Dataset Information

Regulation of articular chondrocyte catabolic genes by growth factor interaction.

ABSTRACT: Osteoarthritis is characterized by a loss of articular cartilage homeostasis in which degradation exceeds formation. Several growth factors have been shown to promote cartilage formation by augmenting articular chondrocyte anabolic activity. This study tests the hypothesis that such growth factors also play an anticatabolic role. We transferred individual or combinations of the genes encoding insulin-like growth factor-I, bone morphogenetic protein-2, bone morphogenetic protein-7, transforming growth factor-?1, and fibroblast growth factor-2, into adult bovine articular chondrocytes and measured the expression of catabolic marker genes encoding A disintegrin and metalloproteinase with thrombospondin motifs-4 and -5, matrix metalloproteinases-3 and -13, and interleukin-6. When delivered individually, or in combination, these growth factor transgenes differentially regulated the direction, magnitude, and time course of expression of the catabolic marker genes. In concert, the growth factor transgenes regulated the marker genes in an interactive fashion that ranged from synergistic inhibition to synergistic stimulation. Synergistic stimulation prevailed over synergistic inhibition, reaching maxima of 15.2- and 2.7-fold, respectively. Neither the magnitude nor the time course of the effect of the transgene combinations could be predicted on the basis of the individual transgene effects. With few exceptions, the data contradict our hypothesis. The results demonstrate that growth factors that are traditionally viewed as chondrogenic tend also to promote catabolic gene expression. The competing actions of these potential therapeutic agents add an additional level of complexity to the selection of regulatory factors for restoring articular cartilage homeostasis or promoting repair.

SUBMITTER: Shi S

PROVIDER: S-EPMC6716380 | biostudies-literature | 2019 Feb

REPOSITORIES: biostudies-literature

ACCESS DATA

Similar Datasets

Project description:Cartilage degeneration driven by catabolic stimuli is a critical pathophysiological process in osteoarthritis (OA). We have defined fibroblast growth factor 2 (FGF-2) as a degenerative mediator in adult human articular chondrocytes. Biological effects mediated by FGF-2 include inhibition of proteoglycan production, up-regulation of matrix metalloproteinase-13 (MMP-13), and stimulation of other catabolic factors. In this study, we identified the specific receptor responsible for the catabolic functions of FGF-2, and established a pathophysiological connection between the FGF-2 receptor and OA.Primary human articular chondrocytes were cultured in monolayer (24 hours) or alginate beads (21 days), and stimulated with FGF-2 or FGF18, in the presence or absence of FGFR1 (FGF receptor 1) inhibitor. Proteoglycan accumulation and chondrocyte proliferation were assessed by dimethylmethylene blue (DMMB) assay and DNA assay, respectively. Expression of FGFRs (FGFR1 to FGFR4) was assessed by flow cytometry, immunoblotting, and quantitative real-time PCR (qPCR). The distinctive roles of FGFR1 and FGFR3 after stimulation with FGF-2 were evaluated using either pharmacological inhibitors or FGFR small interfering RNA (siRNA). Luciferase reporter gene assays were used to quantify the effects of FGF-2 and FGFR1 inhibitor on MMP-13 promoter activity.Chondrocyte proliferation was significantly enhanced in the presence of FGF-2 stimulation, which was inhibited by the pharmacological inhibitor of FGFR1. Proteoglycan accumulation was reduced by 50% in the presence of FGF-2, and this reduction was successfully rescued by FGFR1 inhibitor. FGFR1 inhibitors also fully reversed the up-regulation of MMP-13 expression and promoter activity stimulated by FGF-2. Blockade of FGFR1 signaling by either chemical inhibitors or siRNA targeting FGFR1 rather than FGFR3 abrogated the up-regulation of matrix metalloproteinases 13 (MMP-13) and a disintegrin and metalloproteinase with a thrombospondin type 1 motif 5 (ADAMTS5), as well as down-regulation of aggrecan after FGF-2 stimulation. Flow cytometry, qPCR and immunoblotting analyses suggested that FGFR1 and FGFR3 were the major FGFR isoforms expressed in human articular chondrocytes. FGFR1 was activated more potently than FGFR3 upon FGF-2 stimulation. In osteoarthritic chondrocytes, FGFR3 was significantly down regulated (P < 0.05) with a concomitant increase in the FGFR1 to FGFR3 expression ratio (P < 0.05), compared to normal chondrocytes. Our results also demonstrate that FGFR3 was negatively regulated by FGF-2 at the transcriptional level through the FGFR1-ERK (extracellular signal-regulated kinase) signaling pathway in human articular chondrocytes.FGFR1 is the major mediator with the degenerative potential in the presence of FGF-2 in human adult articular chondrocytes. FGFR1 activation by FGF-2 promotes catabolism and impedes anabolism. Disruption of the balance between FGFR1 and FGFR3 signaling ratio may contribute to the pathophysiology of OA.

Project description:During the development of the appendicular skeleton, the cartilaginous templates undergo hypertrophic differentiation and remodels into bone, except for the cartilage most adjacent to joint cavities where hypertrophic differentiation and endochondral bone formation are prevented, and chondrocytes instead form articular cartilage. The mechanisms that prevent hypertrophic differentiation and endochondral bone formation of the articular cartilage have not been elucidated. To explore the role of the synovial microenvironment in chondrocyte differentiation, osteochondral allografts consisting of articular cartilage, epiphyseal bone, and growth plate cartilage from distal femoral epiphyses of inbred Lewis rats expressing enhanced green fluorescent protein from a ubiquitous promoter were transplanted either in inverted or original (control) orientation to matching sites in wildtype littermates, thereby allowing for tracing of transplanted cells and their progenies. We found that no hypertrophic differentiation occurred in the growth plate cartilage ectopically placed at the joint surface. Instead, the transplanted growth plate cartilage, with time, remodeled into articular cartilage. This finding suggests that the microenvironment at the articular surface inhibits hypertrophic differentiation and supports articular cartilage formation. To explore this hypothesis, rat chondrocyte pellets were cultured with and without synoviocyte-conditioned media. Consistent with the hypothesis, hypertrophic differentiation was inhibited and expression of the articular surface marker lubricin (Prg4) was dramatically induced when chondrocyte pellets were exposed to synovium- or synoviocyte-conditioned media, but not to chondrocyte- or osteoblast-conditioned media. Taken together, we present evidence for a novel mechanism by which synoviocytes, through the secretion of a factor or factors, act directly on chondrocytes to inhibit hypertrophic differentiation and endochondral bone formation and promote articular cartilage formation. This mechanism may have important implications for articular cartilage development, maintenance, and regeneration.

Dataset Information

Regulation of articular chondrocyte catabolic genes by growth factor interaction.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets