Cell differentiation and bone protein synthesis in the lungs of sheep withspontaneous calcinosis

The lungs of three sheep with spontaneous enzootic calcinosis induced by th e calcinogenic plant Nierembergia veitchii (Nv) were examined electron micr oscopically and immunohistochemically. The main ultrastructural changes wer e activation of fibroblasts and modified smooth muscle cells (SMCs) in the pulmonary interstitium, with an increase in extracellular matrix and precip itation of calcium, either in a laminated pattern or as amorphous aggregate s. Macrophages and multinucleated giant cells, some with calcium crystals i n the cytoplasm, were found in areas of increased extracellular matrix. Thi ckening and replication of the basal lamina of capillaries were prominent. The hone proteins osteocalcin? osteopontin and osteonectin were detected im munohistochemically in the cytoplasm of activated fibroblasts, in modified SMCs and in the extracellular matrix. It is suggested that 1,25-dihydroxyvi tamin D-3 in Nv induces cellular differentiation and the synthesis of a cal cifiable matrix. (C) 2000 Harcourt Publishers Ltd.