The biochemistry of bone.

The study of mineralized tissues has witnessed unprecedented advances as a result of recent technical breakthroughs in protein chemistry, and cell and molecular biology. Procedures for the nondegradative extraction of proteins present in mineralized matrices, along with improved chromatographic techniques, have resulted in the identification and purification of most, if not all, of the major structural proteins as well as less abundant (growth factors) proteins in these tissues. Many antibodies have become available against the intact proteins, as well as against synthetic peptides of the amino acid sequence from different parts of molecules. Along with mRNA determinations by in situ hybridization, these have been instrumental in determining when and where a matrix constituent is present in bone. Development of cell culture methods that maintain phenotypic expression has provided experimental systems to study the synthesis, secretion, and deposition of matrix, and the regulation of these processes. These model systems also have served as a source of genetic material for the making of cDNA libraries, which have been used for isolation of cDNA probes and ultimately for the isolation and characterization of the genes. By using these techniques, it is now feasible to develop procedures for the assessment of the role of matrix proteins in mineralized tissue, which will most certainly provide information that is critical to our understanding of bone metabolism in health and disease.