Hypoxia signalling manipulation for bone regeneration

2015 ◽  
Vol 17 ◽  
Author(s):  
Justin Drager ◽  
Edward J. Harvey ◽  
Jake Barralet
Keyword(s):  
Bone Regeneration ◽  
Bone Repair ◽  
Molecular Mechanisms ◽  
Bone Development ◽  
Hypoxia Inducible Factor ◽  
Cell Recruitment ◽  
Substantial Progress ◽  
Hif Pathway

Hypoxia-inducible factor (HIF) signalling is intricately involved in coupling angiogenesis and osteogenesis during bone development and repair. Activation of HIFs in response to a hypoxic bone micro-environment stimulates the transcription of multiple genes with effects on angiogenesis, precursor cell recruitment and differentiation. Substantial progress has been made in our understanding of the molecular mechanisms by which oxygen content regulates the levels and activity of HIFs. In particular, the discovery of the role of oxygen-dependent hydroxylase enzymes in modulating the activity of HIF-1α has sparked interest in potentially promising therapeutic strategies in multiple clinical fields and most recently bone healing. Several small molecules, termed hypoxia mimics, have been identified as activators of the HIF pathway and have demonstrated augmentation of both bone vascularity and bone regeneration in vivo. In this review we discuss key elements of the hypoxic signalling pathway and its role in bone regeneration. Current strategies for the manipulation of this pathway for enhancing bone repair are presented with an emphasis on recent pre-clinical in vivo investigations. These findings suggest promising approaches for the development of therapies to improve bone repair and tissue engineering strategies.

scholarly journals The Hypoxia-Inducible Factor Pathway, Prolyl Hydroxylase Domain Protein Inhibitors, and Their Roles in Bone Repair and Regeneration

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
Lihong Fan ◽  
Jia Li ◽  
Zefeng Yu ◽  
Xiaoqian Dang ◽  
Kunzheng Wang
Keyword(s):  
Cell Fate ◽  
Bone Repair ◽  
Molecular Mechanisms ◽  
Hypoxia Inducible Factor ◽  
Prolyl Hydroxylase ◽  
Bone Tumours ◽  
Cell Fate Decisions ◽  
Tightly Coupled ◽  
Hif Pathway ◽  
Prolyl Hydroxylase Domain

Hypoxia-inducible factors (HIFs) are oxygen-dependent transcriptional activators that play crucial roles in angiogenesis, erythropoiesis, energy metabolism, and cell fate decisions. The group of enzymes that can catalyse the hydroxylation reaction of HIF-1 is prolyl hydroxylase domain proteins (PHDs). PHD inhibitors (PHIs) activate the HIF pathway by preventing degradation of HIF-αvia inhibiting PHDs. Osteogenesis and angiogenesis are tightly coupled during bone repair and regeneration. Numerous studies suggest that HIFs and their target gene, vascular endothelial growth factor (VEGF), are critical regulators of angiogenic-osteogenic coupling. In this brief perspective, we review current studies about the HIF pathway and its role in bone repair and regeneration, as well as the cellular and molecular mechanisms involved. Additionally, we briefly discuss the therapeutic manipulation of HIFs and VEGF in bone repair and bone tumours. This review will expand our knowledge of biology of HIFs, PHDs, PHD inhibitors, and bone regeneration, and it may also aid the design of novel therapies for accelerating bone repair and regeneration or inhibiting bone tumours.

Modern approaches on stem cells and scaffolding technology for osteogenic differentiation and regeneration

2021 ◽  
pp. 153537022110529
Author(s):  
Shivaani Kirankumar ◽  
Narasimman Gurusamy ◽  
Sheeja Rajasingh ◽  
Vinoth Sigamani ◽  
Jayavardini Vasanthan ◽  
...  
Keyword(s):  
Stem Cells ◽  
Bone Regeneration ◽  
Bone Repair ◽  
Molecular Mechanisms ◽  
Bone Cells ◽  
Three Dimensional ◽  
Non Union ◽  
Cell Based Therapy ◽  
Osteogenic Factors

