Sulfur-species in Zinc-specific Condylar Zones of a Rat Temporomandibular Joint

In this study, we performed synchrotron-based micro-X-ray fluorescence (-XRF) imaging of elements Zn and S, and X-ray absorption near edge spectroscopy (XANES) coupled with -XRF for identification of Zn and S species in the condylar zones of a rat temporomandibular joint (TMJ). Histologic localization of Zn and hypoxia-inducible factor-1 (HIF-1) were mapped using an optical microscope. These data were visually correlated with -XRF and XANES data to provide insights into plausible biological S-species in Z-enriched condylar zones of a rat TMJ. Furthermore, -XRF coupled with micro-X-ray diffraction (-XRD) was used to underline Z-incorporated biological apatite in the subchondral bone and bone of the rat TMJ. Results illustrated the potential dependence between biometal Zn and nonmetal S and their collective governance of cell and tissue functions in a zone-specific manner. Elemental Zn with organic and inorganic S-species at the cartilage-bone interface and transformation of plausible Zn-enriched mineralization kinetics of biological apatite from subchondral bone to condylar bone were ascertained using -XRF-XANES and -XRD. The coupled -XRF-XANES complementing with -XRD and immunohistology provided an informative view of S and Zn and their association with zone-specific biological pathways in situ. Understanding the spatial distributions of the main S-species with redox-inert Zn in regions of cartilage, bone, and the interface is essential for further unlocking questions surrounding formation and resorption-related biomineralization pathways as related to osteoarthritis or genetically inherited diseases. Using these complementary techniques with microspectroscopic spatial information provided insights into the associations between biometal Zn and nonmetal S and a window into detecting the plausible early-stage diagnostic biomarkers for humans with TMJ osteoarthritis.