Expression of collagen types I and II on articular cartilage in a rat knee contracture model

Investigating cartilage-related diseases by polarization-resolved second harmonic generation (P-SHG) imaging

Establishing quantitative parameters for differentiating between healthy and diseased cartilage tissues by examining collagen fibril degradation patterns facilitates the understanding of tissue characteristics during disease progression. These findings could also complement existing clinical methods used to diagnose cartilage-related diseases. In this study, cartilage samples from normal, osteoarthritis (OA), and rheumatoid arthritis (RA) tissues were prepared and analyzed using polarization-resolved second harmonic generation (P-SHG) imaging and quantitative image texture analysis. The enhanced molecular contrast obtained from this approach is expected to aid in distinguishing between healthy and diseased cartilage tissues. P-SHG image analysis revealed distinct parameters in the cartilage samples, reflecting variations in collagen fibril arrangement and organization across different pathological states. Normal tissues exhibited distinct χ33/χ31 values compared with those of OA and RA, indicating collagen type transition and cartilage erosion with chondrocyte swelling, respectively. Compared with those of normal tissues, OA samples demonstrated a higher degree of linear polarization, suggesting increased tissue birefringence due to the deposition of type-I collagen in the extracellular matrix. The distribution of the planar orientation of collagen fibrils revealed a more directional orientation in the OA samples, associated with increased type-I collagen, while the RA samples exhibited a heterogeneous molecular orientation. This study revealed that the imaging technique, the quantitative analysis of the images, and the derived parameters presented in this study could be used as a reference for disease diagnostics, providing a clear understanding of collagen fibril degradation in cartilage.

The effect of extracorporeal shock wave on joint capsule fibrosis in rats with knee extension contracture: a preliminary study

The purpose of this study was to observe the therapeutic effect of extracorporeal shock wave (ESW) on extensional joint contracture of knee joint in rats and its mechanism on articular capsule fibrosis. Thirty-two SD rats were randomly divided into blank control, immobilization, natural recovery, and ESW intervention groups. Except for the control group, the left knee joints of other rats were fixed with external fixation brace for 4 weeks when they were fully extended to form joint contracture. The effect of intervention was assessed by evaluating joint contracture, total cell count and collagen deposition in joint capsule, and protein expression levels of TGF-β1, p-Smad2/3, Smad2/3, p-JNK, JNK, I and III collagen in joint capsule. ESW can effectively reduce arthrogenic contracture, improve the histopathological changes of anterior joint capsule, inhibit the high expression of target protein and the excessive activation of TGF-β1/Smad2/3/JNK signal pathway. Inhibition of excessive activation of TGF-β1/Smad2/3/JNK pathway may be one of the potential molecular mechanisms by which extracorporeal shock wave can play a role.

Bone replaces unloaded articular cartilage during knee immobilization. A longitudinal study in the rat

BACKGROUND

Joint immobility results in deleterious changes such as capsule shortening, bone loss and articular cartilage damage. Immobilization of rat knees in flexion for 32 weeks resulted in the distinctive feature of well-established replacement of articular cartilage by bone. Determining the time of onset of bone replacement is critical for the prevention of this likely irreversible complication of joint immobilization.

OBJECTIVES

To determine the onset and progression of bone replacement in the anterior tibial articular cartilage following knee immobilization in flexion.

METHODS

One hundred forty-nine adult male Sprague-Dawley rats were used. The experimental groups had one knee immobilized at 135°of flexion for durations of 2, 4, 8, 16 or 32 weeks and were compared to age-matched controls. The knees were evaluated histologically for the presence and cross-sectional area of bone within the articular cartilage of the tibia. Distance between the anterior aspect of the tibia and intact articular cartilage and cross-sectional bone area of the tibial epiphysis were also measured.

RESULT

Bone replacement in the articular cartilage was observed in 14%, 75%, 95%, 100% and 100% of knees after 2, 4, 8, 16 and 32 weeks of immobilization, respectively. No bone replacement was seen in the control knees. The mean area of bone replacement increased from 0.004 ± 0.007 mm² after 2 weeks to 0.041 ± 0.036 mm²; 0.085 ± 0.077 mm²; 0.092 ± 0.056 mm² and 0.107 ± 0.051 mm² after 4, 8, 16 and 32 weeks of immobilization, respectively, (p < 0.001) largely restricted to the anterior tibial articular cartilage. Mean distance to intact articular cartilage increased from 0.89 ± 0.69 mm at 2 weeks to 1.10 ± 0.35 mm; 1.65 ± 0.77 mm; 1.48 ± 0.63 mm; and 1.78 ± 0.58 mm after 4, 8, 16 and 32 weeks of immobilization, respectively (p = 0.001). Epiphyseal bone cross-sectional area was significantly reduced following 4, 8, and 16 weeks of immobilization compare to controls (all 3 p < 0.05).