The process of bone repair has always been a natural mystery. Although bones do repair themselves, supplemental treatment is required for the initiation of the self-regeneration process. Predominantly, surgical procedures are employed for bone regeneration. Recently, cell-based therapy for bone regeneration has proven to be more effective than traditional methods, as it eliminates the immune risk and painful surgeries. In clinical trials, various stem cells, especially mesenchymal stem cells, have shown to be more efficient for the treatment of several bone-related diseases, such as non-union fracture, osteogenesis imperfecta, osteosarcoma, and osteoporosis. Furthermore, the stem cells grown in a suitable three-dimensional scaffold support were found to be more efficient for osteogenesis. It has been shown that the three-dimensional bioscaffolds support and simulate an in vivo environment, which helps in differentiation of stem cells into bone cells. Bone regeneration in patients with bone disorders can be improved through modification of stem cells with several osteogenic factors or using stem cells as carriers for osteogenic factors. In this review, we focused on the various types of stem cells and scaffolds that are being used for bone regeneration. In addition, the molecular mechanisms of various transcription factors, signaling pathways that support bone regeneration and the senescence of the stem cells, which limits bone regeneration, have been discussed.

scholarly journals Let-7f miRNA regulates SDF-1α- and hypoxia-promoted migration of mesenchymal stem cells and attenuates mammary tumor growth upon exosomal release

2021 ◽  
Vol 12 (6) ◽  
Author(s):  
Virginia Egea ◽  
Kai Kessenbrock ◽  
Devon Lawson ◽  
Alexander Bartelt ◽  
Christian Weber ◽  
...  
Keyword(s):  
Stem Cells ◽  
Mesenchymal Stem Cells ◽  
Tumor Growth ◽  
Molecular Mechanisms ◽  
Hypoxia Inducible Factor ◽  
Human Mesenchymal Stem Cells ◽  
Target Cells ◽  
Autophagic Flux ◽  
Stromal Cell Derived Factor

AbstractBone marrow-derived human mesenchymal stem cells (hMSCs) are recruited to damaged or inflamed tissues where they contribute to tissue repair. This multi-step process involves chemokine-directed invasion of hMSCs and on-site release of factors that influence target cells or tumor tissues. However, the underlying molecular mechanisms are largely unclear. Previously, we described that microRNA let-7f controls hMSC differentiation. Here, we investigated the role of let-7f in chemotactic invasion and paracrine anti-tumor effects. Incubation with stromal cell-derived factor-1α (SDF-1α) or inflammatory cytokines upregulated let-7f expression in hMSCs. Transfection of hMSCs with let-7f mimics enhanced CXCR4-dependent invasion by augmentation of pericellular proteolysis and release of matrix metalloproteinase-9. Hypoxia-induced stabilization of the hypoxia-inducible factor 1 alpha in hMSCs promoted cell invasion via let-7f and activation of autophagy. Dependent on its endogenous level, let-7f facilitated hMSC motility and invasion through regulation of the autophagic flux in these cells. In addition, secreted let-7f encapsulated in exosomes was increased upon upregulation of endogenous let-7f by treatment of the cells with SDF-1α, hypoxia, or induction of autophagy. In recipient 4T1 tumor cells, hMSC-derived exosomal let-7f attenuated proliferation and invasion. Moreover, implantation of 3D spheroids composed of hMSCs and 4T1 cells into a breast cancer mouse model demonstrated that hMSCs overexpressing let-7f inhibited tumor growth in vivo. Our findings provide evidence that let-7f is pivotal in the regulation of hMSC invasion in response to inflammation and hypoxia, suggesting that exosomal let-7f exhibits paracrine anti-tumor effects.

scholarly journals Bone defect reconstruction via endochondral ossification: A developmental engineering strategy

2021 ◽  
Vol 12 ◽  
pp. 204173142110042
Author(s):  
Rao Fu ◽  
Chuanqi Liu ◽  
Yuxin Yan ◽  
Qingfeng Li ◽  
Ru-Lin Huang
Keyword(s):  
Bone Regeneration ◽  
Bone Defect ◽  
Bone Repair ◽  
Endochondral Ossification ◽  
Current Knowledge ◽  
Endochondral Bone ◽  
Defect Reconstruction ◽  
Hypoxic Conditions ◽  
Bone Defect Reconstruction

Traditional bone tissue engineering (BTE) strategies induce direct bone-like matrix formation by mimicking the embryological process of intramembranous ossification. However, the clinical translation of these clinical strategies for bone repair is hampered by limited vascularization and poor bone regeneration after implantation in vivo. An alternative strategy for overcoming these drawbacks is engineering cartilaginous constructs by recapitulating the embryonic processes of endochondral ossification (ECO); these constructs have shown a unique ability to survive under hypoxic conditions as well as induce neovascularization and ossification. Such developmentally engineered constructs can act as transient biomimetic templates to facilitate bone regeneration in critical-sized defects. This review introduces the concept and mechanism of developmental BTE, explores the routes of endochondral bone graft engineering, highlights the current state of the art in large bone defect reconstruction via ECO-based strategies, and offers perspectives on the challenges and future directions of translating current knowledge from the bench to the bedside.

