Perlecan Immunolocalizes to Perichondrial Vessels and Canals in Human Fetal Cartilaginous Primordia in Early Vascular and Matrix Remodeling Events Associated with Diarthrodial Joint Development

The aim of this study was to ascertain how perlecan was localized in human fetal cartilaginous joint rudiment tissues. Perlecan was immunolocalized in human fetal (12–14-week-old) toe, finger, knee, elbow, shoulder, and hip joint rudiments using a monoclonal antibody to domain-1 of perlecan (MAb A76). Perlecan had a widespread distribution in the cartilaginous joint rudiments and growth plates and was also prominent in a network of convoluted hairpin loop-type vessels at the presumptive articulating surfaces of joints. Perlecan was also present in small perichondrial venules and arterioles along the shaft of the developing long bones, small blood vessels in the synovial lining and joint capsules, and in distinctive arrangements of cartilage canals in the knee, elbow, shoulder, and hip joint rudiments. Perlecan was notably absent from CD-31-positive metaphyseal vessels in the hip, knee, shoulder, and fingers. These vessels may have a role in the nutrition of the expanding cell populations in these developing joint tissues and in the establishment of the secondary centers of ossification in the long bones, which is essential for endochondral ossification.