Effects of Frictional Stimulation on the Structure of the Stratum Corneum

Abstract

Although the formation of callus is a change commonly observed in the epidermis, the cellular events underlying this alteration in the structure of the stratum corneum are uncertain. Examination of the effects of friction on mouse ear epidermis and hamster cheek-pouch epithelium [5,6, 11 ] has shown that these keratinizing epithelia respond to repeated mechanical stimulation with marked increases in overall epithelial thickness and rates of cell proliferation; a new steady state, with cell formation balancing cell loss, appears to be established within the nucleated cell compartment within a few days of repeated stimulation. These findings do not entirely agree with earlier suggestions of Rubin [16] and Rothman [14, 15], who interpreted the epithelial response to friction in terms of formation of a “harder” keratin with a reduced shedding rate. However, the epidermis does appear to be more resistant to mechanical damage after adaptation to frictional stimulation [9], and this is difficult to explain solely in terms of a faster rate of cell production. Associated changes in the epithelium possibly producing a stratum corneum of increased mechanical resistance [15] therefore need to be considered. Thus, several aspects of the structure of the stratum corneum of mouse ear epidermis following frictional stimulation have been examined for any change in the type of keratin formed and to investigate possible causes of the thickening and increased mechanical resistance of this tissue following friction.