scholarly journals Decoding the temporal nature of brain GR activity in the NFκB signal transition leading to depressive-like behavior

2021 ◽  
Author(s):  
Young-Min Han ◽  
Min Sun Kim ◽  
Juyeong Jo ◽  
Daiha Shin ◽  
Seung-Hae Kwon ◽  
...  
Keyword(s):  
Inhibitory Action ◽  
Time Course ◽  
Molecular Mechanisms ◽  
Late Phase ◽  
Fine Tuning ◽  
Dependent Manner ◽  
Middle Phase ◽  
Temporal Shift

AbstractThe fine-tuning of neuroinflammation is crucial for brain homeostasis as well as its immune response. The transcription factor, nuclear factor-κ-B (NFκB) is a key inflammatory player that is antagonized via anti-inflammatory actions exerted by the glucocorticoid receptor (GR). However, technical limitations have restricted our understanding of how GR is involved in the dynamics of NFκB in vivo. In this study, we used an improved lentiviral-based reporter to elucidate the time course of NFκB and GR activities during behavioral changes from sickness to depression induced by a systemic lipopolysaccharide challenge. The trajectory of NFκB activity established a behavioral basis for the NFκB signal transition involved in three phases, sickness-early-phase, normal-middle-phase, and depressive-like-late-phase. The temporal shift in brain GR activity was differentially involved in the transition of NFκB signals during the normal and depressive-like phases. The middle-phase GR effectively inhibited NFκB in a glucocorticoid-dependent manner, but the late-phase GR had no inhibitory action. Furthermore, we revealed the cryptic role of basal GR activity in the early NFκB signal transition, as evidenced by the fact that blocking GR activity with RU486 led to early depressive-like episodes through the emergence of the brain NFκB activity. These results highlight the inhibitory action of GR on NFκB by the basal and activated hypothalamic-pituitary-adrenal (HPA)-axis during body-to-brain inflammatory spread, providing clues about molecular mechanisms underlying systemic inflammation caused by such as COVID-19 infection, leading to depression.

scholarly journals Zn-Containing Membranes for Guided Bone Regeneration in Dentistry

Polymers ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1797
Author(s):  
Manuel Toledano ◽  
Marta Vallecillo-Rivas ◽  
María T. Osorio ◽  
Esther Muñoz-Soto ◽  
Manuel Toledano-Osorio ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Bone Regeneration ◽  
Bone Healing ◽  
Bone Repair ◽  
Complex Modulus ◽  
Bacterial Colonization ◽  
Guided Bone Regeneration ◽  
M2 Macrophage

Barrier membranes are employed in guided bone regeneration (GBR) to facilitate bone in-growth. A bioactive and biomimetic Zn-doped membrane with the ability to participate in bone healing and regeneration is necessary. The aim of the present study is to state the effect of doping the membranes for GBR with zinc compounds in the improvement of bone regeneration. A literature search was conducted using electronic databases, such as PubMed, MEDLINE, DIMDI, Embase, Scopus and Web of Science. A narrative exploratory review was undertaken, focusing on the antibacterial effects, physicochemical and biological properties of Zn-loaded membranes. Bioactivity, bone formation and cytotoxicity were analyzed. Microstructure and mechanical properties of these membranes were also determined. Zn-doped membranes have inhibited in vivo and in vitro bacterial colonization. Zn-alloy and Zn-doped membranes attained good biocompatibility and were found to be non-toxic to cells. The Zn-doped matrices showed feasible mechanical properties, such as flexibility, strength, complex modulus and tan delta. Zn incorporation in polymeric membranes provided the highest regenerative efficiency for bone healing in experimental animals, potentiating osteogenesis, angiogenesis, biological activity and a balanced remodeling. Zn-loaded membranes doped with SiO2 nanoparticles have performed as bioactive modulators provoking an M2 macrophage increase and are a potential biomaterial for promoting bone repair. Zn-doped membranes have promoted pro-healing phenotypes.

scholarly journals Endothelin 1-induced retinal ganglion cell death is largely mediated by JUN activation

2020 ◽  
Vol 11 (9) ◽  
Author(s):  
Olivia J. Marola ◽  
Stephanie B. Syc-Mazurek ◽  
Gareth R. Howell ◽  
Richard T. Libby
Keyword(s):  
Transcription Factor ◽  
Molecular Mechanisms ◽  
Ganglion Cells ◽  
Retinal Vessel ◽  
Vessel Diameter ◽  
Retinal Ganglion ◽  
Retinal Ganglion Cell Death ◽  
Ganglion Cell Death

