Regulation of Chondrogenesis and Chondrocyte Differentiation by Stress

Center for Musculoskeletal Research, University of Rochester Medical Center, Rochester, New York 14642, USA.
Journal of Clinical Investigation (Impact Factor: 13.22). 03/2008; 118(2):429-38. DOI: 10.1172/JCI34174
Source: PubMed


Chondrogenesis and endochondral ossification are the cartilage differentiation processes that lead to skeletal formation and growth in the developing vertebrate as well as skeletal repair in the adult. The exquisite regulation of these processes, both in normal development and in pathologic situations, is impacted by a number of different types of stress. These include normal stressors such as mechanical loading and hypoxia as well pathologic stressors such as injury and/or inflammation and environmental toxins. This article provides an overview of the processes of chondrogenesis and endochondral ossification and their control at the molecular level. A summary of the influence of the most well-understood normal and pathologic stressors on the differentiation program is also presented.

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Available from: Matthew J Hilton, Feb 13, 2014
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    • "Analogous to embryonic skeletal development, periosteum-initiated fracture repair implicates endochondral and intramembranous bone formation, which proceed in a sequential and organized manner [5], [6]. While adult bone repair recapitulates some essential regulatory mechanisms that occur in early skeletal development, repair is a unique bone morphogenetic process, orchestrated by an ensemble of genes distinct from early skeletal development [7]. Due to an inability to directly target the periosteum, the molecular mechanisms and the implicated molecular pathway(s) that control the differentiation program of periosteal mesenchymal progenitor cells in bone fracture repair remains poorly understood. "
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    ABSTRACT: Periosteum provides a major source of mesenchymal progenitor cells for bone fracture repair. Combining cell-specific targeted Cox-2 gene deletion approaches with in vitro analyses of the differentiation of periosteum-derived mesenchymal progenitor cells (PDMPCs), here we demonstrate a spatial and temporal role for Cox-2 function in the modulation of osteogenic and chondrogenic differentiation of periosteal progenitors in fracture repair. Prx1Cre-targeted Cox-2 gene deletion in mesenchyme resulted in marked reduction of intramembraneous and endochondral bone repair, leading to accumulation of poorly differentiated mesenchyme and immature cartilage in periosteal callus. In contrast, Col2Cre-targeted Cox-2 gene deletion in cartilage resulted in a deficiency primarily in cartilage conversion into bone. Further cell culture analyses using Cox-2 deficient PDMPCs demonstrated reduced osteogenic differentiation in monolayer cultures, blocked chondrocyte differentiation and hypertrophy in high density micromass cultures. Gene expression microarray analyses demonstrated downregulation of a key set of genes associated with bone/cartilage formation and remodeling, namely Sox9, Runx2, Osx, MMP9, VDR and RANKL. Pathway analyses demonstrated dysregulation of the HIF-1, PI3K-AKT and Wnt pathways in Cox-2 deficient cells. Collectively, our data highlight a crucial role for Cox-2 from cells of mesenchymal lineages in modulating key pathways that control periosteal progenitor cell growth, differentiation, and angiogenesis in fracture repair.
    PLoS ONE 07/2014; 9(7):e100079. DOI:10.1371/journal.pone.0100079 · 3.23 Impact Factor
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    • "Mechanical signals are important for normal cartilage to maintain tissue integrity and homeostasis (61,62). Chondrocytes respond to changes in the levels of pro-inflammatory mediators and mechanical signals in OA (63,64). "
