Figure 6.

Expression of phosphorylated PKR and PERK correlate with the degree of degeneration in human OA tissue. Sections from the MTP of two patients undergoing total knee replacement for OA were stained with toluidine blue to establish the degree of tissue degeneration. The subcellular localization of phosphorylated PKR and PERK were determined by immunohistochemistry. Patient 1 had complete cartilage loss and severe bone changes toward the outer edge of the plateau with the remaining cartilage showing signs of significant fibrillation and proteoglycan loss (A). Five regions (black boxes; i–v) highlight areas of limited damage (joint middle) to severe damage (outer edge). Representative staining for phosphorylated PERK (B) and PKR (C) from these five regions are shown revealing more staining in the cartilage as the damage progresses outwards and significant activation in the remodeling bone in the areas underlying the complete loss of cartilage. Patient 2 had cartilage fibrillations and proteoglycan loss, which were more extensive toward the outer edge but the damage was less extensive that patient 1 (D). Four regions (black boxes; i–iv) highlight areas of limited damage (joint middle) to severe damage (outer edge). Representative staining for phosphorylated PERK (E) and PKR (F) from these four regions are shown revealing more staining in the cartilage as the damage progresses outwards but not the extensive activity in the bone as observed for patient 1. Scale bars = 100 μm.