There is great interest in how bone marrow derived stem cells make fate decisions. Numerous studies have investigated the role of individual growth factors on mesenchymal stem cell differentiation, leading to protocols for cartilage, bone and adipose tissue. However, these protocols overlook the role of biomechanics on stem cell differentiation. There have been various studies that have applied mechanical stimulation to constructs containing mesenchymal stem cells, with varying degrees of success. One critical fate decision is that between cartilage and bone. Articular motion is a combination of compressive, tensile and shear deformations; therefore, one can presume that compression alone is unlikely to be a suffi cient mechanical signal to generate a cartilage-like tissue in vitro. Within this study, we aimed to determine the role of shear on the fate of stem cell differentiation. Specifi cally, we investigated the potential enhancing effect of surface shear, superimposed on cyclic axial compression, on chondrogenic differentiation of human bone marrow-derived stem cells. Using a custom built loading device we applied compression, shear or a combination of both stimuli onto fi brin/polyurethane composites in which human mesenchymal stem cells were embedded, while no exogenous growth-factors were added to the culture medium. Both compression or shear alone was insuffi cient for the chondrogenic induction of human mesenchymal stem cells. However, the application of shear superimposed upon dynamic compression led to signifi cant increases in chondrogenic gene expression. Histological analysis detected sulphated glycosaminoglycan and collagen II only in the compression and shear group. The results obtained may provide insight into post-operative care after cell therapy involving mesenchymal stromal cells.
In physiological conditions, joint function involves continuously moving contact areas over the tissue surface. Such moving contacts play an important role for the durability of the tissue. It is known that in pathological joints these motion paths and contact mechanics change. Nevertheless, limited information exists on the impact of such physiological and pathophysiological dynamic loads on cartilage mechanics and its subsequent biological response. We designed and validated a mechanical device capable of applying simultaneous compression and sliding forces onto cartilage explants to simulate moving joint contact. Tests with varying axial loads (1 – 4 kg) and sliding speeds (1 – 20 mm/s) were performed on mature viable bovine femoral condyles to investigate cartilage mechanobiological responses. High loads and slow sliding speeds resulted in highest cartilage deformations. Contact stress and effective cartilage moduli increased with increasing load and increasing speed. In a pilot study, changes in gene expression of extracellular matrix proteins were correlated with strain, contact stress and dynamic effective modulus. This study describes a mechanical test system to study the cartilage response to reciprocating sliding motion and will be helpful in identifying mechanical and biological mechanisms leading to the initiation and development of cartilage degeneration.
ObjectiveTranslation of the contact zone in articulating joints is an important component of joint kinematics, yet rarely investigated in a biological context. This study was designed to investigate how sliding contact areas affect cartilage mechanobiology. We hypothesized that higher sliding speeds would lead to increased extracellular matrix mechanical stress and the expression of catabolic genes.DesignA cylindrical Teflon indenter was used to apply 50 or 100 N normal forces at 10, 40, or 70 mm/s sliding speed. Mechanical parameters were correlated with gene expressions using a multiple linear regression model.ResultsIn both loading groups there was no significant effect of sliding speed on any of the mechanical parameters (strain, stress, modulus, tangential force). However, an increase in vertical force (from 50 to 100 N) led to a significant increase in extracellular matrix strain and stress. For 100 N, significant correlations between gene expression and mechanical parameters were found for TIMP-3 (r2 = 0.89), ADAMTS-5 (r2 = 0.73), and lubricin (r2 = 0.73).ConclusionsThe sliding speeds applied do not have an effect on the mechanical response of the cartilage, this could be explained by a partial attainment of the “elastic limit” at and above a sliding speed of 10 mm/s. Nevertheless, we still found a relationship between sliding speed and gene expression when the tissue was loaded with 100 N normal force. Thus despite the absence of speed-dependent mechanical changes (strain, stress, modulus, tangential force), the sliding speed had an influence on gene expression.
Sliding loads that increase ECM deformation/strain were found to induce enzyme-mediated catabolic processes in articular cartilage explants. These observations provide further understanding of how changes in cartilage contact mechanics under dynamic conditions can affect the cellular response.
