Biorheology - Volume 41, issue 3-4

Authors: Angoulvant, D. | Clerc, A. | Benchalal, S. | Galambrun, C. | Farre, A. | Bertrand, Y. | Eljaafari, A.

Article Type: Research Article

Abstract: Mesenchymal stem cells (MSC) fail to induce allogeneic responses in mixed lymphocyte reaction assays. Because MSC express HLA class I molecules, here we investaged whether they could be recognized as allogeneic targets by cytolytic T lymphocytes (CTL). With this aim, CTL precursor (CTLp) frequencies were measured following stimulation of T cells with either allogeneic mononuclear cells (MNC) or MSC originated from the same human bone marrow donor. Lysis of MSC was measured at day 10 of culture in standard chromium release assays. In addition, allogeneic PHA blast T cells or B‐EBV lymphoblastoid cell lines (LCLs) generated from the same donor …were used as positive controls of lysis. Our results showed that when allogeneic MNC were used to stimulate T cells, a high CTLp frequency was detected towards MSC targets. However, when MSC were used as stimulators, CTLp frequencies were markedly altered whatever the targets used, i.e.: MSC, PHA blast T cells or EBV‐B LCLs. Moreover, when graded concentrations of MSC were added together with MNC upon stimulation of alloreactive T cells, we observed a dose‐dependent decrease in CTLp frequencies towards MSC targets. This inhibition of MSC lysis was partially overcomed by adding exogenous rh‐IL‐2 from the beginning of cultures. In addition, this suppressive effect was totally reproduced when, instead of MSC, supernatant harvested from MSC cultures was added to allogeneic MNC, upon stimulation of alloreactive T cells. In conclusion, our results demonstrate that MSC which can be recognized as targets by pre‐activated alloreactive CTLs, may be able to suppress differentiation of CTL precursors into CTL effectors through secretion of suppressive factors. Show more

Citation: Biorheology, vol. 41, no. 3‐4, pp. 469-476, 2004

Authors: Schaefer, Dirk B. | Wendt, David | Moretti, Matteo | Jakob, Marcel | Jay, Gregory D. | Heberer, Michael | Martin, Ivan

Article Type: Research Article

Abstract: Cartilage integration in vivo does not occur, such that even cartilage fissures do not heal. This could be due not only to the limited access of chondrocytes to the wound, but also to exogenous factors. In this paper, we tested the hypothesis that lubricin, a lubricating protein physiologically present in the synovial fluid, reduces the integrative cartilage repair capacity. Disk/ring composites of bovine articular cartilage were prepared using concentric circular blades and cultured for 6 weeks with or without treatment with 250 μg/ml lubricin applied three times per week. Following culture, the percentage of contact area between the disks and …the rings, as assessed by light microscopy, were equal in both groups. The adhesive strength of the integration interface, as assessed by push‐out mechanical tests, was markedly and significantly lower in lubricin‐treated specimens (2.5 kPa) than in the controls (28.7 kPa). Histological observation of Safranin‐O stained cross‐sections confirmed the reduced integration in the lubricin treated composites. Our findings suggest that the synovial milieu, by providing lubrication of cartilage surfaces, impairs cartilage–cartilage integration. Show more

Citation: Biorheology, vol. 41, no. 3‐4, pp. 503-508, 2004

Authors: Morel, V. | Quinn, T.M.

Article Type: Research Article

Abstract: The short‐term responses of articular cartilage to mechanical injury have important implications for prevention and treatment of degenerative disease. Cell and matrix responses were monitored for 11 days following injurious compression of cartilage in osteochondral explants. Injury was applied as a single ramp compression to 14 MPa peak stress at one of three strain rates: 7×10−1 , 7×10−3 or 7×10−5 s−1 . Responses were quantified in terms of the appearance of macroscopic matrix cracks, changes in cell viability, and changes in cartilage wet weights. Loading at the highest strain rate resulted in acute cell death near the superficial …zone in association with cracks, followed over the 11 days after compression by a gradual increase in cell death and loss of demarcation between matrix zones containing viable versus nonviable cells. In contrast, loading at the lowest strain rate resulted in more severe, nearly full‐depth cell death acutely, but with no apparent worsening over the 11 days following compression. Between days 4 and 11, all mechanically injured explants significantly increased in wet weight, suggesting loss of matrix mechanical integrity independent of compression strain rate. Results demonstrate that short‐term responses of cartilage depend upon the biomechanical characteristics of injurious loading, and suggest multiple independent pathways of mechanically‐induced cell death and matrix degradation. Modifications to an existing fiber‐reinforced poroelastic finite element model were introduced and the model was used for data interpretation and identification of microphysical events involved in cell and matrix injury. The model performed reasonably well at the slower strain rates and exhibited some capacity for anticipating the formation of superficial cracks during injurious loading. However, several improvements appear to be necessary before such a model could reliably be used to draw upon in vitro experimental results for prediction of injurious loading situations in vivo. Show more

