Abstract

Mast cells are key immunoregulatory cells. They are present in the dermis, where they concentrate around neurovascular bundles. In this study, we hypothesized that the density and distribution of dermal mast cells (MCs) and their level of degranulation could be quantified with the goal of generating reference values for these measures in the occipital and parietal regions of normal scalp. This could provide a basis for comparison of normal and symptomatic scalp. Sixty-micron thick skin sections of 4mm scalp biopsies from 12 adult normal control subjects were labeled with MC-specific anti-tryptase antibody and imaged using confocal microscopy. MC and granule density was calculated in both frontal/parietal and occipital scalp biopsy samples. Three images, one each from superficial, mid and deep dermis, were used. Three blinded investigators performed the quantification using the cell counter function of the FIJI image analysis software. There were significant increases in MC density (p<0.01) and MC degranulation (p<0.01) in deep compared to superficial and mid dermis.  No significant differences were noted between frontoparietal and occipital scalp sites for MC density (p=0.96) and MC granule densities (p=0.36). However, a difference in counts among the three investigators was observed due to overlap of MCs and very small degranulated cells. This set of normal reference data obtained for MCs can be used in future studies of scalp dysesthesia and inflammatory scalp conditions. The observed increase in MCs and granule density in deeper dermis may help in the assessment of pre-treatment and post-treatment biopsies and response in patients.