Xia PLM Lab

We have a Leica DM polarized light microscope, which has two digital imaging systems: (a) a home-built system with a thermoelectrically cooled Sensys camera, where we write our own software to analyze the binary images; and (b) a commercial Abrio system from Cambridge Research & Instrumentation (Wobum, MA), on which we can analyze the proprietary data from CRI.

For each tissue section, our protocol calculates two quantitative images: the angle (in degree) and the retardation (in nm) of the tissue section. For articular cartilage, the 2D angle map displays the orientation of the collagen fibrils in cartilage; and the 2D retardation map illustrates the organization of the fibril and macromolecules in cartilage. We routinely use magnification between 0.25µm/pixel (sufficient for quantitative mapping of the chondrocytes/territorial matrix in the tissue) and 2µm/pixel (suitable for whole-thickness morphology).

Selected Publications

Y Xia, J Moody, N Burton-Wurster, and G Lust,"Quantitative In Situ Correlation Between Microscopic MRI and Polarized Light Microscopy Studies of Articular Cartilage", Osteoarthritis and Cartilage, 9 (5), 393-406 (2001). [PMID: 11467887]

Is there any quantitative correlation between µMRI features and PLM features? A set of quantitative criteria is established, for the first time, in MRI and PLM, which offers an objective means to subdivide the zones in both µMRI and PLM. Applying these criteria to the imaging data has yielded statistically significant agreement between the zones in µMR images and in PLM images. Just as noncalcified cartilage can be conceptually subdivided based on the orientation of the collagen fibers into three distinct structural zones in histology, a cartilage can also be subdivided based on the regional characteristics of the T2 relaxation in NMR into three structural zones.

Y Xia, J B Moody, H Alhadlaq, J Hu, "Imaging the Physical and Morphological Properties of a Multi-Zone Young Articular Cartilage at Microscopic Resolution", Journal of Magnetic Resonance Imaging, 17 (3), 365-374 (2003). [PMID: 12594728]

What are the topographical variations in young cartilage? MRI and PLM can be used to study the epiphyseal expansion of cartilage in young animals during its growth and the subsequent loss in older animals. An illustrative model for the structure of collagen fibrils in a humeral head is suggested as an extension to the classical three-zone model for young articular cartilage.

H Alhadlaq, Y Xia, J B. Moody, J Matyas, "Detection of early experimental osteoarthritis in canine tibial cartilage: A quantitative study by Microscopic MRI and Polarized Light Microscopy", Annals of Rheumatic Diseases, 63 (6), 709-717 (2004). [PMID: 15140779]

Yes, you can detect the early osteoarthritis using MRI, if you have sufficient resolution! µMRI, PLM and biomechanical measurements have the ability to quantitatively detect changes in collagen fiber architecture in early OA and to resolve topographical variations in cartilage microstructure of canine tibia.

H Alhadlaq, Y Xia, F Hansen, C Les, G Lust, "Morphological changes in articular cartilage due to static compression: Polarized light microscopy study", Connective Tissue Research, 48 (2), 76-84 (2007). [PMID: 17453909]

How to preserve a compressed morphology in tissue so that it can be sectioned? A novel paraffin protocol is developed to preserve the altered morphology of the compressed cartilage, which can be subsequently quantified by polarized light microscopy. Both morphological and territorial features of cartilage were quantified using angle (fibril orientation) and retardation (fibril organization).

Y Xia, "Averaged and Depth-dependent Anisotropy of Articular Cartilage by Microscopic Imaging", Seminars in Arthritis and Rheumatism, 37 (5), 317-327 (2008). [PMID: 17888496]

Is there a common model to explain the multi-disciplinary imaging results? An ellipse model is introduced to describe the 3D anisotropic structure of articular cartilage and to identify the common connections among the averaged and depth-dependent anisotropic properties of articular cartilage in microscopic magnetic resonance imaging (µMRI), polarized light microscopy (PLM), Fourier-transform infrared imaging (FTIRI), and transmission electron microscopy (TEM).

TQ Xie, Y Xia, SG Guo, P Hoover, ZP Chen and GM Peavy, "Topographical variations in the polarization sensitivity of articular cartilage as determined by polarization sensitive optical coherence tomography and polarized light microscopy", Journal of Biomedical Optics, 13 (5), 054034 (2008). [PMID: 19021414]

What are the correlations between PLM and OCT results? We used polarized light microscopy (PLM) to quantify the orientation and phase retardation of the collagen architecture in cartilage at the same locations imaged by PS-OCT (polarization-sensitive optical coherence tomography). We show that normal variations in the orientation of the collagen matrix within a joint will manifest as different degrees of polarization sensitivity when imaged by PS-OCT.

Y Xia, H Alhadlaq, N Ramakrishnan, A Bidthanapally, F Badar, M Lu, "Molecular and Morphological Adaptations in Compressed Articular Cartilage by Polarized Light Microscopy and Fourier-Transform Infrared Imaging", Journal of Structural Biology, 164 (10) 88-95 (2008). [PMID: 18634884]

What are the changes in molecular bond directions when one compresses a soft tissue? An excellent correlation is found between the relative depth of the minimum retardance in PLM and the relative depth of the Amide II anisotropic cross-over in FTIRI. The changes in amide anisotropies in different deformed histological zones are explained by a model that describes the strain-dependent tipping angle of the amide bonds. Our images appeared on the cover of this issue.

D Mittelstaedt, Y Xia, A Shmelyov, N Casciani, A Bidthanapally, “Quantitative Determination of Morphological and Territorial Structures of Articular Cartilage from both Perpendicular and Parallel Sections by Polarized Light Microscopy”, Connective Tissue Research, 52 (6), 512-522 (2011).

What are the optical properties of articular cartilage when you slice it layer by layer away from its articular surface? This is the first quantitative PLM study of parallel sections of articular cartilage over the full cartilage thickness using a 6µm step-increment, with both 50x and 400x magnifications. We showed that the birefringence of the parallel sections exhibited some unique features that were very different from the usual perpendicular sections. This orthogonal viewing approach can provide a comprehensive understanding of the 3D territorial and interterritorial fibrils in articular cartilage.

Y Xia, SK Zheng, M Szarko, JH Lee, “Anisotropic Properties of Bovine Nasal Cartilage”, Microscopy Research and Technique, 75 (3), 361-370 (2012).

Is nasal cartilage truly isotropic? This is the first quantitative study of bovine nasal cartilage by µMRI, PLM, and biomechanical indentation, which reveals that the collagen structure in nasal cartilage has a residual anisotropy (in a direction that I was not expected). This fibril anisotropy can complicate any experiment that is sensitive to fibril orientation.

...