Transdifferentiation

Refers to the change in the phenotype of cells without proliferative activity. An example of this process can be found in cutaneous calciphylaxis (conversion of smooth muscle cells into osteoclasts; here phosphate is an essential promoter). This process can be controlled by pH changes to basic, by osteotropic hormones and sclettal morphogens, and by inhibitors of passive tissue mineralisation. In doing so, the gene expression of the cells changes dramatically. Many genes are switched off (e.g., by DNA methylation), while others are upregulated (for example, in order to transfer a muscle cell into an osteoclast/osteoblast, the cell needs completely different proteins).