embedded in paraffin. Six-mm sections were obtained at the medial mid-condylar segment of the knee in the sagittal plane. The sections were stained with hematoxylin-eosin and safranin-O (SO). The modified Mankin's score was applied for histological evaluation of the cartilage degeneration at two areas (contact area and transitional area which located between non-contact and contact) in tibia. About the calcified cartilage and the non-calcified cartilage in each assessment area, the expression intensity of type II collagen by immunohistochemical analysis and SO staining intensity were measured. Results: In experimental group, the cyst formation was observed in transitional area only at 8-week, whereas the degeneration was not observed before 8-week and in contact area. This degeneration existed in the non-calcified cartilage, where the increased hypocellularity was observed with extension of re-mobilization period. However, in the calcified cartilage of the same area, the hypocellularity was not observed. At transitional area in experimental group, the SO staining intensity in both non-calcified and calcified cartilage were decreased throughout experimental period in comparison with the control group (P < 0.05). Although there was no significant difference between the time points, the intensity was decreased after 6-week in both non-calcified and calcified cartilage. On the other hand, the type II collagen expression intensity in both noncalcified and calcified cartilage did not show significant difference between the experimental and the control group and between the time points. About contact area in experimental group, the decreased SO staining intensity were observed at both non-calcified and calcified cartilage throughout experimental period in comparison with the control group (P < 0.05), especially, remarkable reduction of SO staining intensity was observed at 8-week. The collagen II expression intensity did not show significant difference between the experimental and the control group and between the time points, similarly to that at transitional area. The modified Mankin's score at both contact and transitional areas in experimental group was higher than that in the control group throughout experimental periods (P < 0.01). However, there was no significant difference between the time points. Conclusions: Current results showed that the cyst formation would have occurred at non-calcified cartilage between 7 to 8 weeks after remobilization. It might suggest that the cyst formation would occur when degeneration of non-calcified cartilage exceed a certain threshold, however the pathology of cyst formation was not clear in this study. Mechanobiology
The application of four axial forces led to a variety of strains, contact stresses and dynamic moduli depending on the thickness of the tissue and its mechanical properties. The regression coefficients for all genes correlated with the mechanical parameters can be found in Table 1.The analysis revealed significant positive correlations between contact stress and dynamic modulus with collagen IIa and for dynamic modulus with aggrecan ( Figure 2).Conclusions: This study found that a short-term application of simultaneous compression and sliding onto articular cartilage resulted in substantial location-dependent changes in mechanical parameters of the tissue. Both the applied force and intrinsic mechanical properties differed along the curvature of the condyle, leading to varying mechanical responses. Chondrocytes were subjected to different strains and stresses depending on their location, and the mechanical properties of their surrounding matrix, resulting in altered cellular responses in terms of collagen type IIa and aggrecan gene regulation. Additional experiments with different axial loads and/or sliding speeds will be necessary to further quantify the biological response. It is known that anterior cruciate ligament (ACL) deficiencies/tears change APtranslation patterns and accelerate the initiation/progression of OA. Findings of this study might help to identify pathological joint mechanisms leading to OA and provide strategies for prevention and treatment of mechanically induced OA. Purpose: Excessive mechanical loading can lead to damage and loss of matrix components due to metabolic changes by chondrocytes and the synthesis of catabolic enzymes such as MMPs and ADAMTS'. Cartilaginous surfaces, such as the temporomandibular joint (TMJ), spend most of the time in relative motion with a constant translation of the contact zone. From previous tribological studies it is known that these migrating contacts are essential for tissues function. The translation of this knowledge into a Mechanobiological model is however lacking. Recent mechanobiological studies almost exclusively apply relatively simple loading regimens; typically uniaxial compressive and/or shear forces alone or in combination and contact areas are kept stationary. This study was designed to investigate how sliding contact areas affect cartilage mechanobiology in terms of catabolic gene expression. Methods: Cartilage was obtained from bovine nasal septum (BNS) of young calves. The cartilage was cut into appropriate sizes (70Â17Â2 mm 3 ) (LÂWÂH). Following a 72 hours equilibration period, the first 10 mm of the cartilage strip were glued to a Plexiglas plate with and placed into a tank filled with culture medium at 37 C. A cylindrical Teflon indenter (Ø 25 mm) was used to apply a normal force of 50 N or 100 N to the cartilage strip. Three different physiological sliding speeds of 10, 40 or 70 mm/s were applied. The load was cycled for 120 minutes over 50 mm of the specimen and the positions and forces of the indenter in the x-and z-directions recor...
ISI web of knowledge, PEDro and the Cochrane Collaboration. We used the keywords: "knee", "balance", "women" and "rehabilitation" in combination with "osteoarthritis". We selected randomized controlled clinical trials published in English, Portuguese and Spanish over the last 10 years. To verify the methodological quality of selected clinical trials, the PEDro Scale was applied.Results: A total of 20 studies were found in the electronic search. Of these, only 9 met the inclusion criteria and were analyzed in full. Eight of these 9 studies were classified as having high methodological quality on the PEDro Scale. Although the methods and interventions regarding balance varied widely in these studies, most found significant improvement in the balance of women with knee OA. Conclusion: Since the studies included in this systematic review were of high methodological quality, we can conclude that the therapeutic exercises they used improved the balance of women with knee OA. KNEE SYNOVIAL FLUID FROM ACUTELY INJURED PATIENTS CONTAIN PROTEASES THAT CAN DEGRADE AGGRECAN
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