Mechanical Stimulation Enhances Human Keratinocyte Differentiation in Culture: Induction of Cytokeratin 9 Synthesis
Epidermal cells are committed to terminal differentiation, thereby undergoing a series of morphological and biochemical changes. A specific biochemical differentiation marker of keratinocytes is the expression of the cytokeratin pair K1 and K10/11 or K1 and K9 in footpad and palm keratinocytes. Considering that in vivo, keratinocytes are subjected continuously to mechanical stress, we investigated the effect of cyclic mechanical pressure on differentiaton: HaCaT cells (spontaneously transformed human keratinocytes) were cyclically stimulated by the pressure of Teflon weights. The stimulation process lasted 1–6 days. Consequent to the pressure treatment, multilayered culture growth occurred and the pattern of cytokeratin was modified. The relative amount of suprabasal keratins was increased. After 2 days of stimulation a newly synthesized keratin (64 kD, pI 5.4) was demonstrated, and in western blots it was identified as cytokeratin K9. To exclude the possibility that cytokeratin K9 was a mere laboratory contamination, autoradiography was performed. These results, gained in vitro, demonstrate that mechanical pressure is a notable factor regarding the induction of the keratin K9 synthesis, a specific differentiation marker of palmar and plantar keratinocytes.
KeywordsMechanical Stimulation HaCaT Cell Pyknotic Nucleus Plantar Epidermis Keratin Pattern
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