Alteration of cartilage surface collagen fibers differs locally after immobilization of knee joints in rats.
The purpose of this study was to examine the ultrastructural changes of surface cartilage collagen fibers, which differ by region and the length of the experimental period in an immobilization model of rat. Male Wistar rats were randomly divided into histological or macroscopic and ultrastructural assessment groups. The left knees of all the animals were surgically immobilized by external fixation for 1, 2, 4, 8 or 16 weeks (n = 5/time point). Sagittal histological sections of the medial mid-condylar region of the knee were obtained and assessed in four specific regions (contact and peripheral regions of the femur and tibia) and two zones (superficial and deep). To semi-quantify the staining intensity of the collagen fibers in the cartilage, picrosirius red staining was used. The cartilage surface changes of all the assessed regions were investigated by scanning electron microscopy (SEM). From histological and SEM observations, the fibrillation and irregular changes of the cartilage surface were more severe in the peripheral region than in the contact region. Interestingly, at 16 weeks post-immobilization, we observed non-fibrous structures at both the contact and peripheral regions. The collagen fiber staining intensity decreased in the contact region compared with the peripheral region. In conclusion, the alteration of surface collagen fiber ultrastructure and collagen staining intensity differed by the specific cartilage regions after immobilization. These results demonstrate that the progressive degeneration of cartilage is region specific, and depends on the length of the immobilization period.
Department of Motor Function Analysis, Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
Momoko
M
Nagai
Department of Development and Rehabilitation of Motor Function, Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
Tomoki
T
Aoyama
Department of Motor Function Analysis, Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
Akira
A
Ito
Department of Motor Function Analysis, Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
Junichi
J
Tajino
Department of Motor Function Analysis, Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
Hirotaka
H
Iijima
Department of Motor Function Analysis, Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
Shoki
S
Yamaguchi
Department of Motor Function Analysis, Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
Xiangkai
X
Zhang
Department of Motor Function Analysis, Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
Hiroshi
H
Kuroki
D000818:Animals; D001391:Azo Compounds; D002356:Cartilage / Q000254:growth & development* / Q000648:ultrastructure; D003094:Collagen / Q000648:ultrastructure*; D006652:Histological Techniques; D007719:Knee Joint / Q000254:growth & development*; D008297:Male; D008855:Microscopy, Electron, Scanning; D051381:Rats; D017208:Rats, Wistar; D012149:Restraint, Physical; D018709:Statistics, Nonparametric; D013997:Time Factors
D001391:Azo Compounds; C009798:C.I. direct red 80; D003094:Collagen
cartilage; collagen fiber; immobilization; rat model; scanning electron microscopy