Regional variations in proteoglycan content, vasculature, and aggrecanase product abundance (G1-NITEGE) in freshly isolated immature bovine meniscus. (a) Coronal sections of medial meniscus stained for sulfated glycosaminoglycan (red = safranin-O stain; counterstained with fast green), elastin (black = Verhoeff's stain; pink = van Gieson's stain for collagen), or the aggrecan NITEGE neoepitope (green) and collagen type I (red). In immunofluorescent images, the cell nuclei are blue. Inner, middle, and outer refer to the radial position in the coronal plane. Scale bars = 100 μm. (b) The regional variations in aggrecan NITEGE abundance were confirmed by western blot of tissue extracts of both lateral (left lanes) and medial (right lanes) menisci. Equal volumes of tissue extracts (each from about 5 mg wet mass tissue) were loaded in each lane. The migration of globular protein standards are shown at left.