Low-angle X-ray diffraction analysis of the collagen-proteoglycan interactions in articular cartilage

A comparative analysis, by low-angle X-ray diffraction and electron microscopy, of bovine articular cartilage either submitted or not to chemical (0.5-2 M CaCl2, 4 M guanidinium chloride) or enzymatic (hyaluronidase, trypsin) treatments is reported. An analysis of the micrographs using a filtering program on the Fourier transform patterns reveals the absence of modification or alteration of the fibrils after treatment, whereas the X-ray diffraction patterns change. The ratio of the first/third orders intensities increases when the tissue proteoglycans content decreases. These results indicate that proteoglycans are regularly ordered on the type II collagen fibrils in articular cartilage.