Two-dimensional polyacrylamide gel electrophoresis reveals differences between osteoblast and fibroblast extracellular proteins

Normal human skin fibroblast primary cell lines secrete over 50 proteins into culture medium. These have been mapped previously using two‐dimensional polyacrylamide gel electrophoresis (2‐D PAGE) and this technique has now been used to investigate extracellular protein secretion by human osteoblasts in vitro. We report the mapping of a number of consistent markers specific to the osteoblast. In particular, one protein chain with posttranslational modifications was found to be unique to the osteoblast extracellular protein map. The absence of the N‐ and O‐glycoforms of collagenase from the osteoblast profile in this study concurs with findings reported using the immunoprecipitation functional assay and Northern blot analysis. The use of 2‐D PAGE in phenotypic assessment provides a more complete analysis than the standard range of single‐parameter tests for osteobiasts. Mapping of extracellular and cellular proteins in addition to bone matrix protein analysis will allow a comprehensive analysis of normal osteoblast function. This technique may also be applied to the study of osteoblasts in relation to bone disease and in assessing the phenotypic shift within a normal osteoblast culture.