Abstract

Vascular calcification is prominent in the ageing population yet little is understood about the mechanisms involved in senescence-associated phenotypic change in VSMCs. Our previous data showed that VSMCs acquire nuclear defects due to the accumulation of the nuclear lamina protein-prelamin A as they approach senescence both in vitro and in vivo. Over-expression of prelamin A accelerated VSMC senescence and DNA damage1, and prelamin A accumulated at sites of calcification in diseased arteries. In this study, we investigated whether prelamin A accumulation has an effect on VSMC osteogenic differentiation and the mechanisms underlying this process. Using immunostaining and Western blot we show that there was increased prelamin A accumulation in calcifying VSMCs. Adenoviral over-expression of prelamin A significantly accelerated VSMC mineralisation, shown by alizarin red staining, increased 45Calcium incorporation (6.97±0.58-fold [p<0.01]) and alkaline phosphatase (ALP) activity (2.11±0.16-fold [p<0.05]) compared to controls. Moreover, prelamin A over-expression also significantly elevated mRNA levels of Runx2, osteocalcin, BMP2 and ALP in VSMCs. Coculture of VSMC over-expressing prelamin A with C2C12 cells significantly enhanced osteogenic differentiation of C2C12€s due to increased BMP2 secretion. Prelamin A over-expression also induced persistent DNA damage in VSMCs, shown by 53BP1 immunostaining and western blotting for p-ATM/ATR, and p-H2AX. More importantly, the DNA damage response inhibitor, CGK733, significantly blocked prelamin A over-expression induced VSMC osteogenic differentiation. This is the first study to show that prelamin A links DNA damage to VSMC mineralisation and suggests that age-related vascular calcification shares similar mechanisms to the accelerated VSMC ageing observed in patients with progeria syndromes.