CONCLUSION

Knee immobilization in flexion resulted in bone replacement in the anterior tibial articular cartilage that began after 2 weeks and was prevalent after 4 weeks of immobilization. The bone replacement progressed in an anterior-to-posterior direction and stopped at the area of contact between tibia and femur. These findings stress the importance of mobility to maintain joint health.

Joint hemorrhage accelerates cartilage degeneration in a rat immobilized knee model

Background

Joint hemorrhage is caused by trauma, ligament reconstruction surgery, and bleeding disorders such as hemophilia. Recurrence of hemorrhage in the joint space induces hemosiderotic synovitis and oxidative stress, resulting in both articular cartilage degeneration and arthropathy. Joint immobilization is a common treatment option for articular fractures accompanied by joint hemorrhage. Although joint hemorrhage has negative effects on the articular cartilage, there is no consensus on whether a reduction in joint hemorrhage would effectively prevent articular cartilage degeneration. The purpose of this study was to investigate the effect of joint hemorrhage combined with joint immobilization on articular cartilage degeneration in a rat immobilized knee model.

Methods

The knee joints of adult male rats were immobilized at the flexion using an internal fixator from 3 days to 8 weeks. The rats were randomly divided into the following groups: immobilized blood injection (Im-B) and immobilized-normal saline injection (Im-NS) groups. The cartilage was evaluated in two areas (contact and non-contact areas). The cartilage was used to assess chondrocyte count, Modified Mankin score, and cartilage thickness. The total RNA was extracted from the cartilage in both areas, and the expression of metalloproteinase (MMP)-8, MMP-13, interleukin (IL)-1β, and tumor necrosis factor (TNF)-α was measured by quantitative real-time polymerase chain reaction.

Results

The number of chondrocytes in the Im-B group significantly decreased in both areas, compared with that in the Im-NS group. Modified Mankin score from 4 to 8 weeks of the Im-B group was significantly higher than that of the Im-NS group only in the contact area. The expression of MMP-8 and MMP-13 from 2 to 4 weeks and TNF-α from 2 to 8 weeks significantly increased in the Im-B group compared with those in the Im-NS group, but there was no significant difference in IL-1β expression.

Conclusions

The results showed that joint hemorrhage exacerbated immobilization-induced articular cartilage degeneration. Drainage of a joint hemorrhage or avoidance of loading may help prevent cartilage degeneration during joint immobilization with a hemorrhage.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-020-03795-0.

Electroacupuncture alleviates cartilage degradation: Improvement in cartilage biomechanics via pain relief and potentiation of muscle function in a rabbit model of knee osteoarthritis

Knee osteoarthritis (KOA) is a chronic degenerative joint disorder characterized by loss of articular cartilage and progressive deterioration, leading to pain and functional limitation. Abnormal biomechanics play a core role in the onset and development of KOA. The aim of this study was to explore whether electroacupuncture (EA) may relieve pain and adjust the biomechanical properties of the extensor-flexor muscles to improve abnormal joint loading, thus alleviating the degradation of cartilage in a rabbit model of KOA. Firstly, a KOA model was induced by immobilization for 6 weeks. Then, different interventions (EA and celecoxib) were applied for 4 weeks. The levels of pain and disability were assessed using the Lequesne MG index. Muscle function, including function of the rectus femoris and biceps femoris, was tested through hematoxylin-eosin staining (HE staining) and use of a microforce tension-torsion instrument. The cartilage was tested using nanoindentation, Safranin O-Fast Green staining, confocal laser scanning microscopy (immunofluorescence), immunohistochemistry and the enzyme-linked immunosorbent assay (ELISA). Finally, we found that EA and celecoxib resulted in lower behavioral and pain scores than the model group. In addition, it improved the function of muscles. Furthermore, those treatments alleviated the rate of cartilage degradation, manifested as increased loss factor without statistical difference and a significant reduction in the Mankin score. This promoted the metabolism of type II collagen in the cartilage layer and drastically reduced the expression of CTX-II in the synovial fluid and peripheral serum. Concisely, EA promotes pain limitation and ameliorates muscular atrophy-induced inappropriate biomechanical loading on the articular cartilage through pain relief and potentiation of muscle function, thus improving cartilage viscoelasticity, as demonstrated by the retarded degradation of type II collagen in our KOA model.

