MT1-MMP modulates the mechanosensitivity of osteocytes.

Academic Centre for Dentistry Amsterdam, University of Amsterdam and VU University Amsterdam, Department of Oral Cell Biology, Research Institute MOVE, Amsterdam, The Netherlands.
Biochemical and Biophysical Research Communications (Impact Factor: 2.28). 12/2011; 417(2):824-9. DOI: 10.1016/j.bbrc.2011.12.045
Source: PubMed

ABSTRACT Membrane-type matrix metalloproteinase-1 (MT1-MMP) is expressed by mechanosensitive osteocytes and affects bone mass. The extracellular domain of MT1-MMP is connected to extracellular matrix, while its intracellular domain is a strong modulator of cell signaling. In theory MT1-MMP could thus transduce mechanical stimuli into a chemical response. We hypothesized that MT1-MMP plays a role in the osteocyte response to mechanical stimuli. MT1-MMP-positive and knockdown (siRNA) MLO-Y4 osteocytes were mechanically stimulated with a pulsating fluid flow (PFF). Focal adhesions were visualized by paxillin immunostaining. Osteocyte number, number of empty lacunae, and osteocyte morphology were measured in long bones of MT1-MMP(+/+) and MT1-MMP(-/-) mice. PFF decreased MT1-MMP mRNA and protein expression in MLO-Y4 osteocytes, suggesting that mechanical loading may affect pericellular matrix remodeling by osteocytes. MT1-MMP knockdown enhanced NO production and c-jun and c-fos mRNA expression in response to PFF, concomitantly with an increased number and size of focal adhesions, indicating that MT1-MMP knockdown osteocytes have an increased sensitivity to mechanical loading. Osteocytes in MT1-MMP(-/-) bone were more elongated and followed the principle loading direction, suggesting that they might sense mechanical loading. This was supported by a lower number of empty lacunae in MT1-MMP(-/-) bone, as osteocytes lacking mechanical stimuli tend to undergo apoptosis. In conclusion, mechanical stimulation decreased MT1-MMP expression by MLO-Y4 osteocytes, and MT1-MMP knockdown increased the osteocyte response to mechanical stimulation, demonstrating a novel and unexpected role for MT1-MMP in mechanosensing.

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The human skeleton is a miracle of engineering, combining both toughness and light weight. It does so because bones possess cellular mechanisms wherein external mechanical loads are sensed. These mechanical loads are transformed into biological signals, which ultimately direct bone formation and/or bone resorption. Osteocytes, since they are ubiquitous in the mineralized matrix, are the cells that sense mechanical loads and transduce the mechanical signals into a chemical response. The osteocytes then release signaling molecules, which orchestrate the recruitment and activity of osteoblasts or osteoclasts, resulting in the adaptation of bone mass and structure. In this review, we highlight current insights in bone adaptation to external mechanical loading, with an emphasis on how a mechanical load placed on whole bones is translated and amplified into a mechanical signal that is subsequently sensed by the osteocytes. This article is part of a Special Issue entitled Osteocyte.
    Bone 10/2012; · 4.46 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Zebrafish keratocytes collectively migrate rapidly when established in explant cultures but little is known about the signals that initiate motility or the signal transduction pathways that result in an epithelial to mesenchymal transition. Matrix metalloproteinases (MMPs) are strong candidates for playing a role in this regulation and have previously not been analysed in this wound healing model system. Results presented here document a rapid and dramatic rise in MMP14a, MMP2, MMP9 and MMP13a mRNA levels over time. In a motility assay, a broad-spectrum MMP inhibitor and an inhibitor specific for MMP2 and MMP9 significantly decrease cell migration in a dose dependent manner but treatment with an MMP13 specific inhibitor significantly increases cell sheet area. Immunofluorescence staining with an antibody specific for the catalytic domain of MMP14 indicates that activated MMP14 protein is highly expressed on cells at the leading edge of a sheet compared with follower cells in the centre of the sheet, and is augmented further in leader cells that are stretched, thus likely in the process of detaching from the cell sheet. These data are consistent with a model in which active MMP14 at the leading edge of cell sheets in explant cultures triggers activation of MMP2 and/or MMP9, thus creating promigratory signal(s) that outweigh the inhibitory role of targets cleaved by MMP13. Taken together, these data suggest that MMPs play an important but complex role in regulating the collective cell migration of zebrafish keratocytes and provide support for the relevance of using zebrafish as a model for human disease.
    Cell Biology International Reports. 12/2013; 20(2).
  • [Show abstract] [Hide abstract]
    ABSTRACT: Matrix metalloproteinases (MMPs) are extracellular matrix (ECM) degrading enzymes and have complex and specific regulation networks. This includes activation interactions, where one MMP family member activates another. ECM degradation and MMP activation can be initiated by several different stimuli including changes in ECM mechanical properties or intracellular contractility. These mechanical stimuli are known enhancers of metastatic potential. MMP-14 facilitates local ECM degradation and is well known as a major mediator of cell migration, angiogenesis and invasion. Recently, function blocking antibodies have been developed to specifically block MMP-14, providing a useful tool for research as well as therapeutic applications. Here we utilize a selective MMP-14 function blocking antibody to delineate the role of MMP-14 as an activator of other MMPs in response to changes in cellular contractility and ECM stiffness. Inhibition using function blocking antibodies reveals that MMP-14 activates soluble MMPs like MMP-2 and -9 under various mechanical stimuli in the pancreatic cancer cell line, Panc-1. In addition, inhibition of MMP-14 abates Panc-1 cell extension into 3D gels to levels seen with non-specific pan-MMP inhibitors at higher concentrations. This strengthens the case for MMP function blocking antibodies as more potent and specific MMP inhibition therapeutics.
    Biochemical and Biophysical Research Communications 05/2014; · 2.28 Impact Factor

Full-text (2 Sources)

Available from
May 23, 2014