Changes of microstructure in cartilage and subchondral bone of patients with knee osteoarthritis

Abstract

Objective To investigate microstructure changes of cartilage and subchondral bone in the nonsclerotic and sclerotic zones of the tibial plateau in patients with knee osteoarthritis (OA), and explore the pathological features of different parts and stages of knee OA. Methods Tibial plateau tissues abandoned after total knee arthroplasty were collected in OA patients. After gross observation, the cartilage and subchondral bone were divided into nonsclerotic and sclerotic zones. The pathologic changes of tissue and cell microstructure characteristics were observed by scanning and transmission electron microscopies, and the microstructure of subchondral bone was evaluated by Micro-CT scanning system. Results As compared with the nonscleroic zone, scanning electron microscopy showed that the cartilage morphology of the scleroic zone was chaotic and thinner, and surface collagen fibers were disarranged. The cracks to the subchondral bone were observed. The subchondral bone plate and trabecular bone were thickened, and gap narrowed. The transmission electron microscopy showed that the nucleus of the chondrocytes in the scleroic zone was irregular, and the rough endoplasmic reticulum was dilated, the Golgi apparatus was underdeveloped, and mitochondria displayed edema. Bone matrix collagen arranged sparsely. Secondary lysosomes increased and bright microfilament reduced in osteoclasts. The osteoblast envelope was wrinkled with no small protuberances on the surface. The microvascular formation was seen in the scleroic zones. The micro-computed tomography showed bone mineral density (BMD, 98.040±20.600), BV/TV (40.060±7.110), Tb.N (1.540±0.181) and Tb.Th (0.250±0.039) were increased, and Tb.Sp (0.43±0.047) and SMI (0.83±0.124) decreased in the scleroic zone as compared with the non-sclerotic zone (t=7.931, 11.959, 6.212, 8.070, 8.566, 10.803, P<0.05). Conclusion The microstructure of cartilage and subchondral bone in OA sclerotic area is different from that in nonsclerotic area. The microstructure of cartilage and subchondral bone in the sclerotic area should be further studied. Key words: Osteoarthritis; Cartilage; Subchondral bone; Microstructure