Differential regulation of gene expression in isolated tendon fascicles exposed to cyclic tensile strain in vitro

ArticleinJournal of Applied Physiology 106(2):506-12 · December 2008with4 Reads
DOI: 10.1152/japplphysiol.90981.2008 · Source: PubMed
Mechanical stimulus is a regulator of tenocyte metabolism. The present study investigated temporal regulation of the expression of selected genes by tenocytes in isolated fascicles subjected to tensile strain in vitro. Cyclic tensile strain with a 3% amplitude superimposed on a 2% static strain was provided for 10 min, followed by either an unstrained period or continuous cyclic strain until the end of a 24-h incubation period. mRNA expression of selected anabolic and catabolic genes were evaluated with quantitative PCR at 10 min, 1 h, 6 h, and 24 h. The application of 6-h cyclic strain significantly upregulated type III collagen mRNA expression in strained fascicles compared with unstrained controls, but no alterations were observed in mRNA expression of type I collagen and biglycan. Significant downregulation in the expression of the decorin core protein was observed in fascicles subjected to 24-h cyclic strain. MMP3 and MMP13 expression levels were upregulated by the application of 10 min of cyclic strain, followed by a progressive downregulation until the end of the incubation period in both the absence and the presence of the continuing cyclic strain. Accordingly, alterations in the expression of anabolic genes were limited to the upregulation of type III collagen by prolonged exposure to cyclic strain, whereas catabolic genes were upregulated by a small number of strain cycles and downregulated by a prolonged cyclic strain. These findings demonstrate distinctive patterns of mechanoregulation for anabolic and catabolic genes and help our understanding of tenocyte response to mechanical stimulation.
    • "In addition, humans show dramatic increases in the levels of MMP2, MMP9 and MMP14 in adult tendons following endurance exercise, suggesting that these proteins aid MTJ repair in response to mechanotransduction (Rullman et al., 2009). This effect depends on the timing of loading as, in cultured tendon fascicles, cells upregulate MMP2 and MMP13 after very short cycles of loading, but downregulate MMP1 after longer cycles (Maeda et al., 2009Maeda et al., , 2013). Similarly, in vitro studies of mechanical loading on mouse tenocytes have shown that, whereas low levels of shear force lead to upregulation of Col1a and Tmnd, increasing the force leads to upregulation of Runx2 and Sox9 (Zhang and Wang, 2015). "
    [Show abstract] [Hide abstract] ABSTRACT: Tendons and ligaments are extracellular matrix (ECM)-rich structures that interconnect muscles and bones. Recent work has shown how tendon fibroblasts (tenocytes) interact with muscles via the ECM to establish connectivity and strengthen attachments under tension. Similarly, ECM-dependent interactions between tenocytes and cartilage/bone ensure that tendon-bone attachments form with the appropriate strength for the force required. Recent studies have also established a close lineal relationship between tenocytes and skeletal progenitors, highlighting the fact that defects in signals modulated by the ECM can alter the balance between these fates, as occurs in calcifying tendinopathies associated with aging. The dynamic fine-tuning of tendon ECM composition and assembly thus gives rise to the remarkable characteristics of this unique tissue type. Here, we provide an overview of the functions of the ECM in tendon formation and maturation that attempts to integrate findings from developmental genetics with those of matrix biology.
    Full-text · Article · Dec 2015
    • "Little is known about the alterations in proteoglycan expression levels in tendons, triggered by mechanical loading. Only few studies have reported that decorin and biglycan expression was not influenced by mechanical stimulation [5,30,31], while versican was significantly upregulated [31]. Taken together, our results are in line with the above literature and demonstrated that high levels of mechanical stress can upregulate the gene expression of fibromodulin, lumican and versican. "
    [Show abstract] [Hide abstract] ABSTRACT: Background Tendons are dense connective tissues subjected periodically to mechanical stress upon which complex responsive mechanisms are activated. These mechanisms affect not only the development of these tissues but also their healing. Despite of the acknowledged importance of the mechanical stress for tendon function and repair, the mechanotransduction mechanisms in tendon cells are still unclear and the elucidation of these mechanisms is a key goal in tendon research. Tendon stem/progenitor cells (TSPC) possess common adult stem cell characteristics, and are suggested to actively participate in tendon development, tissue homeostasis as well as repair. This makes them an important cell population for tendon repair, and also an interesting research target for various open questions in tendon cell biology. Therefore, in our study we focused on TSPC, subjected them to five different mechanical protocols, and investigated the gene expression changes by using semi-quantitative, quantitative PCR and western blotting technologies. Results Among the 25 different genes analyzed, we can convincingly report that the tendon-related genes - fibromodulin, lumican and versican, the collagen I-binding integrins - α1, α2 and α11, the matrix metalloproteinases - MMP9, 13 and 14 were strongly upregulated in TSPC after 3 days of mechanical stimulation with 8% amplitude. Molecular signaling analyses of five key integrin downstream kinases suggested that mechanical stimuli are mediated through ERK1/2 and p38, which were significantly activated in 8% biaxial-loaded TSPC. Conclusions Our results demonstrate the positive effect of 8% mechanical loading on the gene expression of matrix proteins, integrins and matrix metalloproteinases, and activation of integrin downstream kinases p38 and ERK1/2 in TSPC. Taken together, our study contributes to better understanding of mechanotransduction mechanisms in TPSC, which in long term, after further translational research between tendon cell biology and orthopedics, can be beneficial to the management of tendon repair.
    Full-text · Article · Dec 2015
    • "Further, amplitude and frequency of cyclic strain has been shown to modulate MMP and tissue inhibitor of metalloproteinase (TIMP) expression in tenocytes from various species and tissues160161162. Several studies have also demonstrated differential regulation of protein and gene expression in tenocytes, as a function of applied load regime, on isolated tendon fascicles from various species163164165166167168169. In a proteomics analysis study of human tenocytes loaded on aligned PGA scaffolds and subjected to dynamic loading revealed that, when compared the loaded to the unloaded counterparts, 195 proteins were significantly upregulated and 189 proteins were significantly downregulated [170], which not only indicates the complexity of mechanotransduction in cellular function, but also clearly demonstrates the need for sophisticated readout systems to appreciate the induced changes. "
    [Show abstract] [Hide abstract] ABSTRACT: The last decade has seen significant developments in cell therapies, based on permanently differentiated, reprogrammed / engineered and stem cells, for tendon injuries and degenerative conditions. In vitro studies assess the influence of biophysical, biochemical and biological signals on tenogenic phenotype maintenance and / or differentiation towards tenogenic lineage. However, the ideal culture environment has yet to be identified due to the lack of standardised experimental setup and readout system. Bone marrow mesenchymal stem cells and tenocytes / dermal fibroblasts appear to be the cell populations of choice for clinical translation in equine and human patients respectively based on circumstantial, rather than on hard evidence. Collaborative, inter- and multi- disciplinary efforts are expected to provide clinically relevant and commercially viable cell-based therapies for tendon repair and regeneration in the years to come.
    Full-text · Article · Dec 2014
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