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    ABSTRACT: MicroRNA (miR)-146a is known to be overexpressed in osteoarthritis (OA). However, the role of miR-146a in OA has not yet been fully elucidated. In the present study, we applied mechanical pressure of 10 MPa to human chondrocytes for 60 min in order to investigate the expression of miR-146a and apoptosis following the mechanical pressure injury. Normal human chondrocytes were transfected with an miR-146a mimic or an inhibitor to regulate miR-146a expression. Potential target genes of miR-146a were predicted using bioinformatics. Moreover, luciferase reporter assay confirmed that Smad4 was a direct target of miR-146a. The expression levels of miR-146a, Smad4 and vascular endothelial growth factor (VEGF) were quantified by quantitative reverse transcription PCR and/or western blot analysis. The effects of miR-146a on apoptosis were detected by Annexin V-fluorescein isothiocyanate (FITC)/propidium iodide (PI) flow cytometry. The results indicated that mechanical pressure affected chondrocyte viability and induced the early apoptosis of chondrocytes. Mechanical pressure injury increased the expression levels of miR-146a and VEGF and decreased the levels of Smad4 in the chondrocytes. In the human chondrocytes, the upregulation of miR-146a induced apoptosis, upregulated VEGF expression and downregulated Smad4 expression. In addition, the knockdown of miR-146a reduced cell apoptosis, upregulated Smad4 expression and downregulated VEGF expression. Smad4 was identified as a direct target of miR-146a by harboring a miR‑146a binding sequence in the 3'-untranslated region (3'-UTR) of its mRNA. Furthermore, the upregulation of VEGF induced by miR‑146a was mediated by Smad4 in the chondrocytes subjected to mechanical pressure injury. These results demonstrated that miR-146a was overexpressed in our chondrocyte model of experimentally induced human mechanical injury, accompanied by the upregulation of VEGF and the downregulation of Smad4 in vitro. Moreover, our data suggest that miR-146a is involved in human chondrocyte apoptosis in response to mechanical injury, and may contribute to the mechanical injury of chondrocytes, as well as to the pathogenesis of OA by increasing the levels of VEGF and damaging the transforming growth factor (TGF)-β signaling pathway through the targeted inhibition of Smad4 in cartilage.
    International Journal of Molecular Medicine 06/2014; 34(2). DOI:10.3892/ijmm.2014.1808 · 2.09 Impact Factor
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    • "We speculate that a relatively softer scaffold than the studied collagen-I/III scaffold would enhance chondrogenic differentiation even further. Hypoxia is believed to trigger the embryonic condensation of mesenchymal cells and the activation of various transcriptional factors resulting in cartilage formation (Zuscik et al. 2008). Mature chondrocytes and MSCs express genes for αsmooth muscle actin (SMA), which plays a major role in cell cytoskeleton (Kim and Spector 2000; Kinner and Spector 2001; Ng et al. 2011). "
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    ABSTRACT: Human adipose-derived stromal cells (hASCs) possess the potential for chondrogenic differentiation. Recent studies imply that this differentiation process may be enhanced by culturing the cells in low oxygen tension in combination with three-dimensional (3D) scaffolds. We report the evaluation of the chondrogenic potential of hASC pellets in 5 and 21 % O2 and as cell-scaffold constructs using a collagen I/III scaffold with chemical induction using TGF-β3. hASCs from four human donors were cultured both in a micromass pellet system and in 3D collagen I/III scaffolds in either 5 or 21 % O2. Chondrogenesis was evaluated by quantitative gene expression analysis of aggrecan, SOX9, collagen I, II and X and histological evaluation with H&E and toluidine blue staining. Induced pellets cultured in 5 % O2 showed increased peripheral cellularity and matrix deposition compared with 21 % O2. Induced pellets cultured in 5 % O2 had increased control-adjusted gene expression of aggrecan, SOX9 and collagen I and decreased collagen X compared with 21 % O2 cultures. Induced pellets had higher gene expression of aggrecan, SOX9, collagen I, II and X and increased ratios of collagen II/I and collagen II/X compared with controls. As for pellets, scaffold cultures showed cellularity and matrix deposition organized in a zonal manner as a function of the oxygen tension, with a cartilage-like morphology and matrix deposition peripherally in the 5 % O2 group and a more centrally located matrix in the 21 % O2 group. There were no differences in histology and gene expressions between pellet and scaffold cultures. Five percent O2 in combination with chondrogenic culture medium stimulated chondrogenic differentiation of hASCs in vitro. We observed similar patterns of differentiation and matrix disposition in pellet and scaffold cultures.
    Cell and Tissue Research 11/2013; 355(1). DOI:10.1007/s00441-013-1732-5 · 3.57 Impact Factor
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