Loss of proteoglycans during decalcification of fresh metaphyses with disodium ethylenediaminetetraacetate (EDTA).

Abstract

Recent immunofluorescent and histochemical data did not detect changes in the concentration of proteoglycans between noncalcified and calcified cartilage in fetal bovine growth plate or metaphyseal bone. These findings were constant, regardless of prior fixation before demineralization with disodium ethylenediaminetetraacetate (EDTA) or prior demineralization before fixation. Previous experience has shown that EDTA can extract proteoglycans from calcified cartilage. With this in mind, we determined the amount of proteoglycan extracted from calcified cartilage in metaphyseal bone and uncalcified growth plate cartilages during decalcification of unfixed fresh tissues with EDTA. To this end, fresh growth plate cartilages and metaphyses were decalcified at 5 degrees C for 48 hours in a buffered solution of EDTA to which several protease inhibitors were added. Under these conditions 20-25% of the total proteoglycan (measured as uronic acid and hexosamine) was extracted from mineralized cartilage but only about 1% from the uncalcified (growth plate) cartilages. Thus, histochemical and immunohistochemical studies appear to be insensitive measures of proteoglycan concentrations in histological sections of mineralized tissue and may not give quantitative information.