Electrical Impedance Spectroscopy Quantifies Skin Barrier Function in Organotypic In Vitro Epidermis Models

Area of Science:

• Dermatology
• Toxicology
• Biomedical Engineering

Background:

• Three-dimensional human epidermal equivalents (HEEs) are advanced organotypic models for skin research.
• Assessing epidermal barrier function is crucial in dermatology and toxicology.
• Noninvasive methods for evaluating HEEs are highly desirable.

Purpose of the Study:

• To investigate the utility of electrical impedance spectroscopy (EIS) for noninvasive assessment of HEE epidermal barrier function.
• To correlate EIS measurements with key epidermal parameters like differentiation and thickness.
• To evaluate EIS's sensitivity to inflammatory conditions and therapeutic interventions.

Main Methods:

• Developed a custom EIS setup integrated with a 24-transwell system for HEEs.
• Performed serial EIS measurements over 7 days without affecting HEE morphology.
• Analyzed impedance spectra to identify frequency ranges correlating with epidermal properties.
• Utilized CRISPR/Cas9-engineered HEEs lacking differentiation genes.
• Applied cytokine cocktails and therapeutic molecules to HEEs.

Main Results:

• EIS measurements showed comparable trends whether performed serially or once.
• Identified two frequency ranges: EIS^diff correlated with keratinocyte terminal differentiation, and EIS^SC correlated with stratum corneum thickness.
• Confirmed keratinocyte terminal differentiation as the primary determinant of EIS^diff.
• Proinflammatory cytokines reduced EIS^diff, reflecting decreased differentiation markers.
• Therapeutic molecule stimulation normalized the cytokine-induced decrease in EIS^diff.

Conclusions:

• EIS offers a noninvasive, quantitative method for consecutively assessing HEE barrier function.
• EIS can sensitively and objectively measure epidermal barrier development, defects, and repair.
• This technique holds promise for preclinical research and regulatory toxicology applications.