Human skin-derived mast cells can proliferate while retaining their characteristic functional and protease phenotypes

Human mast cells in adult tissues have been thought to have limited, if any , proliferative potential. The current study examined mast cells obtained f rom adult skin and cultured in serum-free medium with recombinant human ste m cell factor. During the first 4 weeks of culture, the percentages of mast cells increased from 10 to almost 100. After 8 weeks, a 150-fold increase in the number of mast cells was observed. When freshly dispersed mast cells were individually sorted onto human fibroblast monolayers and cultured for 3 weeks, one or more mast cells were detected in about two thirds of the w ells, and in about two thirds of these wells the surviving mast cells showe d evidence of proliferation, indicating most mast cells in skin can prolife rate. Such mast cells all expressed high surface levels of Kit and Fc epsil on RI, each of which were functional, indicating IgE was not required for F c epsilon RI expression on mast cells. Such mast cells also retained the MC TC protease phenotype of mast cells that normally reside in the dermis. Aft er 4 to 8 weeks of culture these mast cells degranulated in response to sub stance P and compound 48/80, characteristics of skin-derived mast cells tha t persist outside of the cutaneous microenvironment. (Blood, 2001;97:2045-2 052) (C) 2001 by The American Society of Hematology.