We employed topographical patterning to analyze early keratinocyte differentiation on top of microfabricated pillar arrays. Fibronectin immobilized on pillar "heads" yielded a nucleus-associated granular keratin 1 (K1) pattern in immortalized human gingival keratinocytes (IHGK) at pillar interspaces of 14 µm. Decreasing distances of 11and 8 µm revealed cytoplasmic extension of the early differentiation marker K1 on poly-(dimethylsiloxane) (PDMS) pillars. The most extensive cytoplasmic K1 protein distribution noted at the smallest pillar scale coincided with higher ratios of K1 mRNA gene transcription. These experiments suggest that early keratinocyte differentiation was governed by the topographical characteristics of the pillar pattern. Moreover, they form the basis to study cell functions such as differentiation in a defined topologically structured environment.

The clinical examples show the good applicability of DVT with a reduced radiation dose.

BackgroundMechano-transduction in periodontal ligament (PDL) cells is crucial for physiological and orthodontic tooth movement-associated periodontal remodelling. On the mechanistic level, molecules involved in this mechano-transduction process in PDL cells are not yet completely elucidated.ResultsIn the present study we show by western blot (WB) analysis and/or indirect immunofluorescence (IIF) that mechanical strain modulates the amount of the matrix metalloproteinase MMP-13, and induces non-coherent modulation in the amount and activity of signal transducing molecules, such as FAK, MAP-kinases p42/44, and p38 stress kinase, suggesting their mechanistic role in mechano-transduction. Increase in the amount of FAK occurs concomitant with increased levels of the focal contact integrin subunits β3 and β1, as indicated by WB or optionally by IIF. By employing specific inhibitors, we further identified p42/44 and p38 in their activated, i.e. phosphorylated state responsible for the expression of MMP-13. This finding may point to the obedience in the expression of this MMP as extracellular matrix (ECM) remodelling executioner from the activation state of mechano-transducing molecules. mRNA analysis by pathway-specific RT-profiler arrays revealed up- and/or down-regulation of genes assigning to MAP-kinase signalling and cell cycle, ECM and integrins and growth factors. Up-regulated genes include for example focal contact integrin subunit α3, MMP-12, MAP-kinases and associated kinases, and the transcription factor c-fos, the latter as constituent of the AP1-complex addressing the MMP-13 promotor. Among others, genes down-regulated are those of COL-1 and COL-14, suggesting that strain-dependent mechano-transduction may transiently perturbate ECM homeostasis.ConclusionsStrain-dependent mechano-/signal-transduction in PDL cells involves abundance and activity of FAK, MAP-kinases p42/44, and p38 stress kinase in conjunction with the amount of MMP-13, and integrin subunits β1 and β3. Identifying the activated state of p42/44 and p38 as critical for MMP-13 expression may indicate the mechanistic contribution of mechano-transducing molecules on executioners of ECM homeostasis.

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