The Center for Musculoskeletal Research

Rochester, NY, United States

The Center for Musculoskeletal Research

Rochester, NY, United States

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Farhat Y.M.,01 Elmwood Ave | Farhat Y.M.,The Center for Musculoskeletal Research | Al-Maliki A.A.,The Center for Musculoskeletal Research | Easa A.,The Center for Musculoskeletal Research | And 7 more authors.
Journal of Cellular Physiology | Year: 2015

Flexor tendon injuries caused by deep lacerations to the hands are a challenging problem as they often result in debilitating adhesions that prevent the movement of the afflicted fingers. Evidence exists that tendon adhesions as well as scarring throughout the body are largely precipitated by the pleiotropic growth factor, Transforming Growth Factor Beta 1(TGF-β1), but the effects of TGF-β1 are poorly understood in tendon healing. Using an in vitro model of tendon healing, we previously found that TGF-β1 causes gene expression changes in tenocytes that are consistent with scar tissue and adhesion formation, including upregulation of the anti-fibrinolytic protein, PAI-1. Therefore, we hypothesized that TGF-β1 contributes to scarring and adhesions by reducing the activity of proteases responsible for ECM degradation and remodeling, such as plasmin and MMPs, via upregulation of PAI-1. To test our hypothesis, we examined the effects of TGF-β1 on the protease activity of tendon cells. We found that flexor tendon tenocytes treated with TGF-β1 had significantly reduced levels of active MMP-2 and plasmin. Interestingly, the effects of TGF-β1 on protease activity were completely abolished in tendon cells from homozygous plasminogen activator inhibitor 1 (PAI-1) knockout (KO) mice, which are unable to express PAI-1. Our findings support the hypothesis that TGF-β1 induces PAI-1, which suppresses plasmin and plasmin-mediated MMP activity, and provide evidence that PAI-1 may be a novel therapeutic target for preventing adhesions and promoting a scarless, regenerative repair of flexor tendon injuries. © 2014 Wiley Periodicals, Inc.


PubMed | Biostatistic, The Center for Musculoskeletal Research, University of Rochester, Tianjin Medical University and 5 more.
Type: | Journal: Journal of cellular physiology | Year: 2016

DC-STAMP is a multi-pass transmembrane protein essential for cell-cell fusion of osteoclast precursors during osteoclast (OC) development. DC-STAMP-/- mice have mild osteopetrosis and form mononuclear cells with limited resorption capacity. The identification of an Immunoreceptor Tyrosine-based Inhibitory Motif (ITIM) on the cytoplasmic tail of DC-STAMP suggested a potential signaling function but the absence of known DC-STAMP ligand has hindered examination of downstream signaling pathways. To address this problem, we engineered a light-activatable DC-STAMP chimeric molecule in which light exposure mimics ligand engagement that can be traced by downstream Ca2+ signaling. Deletion of the cytoplasmic ITIM resulted in a significant elevation in the amplitude and duration of intracellular Ca2+ flux. We also found that decreased NFATc1 expression in DC-STAMP-/- cells was restored by DC-STAMP over-expression. Multiple biological phenotypes including cell-cell fusion, bone erosion, cell mobility, DC-STAMP cell surface distribution, and NFATc1 nuclear translocation were altered by deletion of the ITIM and adjacent amino acids. In contrast, mutations on each of tyrosine residues in the ITIM showed no effect on DC-STAMP function. Collectively, our results suggest that ITIM on DC-STAMP is a functional motif that regulates osteoclast differentiation through the NFATc1 / Ca2+ axis. This article is protected by copyright. All rights reserved.


PubMed | The Center for Musculoskeletal Research and 01 Elmwood Ave
Type: Journal Article | Journal: Journal of cellular physiology | Year: 2015

Flexor tendon injuries caused by deep lacerations to the hands are a challenging problem as they often result in debilitating adhesions that prevent the movement of the afflicted fingers. Evidence exists that tendon adhesions as well as scarring throughout the body are largely precipitated by the pleiotropic growth factor, Transforming Growth Factor Beta 1(TGF-1), but the effects of TGF-1 are poorly understood in tendon healing. Using an in vitro model of tendon healing, we previously found that TGF-1 causes gene expression changes in tenocytes that are consistent with scar tissue and adhesion formation, including upregulation of the anti-fibrinolytic protein, PAI-1. Therefore, we hypothesized that TGF-1 contributes to scarring and adhesions by reducing the activity of proteases responsible for ECM degradation and remodeling, such as plasmin and MMPs, via upregulation of PAI-1. To test our hypothesis, we examined the effects of TGF-1 on the protease activity of tendon cells. We found that flexor tendon tenocytes treated with TGF-1 had significantly reduced levels of active MMP-2 and plasmin. Interestingly, the effects of TGF-1 on protease activity were completely abolished in tendon cells from homozygous plasminogen activator inhibitor 1 (PAI-1) knockout (KO) mice, which are unable to express PAI-1. Our findings support the hypothesis that TGF-1 induces PAI-1, which suppresses plasmin and plasmin-mediated MMP activity, and provide evidence that PAI-1 may be a novel therapeutic target for preventing adhesions and promoting a scarless, regenerative repair of flexor tendon injuries.

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