Abstract Glaucoma is a neurodegenerative disease characterized by loss of retinal ganglion cells (RGCs), the output neurons of the retina. Multiple lines of evidence show the endothelin (EDN, also known as ET) system is important in glaucomatous neurodegeneration. To date, the molecular mechanisms within RGCs driving EDN-induced RGC death have not been clarified. The pro-apoptotic transcription factor JUN (the canonical target of JNK signaling) and the endoplasmic reticulum stress effector and transcription factor DNA damage inducible transcript 3 (DDIT3, also known as CHOP) have been shown to act downstream of EDN receptors. Previous studies demonstrated that JUN and DDIT3 were important regulators of RGC death after glaucoma-relevant injures. Here, we characterized EDN insult in vivo and investigated the role of JUN and DDIT3 in EDN-induced RGC death. To accomplish this, EDN1 ligand was intravitreally injected into the eyes of wildtype, Six3-cre+Junfl/fl (Jun−/−), Ddit3 null (Ddit3−/−), and Ddit3−/−Jun−/− mice. Intravitreal EDN1 was sufficient to drive RGC death in vivo. EDN1 insult caused JUN activation in RGCs, and deletion of Jun from the neural retina attenuated RGC death after EDN insult. However, deletion of Ddit3 did not confer significant protection to RGCs after EDN1 insult. These results indicate that EDN caused RGC death via a JUN-dependent mechanism. In addition, EDN signaling is known to elicit potent vasoconstriction. JUN signaling was shown to drive neuronal death after ischemic insult. Therefore, the effects of intravitreal EDN1 on retinal vessel diameter and hypoxia were explored. Intravitreal EDN1 caused transient retinal vasoconstriction and regions of RGC and Müller glia hypoxia. Thus, it remains a possibility that EDN elicits a hypoxic insult to RGCs, causing apoptosis via JNK-JUN signaling. The importance of EDN-induced vasoconstriction and hypoxia in causing RGC death after EDN insult and in models of glaucoma requires further investigation.

scholarly journals Cathepsin B Localizes in the Caveolae and Participates in the Proteolytic Cascade in Trabecular Meshwork Cells. Potential New Drug Target for the Treatment of Glaucoma

2020 ◽  
Vol 10 (1) ◽  
pp. 78
Author(s):  
April Nettesheim ◽  
Myoung Sup Shim ◽  
Angela Dixon ◽  
Urmimala Raychaudhuri ◽  
Haiyan Gong ◽  
...  
Keyword(s):  
Trabecular Meshwork ◽  
Cathepsin B ◽  
Molecular Mechanisms ◽  
Culture Media ◽  
Ecm Remodeling ◽  
Trabecular Meshwork Cells ◽  
Proteolytic Cascade

Extracellular matrix (ECM) deposition in the trabecular meshwork (TM) is one of the hallmarks of glaucoma, a group of human diseases and leading cause of permanent blindness. The molecular mechanisms underlying ECM deposition in the glaucomatous TM are not known, but it is presumed to be a consequence of excessive synthesis of ECM components, decreased proteolytic degradation, or both. Targeting ECM deposition might represent a therapeutic approach to restore outflow facility in glaucoma. Previous work conducted in our laboratory identified the lysosomal enzyme cathepsin B (CTSB) to be expressed on the cellular surface and to be secreted into the culture media in trabecular meshwork (TM) cells. Here, we further investigated the role of CTSB on ECM remodeling and outflow physiology in vitro and in CSTBko mice. Our results indicate that CTSB localizes in the caveolae and participates in the pericellular degradation of ECM in TM cells. We also report here a novel role of CTSB in regulating the expression of PAI-1 and TGFβ/Smad signaling in TM cells vitro and in vivo in CTSBko mice. We propose enhancing CTSB activity as a novel therapeutic target to attenuate fibrosis and ECM deposition in the glaucomatous outflow pathway.

scholarly journals Low Intensity Shockwave Treatment Modulates Macrophage Functions Beneficial to Healing Chronic Wounds

2021 ◽  
Vol 22 (15) ◽  
pp. 7844
Author(s):  
Jason S. Holsapple ◽  
Ben Cooper ◽  
Susan H. Berry ◽  
Aleksandra Staniszewska ◽  
Bruce M. Dickson ◽  
...  
Keyword(s):  
Macrophage Activation ◽  
Molecular Mechanisms ◽  
Chronic Wounds ◽  
Immunohistochemical Analysis ◽  
Therapeutic Effects ◽  
Gene Expressions ◽  
Extracorporeal Shock Wave

