Protein disulfide isomerase cleaves allosteric disulfides in histidine-rich glycoprotein to regulate thrombosis.

The essence of difference between hemostasis and thrombosis is that the clotting reaction is a highly fine-tuned process. Vascular protein disulfide isomerase (PDI) represents a critical mechanism regulating the functions of hemostatic proteins. Herein we show that histidine-rich glycoprotein (HRG) is a substrate of PDI. Reduction of HRG by PDI enhances the procoagulant and anticoagulant activities of HRG by neutralization of endothelial heparan sulfate (HS) and inhibition of factor XII (FXIIa) activity, respectively. Murine HRG deficiency (Hrg-/-) leads to delayed onset but enhanced formation of thrombus compared to WT. However, in the combined FXII deficiency (F12-/-) and HRG deficiency (by siRNA or Hrg-/-), there is further thrombosis reduction compared to F12-/- alone, confirming HRG's procoagulant activity independent of FXIIa. Mutation of target disulfides of PDI leads to a gain-of-function mutant of HRG that promotes its activities during coagulation. Thus, PDI-HRG pathway fine-tunes thrombosis by promoting its rapid initiation via neutralization of HS and preventing excessive propagation via inhibition of FXIIa.

Novel Pressure-Regulated Deployment Strategy for Improving the Safety and Efficacy of Balloon-Expandable Transcatheter Aortic Valves.

OBJECTIVES: The authors propose a novel pressure-regulated method for balloon-expandable transcatheter heart valve (THV) deployment, aimed at optimizing prosthesis-annulus apposition while preventing significant tissue injury. BACKGROUND: The optimal method for balloon-expandable THV deployment remains debated. Current protocols are volume dependent, relying on under- and overfilling of the deployment apparatus. During deployment, the annular wall tension exerted by the expanding prosthesis is determined by maximal THV diameter and balloon pressure (Laplace's law). METHODS: Three hundred thirty consecutive patients with severe native aortic stenosis who underwent TAVR with SAPIEN 3 THVs were included. One hundred and six patients were considered at high risk for annular rupture. THVs were deployed until reaching a predetermined balloon pressure. Postdilatation was performed to reduce mild or greater angiographic paravalvular regurgitation (PVR). Using a biomechanical model, annular wall stress was estimated for each case and assessed against rates of postdilatation, mild or greater PVR on transthoracic echocardiography, new permanent pacemaker placement or left bundle branch block, and annular rupture. RESULTS: Patients with wall stress >3 MPa had reduced postdilatation rate (P < 0.001) and reduced final PVR (P = 0.014). Annular rupture occurred in 2 of 3 high-risk patients with wall stress >3.5 MPa (3.69 and 3.84 MPa); no rupture occurred in 95 high-risk patients with wall stress ≤3.5 MPa. We defined a single target deployment pressure per THV size to ensure deployment within target wall stress levels of 3 to 3.5 MPa: 6.25 atm for 23-mm THVs, 5.5 atm for 26-mm THVs, and 5 atm for 29-mm THVs. Patients within this target range (n = 136) had a 10.0% postdilatation rate, 12.7% mild PVR, and no moderate to severe PVR. The relationship between balloon filling volume and associated pressure and wall stress was inconsistent. CONCLUSIONS: Pressure-regulated THV deployment is a simple, reproducible, safe, and effective method, regardless of high-risk anatomical complexities.

A mechanosensitive peri-arteriolar niche for osteogenesis and lymphopoiesis.

Stromal cells in adult bone marrow that express leptin receptor (LEPR) are a critical source of growth factors, including stem cell factor (SCF), for the maintenance of haematopoietic stem cells and early restricted progenitors1-6. LEPR+ cells are heterogeneous, including skeletal stem cells and osteogenic and adipogenic progenitors7-12, although few markers have been available to distinguish these subsets or to compare their functions. Here we show that expression of an osteogenic growth factor, osteolectin13,14, distinguishes peri-arteriolar LEPR+ cells poised to undergo osteogenesis from peri-sinusoidal LEPR+ cells poised to undergo adipogenesis (but retaining osteogenic potential). Peri-arteriolar LEPR+osteolectin+ cells are rapidly dividing, short-lived osteogenic progenitors that increase in number after fracture and are depleted during ageing. Deletion of Scf from adult osteolectin+ cells did not affect the maintenance of haematopoietic stem cells or most restricted progenitors but depleted common lymphoid progenitors, impairing lymphopoiesis, bacterial clearance, and survival after acute bacterial infection. Peri-arteriolar osteolectin+ cell maintenance required mechanical stimulation. Voluntary running increased, whereas hindlimb unloading decreased, the frequencies of peri-arteriolar osteolectin+ cells and common lymphoid progenitors. Deletion of the mechanosensitive ion channel PIEZO1 from osteolectin+ cells depleted osteolectin+ cells and common lymphoid progenitors. These results show that a peri-arteriolar niche for osteogenesis and lymphopoiesis in bone marrow is maintained by mechanical stimulation and depleted during ageing.

Partial loss of actin nucleator actin-related protein 2/3 activity triggers blebbing in primary T lymphocytes.

T lymphocytes utilize amoeboid migration to navigate effectively within complex microenvironments. The precise rearrangement of the actin cytoskeleton required for cellular forward propulsion is mediated by actin regulators, including the actin-related protein 2/3 (Arp2/3) complex, a macromolecular machine that nucleates branched actin filaments at the leading edge. The consequences of modulating Arp2/3 activity on the biophysical properties of the actomyosin cortex and downstream T cell function are incompletely understood. We report that even a moderate decrease of Arp3 levels in T cells profoundly affects actin cortex integrity. Reduction in total F-actin content leads to reduced cortical tension and disrupted lamellipodia formation. Instead, in Arp3-knockdown cells, the motility mode is dominated by blebbing migration characterized by transient, balloon-like protrusions at the leading edge. Although this migration mode seems to be compatible with interstitial migration in three-dimensional environments, diminished locomotion kinetics and impaired cytotoxicity interfere with optimal T cell function. These findings define the importance of finely tuned, Arp2/3-dependent mechanophysical membrane integrity in cytotoxic effector T lymphocyte activities.

Anisotropic functionalization of upconversion nanoparticles.

Despite significant advances toward accurate tuning of the size and shape of colloidal nanoparticles, the precise control of the surface chemistry thereof remains a grand challenge. It is desirable to conjugate functional bio-molecules onto the selected facets of nanoparticles owing to the versatile capabilities rendered by the molecules. We report here facet-selective conjugation of DNA molecules onto upconversion nanoparticles via ligand competition reaction. Different binding strengths of phosphodiester bonds and phosphate groups on DNA and the surfactant molecules allow one to create heterogeneous bio-chemistry surface for upconversion nanoparticles. The tailored surface properties lead to the formation of distinct self-assembly structures. Our findings provide insight into the interactions between biomolecules and nanoparticles, unveiling the potential of using nanoparticles as fundamental building blocks for creating self-assembled nano-architectures.