Graduate student Farid Badar is coauthor on paper in Magnetic Resonance in Medicine

CBR member Yang Xia, of the Department of Physics, is internationally known for his studies of articular cartilage and its role in osteoarthritis. In the March issue of Magnetic Resonance in Medicine (Volume 65, Pages 656-663, 2011), Xia published Further Studies on the Anisotropic Distribution of Collagen in Articular Cartilage by μMRI. One hallmark of Xia’s research is the use of very high resolution Magnetic Resonance Imaging; he is able to analyze the tissue on the scale of tens of microns, rather than the much larger millimeter scale of a clinical MRI. Coauthors on the publication include ShaoKuan Zheng, a former post doc in Xia’s laboratory who is now at the University of Massachusetts Medical School, and Farid Badar, a graduate student in the Biomedical Sciences: Medical Physics PhD program. The paper begins

“Structural architecture of articular cartilage plays a critical role in the biomechanical functions and morphological properties of the tissue as a load-bearing material in joints, whose degradation is the hallmark of clinical joint diseases such as osteoarthritis. As the collagen fibril is the principal macromolecule that provides a depth-dependent structural integrity to articular cartilage, continuing efforts have been focused on the specific features of the three-dimensional (3D) collagen structure in cartilage. Histologically, the collagen matrix in noncalcified cartilage is commonly considered to contain three structural zones from the articular surface to the cartilage bone interface, namely, the superficial zone (SZ) with the collagen fibrils parallel with the tissue surface, the transitional zone (TZ) with mostly random fibrils, and the radial zone (RZ) with the perpendicular fibrils anchored to the underlining bone...

This work further investigated the 3D structural anisotropy of the collagen matrix in articular cartilage from SZ to RZ, by rotating the cartilage along two orthogonal axes … relative to B0 [The large static magnetic field in MRI], both perpendicular to the normal axis of the articular surface. A collagen matrix with a z-axial symmetry would produce an identical result in both regular and cross rotations. Any difference between these two rotations would consequently indicate an anisotropic structure of 3D collagen matrix along the z-axis. To the best of knowledge, an investigation of this type of tissue anisotropy had not been systematically carried out. mMRI experiments in this project were completed at 13 mm resolution along the direction of the tissue depth (z). Quantitative T2 anisotropy data were fitted with three fibril structural models to determine the 3D anisotropic distribution of the collagen matrix in articular cartilage.”

The study was carried out using the Bennett NMR Facility, which is supported by a generous donation from Ronald and Janet Bennett. The research was also funded by grants from the National Institutes of Health.