Multinucleated Tartrate Resistant Acid Phosphatase Positive Cells with Macrophage and Osteoclast Phenotypes in Bone

Prothrombin (PT) and osteopontin (OPN) promotes adhesion of different TRAP-positive multinucleated cells isolated from rat long bone (Hu et al. Exp Cell Res. 2008; 314: 638-50). The PT-adhering cell could represent either an immature precursor to the OPN-adherent osteoclast or constitute a distinct multinucleated cell population with a unique role in bone. Herein, phenotypic differences between PT- and OPN- cells were investigated with microarray- expression analysis. Characteristic for PT-cells was expression of innate immune response genes and scavenger receptors whereas OPN-cells expressed typical osteoclast proteins such as collagenases implicated in bone degradation. Bone cells were extracted from neonatal Sprague Dawley rat long bones. The extracted cells were attached to PT or OPN, and thereby two cell populations were isolated. mRNA was extracted from these cells and their expression was compared with the Affymetrix GeneChip Rat Gene 1.0 ST Array.