OBJECTIVETo observe the distribution of epidermal stem cell (ESC) after soft tissue expansion, and to explore dynamic change in ESC under mechanical stress and kinetic mechanism of skin expansion.

METHODSSkin samples were collected from patients after expansion of the scalp. They were divided into three groups: A group (scalp harvested 3 cm away from the center of dilator), B group (scalp tissues at the edge of dilator), and control group (scalp without dilatation). The tissue structures were observed with optical microscope with HE staining. The distribution and differentiation characteristics of cell keratin 19 (CK19) positive cells were observed with inverted phase contrast microscope after immunohistochemistry staining.

RESULTSHE staining showed that the epidermis was thickened and distributed densely with uneven, rugged and increased layers in A, B groups. With immunohistochemistry staining, CK19 positive cells appeared in multilayers in basal membrane, a few of them were in cluster or dispersed , with" hollowing" structure formation. These phenomena were not seen in control group.

CONCLUSIONESC can proliferate with abnormal distribution and "hollowing" structure formation after mechanical dilatation, which may be related to dynamic changes in basal layer cells.