title: Remobilization causes site-specific cyst formation in immobilization-induced knee cartilage degeneration in an immobilized rat model.
abstract: An understanding of the articular cartilage degenerative process is necessary for the prevention and treatment of joint disease. The present study aimed to examine how long-term immobilization-induced cartilage degeneration is aggravated by remobilization. Sixty 8-week-old male Wistar rats were used in this study. The unilateral knee joint was immobilized using an external fixator for 8 weeks. The rats were killed at 0 and 3 days, and at 1, 2, 4 and 8 weeks after removing the fixator. After the rats were killed, the maximum knee extension angles were measured. Histological sections at the medial mid-condylar region (non-contact, transitional and contact regions of the femur and tibia) were prepared and scored. The cartilage thickness and number of chondrocytes were measured, and CD44 and Col2-3/4c expression levels were assessed immunohistochemically. The histological assessment revealed progressive aggravation of cartilage degeneration in the transitional region, with a decreased number of chondrocytes and CD44-positive chondrocytes as well as poor scoring over time, particularly in the tibia. Cyst formation was confirmed in the transitional region of the tibia at 8 weeks post-remobilization. The cartilage thickness in the transitional region was thicker than that in the contact region, particularly in the tibia. Col2-3/4c expression was observed in the non-contact and transitional regions, and the knee extension angle was recovered. In conclusion, immobilization-induced cartilage degeneration was aggravated by remobilization over time in the transitional region, followed by observations of a decreased number of chondrocytes and morphological disparity between different cartilage regions.
authors.affiliation: Department of Motor Function Analysis, Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan.|Department of Congenital Anomaly Research Center, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
authors.forename: Momoko
authors.initials: M
authors.lastname: Nagai
authors.affiliation: Department of Motor Function Analysis, Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan.|Department of Orthopedic Surgery, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Ito
authors.affiliation: Department of Motor Function Analysis, Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
authors.forename: Junichi
authors.initials: J
authors.lastname: Tajino
authors.affiliation: Department of Motor Function Analysis, Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
authors.forename: Hirotaka
authors.initials: H
authors.lastname: Iijima
authors.affiliation: Department of Motor Function Analysis, Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
authors.forename: Shoki
authors.initials: S
authors.lastname: Yamaguchi
authors.affiliation: Department of Motor Function Analysis, Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
authors.forename: Xiangkai
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Department of Development and Rehabilitation of Motor Function, Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
authors.forename: Tomoki
authors.initials: T
authors.lastname: Aoyama
authors.affiliation: Department of Motor Function Analysis, Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kuroki
mesh_terms: D000818:Animals; D002357:Cartilage Diseases / Q000209:etiology* / Q000473:pathology; D002358:Cartilage, Articular / Q000473:pathology / Q000502:physiology*; D002452:Cell Count; D019902:Chondrocytes; D024043:Collagen Type II / Q000378:metabolism; D003560:Cysts / Q000209:etiology* / Q000473:pathology; D018960:Hyaluronan Receptors / Q000378:metabolism; D007103:Immobilization / Q000009:adverse effects*; D008297:Male; D051381:Rats; D017208:Rats, Wistar
chemical_list: D024043:Collagen Type II; D018960:Hyaluronan Receptors
keywords: aggravation; cartilage; cyst; degeneration; immobilization; remobilization