Search

This study aimed to examine the effects of an episode of in vivo cyclic loading on rat knee articular cartilage (AC) under medium‐term observation, while also investigating relevant factors associated with the progression of post‐traumatic osteoarthritis (PTOA). Twelve‐week‐old Wistar rats underwent one episode comprising 60 cycles of 20 N or 50 N dynamic compression on the right knee joint. Spatiotemporal changes in the AC after loading were evaluated using histology and immunohistochemistry at 3 days and 1, 2, 4, and 8 weeks after loading (n = 6 for each condition). Chondrocyte vitality was assessed at 1, 3, 6, and 12 hours after loading (n = 2 for each condition). A localized AC lesion on the lateral femoral condyle was confirmed in all subjects. The surface and intermediate cartilage in the affected area degenerated after loading, but the calcified cartilage remained intact. Expression of type II collagen in the lesion cartilage was upregulated after loading, whereas the superficial lubricin layer was eroded in response to cyclic compression. However, the distribution of superficial lubricin gradually recovered to the normal level 4 weeks after loading‐induced injury. We confirmed that 60 repetitions of cyclic loading exceeding 20 N could result in cartilage damage in the rat knee. Endogenous repairs in well‐structured joints work well to rebuild protective layers on the lesion cartilage surface, which may be the latent factor delaying the progression of PTOA. [ABSTRACT FROM AUTHOR]

Elucidating whether there is a correlation between biomechanical functions and histomorphometric data in the rat sciatic nerve crush injury model would contribute to an accurate evaluation of the regeneration state without sacrificing animals. The gold standard for functional evaluation is the sciatic functional index (SFI) despite there being intrinsic shortcomings. Kinematic analysis is considered a reliable and sensitive approach for functional evaluation, most commonly assessed as ankle angle at various phases of a gait cycle. Studies utilizing the toe angle for functional evaluation are scarce, and changes in the toe angle following surgery remain unknown. The present study assessed correlations of ankle angle, toe angle and SFI with histomorphometric data, aiming to determine which parameters most accurately reflect changes in histomorphometric data over time. Six Lewis rats were designated as the control group. 30 animals received surgery, six of them were randomly selected on the first, second, third, fourth, and sixth week after surgery for measurements of ankle and toe angles in the “toe-off” phase, and for evaluation of SFI. Histomorphometric analysis were also performed, to determine the number of myelinated nerve fibers, diameters of myelinated nerve fibers, axon diameters, and myelin sheath thicknesses. Furthermore, we investigated changes in ankle angle, toe angle, SFI, and histomorphometric data over time, as well as correlations between ankle angle, toe angle, and SFI with histomorphometric data. The results revealed that changes in SFI, ankle angle, and toe angle highly correlate with histomorphometric data in the rat sciatic nerve crush injury model. Toe angle reflected changes in histomorphometric data with time more precisely than ankle angle or SFI did, and ankle angle was a better prognostic parameter than SFI. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the histopathological changes in the patellofemoral joint using a rat model of osteoarthritis that was induced using monosodium iodoacetate, and to establish a novel model of patellofemoral osteoarthritis in a rat model using histopathological analysis. Sixty male rats were used. Osteoarthritis was induced through a single intra-articular injection of monosodium iodoacetate in both knee joints. Animals were equally divided into two experimental groups based on the monosodium iodoacetate dose: 0.2 mg and 1.0 mg. Histopathological changes in the articular cartilage of the patellofemoral joint and the infrapatellar fat pad were examined at 3 days, 1 week, 2 weeks, 4 weeks, 8 weeks, and 12 weeks after the monosodium iodoacetate injection. In the 1.0-mg group, the representative histopathological findings of osteoarthritis were observed in the articular cartilage of the patellofemoral joint over time. Additionally, the Osteoarthritis Research Society International scores of the patellofemoral joint increased over time. The synovitis scores of the infrapatellar fat pad in both groups were highest at 3 days, and then the values decreased over time. The fibrosis score of the infrapatellar fat pad in the 1.0-mg group increased with time, whereas the fibrosis score in the 0.2-mg group remained low. Representative histopathological findings of osteoarthritis were observed in the articular cartilage of the patellofemoral joint in a rat model of osteoarthritis induced using monosodium iodoacetate. With appropriate selection, this model may be regarded as an ideal patellofemoral osteoarthritis model. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The repair of articular cartilage is challenging owing to the restriction in the ability of articular cartilage to repair itself. Therefore, cell supplementation therapy is possible cartilage repair method. However, few studies have verified the efficacy and safety of cell supplementation therapy. The current study assessed the effect of exercise on early the phase of cartilage repair following cell supplementation utilizing mesenchymal stromal cell (MSC) intra-articular injection. An osteochondral defect was created on the femoral grooves bilaterally of Wistar rats. Mesenchymal stromal cells that were obtained from male Wistar rats were cultured in monolayer. After 4 weeks, MSCs were injected into the right knee joint and the rats were randomized into an exercise or no-exercise intervention group. The femurs were divided as follows: C group (no exercise without MSC injection); E group (exercise without MSC injection); M group (no exercise with MSC injection); and ME group (exercise with MSC injection). At 2, 4, and 8 weeks after the injection, the femurs were sectioned and histologically graded using the Wakitani cartilage repair scoring system. At 2 weeks after the injection, the total histological scores of the M and ME groups improved significantly compared with those of the C group. Four weeks after the injection, the scores of both the M and ME groups improved significantly. Additionally, the scores in the ME group showed a significant improvement compared to those in the M group. The improvement in the scores of the E, M, and ME groups at 8 weeks were not significantly different. The findings indicate that exercise may enhance cartilage repair after an MSC intra-articular injection. This study highlights the importance of exercise following cell transplantation therapy. [ABSTRACT FROM AUTHOR]

