Serpine1 Knockdown Enhances MMP Activity after Flexor Tendon Injury in Mice: Implications for Adhesions Therapy

Freeberg, M.A.T.; Farhat, Youssef M.; Easa, Anas; Kallenbach, Jacob G.; Malcolm, Dominic W.; Buckley, Mark R.; Benoit, Danielle S. W.; Awad, Hani A.

doi:10.1038/s41598-018-24144-1

Cited by 42 publications

(75 citation statements)

References 64 publications

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“…The mouse strains utilized in this study were C57Bl/6J (WT) and B6.129S2‐Serpine1 tm1Mlg /J (PAI‐1 KO) mice (Jackson Laboratory). The mouse surgery protocol involves partial laceration of the deep digital flexor tendon of the third digit of the hind paw, as previously described . Briefly, a transverse volar skin incision was made on the middle digit between the metatarsophalangeal and the proximal interphalangeal joints.…”

Section: Methodsmentioning

confidence: 99%

“…2‐1.14.1 with an adjusted p value threshold of 0.05 within an R v3.3.2 environment. Verification of differential gene expression with real‐time RT‐PCR was performed using taqman low‐density array (TLDA) card for a select group of genes that exhibited a range of upregulation or downregulation, as previously described …”

Section: Methodsmentioning

confidence: 99%

“…We have previously shown that the pleiotropic protease suppressor, plasminogen activator inhibitor 1 (PAI‐1), is ubiquitously secreted in the extracellular matrix of scar tissue in injured flexor tendons of C57Bl/6J mice. Incidentally, elevated levels of PAI‐1 were also observed in fibrotic flexor tendon tissue of Dupuytren's contracture hands . Further, PAI‐1 polymorphisms are predisposing factors to post‐operative adhesions following general surgery .…”

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confidence: 99%

“…The reduced activity of MMPs slows the remodeling of scar tissue, which we hypothesized precipitates flexor tendon adhesions. In concordance with this hypothesis, we have shown that zone II flexor tendon healing in PAI‐1 knockout (KO) mice exhibits reduced adhesion formation and accelerated the reestablishment of injured tendon mechanical properties compared to wild‐type C57Bl/6J mice . Based on these findings, PAI‐1 has been identified as a therapeutic target for the treatment of flexor tendon fibrotic adhesions.…”

mentioning

confidence: 99%

“…The mechanisms through which PAI‐1 specifically modulates fibrosis are complex. They include inhibitory effects on matrix remodeling, proinflammatory effects including macrophage activation and infiltration, possibly in association with cellular senescence as a precipitating factor, and epithelial/endothelial‐to‐mesenchymal transition (EMT) . Regardless of the mechanism, a variety of small‐molecule inhibitors of PAI‐1 have been developed and investigated, with the majority of these inhibitors either targeting the PAI‐1 binding domain to tPA/uPA or designed to induce a conformational change in PAI‐1 to convert it to its inactive form .…”

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confidence: 99%

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Transcriptomic Analysis of Cellular Pathways in Healing Flexor Tendons of Plasminogen Activator Inhibitor 1 (PAI‐1/Serpine1) Null Mice

Freeberg

Easa

Lillis

et al. 2019

Journal Orthopaedic Research

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Injuries to flexor tendons can be complicated by fibrotic adhesions, which severely impair the function of the hand. Plasminogen activator inhibitor 1 (PAI‐1/SERPINE1), a master suppressor of fibrinolysis and protease activity, is associated with adhesions. Here, we used next‐generation RNA sequencing (RNA‐Seq) to assess genome‐wide differences in messenger RNA expression due to PAI‐1 deficiency after zone II flexor tendon injury. We used the ingenuity pathway analysis to characterize molecular pathways and biological drivers associated with differentially expressed genes (DEG). Analysis of hundreds of overlapping and DEG in PAI‐1 knockout (KO) and wild‐type mice (C57Bl/6J) during tendon healing revealed common and distinct biological processes. Pathway analysis identified cell proliferation, survival, and senescence, as well as chronic inflammation as potential drivers of fibrotic healing and adhesions in injured tendons. Importantly, we identified the activation of PTEN signaling and the inhibition of FOXO1‐associated biological processes as unique transcriptional signatures of the healing tendon in the PAI‐1/Serpine1 KO mice. Further, transcriptomic differences due to the genetic deletion of PAI‐1 were mechanistically linked to PI3K/Akt/mTOR, PKC, and MAPK signaling cascades. These transcriptional observations provide novel insights into the biological roles of PAI‐1 in tendon healing and could identify therapeutic targets to achieve scar‐free regenerative healing of tendons. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:43–58, 2020