Citation: Biorheology, vol. 41, no. 3‐4, pp. 509-519, 2004

Authors: Henrotin, Y. | Deberg, M. | Dubuc, J.‐E. | Quettier, E. | Christgau, S. | Reginster, J.‐Y.

Article Type: Research Article

Abstract: This paper describes two new immunoassays for a peptide of the triple helix of type II collagen (Coll 2‐1) and its nitrated form (Coll 2‐1 NO2 ). In healthy subjects aged between 20 and 65 years old, Coll 2‐1 and Coll 2‐1 NO2 levels in serum were in means 125.13±3.71 and 0.16±0.08 nmol/l, respectively. These levels did not significantly vary with age. However, up to 45 years of age, Coll 2‐1 NO2 levels in women were significantly higher than in men. In patients with knee osteoarthritis (OA), Coll 2‐1 in serum was found to be elevated compared to …healthy controls (267.45±26.42 nmol/l vs 126.78±6.61 nmol/l). Further, we have demonstrated that an increase of the urinary levels of Coll 2‐1 or Coll 2‐1 NO2 over 1 year was predictive of joint space narrowing progression in OA patients. In conclusion, these preliminary results indicate that Coll 2‐1 could be a predictive marker of knee OA progression. Show more

Keywords: Ageing, osteoarthritis, biological markers, nitric oxide, oxygen

Citation: Biorheology, vol. 41, no. 3‐4, pp. 543-547, 2004

Authors: Martin, G. | Bogdanowicz, P. | Domagala, F. | Ficheux, H. | Pujol, J.‐P.

Article Type: Research Article

Abstract: In the present report, we show that bovine articular chondrocytes cultured in low oxygen tension, i.e. in conditions mimicking their hypoxic in vivo environment, respond to IL‐1β (10 ng/ml) by an increased DNA binding activity of NF‐κB and AP‐1 transcription factors. Incubation of the cells with 10−5 M rhein for 24 h was found to reduce this activity, particularly in the case of AP‐1. Mitogen activated kinases (ERK‐1 and ERK‐2) were activated by exposure of the chondrocytes to 1‐h treatment with IL‐1β. This effect was greater in hypoxia (3% O2 ) than in normoxia (21% O2 ). Rhein was …capable of reducing the IL‐1β‐stimulated ERK1/ERK2 pathway whatever the tension of oxygen present in the environment. The mRNA steady‐state levels of collagen type II (COL2A1) and aggrecan core protein were found to be significantly increased by a 24‐h treatment with 10−5 M rhein. This stimulating effect was also observed in the presence of IL‐1β, suggesting that the drug could prevent or reduce the IL‐1β‐induced inhibition of extracellular matrix synthesis. IL‐1‐induced collagenase (MMP1) expression was significantly decreased by rhein in the same conditions. In conclusion, rhein can effectively inhibit the IL‐1‐activated MAPK pathway and the binding of NF‐κB and AP‐1 transcription factors, two key factors involved in the expression of several pro‐inflammatory genes by chondrocytes. In addition, the drug can reduce the procatabolic effect of the cytokine, by reducing the MMP1 synthesis, and enhance the synthesis of matrix components, such as type II collagen and aggrecan. These results may explain the anti‐osteoarthritic properties of rhein and its disease‐modifying effects on OA cartilage, in spite of absence of inhibition at prostaglandin level. Show more

Keywords: Cartilage, chondrocytes, interleukin‐1, osteoarthritis, rhein

Citation: Biorheology, vol. 41, no. 3‐4, pp. 549-561, 2004