Figure 2From: Sensory and sympathetic nerve fibers undergo sprouting and neuroma formation in the painful arthritic joint of geriatric mice CFA injection into the geriatric knee joint induces synovial inflammation, macrophage infiltration, and neovascularization. (A) Schematic of the frontal view of a cross-sectioned mouse knee joint, indicating the location of the major cellular and structural changes occurring in the arthritic knee joint. (B-G) Longitudinal cross sections (10 μm thick) of the knee joint stained with safranin-O/fast green display the histopathologic changes in the synovium and capsule 28 days after initial injection of complete Freund's adjuvant (CFA). In the vehicle-injected mice, the synovium is very thin and relatively intact (B), whereas in CFA-injected mice, an extensive inflammation in the synovial membrane and thickening of the joint capsule are found (C). The outlined boxes in B and C illustrate the region from which the subsequent confocal images were obtained. Representative confocal images of CD68+ macrophages (D, E, red/orange), DAPI-labeled nuclei (blue), and a vascular endothelial marker, PECAM+ (F, G, red) in vehicle-injected (D, F) and CFA-injected (E, G) mouse knee-joint sections (20 μm-thick). Injections of CFA induce a significant infiltration of CD68+ macrophages into the synovium (E), as compared with vehicle-treated mice (D). In vehicle-injected mice, a low-level vascularization by PECAM+ vessels is observed in the synovial space of the knee joint (F). In contrast, in CFA-treated knee joints, a significant number of PECAM+ vessels have developed and have an enlarged and disorganized morphology (G), as compared with vehicle-treated mice.Back to article page