acid-phosphatase and cimadronate

To determine the effects of a bisphosphonate on the quality of bone morphogenetic protein-(BMP-) induced bone, incadronate was administered to rats in which subcutaneous ectopic bones were induced by recombinant human BMP-2. Incadronate (1 microg/kg/day) was administered to rats carrying the BMP-induced bones three times per week, from the 3rd to 7th week after BMP implantation (incadronate group). Aliquots of phosphate-buffered saline were administered in the same protocol without incadronate to the control group. During the 3rd, 4th, 7th, or 10th week, the BMP-induced bones were removed and observed by contact microradiography (CMR), H&E staining, enzyme histochemistry for tartrate-resistant acid phosphatase (TRAP), and immunohistochemistry for cathepsin K. By 3 weeks when administration of incadronate began, woven bones formed in the periphery of the BMP pellets and osteoclasts were attached to these bones. At 4 weeks, in both the incadronate and control groups, bone formation advanced inward. However, in the incadronate group, poorly calcified areas, corresponding to the remaining BMP pellets, were found in the middle areas of bone formation, whereas osteoclasts decreased when compared with those of the control group. During the 10 weeks, bone marrow was formed and the characteristics of lamellar bones, in which the lacunae of small osteocytes were regularly arranged, were noted in the control group. In contrast, the poorly calcified areas were still present up to 10 weeks in incadronate group in which the osteoclasts were also scarcer than in the control group. These findings suggested that osteoclast-mediated bone resorption was inhibited by incadronate administration, and that immature bones including the BMP pellets remained for a long time, indicating that the process of bone maturation was blocked. The possibility of using incadronate for the purpose of inhibiting osteoclastic bone resorption was confirmed, but further study is needed before clinical application.

Topics: Acid Phosphatase; Animals; Bone and Bones; Bone Development; Bone Morphogenetic Protein 2; Bone Morphogenetic Proteins; Cathepsin K; Cathepsins; Diphosphonates; Isoenzymes; Male; Rats; Rats, Wistar; Recombinant Proteins; Tartrate-Resistant Acid Phosphatase; Transforming Growth Factor beta

The effects of a third-generation bisphosphonate, YM175 (disodium dihydrogen (cycloheptylamino)-methylene-1,1-bisphosphonate), on bone resorption induced by a metastatic human melanoma cell line (A375) were investigated morphologically using an experimental model of bone metastases in nude mice. An injection of A375 in the left cardiac ventricle produced multiple osteolytic lesions. Then, 4 weeks after the cell injection, we administrated YM175 (1 mg/kg) intravenously once and sacrificed the animals 3 days later. On histochemical observation, there was a layer of stromal cells with numerous mononuclear and multinucleated tartrate-resistant acid phosphatase (TRAPase)-positive cells in the untreated control group. In contrast, this layer was extensively reduced in most areas, and only a few TRAPase-positive cells were seen around tumor nests and on the bone surface in the experimental group. Most of the TRAPase-positive cells were stained only weakly and/or homogeneously, and there was little evidence of cell polarity. Some of them were vacuolated. Ultrastructurally, they were round and devoid of ruffled borders and clear zones. The findings suggest that YM175 decreases the number and activity of osteoclasts. In addition, a few showed the morphology of cell death, which seemed to be one of the reasons leading to the decrease of osteoclasts. There was no substantial change in the morphological relationships or ultrastructure of osteoclast precursor cells, stromal cells, extracellular matrices, and tumor cells between the experimental and the control groups. In the experimental group, the distribution of extracellular matrices (heparan sulfate proteoglycan and fibronectin) was less conspicuous, but the localization of osteotropic cytokines (interleukin-6 and prostaglandin E2) was essentially similar to that of the control group. The cause leading to the decrease of osteoclast precursor cells remains to be clarified. In conclusion, YM175 inhibits bone resorption induced by tumor, by decreasing the activity of mature osteoclasts and possibly affecting the production of osteoclast precursor cells.

Topics: Acid Phosphatase; Animals; Biomarkers, Tumor; Bone Neoplasms; Bone Resorption; Diphosphonates; Humans; Immunohistochemistry; Isoenzymes; Male; Melanoma; Mice; Mice, Nude; Neoplasm Transplantation; Tartrate-Resistant Acid Phosphatase; Tumor Cells, Cultured