Extracorporeal Shock Wave Therapy (ESWT) is used clinically in various disorders including chronic wounds for its pro-angiogenic, proliferative, and anti-inflammatory effects. However, the underlying cellular and molecular mechanisms driving therapeutic effects are not well characterized. Macrophages play a key role in all aspects of healing and their dysfunction results in failure to resolve chronic wounds. We investigated the role of ESWT on macrophage activity in chronic wound punch biopsies from patients with non-healing venous ulcers prior to, and two weeks post-ESWT, and in macrophage cultures treated with clinical shockwave intensities (150–500 impulses, 5 Hz, 0.1 mJ/mm2). Using wound area measurements and histological/immunohistochemical analysis of wound biopsies, we show ESWT enhanced healing of chronic ulcers associated with improved wound angiogenesis (CD31 staining), significantly decreased CD68-positive macrophages per biopsy area and generally increased macrophage activation. Shockwave treatment of macrophages in culture significantly boosted uptake of apoptotic cells, healing-associated cytokine and growth factor gene expressions and modulated macrophage morphology suggestive of macrophage activation, all of which contribute to wound resolution. Macrophage ERK activity was enhanced, suggesting one mechanotransduction pathway driving events. Collectively, these in vitro and in vivo findings reveal shockwaves as important regulators of macrophage functions linked with wound healing. This immunomodulation represents an underappreciated role of clinically applied shockwaves, which could be exploited for other macrophage-mediated disorders.

Abstract P780: Myosin Light Chain Dephosphorylation by Ppp1r12c Promotes Atrial Hypocontractility in Atrial Fibrillation

Stroke ◽  
2021 ◽  
Vol 52 (Suppl_1) ◽  
Author(s):  
Francisco J Gonzalez-Gonzalez ◽  
Perike Srikanth ◽  
Andrielle E Capote ◽  
Alsina Katherina M ◽  
Benjamin Levin ◽  
...  
Keyword(s):  
Atrial Fibrillation ◽  
Light Chain ◽  
Myosin Light Chain ◽  
Molecular Mechanisms ◽  
Contractile Function ◽  
Right Atrial ◽  
Western Blots

Atrial fibrillation (AF) is the most common sustained arrhythmia, with an estimated prevalence in the U.S.of 6.1 million. AF increases the risk of a thromboembolic stroke in five-fold. Although atrial hypocontractility contributes to stroke risk in AF, the molecular mechanisms reducing myofilament contractile function in AF remains unknown. We have recently identified protein phosphatase 1 subunit 12c (PPP1R12C) as a key molecule targeting myosin light-chain phosphorylation in AF. Objective: We hypothesize that the overexpression of PPP1R12C causes hypophosphorylation of atrial myosin light-chain 2 (MLC2a), thereby decreasing atrial contractility in AF. Methods and Results: Left and right atrial appendage tissues were isolated from AF patients versus sinus rhythm (SR). To evaluate the role of the PP1c-PPP1R12C interaction in MLC2a de-phosphorylation, we utilized Western blots, co-immunoprecipitation, and phosphorylation assays. In patients with AF, PPP1R12C expression was increased 3.5-fold versus SR controls with an 88% reduction in MLC2a phosphorylation. PPP1R12C-PP1c binding and PPP1R12C-MLC2a binding were significantly increased in AF. In vitro studies of either pharmacologic (BDP5290) or genetic (T560A), PPP1R12C activation demonstrated increased PPP1R12C binding with both PP1c and MLC2a, and dephosphorylation of MLC2a. Additionally, to evaluate the role of PPP1R12C expression in cardiac function, mice with lentiviral cardiac-specific overexpression of PPP1R12C (Lenti-12C) were evaluated for atrial contractility using echocardiography, versus wild-type and Lenti-controls. Lenti-12C mice demonstrated a 150% increase in left atrium size versus controls, with reduced atrial strain and atrial ejection fraction. Also, programmed electrical stimulation was performed to evaluate AF inducibility in vivo. Pacing-induced AF in Lenti-12C mice was significantly higher than controls. Conclusion: The overexpression of PPP1R12C increases PP1c targeting to MLC2a and provokes dephosphorylation, associated with a reduction in atrial contractility and an increase in AF inducibility. All these discoveries suggest that PP1 regulation of sarcomere function at MLC2a is a main regulator of atrial contractility in AF.

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