Methods for Preparing Extracellular Matrix and Quantifying Insulin-like Growth Factor-Binding Protein Binding to the ECM

The insulin-like growth factor-binding proteins (IGFBPs) are carrier proteins that are present in all extracellular fluids (1 ). Similarly, insulin-like growth factor-I (IGF-I) and -II are synthesized by connective tissue cells that are present within the stroma of all tissues, and therefore their presence is ubiquitous in all organs (2 ). IGF receptors are present in all tissues, which accounts for balanced growth of organs, and deletion of the IGF-I gene results in a balanced decrease in organ growth, whereas overexpression of IGF-I results in a symmetric increase in growth (3 ).