TEM examination and TUNEL staining of the ossification front. The typical structure of the elastic fibers had disappeared with an increase in the number of collagen fibers (a: control, b: OLF). Note the presence of matrix vesicles containing electron-dense material (c) and also the presence of pigmented chondrocytes (d) near the ossified layer (a, b: magnification ×1,000, c; magnification ×4,000, d; magnification ×2000). Note the presence of TUNEL-positive chondrocytes near the ossified layer (arrow) (e, scale bar = 100 μm). OLF: ossification of the ligamentum flavum; TEM: transmission electron microscopy; TUNEL: terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling.
Uchida et al. Arthritis Research & Therapy 2011 13:R144 doi:10.1186/ar3458