Exposure to a microgravity environment leads to adverse effects in motion and musculoskeletal properties. However, few studies have investigated the recovery of altered locomotion and muscle atrophy simultaneously. The authors investigated altered locomotion in rats submitted to simulated microgravity by hindlimb unloading for 2 weeks. Motion deficits were characterized by hyperextension of the knees and ankle joints and forward-shifted limb motion. Furthermore, these locomotor deficits did not revert to their original form after a 2-week recovery period, although muscle atrophy in the hindlimbs had recovered, implying discordance in recovery between altered locomotion and muscle atrophy, and that other factors such as neural drives might control behavioral adaptations to microgravity. [ABSTRACT FROM AUTHOR]

This study aimed to analyze the spatial developmental changes of rat cruciate ligaments by three-dimensional (3D) reconstruction using episcopic fluorescence image capture (EFIC). Cruciate ligaments of Wister rat embryos between embryonic day (E) 16 and E20 were analyzed. Samples were sectioned and visualized using EFIC. 3D reconstructions were generated using Amira software. The length of the cruciate ligaments, distances between attachment points to femur and tibia, angles of the cruciate ligaments and the cross angle of the cruciate ligaments were measured. The shape of cruciate ligaments was clearly visible at E17. The lengths of the anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) increased gradually from E17 to E19 and drastically at E20. Distances between attachment points to the femur and tibia gradually increased. The ACL angle and PCL angle gradually decreased. The cross angle of the cruciate ligaments changed in three planes. The primordium of the 3D structure of rat cruciate ligaments was constructed from the early stage, with the completion of the development of the structures occurring just before birth. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

ABSTRACT The aim of this study was to elucidate whether the levels of serum biomarkers reflect the progression of osteoarthritis (OA) induced by different levels of exercise. Thirty-five Wistar rats subjected to anterior cruciate ligament transaction (ACLT) were divided into three groups: Control, moderate running, and intense running. Twelve rats (moderate running without ACLT) were allocated as a naive group. Running was performed on a motorized treadmill, at a speed of 18 m/min for 30 min/day (moderate and naive) or 60 min/day (intense) for 3 days per week. After 2 or 4 weeks, OA histopathology in the knees was evaluated using the Osteoarthritis Research Society International (OARSI) score, and the serum levels of cleaved collagen type II (C2C) and procollagen II C-propeptide (CPII) were analyzed. The OARSI score deteriorated in the intense running group after 2 weeks and the serum C2C/CPII ratio suggested the development of OA. At 4 weeks, the C2C/CPII ratio suggested there would be deterioration in the OARSI score but the score did not differ significantly between the moderate and intense running groups. C2C/CPII ratio had 13-25% correlation with the OARSI histological score. Thus, in rat experimental OA, the OARSI score could be partially predicted by the C2C/CPII ratio as a serum biomarker of OA. © 2013 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 31:1026-1031, 2013 [ABSTRACT FROM AUTHOR]

The effects of intermittent hypergravity on gait alterations and hindlimb muscle atrophy in rats induced by 2 weeks of simulated microgravity were investigated. Rats were submitted to hindlimb unloading for 2 weeks (unloading period), followed by 2 weeks of reloading (recovery period). During the unloading period, animals were subjected to the following treatments: (1) free in cages (Control); (2) continuous unloading (UL); (3) released from unloading for 1 hour per day (UL + 1G); (4) hypergravity for 1 h per day using a centrifuge for small animals (UL + 2G). The relative weights of muscles to the whole body weight and kinematics properties of hindlimbs during gait were evaluated. UL rats walked with their hindlimbs overextended, and the oscillation of their limb motion had become narrowed and forward-shifted after the unloading period, and this persisted for at least 2 weeks after the termination of unloading. However, these locomotor alterations were attenuated in rats subjected to UL + 2G centrifugation despite minor systematic changes in muscle recovery. These findings indicate hypergravity application could counteract the adverse effects of simulated or actual microgravity environments. [ABSTRACT FROM AUTHOR]