AFM imaging analysis of alopecia areata by edge detection

Alopecia areata(AA) is a common type of autoimmune disorder that produced sudden patch-like hair loss. Owing to the dysfunction of keratogenous zone in affected hair at early anagen, hair shaft with AA had abnormal structure or total disintegration. Typically, it showed characteristic(or unique) broken hair shafts on the hair-less patch. Few techniques were introduced to investigate hair surface. Recently, atomic force microscopy(AFM) became an ideal method for non-invasive examination of hair surface. When the cortical keratinocytes were affected in AA, the topographic changes of hair cuticles could be examined by AFM in nanoscale. In this experiment, we compared the AFM images of hair surface and extracted parameters from the cuticle between control group and patient group with AA(n=12, each). Data demonstrated that the shaft surface of AA patient's hair was more damaged than that of normal group. Various types of damage such as crack of scale, longitudinal striation, endocuticular ghost and debris were observed on hair cuticles with AA. In order to find cuticle parameters, we performed the edge detection of cuticle with canny mask. The curvature was defined as a secondary differentiation with the x and y coordinates of cuticle edge on AFM images to compare the cuticle edge between two groups. As a result, the cuticle scale parameters showed frequent changes in AA patient groups. In particular, top distance and step height of cuticle in AA group were lower than those of control group and the curvature of cuticle edge in AA patient group was higher than those of healthy one. In conclusion, the cortical keratinocytes might affect the pathogenesis of AA. This is the first comparison study about hair shaft surfaces over the whole lengths between AA and healthy group, to our knowledge.