In addition, the DHM-based approach for determination of the dry mass is independent of the intracellular water content which may be influenced by the osmolality of the cell culture medium or the tested agent. Importantly, simultaneous determination of cellular dry mass changes during wound healing in vitro is not provided by traditional approaches. There is evidence, that wound healing is significantly influenced by the environment, surrounding cells and tissues. Recently, it was Nutlin-3 demonstrated that deformation and extracellular pressure can stimulate intracellular enzyme activity and may influence cell proliferation and healing. For example, in a murine model, intestinal obstruction resulted in decreased wound healing of chemically induced mucosal ulcers. Thus, beside measurement of migration and proliferation, a comprehensive evaluation of epithelial wound healing requires the assessment of cellular morphological features such as thickness. Interestingly, cellular thickness may also be used to evaluate proliferation since doubling of dry mass and increase in cell size is routinely observed before each division. Recently, Pavillon et al. demonstrated that DHM may also be used to differentiate between apoptosis and necrosis by assessment of cellular volume. While apoptosis is initially associated with a reduced cellular volume, necrosis is characterized by a significant increase of cellular volume prior the cell collapse. It has been shown that alterations of cellular volume are modulated by ionic pathways and changes of cellular volume as assessed by DHM were successfully linked to apoptotic rates in murine cortical neurons in vitro. Moreover, toxic effects of methanol were detected by optical thickness measurements since altered optical thickness of epithelial HeLa cells was indicative of pyknosis within these cells. Similarly, Ku¨hn et al. demonstrated DHM to be ready to use for assessment of cytotoxicity and cell viability by determination of morphological and biomolecule changes. The authors additionally report DHM to be a magnitude faster than automated standard fluorescence microscopy. It should be mentioned that our results revealed that EGFstimulated Caco-2 cells grow with a similar dry mass rate like untreated control cells but show different morphological features which is indicated by a significant difference in the cell layer thickness. These findings may be explained by the specific design of our experiments in which EGF and mitomycin c were applied in a single assay. Nevertheless, the obtained results also demonstrate that the accuracy of the applied DHM method is sufficient to detect, for example interference of different cytokine in an assay. In summary, our results demonstrate that DHM provides several advantages with regard to previously established methods for monitoring of wound healing in vitro. Although the detection of individual cells is limited as successful identification depends strong.