Mesenchymal stromal cells (MSCs) seeded onto biocompatible scaffolds have been proposed for repairing bone defects. When transplanted in vivo, MSCs (expanded in vitro in 21% O(2)) undergo temporary oxygen deprivation due to the lack of pre-existing blood vessels within these scaffolds. In the present study, the effects of temporary (48 h) exposure to hypoxia (

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In osteoarthritis (OA), interleukin-1 (IL-1) stimulates the expression of metalloproteinases and aggrecanases, which induce cartilage degradation. IL-1 is also capable of reducing the production of cartilage-specific macromolecules, including type II collagen, through modulation of the transcription factors Sp1 and Sp3. Conversely, Transforming growth factor-beta (TGF-beta) counteracts with most of the IL-1 deleterious effects and contributes to cartilage homeostasis. However, OA chondrocytes progressively loose the expression of TGF-beta type II receptor and become insensitive to the factor. This downregulation is also driven by IL-1. This review provides insights into the molecular mechanisms that underly the interplay between IL-1 and TGF-beta in OA cartilage metabolism and enlightens the central role of Sp1 and Sp3 transcription factors in the matrix pathological alterations.

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Objective. To determine the effects of hypoxia and reoxygenation on the metabolism of chondrocytes and their response to interleukin-1␤ (IL-1␤). The study included activation of hypoxia-inducible factor 1 (HIF-1), NF-B, and activator protein 1 (AP-1) transcription factors, expression of matrix components and metalloproteases and transforming growth factor ␤ (TGF␤) and TGF␤ receptors, and production of nitric oxide (NO) and prostaglandin E 2 (PGE 2 ).Methods. Bovine articular chondrocytes (BACs) were cultured to confluency in either 5% O 2 (hypoxia) or 21% O 2 (normoxia) in media supplemented with 10% fetal calf serum (FCS). BACs were preincubated for 18 hours in media with 1% FCS only and then incubated for 24 hours in the presence of IL-1␤. For reoxygenation experiments, cells were treated in the same way in 5% O 2 , except that cultures were transferred to normal atmospheric conditions and used after 4 hours for RNA extraction or after 30 minutes for cytoplasmic or nuclear protein extraction.Results. In hypoxic and reoxygenated chondrocytes, we observed strong DNA binding of HIF-1. IL-1␤-induced DNA binding of NF-B and AP-1 was significantly higher in hypoxic and reoxygenated cultures than in normoxia. Greater activation of the MAPKs was also observed with IL-1␤ treatment in hypoxia compared with normoxia. Steady-state levels of type II collagen and aggrecan core protein messenger RNA (mRNA) were decreased by IL-1␤ in all instances. Matrix metalloprotease 1 (MMP-1) and MMP-3 mRNA were increased by IL-1␤ in normoxia and hypoxia, whereas only MMP-3 mRNA was enhanced in reoxygenated cultures. The MMP-2 mRNA level was not significantly affected by IL-1␤ in normoxia or hypoxia, whereas it was enhanced in reoxygenated cultures. MMP-9 mRNA was dramatically decreased by IL-1␤ only in low oxygen tension. Tissue inhibitor of metalloproteinases 1 (TIMP-1) message was significantly enhanced by the cytokine in most instances, whereas TIMP-2 message was markedly decreased by IL-1␤ in reoxygenated cultures. Stimulation of TGF␤1 expression by IL-1␤ was observed only in normal atmospheric conditions. One of the more striking findings of the study was the greater stimulating effect of IL-1␤ on NO production observed in hypoxia, which was much higher than in normoxia, whereas the reverse was observed for IL-1␤-induced PGE 2 production.Conclusion. Oxygen level and reoxygenation stress significantly modulate gene expression and the response of articular chondrocytes to cytokines such as IL-1␤. In hypoxic conditions, which mimic the in vivo condition of cartilage, the effects of IL-1␤ on both synthesis and degradative processes are significantly different from those in normoxia, conditions that are unlikely encountered by chondrocytes in a normal state. In low oxygen tension, high IL-1␤-induced NO production is associated with a significant decrease in PGE 2 synthesis. These data should influence our concept of the role of oxygen in the pathophysiology of joint disease and may help define the best conditions in which to develop bio...

The different regulation of NF-kappaB and AP-1 by H(2)O(2) and IL-1beta underlines the distinct roles played by the two transcription factors in the regulation of gene expression. H(2)O(2) and IL-1beta exert similar effects on matrix, MMPs and TGF-beta1 gene expression. However, the association of H(2)O(2) and IL-1beta does not cause synergic effect, and rather leads, in some cases, to an opposite effect. These data provide further insights into the respective roles of reactive oxygen species and cytokine in the pathophysiology of joint diseases.

The results indicate that the IL-1beta-driven erosive effect in periodontitis could be enhanced by a decreased expression of members of the TGF-beta family. The ASU stimulation of TGF-beta1, TGF-beta2, and BMP-2 expression may explain their promoting effects in the treatment of periodontal disorders, at least partly. These findings support the hypothesis that ASU could exert a preventive action on the deleterious effects exerted by IL-1beta in periodontal diseases.

Objective. Interleukin-1 (IL-1) and transforming growth factor ␤1 (TGF␤1) play major roles in osteoarticular diseases, exerting opposite effects on both the catabolism and anabolism of cartilage matrix. Previous findings suggest that IL-1 and TGF␤1 could function in a feedback interaction. However, the effect exerted by IL-1 on expression of TGF␤ by articular chondrocytes is, so far, poorly understood. The present study was carried out to determine the influence of IL-1␤ on the expression of TGF␤1 by bovine articular chondrocytes (BACs) in primary culture.Methods. BAC primary cultures were treated with IL-1␤, and TGF␤1 messenger RNA (mRNA) steadystate levels and protein expression were measured by real-time reverse transcription-polymerase chain reaction and enzyme-linked immunosorbent assay, respectively. Transient transfection of TGF␤1 gene promoter constructs was performed to delineate the DNA sequences that mediate the IL-1␤ effect. Electrophoretic mobility shift assays (EMSAs) and supershift analysis were used to characterize the transcription factors binding to these sequences. Results. Cultured BACs responded to IL-1␤ ex-