Increased accumulation of superficial zone protein (SZP) in articular cartilage in response to bone morphogenetic protein-7 and growth factors
Center for Tissue Regeneration and Repair, Department of Orthopaedic Surgery, University of California-Davis, Sacramento, California 95817, USA.Journal of Orthopaedic Research (Impact Factor: 2.99). 03/2007; 25(3):293-303. DOI: 10.1002/jor.20329
The purpose of this study was to investigate the role of bone morphogenetic proteins (BMPs), such as BMP-7, growth factors, and cytokines, in the accumulation of superficial zone protein (SZP) in bovine articular cartilage. Calf superficial articular cartilage discs and chondrocytes were obtained for explant and monolayer culture systems, respectively. Dose- and time-dependent actions of BMP-7 on SZP accumulation were investigated in both explant and monolayer culture systems. In addition, actions of various morphogens and growth factors [BMP-2, BMP-4, fibroblast growth factor 2 (FGF-2), insulin-like growth factor 1 (IGF-1), platelet-derived growth factor (PDGF), and transforming growth factor beta (TGF-beta1)], and cytokines [interleukin (IL)-1alpha, IL-1beta, and tumor necrosis factor (TNF-alpha)] alone, and in combination with BMP-7, on SZP accumulation were investigated in monolayer culture systems. SZP accumulation was quantified in both the cartilage and the medium using SDS-PAGE and subsequent immunoblotting. In both explant and monolayer cultures, BMP-7 increased SZP accumulation in a dose- and time-dependent fashion (p < 0.05). Furthermore, SZP accumulation was significantly increased in monolayer cultures by FGF-2, IGF-1, PDGF, and TGF-beta1 (p < 0.05). Both IL-1alpha and TNF-alpha significantly reduced SZP accumulation (p < 0.05). The inhibition of SZP accumulation by TNF-alpha was partially alleviated by concurrent treatment with BMP-7. The results of this investigation provide novel insights into the role of morphogens, especially BMP-7, growth factors, and cytokines in the accumulation of SZP in articular cartilage. This information has clinical implications because stimulation of SZP may ameliorate the pathology of joint function in arthritis. Furthermore, tissue engineering approaches to articular cartilage may depend on the optimal synthesis and assembly of SZP in the superficial zone to ensure functional tissue architecture.
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- "BMP-2/BMP-7 and BMP-4/BMP-7 have been suggested to exist and function in vivo. These are more potent inducers of bone formation than their respective homodimers, which are widely used in bone tissue engineering678. "
ABSTRACT: Background & objectives: BMP (bone morphogenetic protein)-4/7 and bFGF (basic fibroblast growth factor) significantly promote the osteogenic activity and the proliferation of rabbit BMSCs (bone marrow stromal cells), respectively. However, their synergistic effects on the proliferation and the differentiation of BMSCs remain unclear. In the present study, the effects of bFGF and BMP-4/7 were investigated on the proliferation and the differentiation of rat BMSCs in vitro. Methods: BMSCs were isolated from New Zealand white rabbits and cultured to the third passage. The samples were divided into five groups according to the material implanted: (A) 80 ng/ml BMP-4/7; (B) 80 ng/ml bFGF; (C) 30 ng/ml BMP-4/7 and 30 ng/ml bFGF; (D) 50 ng/ml BMP-4/7 and 50 ng/ml bFGF; and (E) 80 ng/ml BMP-4/7 and 80 ng/ml bFGF. Cell proliferation was analyzed using methyl thiazolyl tetrazolium (MTT) assay. Alkaline phosphatase activity and osteocalcin (OC) dynamics were also measured. Results: BMP-4/7 alone significantly (P<0.05) promoted the proliferation of BMSCs. At the same time, it also promoted or inhibited the osteogenic differentiation of BMSCs. The synergistic effects of BMP-4/7 and bFGF significantly promoted both the proliferation and the osteogenic differentiation of BMSCs. The treatment of the synergistic effects was dose and time dependent. Interpretation & conclusions: A rational combination of BMP-4/7 and bFGF can promote the proliferation and the osteogenic differentiation of BMSCs. In addition, the synergistic functions are effective.
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- "Bovine stifle (knee joints) from 3 month-old calves were obtained from an abattoir and dissected under aseptic conditions to expose the femoral condyles as described previously in our laboratory (Niikura and Reddi, 2007; Khalafi et al., 2007). The superficial zone cartilage (100 µm) of the femoral condyles was harvested using a dermatome (Integra, Plainsboro, NJ, USA). "
ABSTRACT: Cartilage oligomeric matrix protein (COMP) is a prominent non-collagenous component of the extracellular matrix (ECM) in articular cartilage. The regulation of COMP synthesis and secretion is critical for the understanding of cartilage homeostasis in health and disease. We therefore investigated the role of bone morphogenetic protein/transforming growth factor-β (BMP/TGFβ) superfamily members on COMP. Articular chondrocytes were isolated from three distinct zones (surface, middle and deep) and cultured as monolayers in serum-free chemically defined medium. Protein levels of COMP were determined in the medium by enzyme-linked immunosorbent assay. The mRNA expression was determined by quantitative real-time reverse-transcription polymerase chain reaction (RT-PCR). TGFβ1 significantly stimulated the expression of COMP at the mRNA and protein levels in the superficial zone in a time-dependent manner. An unexpected discovery was that surface chondrocytes were more responsive to TGFβ isoforms than those in the deep layer. However, BMP-7 and growth differentiation factor-5 (GDF-5) also upregulate COMP expression; the effects were not as potent as those of TGFβ1. Activins A, B and AB demonstrated no effects on COMP in any of the zones. In conclusion, COMP synthesis is differentially regulated by TGFβ1 in the surface and middle zones of bovine articular cartilage.
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- "Importantly, the 0% and 10% FBS samples were used to replicate standard cell and organ culture systems for articular cartilage (e.g. (Khalafi et al. 2007)). The BMP-7 model was chosen considering bone morphogenetic proteins promote new cartilage and bone growth (Reddi 1998; Reddi 2002). "
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