Detection of vascular dendritic cells accumulating calcified deposits in their cytoplasm

The distribution of calcified microdeposits in non-atherosclerotic intima of the human aorta was studied by electron microscopy. Aortic specimens were obtained during aortic reconstruction and were embedded in Lowicryl resin. Non-stained ultrathin sections were analysed using an electron microscope equipped with an energy-dispersive X-ray microanalyser. Subsequent staining of these ultrastructural sections with lead citrate allowed us to view the tissue structures and allowed the precise location of calcified deposits in the intimal tissue to be determined. Calcium-containing microstructures were found in the extracellular matrix of the intima but, occasionally, calcium-containing microdeposits were also seen in the cytoplasm of intimal cells. Cisterns of a tubulovesicular system which is uniquely developed in cells from the dendritic cell family were detected in the calcium-containing intimal cells, which enabled these calcium-accumulating cells to be identified as a phenotype of vascular dendritic cells. These modified vascular dendritic cells might be the 'calcifying vascular cells' described previously by others.