Amanda Jiang

An extracorporeal blood-cleansing device for sepsis therapy

Here we describe a blood-cleansing device for sepsis therapy inspired by the spleen, which can continuously remove pathogens and toxins from blood without first identifying the infectious agent. Blood flowing from an infected individual is mixed with magnetic nanobeads coated with an engineered human opsonin—mannose-binding lectin (MBL)—that captures a broad range of pathogens and toxins without activating complement factors or coagulation. Magnets pull the opsonin-bound pathogens and toxins from the blood; the cleansed blood is then returned back to the individual. The biospleen efficiently removes multiple Gram-negative and Gram-positive bacteria, fungi and endotoxins from whole human blood flowing through a single biospleen unit at up to 1.25 liters per h in vitro. In rats infected with Staphylococcus aureus or Escherichia coli, the biospleen cleared >90% of bacteria from blood, reduced pathogen and immune cell infiltration in multiple organs and decreased inflammatory cytokine levels. In a model of endotoxemic shock, the biospleen increased survival rates after a 5-h treatment.

Control of lung vascular permeability and endotoxin-induced pulmonary oedema by changes in extracellular matrix mechanics

Increased vascular permeability contributes to many diseases, including acute respiratory distress syndrome, cancer and inflammation. Most past work on vascular barrier function has focused on soluble regulators, such as tumour-necrosis factor-α. Here we show that lung vascular permeability is controlled mechanically by changes in extracellular matrix structure. Our studies reveal that pulmonary vascular leakage can be increased by altering extracellular matrix compliance in vitro and by manipulating lysyl oxidase-mediated collagen crosslinking in vivo. Either decreasing or increasing extracellular matrix stiffness relative to normal levels disrupts junctional integrity and increases vascular leakage. Importantly, endotoxin-induced increases of vascular permeability are accompanied by concomitant increases in extracellular matrix rigidity and lysyl oxidase activity, which can be prevented by inhibiting lysyl oxidase activity. The identification of lysyl oxidase and the extracellular matrix as critical regulators of lung vascular leakage might lead to the development of new therapeutic approaches for the treatment of pulmonary oedema and other diseases caused by abnormal vascular permeability.

Role of Collagen Matrix in Tumor Angiogenesis and Glioblastoma Multiforme Progression

Glioblastoma is a highly vascularized brain tumor, and antiangiogenic therapy improves its progression-free survival. However, current antiangiogenic therapy induces serious adverse effects including neuronal cytotoxicity and tumor invasiveness and resistance to therapy. Although it has been suggested that the physical microenvironment has a key role in tumor angiogenesis and progression, the mechanism by which physical properties of extracellular matrix control tumor angiogenesis and glioblastoma progression is not completely understood. Herein we show that physical compaction (the process in which cells gather and pack together and cause associated changes in cell shape and size) of human glioblastoma cell lines U87MG, U251, and LN229 induces expression of collagen types IV and VI and the collagen crosslinking enzyme lysyl oxidase and up-regulates in vitro expression of the angiogenic factor vascular endothelial growth factor. The lysyl oxidase inhibitor β-aminopropionitrile disrupts collagen structure in the tumor and inhibits tumor angiogenesis and glioblastoma multiforme growth in a mouse orthotopic brain tumor model. Similarly, d-penicillamine, which inhibits lysyl oxidase enzymatic activity by depleting intracerebral copper, also exhibits antiangiogenic effects on brain tumor growth in mice. These findings suggest that tumor microenvironment controlled by collagen structure is important in tumor angiogenesis and brain tumor progression.

