Establishment and characterization of tartrate-resistant acid phosphatase and alkaline phosphatase double positive cell lines

Morphologically macrophage-like cells were cloned from hamster bone marrow cells by coculturing bone marrow cells with hamster chondrocytes. One of the clones (CCP-2) was characterized in the present study. CCP-2 cells were positive in an osteoclast marker enzyme, tartrate-resistant acid phosphatase (TRAP), alkaline phosphatase (ALP) and non-specific esterase (NSE). We showed CCP-2 cells degraded cartilage matrix and hydroxyapatite coated on Osteologic disks. A gelatinase secreted from CCP-2 cells was observed and purified from serum-free conditioned medium of the cells. N-terminal amino acid sequencing of the purified enzyme revealed it was matrix metalloproteinase-9. However, CCP-2 cells failed to express calcitonin receptors, a mature osteoclast marker, even after coculture with osteoblast ST2 cells in the presence of 1 alpha, 25-dihydroxyvitamin D-3 [1 alpha, 25-(OH)(2)D-3]. The cells showed high affinity to types X and I but not to type II collagen. In addition, histochemical studies have shown the presence of tartrate-resistant acid phosphatase and alkaline phosphatase double positive cells at the secondary ossification site of the hamster humerus. From these observations, we concluded that CCP-2 cells are similar to osteoclast but not the same. CCP-2 cells are therefore important tools for investigating chondroclastogenesis/ osteoclastogenesis and endochondral ossification.