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Transcriptomic Analysis of Cellular Pathways in Healing Flexor Tendons of Plasminogen Activator Inhibitor 1 (PAI‐1/Serpine1) Null Mice

Freeberg

Easa

Lillis

et al. 2019

Journal Orthopaedic Research

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Human Tendon‐on‐a‐Chip for Modeling the Myofibroblast Microenvironment in Peritendinous Fibrosis

Ajalik,

Linares,

Alenchery

et al. 2024

Adv Healthcare Materials

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Understanding the myofibroblast microenvironment is critical to developing therapies for fibrotic diseases. Here the development of a novel human tendon‐on‐a‐chip (hToC) is reported to model this crosstalk in peritendinous adhesions, which currently lacks biological therapies. The hToC facilitates cellular and paracrine interactions between a vascular component, which contains endothelial cells and monocytes, and a tissue hydrogel component that houses tendon cells and macrophages. It is found that the hToC replicates some aspects of in vivo inflammatory and fibrotic phenotypes in preclinical and clinical samples, including activated mTOR signaling, vascular inflammation, tissue contraction induced by myofibroblast activation, inflammatory cytokines secretion, and transendothelial migration of monocytes to the tissue hydrogel. Transcriptional analysis demonstrates significant overlap in enriched pathways in the hToC with human tenolysis samples, including the activation of mTOR signaling. Rapamycin suppresses the vascular inflammation and fibrotic phenotype in the hToC, which provides proof‐of‐concept of its utility as an in vitro tool for investigating multicellular crosstalk in fibrosis and testing therapeutics to mitigate it.

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PAI‐1 mediates TGF‐β1‐induced myofibroblast activation in tenocytes via mTOR signaling

Alenchery

Ajalik

Jerreld

et al. 2023

Journal Orthopaedic Research

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Transforming growth factor‐beta (TGF‐β1) induces plasminogen activator inhibitor 1 (PAI‐1) to effect fibrotic pathologies in several organs including tendon. Recent data implicated PAI‐1 with inhibition of phosphatase and tensin homolog (PTEN) suggesting that PAI‐1‐induced adhesions involves phosphoinositide 3‐kinase/protein kinase B/mammalian target of rapamycin (mTOR) signaling. Ergo, we investigated effects of TGF‐β1, PAI‐1, and mTOR signaling crosstalk on myofibroblast activation, senescence, and proliferation in primary flexor tenocytes from wild‐type (WT) and PAI‐1 knockout (KO) mice. PAI‐1 deletion blunted TGF‐β1‐induced myofibroblast activation in murine flexor tenocytes and increased the gene expression of Mmp‐2 to confer protective effects against fibrosis. While TGF‐β1 significantly reduced phosphorylation of PTEN in WT cells, PAI‐1 deletion rescued the activation of PTEN. Despite that, there were no differences in TGF‐β1‐induced activation of mTOR signaling (AKT, 4EBP1, and P70S6K) in WT or KO tenocytes. Phenotypic changes in distinct populations of WT or KO tenocytes exhibiting high or low mTOR activity were then examined. TGF‐β1 increased alpha‐smooth muscle actin abundance in WT cells exhibiting high mTOR activity, but this increase was blunted in KO cells exhibiting high 4EBP1 activity but not in cells exhibiting high S6 activity. DNA damage (γH2AX) was increased with TGF‐β1 treatment in WT tenocytes but was blunted in KO cells exhibiting high mTOR activity. Increased mTOR activity enhanced proliferation (Ki67) in both WT and KO tenocytes. These findings point to a complex nexus of TGF‐β1, PAI‐1, and mTOR signaling in regulating proliferation, myofibroblast differentiation, and senescence in tenocytes, which could define therapeutic targets for chronic tendon adhesions and other fibrotic pathologies.

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Serpine1 Knockdown Enhances MMP Activity after Flexor Tendon Injury in Mice: Implications for Adhesions Therapy

Cited by 42 publications

References 64 publications

Transcriptomic Analysis of Cellular Pathways in Healing Flexor Tendons of Plasminogen Activator Inhibitor 1 (PAI‐1/Serpine1) Null Mice

Transcriptomic Analysis of Cellular Pathways in Healing Flexor Tendons of Plasminogen Activator Inhibitor 1 (PAI‐1/Serpine1) Null Mice

Human Tendon‐on‐a‐Chip for Modeling the Myofibroblast Microenvironment in Peritendinous Fibrosis

PAI‐1 mediates TGF‐β1‐induced myofibroblast activation in tenocytes via mTOR signaling

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