Platelet rich plasma extract promotes angiogenesis through the angiopoietin1-Tie2 pathway

Development and regeneration of tissues and organs require precise coordination among endothelial, epithelial and mesenchymal morphogenesis. Angiogenesis plays key roles in normal development, wound healing, recovery from ischemic disease, and organ regeneration. It has been recognized that the combination of various angiogenic factors in an appropriate physiological ratio is critical for long-term functional blood vessel formation. Here we show that mouse soluble platelet-rich-plasma (PRP) extract, which includes abundant angiopoetin-1 (Ang1) and other angiogenic factors, stimulates endothelial cell growth, migration and differentiation in cultured human dermal microvascular endothelial cells in vitro and neonatal mouse retinal angiogenesis in vivo. Mouse platelet rich fibrin (PRF) matrix, the three-dimensional fibrin matrix that releases angiogenic factors with similar concentrations and proportions to the PRP extract, also recapitulates robust angiogenesis inside the matrix when implanted subcutaneously on the living mouse. Inhibition of Ang1-Tie2 signaling suppresses PRP extract-induced angiogenesis in vitro and angiogenic ability of the PRF matrix in vivo. Since human PRP extract and PRF matrix can be prepared from autologous peripheral blood, our findings may lead to the development of novel therapeutic interventions for various angiogenesis-related diseases as well as to the improvement of strategies for tissue engineering and organ regeneration.

Extracellular Matrix Structure and Tissue Stiffness Control Postnatal Lung Development through the Lipoprotein Receptor–Related Protein 5/Tie2 Signaling System

Physical properties of the tissues and remodeling of extracellular matrix (ECM) play an important role in organ development. Recently, we have reported that low-density lipoprotein receptor-related protein (LRP) 5/Tie2 signaling controls postnatal lung development by modulating angiogenesis. Here we show that tissue stiffness modulated by the ECM cross-linking enzyme, lysyl oxidase (LOX), regulates postnatal lung development through LRP5-Tie2 signaling. The expression of LRP5 and Tie2 is up-regulated twofold in lung microvascular endothelial cells when cultured on stiff matrix compared to those cultured on soft matrix in vitro. LOX inhibitor, β-aminopropionitrile, disrupts lung ECM (collagen I, III, and VI, and elastin) structures, softens neonatal mouse lung tissue by 20%, and down-regulates the expression of LRP5 and Tie2 by 20 and 60%, respectively, which leads to the inhibition of postnatal lung development (30% increase in mean linear intercept, 1.5-fold increase in air space area). Importantly, hyperoxia treatment (Postnatal Days 1-10) disrupts ECM structure and stiffens mouse lung tissue by up-regulating LOX activity, thereby increasing LRP5 and Tie2 expression and deregulating alveolar morphogenesis in neonatal mice, which is attenuated by inhibiting LOX activity. These findings suggest that appropriate physical properties of lung tissue are necessary for physiological postnatal lung development, and deregulation of this mechanism contributes to postnatal lung developmental disorders, such as bronchopulmonary dysplasia.

LRP5 Regulates Development of Lung Microvessels and Alveoli through the Angiopoietin-Tie2 Pathway

Angiogenesis is crucial for lung development. Although there has been considerable exploration, the mechanism by which lung vascular and alveolar formation is controlled is still not completely understood. Here we show that low-density lipoprotein receptor-related protein 5 (LRP5), a component of the Wnt ligand-receptor complex, regulates angiogenesis and alveolar formation in the lung by modulating expression of the angiopoietin (Ang) receptor, Tie2, in vascular endothelial cells (ECs). Vascular development in whole mouse lungs and in cultured ECs is controlled by LRP5 signaling, which is, in turn, governed by a balance between the activities of the antagonistic Tie2 ligands, Ang1 and Ang2. Under physiological conditions when Ang1 is dominant, LRP5 knockdown decreases Tie2 expression and thereby, inhibits vascular and alveolar development in the lung. Conversely, when Ang2 dominates under hyperoxia treatment in neonatal mice, high LRP5 and Tie2 expression suppress angiogenesis and lung development. These findings suggest that the LRP5-Tie2-Ang signaling axis plays a central role in control of both angiogenesis and alveolarization during postnatal lung development, and that deregulation of this signaling mechanism might lead to developmental abnormalities of the lung, such as are observed in bronchopulmonary dysplasia (BPD).

Developmentally-inspired shrink-wrap polymers for mechanical induction of tissue differentiation.

A biologically inspired thermoresponsive polymer has been developed that mechanically induces tooth differentiation in vitro and in vivo by promoting mesenchymal cell compaction as seen in each pore of the scaffold. This normally occurs during the physiological mesenchymal condensation response that triggers tooth formation in the embryo.

