Effects of RF Electric Currents on Hair Follicle Growth and Differentiation: A Possible Treatment for Alopecia

Background / Purpose

Androgenic alopecia (AGA) is the most common form of hair loss, caused by the progressive miniaturization of hair follicles due to stem cell dysfunction and hormonal imbalance. Standard drug treatments—such as finasteride and minoxidil—carry notable side effects and limited long-term efficacy. This study aimed to examine, ex vivo, the cellular and tissue-level effects of subthermal 448 kHz capacitive-resistive electrical transfer (CRET) currents on human hair follicles affected by AGA, to determine whether Tecar-based RF stimulation can promote cell proliferation, follicle regeneration, and melanocyte differentiation.

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Methods

Hair follicles were obtained from six male patients (30–45 years) undergoing hair transplant surgery for AGA. Each follicle was cultured in Williams E medium and exposed for 48 hours to one of two subthermal CRET signals delivered intermittently (5-minute pulses, 100 µA/mm²):

• Standard 448 kHz signal (CRET-Std)
• Modulated signal (CRET-Mod): 448 kHz modulated 40% in amplitude at 20 kHz
  Controls were sham-exposed under identical conditions.

After exposure, immunohistochemistry and histomorphometry were used to quantify:

• Cell proliferation (Ki67)
• Apoptosis (TUNEL assay)
• Differentiation (β-catenin)
• Structural integrity markers (collagen I, MMP-9)
• Stem cell and pigment-related markers (CD200 for bulge cells, NKI/beted-gp100 for melanoblasts)
• Epidermal layer thickness

Statistical significance was determined using two-tailed Student’s t-test (p < 0.05).

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Results

• Cell Proliferation: CRET-Std significantly increased Ki67+ cells in the matrix, bulge, and epidermis regions, indicating activation of follicular stem and progenitor cells. CRET-Mod produced smaller, localized increases in the inner and outer root sheath.
• Apoptosis: CRET-Std reduced apoptotic (TUNEL+) cells by 32.3% in follicular sheaths, suggesting improved cell survival and follicle stability.
• Epidermal Thickness: The epidermal layer surrounding the follicle thickened significantly after CRET-Std, strengthening follicular anchorage.
• Collagen and MMP9: Total collagen remained unchanged, but MMP-9 expression decreased in CRET-Std follicles, reflecting reduced extracellular matrix degradation and structural preservation. CRET-Mod slightly increased collagen I expression.
• β-Catenin Pathway: CRET-Mod tended to increase β-catenin expression (+70%), though inter-individual variability prevented statistical confirmation.
• Melanoblast Activity: CRET-Std significantly elevated the number of melanoblasts in the follicular bulb, suggesting stimulated pigment cell differentiation and potential reversal of depigmentation processes.
• Bulge Cells: No significant change in CD200+ bulge stem cell count was observed, indicating that CRET primarily affects progenitor activation rather than stem cell quantity.

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Discussion

Subthermal 448 kHz CRET currents enhanced follicular viability through simultaneous proliferative, anti-apoptotic, and differentiative effects. The standard CRET signal was particularly effective in promoting matrix and bulge proliferation, reducing cell death, and reinforcing follicular structure by downregulating MMP9 activity. The increased number of melanoblasts indicates stimulation of pigment regeneration, which may help prevent hair graying alongside promoting regrowth.

Mechanistically, CRET appears to act via pathways linked to ERK1/2, p38 MAPKs, β-catenin, and cell–matrix adhesion proteins (E-cadherin, vinculin, FAK), supporting follicular regeneration and re-entry into the anagen growth phase. These findings align with previous in vitro and clinical observations of enhanced neocollagenesis, angiogenesis, and stem cell activation under Tecar therapy.

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Conclusion

Exposure of AGA-affected follicles to subthermal 448 kHz Tecar (CRET) currents increased cellular proliferation, decreased apoptosis, and promoted melanoblast differentiation, leading to a structurally stronger and metabolically active follicle. These biological changes suggest that Tecar therapy may prolong or restore the anagen phase, reduce hair miniaturization, and help recover pigmentation. While this ex vivo evidence supports Tecar therapy as a promising treatment for alopecia, clinical trials are required to confirm its full regenerative potential in patients.