Effect of 1-hydroxyethane-1,1-diphosphonic acid (HEDP) on new bone formation induced by bone matrix gelatin (BMG).

The effect of the biphosphonate 1-hdroxyethane-1,1 diphosphonic acid (HEDP) on induced ectopic osteoneogenesis was studied by light and electron microscopy. Demineralized bone matrix gelatin (BMG) was implanted into the rectus abdominis muscle of 8-week-old Sprague-Dawley rats, HEDP was administered subcutaneously with a mini-osmotic pump, and histological changes were examined 4 days, 1, 2 and 3 weeks later. Four days after implantation, "acellular mineral deposition" in the control group was suppressed in the HEDP group. Two weeks after BMG implantation, cartilage formation was more intensive in the HEDP-treated group than in the control group. Three weeks after implantation, new lamellar bone with bone marrow was observed in the control group, while immature osteoid tissue detected by type II collagen in the central area was prominent in the HEDP-treated group. HEDP-treatment also suppressed the appearance and activity of osteoclast-like cell.