications?

BACKGROUND

Many studies have reported the role of hair follicles (HFs) in the wound healing response, and vice versa, the creation of superficial injuries may stimulate hair growth, which has encouraged new treatments for hair loss.

OBJECTIVE

To review the phenomenon of wound-induced hair growth and the usefulness of therapeutic procedures based on skin wounding in androgenetic alopecia (AGA).

METHODS

A literature search was conducted to review cases of localized hypertrichosis induced by wounds and the role of microneedling, fractional laser, and scalp threading as monotherapy for AGA.

RESULTS

Localized hypertrichosis has been extensively reported after bone fractures, burn injury, chronic venous ulcer, etc. Only 2 cases of wound-induced hair neogenesis in humans have been reported. As monotherapy for AGA, 1 of 3 studies of microneedling, 4 of 6 of fractional lasers, and 2 of 3 studies of scalp threading show good efficacy.

CONCLUSION

Certain types of wounds seem to stimulate localized hair growth in humans, but the underlying mechanism is unclear. Reports on wound-induced HF neogenesis in humans are anecdotal and questions remain as to whether this is a true phenomenon in humans. Further clinical studies are needed before recommending wound-induced hair growth procedures as therapies for AGA.

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.