Effects of Bordetella bronchiseptica dermonecrotic toxin on the structure and function of osteoblastic clone MC3T3-e1 cells.

The effects of Bordetella bronchiseptica dermonecrotic toxin on the structure and function of a clonal osteoblastic cell line, MC3T3-E1, were investigated. The toxin induced a morphological change in the cells from a spindle shape to a spherical form with many blebs. The toxin-treated cells were viable and grew to form confluent cell layers composed of irregularly shaped cells and multinuclear cells. The toxin inhibited elevation of alkaline phosphatase activity in the cells in a dose-dependent manner at concentrations from 10 pg to 10 ng/ml. The accumulation of type I collagen in the cells was also reduced by the toxin. Since high alkaline phosphatase activity and accumulation of collagen are closely linked to differentiation of the cells into osteoblasts, it is considered likely that B. bronchiseptica dermonecrotic toxin impairs the ability of the cells to differentiate.