27] Purification of bovine skeletal growth factor

Abstract

Unlike most of the organ systems, the specific cellular components of bone—osteoblasts, osteocytes, and osteoclasts—account for only a minor portion (5–10%) of tissue weight. The major component of bone is matrix (90–95%), which consists of a mineral phase (60–65% of noncellular bone weight) and a protein phase (35–40%). The largest protein component (90% of matrix protein) is type I collagen. The noncollagenous proteins (10%) are heterogeneous in origin; some appear to be produced by bone cells, while others are incorporated from or are concentrated from serum. This chapter discusses the chick embryo calvarial cell bioassay that is used to monitor the purification of skeletal growth factor (SGF) because a sensitive assay procedure is needed for purification. To obtain greater quantities of SGF, bovine bone is used because large quantities of fresh bone are readily available for the extraction of matrix proteins.