Changes in Dermal Fibroblasts from Abcc6-/- Mice Are Present before and after the Onset of Ectopic Tissue Mineralization

Pseudoxanthoma elasticum (PXE), a rare genetic disease caused by mutations in the ABCC6 gene, is characterized by progressive calcification of elastic fibers in the skin, eyes, and the cardiovascular system. The pathomechanism of the mineralization is still obscure. Several hypotheses have been proposed, one of them suggesting a role for fibroblasts in controlling the amount and the quality of the calcified extracellular matrix. This hypothesis raises the question whether changes in mesenchymal cells are the cause and/or the consequences of the calcification process. In this study, fibroblasts were isolated and cultured from Abcc6(+/+) and Abcc6(-/-) mice of different ages to investigate parameters known to be associated with the phenotype of fibroblasts from PXE patients. Results demonstrate that a few changes (Ank and Opn downregulation) are already present before the occurrence of calcification. By contrast, a modification of other parameters (intracellular O-2(-) content, Tnap activity, and Bmp2 upregulation) can be observed in Abcc6(-/-) mice after the onset of tissue mineralization. These data suggest that in the Abcc6(-/-) genotype, dermal fibroblasts actively contribute to changes that promote matrix calcification and that these cells can be further modulated with time by the calcified environment, thus contributing to the age-dependent progression of the disease.