Non-Invasive Monitoring of Functional State of Articular Cartilage Tissue with Label-Free Unsupervised Hyperspectral Imaging

Damage and degradation of articular cartilage leads to severe pain and loss of mobility. The development of new therapies for cartilage regeneration for monitoring their effect requires further study of cartilage, ideally at a molecular level and in a minimally invasive way. Hyperspectral microscopy is a novel technology which utilises endogenous fluorophores to non-invasively assess the molecular composition of cells and tissue. In this study, we applied hyperspectral microscopy to healthy bovine articular cartilage and osteoarthritic human articular cartilage to investigate its capacity to generate informative molecular data and characterise disease state and treatment effects. We successfully demonstrated label-free fluorescence identification of collagen type I and II - isolated in cartilage here for the first time and the co-enzymes free NADH and FAD which together give the optical redox ratio that is an important measure of metabolic activity. The intracellular composition of chondrocytes was also examined. Differences were observed in the molecular ratios within the superficial and transitional zones of the articular cartilage which appeared to be influenced by disease state and treatment. These findings show that hyperspectral microscopy could be useful for investigating the molecular underpinnings of articular cartilage degradation and repair. As it is non-invasive and non-destructive, samples can be repeatedly assessed over time, enabling true time-course experiments with in-depth molecular data. Additionally, there is potential for the hyperspectral approach to be adapted for patient examination to allow the investigation of cartilage state. This could be of advantage for assessment and diagnosis as well as treatment monitoring.

Extension of knee immobilization delays recovery of histological damages in the anterior cruciate ligament insertion and articular cartilage in rabbits

[Purpose] To investigate the influence of knee immobilization period on recovery of histological damages in the anterior cruciate ligament (ACL) insertion and articular cartilage in rabbits. This knowledge is important for determining the appropriate rehabilitation approach for patients with ligament injuries, fracture, disuse atrophy, and degenerative joint disease. [Materials and Methods] Forty-eight male Japanese white rabbits were divided equally into the remobilization and control groups. The remobilization group had the right knee surgically immobilized, and was divided equally into four subgroups according to the duration of immobilization (1, 2, 4 and 8 weeks). After the immobilization was removed, the rabbits moved freely for 8 weeks. The control group underwent sham operation and followed the same time course as the remobilization group. The chondrocyte apoptosis rate and chondrocyte proliferation rate in the ACL insertion and articular cartilage were analyzed after remobilization. [Results] In the ACL insertion, the remobilization group had a higher chondrocyte apoptosis rate than the control group after 8 weeks of immobilization, and a lower chondrocyte proliferation rate than the control group after 4 and 8 weeks of immobilization. In the articular cartilage, the remobilization group had a lower chondrocyte proliferation rate than the control group after 8 weeks of immobilization. After 8 weeks of remobilization, the ACL insertion and articular cartilage are not completely recovered after 4 and 8 weeks of immobilization, respectively. [Conclusion] Our results suggest that 8 weeks of remobilization will result in recovery of the ACL insertion after 2 weeks of knee immobilization, and recovery of the articular cartilage after 4 weeks of knee immobilization. If 8 weeks of immobilization occurs, a remobilization duration of more than 8 weeks may be necessary.

Thinning of articular cartilage after joint unloading or immobilization. An experimental investigation of the pathogenesis in mice

OBJECTIVE

Moderate mechanical stress generated by normal joint loading and movement is essential for the maintenance of healthy articular cartilage. However, the effects of reduced loading caused by the absence of weight bearing or joint motion on articular cartilage and subchondral bone is still poorly understood. We aimed to characterize morphological and metabolic responses of articular cartilage and subchondral bone to decreased mechanical stress in vivo.

METHODS

Mice were subjected to periods of hindlimb unloading by tail suspension or external fixation of the knee joints. The articular surface was observed with digital microscope and the epiphyseal bone was assessed by micro-CT analysis. Articular cartilage and subchondral bone were further evaluated by histomorphometric, histochemical, and immunohistochemical analyses.

RESULTS

The joint surface was intact, but thickness of both the total and uncalcified layer of articular cartilage were decreased both after joint unloading and immobilization. Subchondral bone atrophy with concomitant marrow expansion predisposed osteoclast activity at bone surface to invade into cartilaginous layer. Uncalcified cartilage showed decreased aggrecan content and increased aggrecanase expression. Alkaline phosphatase (ALP) activity was increased at uncalcified cartilage, whereas decreased at calcified cartilage. The distributions of hypertrophic chondrocyte markers remained unchanged.

