Electrophoretic mobility of corneocytes measured by laser Doppler spectroscopy

Summary

A new approach studying the characteristics of the stratum corneum is presented: the electrophoretic mobility of corneocytes by laser Doppler spectroscopy. The detergent scrub technique was used for harvesting corneocytes from three body regions (forehead, palm, and sole) of normal persons (n=20) under casual conditions and after thorough defattening of the skin with 70% isopropyl alcohol or petrol. Similarly, cells from the forehead, shoulder, and palm were obtained from 22 acne patients treated with isotretinoin (13-cis retinoic acid) 0.5–0.7 mg/kg body weight (b.wt.)/day for 12–16 weeks, and in patients receiving arotinoid (Ro 15-0778) 192 mg (n=5) or 500 mg (n=5) per kg/b.wt./day for 6 weeks (forehead and shoulder). In another experiment, cell suspensions with a pH ranging from 5.0–7.3 were evaluated.

Measurements were performed by dynamic laser light scattering. This laser application allows exact electrophoretic mobility measurements in a short time (3 min). When cells pass the laser beam, the scattered light is frequency-shifted due to the optical Doppler effect. These frequency shifts are analyzed by the heterodyne light beating technique. The analog signal of the photodetector is converted into a power spectrum by Fourier analysis. This power spectrum represents the spectrum of electrophoretic cell mobility distribution. Results showed different electrophoretic mobility values for corneocytes dependent on the topographic region: forehead 1.18±0.16, palm 1.10±0.14, and sole 0.83±0.10 (means±2 SEM) μm cm/Vs. Defattening with isopropyl alcohol decreased the mobility values to 0.90±0.09 (p≤0.01), 0.95±0.10, and 0.77±0.10 μm cm/Vs respectively. Defattening with petrol yielded similar effects as with isoproply alcohol.

During treatment with isotretinoin acid, the mobility was consistently reduced, i.e., forehead from 1.18±0.18 to 0.92±0.12 (means ±2 SEM) μm cm/Vs (12th week,p≤0.01). The arotinoid was much less effective than isotretinoin in this respect.

It is assumed that the electrophoretic mobility of corneocytes mainly depends on stratum corneum lipids. This is consistent with the results of the topical defattening experiments and the systemic treatment.