Resumo

Objectives: To evaluate whether low‑density (<5%) fractional CO₂ laser immediately followed by autologous hair‑follicle–derived stem cells (HF‑SCs) can repigment gray hair in adults aged 25–40 years using a clinic protocol. We aimed to define clinically laser and cell‑delivery parameters, quantify changes in gray‑hair proportion, shaft colorimetry (CIE Lab*), and perifollicular melanin index, and describe safety using standardized adverse‑event capture. q8 weekly sessions ×3; effect sizes and CIs were estimated. Introduction: Hair graying reflects melanocyte stem‑cell (McSC) dysfunction and niche failure, manifesting as reduced melanogenesis within the anagen hair bulb. Controlled microthermal zones from fractional CO₂ can activate wound‑repair cascades and enable laser‑assisted drug delivery, while hair‑follicle–derived cellular suspensions supply melanocytic/epithelial progenitors to re‑seed the pigmentary unit. Integrating both modalities may overcome McSC depletion or immobility; however, clinic‑level protocols and quantitative outcomes remain underreported. We report a series. Materials / method: Retrospective single‑center series of 22 adults (25–40 y; 11F/11M) with scalp canities. Intervention: fractional CO₂ (10,600 nm) at low density 2–4% (<5%), 1 pass, 12.5–20 mJ/MTZ; immediate delivery of autologous HF‑derived cellular suspension (micrografts or ORS) at ~0.05–0.10 mL/cm² via intradermal micro‑aliquots plus thin topical overlay. Sessions occurred every 8 weeks ×3. Outcomes: % gray hairs/cm² (trichoscopy), CIE Lab* colorimetry, perifollicular Mexameter melanin index, and safety (AEs, POSAS 3.0). Analysis: paired tests, 95% CI, Cohen’s d. Results: N=22 (age 31.8±3.4 y). Gray fraction fell from 43.2±9.3% to 28.4±13.5% at week 24; absolute Δ −14.8±7.3% (95% CI −18.1 to −11.6), relative −37.6±24.1%, paired t p=4.23×10⁻⁹, Cohen’s d=2.04. Hair shafts darkened: ΔL*=+4.3 (95% CI 3.5–5.0; p=1.22×10⁻¹⁰); ΔE=4.38±1.70. MI +13.5±11.1 (p=1.15×10⁻⁵). Safety: erythema median 2 days/session; crusting 31.8%, pruritus 54.5%, no serious events; density stable. Pigmented:gray ratio improved in 19/22; week 16 achieved ~70% of final reduction. POSAS unchanged. No infections observed. Conclusion: sequence of low‑density (<5%) fractional CO₂ immediately followed by HF‑derived cellular suspension, delivered every 8 weeks for three sessions, produced clinically meaningful repigmentation signals in young adults, with large effect on gray‑hair proportion and objective darkening of hair shafts, and acceptable, self‑limited adverse events. Findings support biological plausibility (niche signaling + progenitor support) and justify controlled trials to define durability, dose–response, and patient selection. Use POSAS and colorimetry for monitoring