Inhibition of osteoclast recruitment at a local site by 1-hydroxyethylidene-1,1-bisphosphonate (HEBP).

We hypothesized that bisphosphates, a class of antiosteolytic drugs that affect bone cells, may block localized bone modeling in the middle ear. Prior studies have shown that transmitted pressure in the middle ear leads to osteoclastic bone resorption. Catheters were surgically implanted into the middle ear cavity (bulla) of 31 Mongolian gerbils. The animals were then divided into two groups, one subset receiving a bisphosphonate, and the other receiving no drug. Positive air pressure was applied to one middle ear, and the other side served as a control. At the end of the experimental period, tissue specimens were obtained, and histomorphometric evaluation of the ventral bullae was performed. Significant differences in osteoclast surface, osteoclast number, and mean individual osteoclast profile area led us to conclude that administration of the bisphosphonate used at the dose studied inhibits localized recruitment and activation of osteoclasts.