DETECTION OF VASCULAR DENDRITIC CELLS ACCUMULATING CALCIFIED DEPOSITSIN THEIR CYTOPLASM

The distribution of calcified microdeposits in non-atherosclerotic int ima of the human aorta was studied by electron microscopy, Aortic spec imens 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 microanal yser, Subsequent staining of these ultrastructural sections with lead citrate allowed us to view the tissue structures and allowed the preci se location of calcified deposits in the intimal tissue to be determin ed. Calcium-containing microstructures were found in the extracellular matrix of the intima but, occasionally, calcium-containing microdepos its were also seen in the cytoplasm of intimal cells. Cisterns of a tu bulovesicular system which is uniquely developed in cells from the den dritic cell family were detected in the calcium-containing intimal cel ls, which enabled these calcium-accumulating cells to be identified as a phenotype of vascular dendritic cells. These modified vascular dend ritic cells might be the 'calcifying vascular cells' described previou sly by others.