MIA Induced TMJOA in Rat Figure 2. Ultrastructural changes in disc 1 day after MIA injection into upper compartment of TMJ. A. SEM view of the disc. (a). The furrowed surface (arrow) of the control joint. (b). The surface 1 day after MIA treatment, showing regional flattening in the intermediate zone (dotted arrow) with residual gelatin condensed to a mass (hollow arrow), surrounded by an area with a rough and uneven surface (arrow). (c). Section view of the control disc showed the disc cells studded in the collagen fibrils (white arrow). (d). Section view of the disc of the MIA-treated group showed that disc cells were crimpled and detached from the collagen fibrils (white arrow). B. TEM view of the intermediate zone of the disc. (a). Cells in the control disc were closely attached to the collagen fibrils (arrowhead) and cell junctions were tight (arrow). (b). The cells in the MIA-treated disc were shrunken with condensed chromatin (white arrow), detached from the disrupted ECM (arrowhead), and had loose cell junctions (arrow). (c). Mitochondria were regularly tubular-shaped (arrow) around the nuclei in the control disc. (d). Chromatin compaction (white arrow), swollen mitochondria (arrowhead), and vacuolar degeneration (dotted arrow) were observed in the disc cells 1 day after MIA treatment. (CF: collagen fibers; N: nucleus; Bar = 50 mm in A- a, b; Bar = 20 mm in A-c, d; Bar = 0.5 mm in B). doi:10.1371/journal.pone.0045036.g002 PLOS ONE | www.plosone.org 5 September 2012 | Volume 7 | Issue 9 | e45036