CONCLUSION

Thinning of articular cartilage induced by mechanical unloading may be mediated by metabolic changes in chondrocytes, including accelerated aggrecan catabolism and exquisitely modulated matrix mineralization, and cartilage matrix degradation and resorption by subchondral osteoclasts. Cartilage degeneration without chondrocyte hypertrophy under unloading condition indicate the possible existence of mechanism which is different from osteoarthritis pathogenesis.

Exploring the structural requirements of collagen-binding peptides

Collagen synthesis and tissue remodeling are involved in many diseases; therefore, collagen-specific binding agents have been developed to study collagen changes in various tissues. Based on a recently reported collagen binding peptide, which contains unnatural biphenylalanine (Bip) amino acid residue, constructs with various structure variations were synthesized to explore the contributions of unnatural Bip residue, conformational restrain, and amino acid sequence in collagen recognition. Their binding efficiency to collagens was evaluated in vitro using pure collagens. The results indicate that the C-terminal unnatural Bip residue, rather than the peptide sequence or conformational restrain, dominated the collagen I binding. Subsequent tissue binding study showed that the selected peptide did not offer preferential selectivity over collagen I in tissue, suggesting that a simple in vitro binding assay cannot adequately model the complex biological environment.

Remobilization causes site-specific cyst formation in immobilization-induced knee cartilage degeneration in an immobilized rat model

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.

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.

Is protecting the healing ligament beneficial after immobilization in external rotation for an initial shoulder dislocation?

BACKGROUND

Immobilization in external rotation is one of the treatment options for an initial dislocation of the shoulder. However, it remains unclear how long it takes for a Bankart lesion to heal.

HYPOTHESIS

Protection of a healing Bankart lesion from stretching would promote the healing process and decrease the recurrence rate after an initial dislocation of the shoulder.

STUDY DESIGN

Randomized controlled trial; Level of evidence, 2.

METHODS

This was a multicenter, prospective randomized study. Between January 2005 and August 2009, 109 patients (71 male and 38 female; mean age, 30 years) with an initial traumatic dislocation of the shoulder were enrolled. After 3 weeks of immobilization in external rotation, a shoulder motion restriction band designed to avoid stretching the anteroinferior shoulder capsule was used for 0 weeks (36 patients), 3 weeks (37 patients), or 6 weeks (36 patients). After using the band, patients were allowed to use their shoulders freely, but they were advised to avoid vigorous sport activities for at least 3 months after the injury. Any recurrent dislocation and return to sports were assessed at 2-year follow-up.

RESULTS

Of 109 patients, 90 were followed up for 2 years. The compliance rates were 60% to 72% among the groups (P = .54). The recurrence rate of dislocation was 28% in the 0-week group, 33% in the 3-week group, and 32% in the 6-week group (P = .88) according to the intention-to-treat analysis, and they were a respective 24%, 28%, and 27% according to the per-protocol analysis (P = .95). Based on the sport activity level, the recurrence rates for patients involved in contact sports (7/15, 47%) and those involved in noncontact sports (19/51, 37%) were significantly higher than for those not involved in sport activities (2/24, 8.3%) (P = .0076). Among the 3 groups, there were no significant differences in the recurrence rates. There was no significant difference in the rate of return to sports (P = .39).

CONCLUSION

No difference in the recurrence rate was seen with the use of a shoulder motion restriction band after 3 weeks of immobilization in external rotation after an initial dislocation of the shoulder.

Effects of aging and exercise training on the histological and mechanical properties of articular structures in knee joints of male rat

The impact of aging on joints can have a profound effect on an individual's functioning. Our objectives were to assess the histological and mechanical properties of the knee joint capsule and articular cartilage with aging, and to examine the effects of exercise on age-related changes in the knee joint. 2-year-old Wistar rats were divided into a sedentary control group and an exercise-trained group. 10-week-old animals were used to investigate the changes with aging. The joint capsule and cartilage were evaluated with histological, histomorphometric, immunohistochemical, and mechanical analyses. Severe degenerative changes in articular cartilage were observed with aging, whereas exercise apparently did not have a significant effect. The articular cartilage of aged rats was characterized by damage to the cartilage surface, cell clustering, and an abnormal cartilage matrix. Histomorphometric analysis further revealed changes in cartilage thickness as well as a decreased number of chondrocytes. Aging led to stiffness of the articular cartilage and reduced the ability to dissipate the load and distribute the strain generated within the joint. Joint stiffness with aging was independent of capsular stiffness and synovitis was not a characteristic feature of the aging joint. This study confirms that aging alone eventually leads to joint degeneration in a rat model. The lack of recovery in aging joint changes may be due to several factors, such as the duration of the intervention and the regeneration ability of the cartilage.