Twist1 Controls Lung Vascular Permeability and Endotoxin-Induced Pulmonary Edema by Altering Tie2 Expression

Tight regulation of vascular permeability is necessary for normal development and deregulated vascular barrier function contributes to the pathogenesis of various diseases, including acute respiratory distress syndrome, cancer and inflammation. The angiopoietin (Ang)-Tie2 pathway is known to control vascular permeability. However, the mechanism by which the expression of Tie2 is regulated to control vascular permeability has not been fully elucidated. Here we show that transcription factor Twist1 modulates pulmonary vascular leakage by altering the expression of Tie2 in a context-dependent way. Twist1 knockdown in cultured human lung microvascular endothelial cells decreases Tie2 expression and phosphorylation and increases RhoA activity, which disrupts cell-cell junctional integrity and increases vascular permeability in vitro. In physiological conditions, where Ang1 is dominant, pulmonary vascular permeability is elevated in the Tie2-specific Twist1 knockout mice. However, depletion of Twist1 and resultant suppression of Tie2 expression prevent increase in vascular permeability in an endotoxin-induced lung injury model, where the balance of Angs shifts toward Ang2. These results suggest that Twist1-Tie2-Angs signaling is important for controlling vascular permeability and modulation of this mechanism may lead to the development of new therapeutic approaches for pulmonary edema and other diseases caused by abnormal vascular permeability.

Ultrasound-sensitive nanoparticle aggregates for targeted drug delivery

Here we describe injectable, ultrasound (US)-responsive, nanoparticle aggregates (NPAs) that disintegrate into slow-release, nanoscale, drug delivery systems, which can be targeted to selective sites by applying low-energy US locally. We show that, unlike microbubble based drug carriers which may suffer from stability problems, the properties of mechanical activated NPAs, composed of polymer nanoparticles, can be tuned by properly adjusting the polymer molecular weight, the size of the nanoparticle precursors as well as the percentage of excipient utilized to hold the NPA together. We then apply this concept to practice by fabricating NPAs composed of nanoparticles loaded with Doxorubicin (Dox) and tested their ability to treat tumors via ultrasound activation. Mouse studies demonstrated significantly increased efficiency of tumor targeting of the US-activated NPAs compared to PLGA nanoparticle controls (with or without US applied) or intact NPAs. Importantly, when the Dox-loaded NPAs were injected and exposed to US energy locally, this increased ability to concentrate nanoparticles at the tumor site resulted in a significantly greater reduction in tumor volume compared to tumors treated with a 20-fold higher dose of the free drug.

Platelet-rich plasma extract prevents pulmonary edema through angiopoietin-Tie2 signaling.

Increased vascular permeability contributes to life-threatening pathological conditions, such as acute respiratory distress syndrome. Current treatments for sepsis-induced pulmonary edema rely on low-tidal volume mechanical ventilation, fluid management, and pharmacological use of a single angiogenic or chemical factor with antipermeability activity. However, it is becoming clear that a combination of multiple angiogenic/chemical factors rather than a single factor is required for maintaining stable and functional blood vessels. We have demonstrated that mouse platelet-rich plasma (PRP) extract contains abundant angiopoietin (Ang) 1 and multiple other factors (e.g., platelet-derived growth factor), which potentially stabilize vascular integrity. Here, we show that PRP extract increases tyrosine phosphorylation levels of Tunica internal endothelial cell kinase (Tie2) and attenuates disruption of cell-cell junctional integrity induced by inflammatory cytokine in cultured human microvascular endothelial cells. Systemic injection of PRP extract also increases Tie2 phosphorylation in mouse lung and prevents endotoxin-induced pulmonary edema and the consequent decreases in lung compliance and exercise intolerance resulting from endotoxin challenge. Soluble Tie2 receptor, which inhibits Ang-Tie2 signaling, suppresses the ability of PRP extract to inhibit pulmonary edema in mouse lung. These results suggest that PRP extract prevents endotoxin-induced pulmonary edema mainly through Ang-Tie2 signaling, and PRP extract could be a potential therapeutic strategy for sepsis-induced pulmonary edema and various lung diseases caused by abnormal vascular permeability.