Abstract
Mechanical stress has profound influences on human body. Muscle training strengthens the muscles, and high blood pressure thickens the vessel walls. Intense studies have been made by various investigators on how mechanical stress influences the human tissues. Epidermal keratinocytes are continuously exposed to mechanical forces. The human skin surface can be thickened and enlarged by various stress such as tissue expander or abrasive pressure. Keratinocytes were plated on flexible silicone dishes, and they were continuously stretched. Stretching of keratinocytes caused up-regulation of 5-bromo-2'-deoxyuridine (BrdU)-positive cells and activation of extracellular signal-regulated kinases (ERK) 1/2. EGF receptor, calcium channel, and ERK were involved in stretch-induced BrdU incorporation. Stretching also induced keratin K6, which is expressed in activated and proliferating keratinocytes, and suppressed keratin K10, which is expressed in differentiated keratinocytes, and their regulation was inhibited by MEK1/2 inhibitor. EGF receptor as well as adhesion molecules have been reported to be involved in transducing mechanical stresses. Several diseases involving heart and palmoplantar skin are caused by the mutation in desmosomal proteins, indicating that adhesion molecules play an important part in sustaining normal structure of skin under the mechanical stress.
