Loss of ABCC6 in Human Mesenchymal Stem Cells Leads to Elevated Reactive Oxygen Species Formation and a Senescence-like Phenotype.

Pseudoxanthoma elasticum (PXE) is an autosomal-recessive disorder caused by mutations in ATP-binding cassette subfamily C member 6 (ABCC6). In addition to the calcification and fragmentation of elastic fibers as the pathomechanistic cause of PXE, systemic and cellular oxidative stress have been reported. Human mesenchymal stem cells (hMSCs) with an ABCC6 knockdown were chosen to further investigate the oxidative stress associated with ABCC6 deficiency. The cells were treated with hydrogen peroxide to mimic external oxidative stress and the antioxidant Trolox to examine the cells' reaction to decreased oxidative stress. The level of different types of reactive species (RS) like nitric oxide and reactive oxygen species, the senescent phenotype, oxidative damage and mRNA expression of oxidative stress-related genes were evaluated. Knockdown of ABCC6 was shown to increase RS levels in hMSCs, induce a p53-dependent senescence-like phenotype and increase oxidative damage, while the mRNA expression of oxidative defense genes was elevated. The ABCC6-deficient cells exhibited an altered reaction to additional oxidative stress and the incubation with Trolox reversed these changes induced by ABCC6 knockdown. Our findings provide further evidence linking ABCC6-deficiency to oxidative stress and a senescence-like phenotype, while pointing towards antioxidants as part of a potential treatment for PXE.