Cellular mechanism of calcification and its prevention in glutaraldehyde treated vascular tissue

Prevention of calcification in glutaraldehyde (GA) treated porcine aortic valve fibroblasts and rat aorta with Ca2+ channel blockers (Ca(2+)-CBs).

GA causes a massive increase in [Ca2+]i and a many fold increase in [Pi]i followed by calcification of porcine aortic valve fibroblasts. The influx of extracellular Ca2+ into [Pi]i rich cells apparently underlies the mechanism of calcification. Inhibition of Ca2+ influx is likely to prevent calcification in GA-treated cells.

[Ca2+]i in GA-treated cells was measured by fluorescence image analysis. [Ca2+]i increase in fibroblasts treated with various Ca(2+)-CBs was compared with the untreated control. To study the role of Ca2+ influx in calcification and to find out the portals of Ca2+ entry, porcine aortic valve fibroblasts and freshly removed rat aorta were treated with verapamil + ryanodine, or verapamil + econazole, fixed with GA and incubated in Hank's balanced salt solution with 2.5 mmol/L calcium. The progress of calcification was monitored by the rate of Ca and Pi depletions from the supernatant. Calcified cells and tissues were identified by calcein fluorescence.

Verapamil + ryanodine or econazole inhibited the GA-induced Ca2+ influx and prevented calcification of the cells and rat aorta. The effect of verapamil was additive to that of ryanodine and econazole.

Findings further support the influx theory of calcification. Ca2+ enters GA-treated cells mainly through the store operated and the L-type Ca2+ channels. Ca(2+)-CBs may be useful for prevention of calcification in GA-treated vascular bioprostheses. Cell culture serves as a convenient model for screening drug effects on calcification.