Investigation of extracorporeal immobilized enzyme device : a potential treatment for blood deheparinization

Thesis (Sc.D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1999.Includes bibliographical references.by Guillermo A. Ameer.Sc.D

Growth factor release from a chemically modified elastomeric poly(1,8‐octanediol‐co‐citrate) thin film promotes angiogenesis in vivo

The ultimate success of in vivo organ formation utilizing ex vivo expanded “starter” tissues relies heavily upon the level of vascularization provided by either endogenous or artificial induction of angiogenic or vasculogenic events. To facilitate proangiogenic outcomes and promote tissue growth, an elastomeric scaffold previously shown to be instrumental in the urinary bladder regenerative process was modified to release proangiogenic growth factors. Carboxylic acid groups on poly(1,8‐octanediol‐co‐citrate) films (POCfs) were modified with heparan sulfate creating a heparan binding POCf (HBPOCf). Release of proangiogenic growth factors vascular endothelial growth factor (VEGF), fibroblast growth factor 2 (FGF2), and insulin‐like growth factor 1 (IGF‐1) from HBPOCfs demonstrated an approximate threefold increase over controls during a 30‐day time course in vitro . Atomic force microscopy demonstrated significant topological differences between films. Subcutaneous implantation of POCf alone, HBPOCf, POCf‐VEGF, and HBPOCf‐VEGF within the dorsa of nude rats yielded increased vascular growth in HBPOCf‐VEGF constructs. Vessel quantification studies revealed that POCfs alone contained 41.1 ± 4.1 vessels/mm 2 , while HBPOCf, POCf‐VEGF, and HBPOCF‐VEGF contained 41.7 ± 2.6, 76.3 ± 9.4, and 167.72 ± 15.3 vessels/mm 2 , respectively. Presence of increased vessel growth was demonstrated by CD31 and vWF immunostaining in HBPOCf‐VEGF implanted areas. Data demonstrate that elastomeric POCfs can be chemically modified and possess the ability to promote angiogenesis in vivo . © 2011 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2012.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90248/1/33306_ftp.pd

The Changing Landscape for Stroke\ua0Prevention in AF: Findings From the GLORIA-AF Registry Phase 2

Background GLORIA-AF (Global Registry on Long-Term Oral Antithrombotic Treatment in Patients with Atrial Fibrillation) is a prospective, global registry program describing antithrombotic treatment patterns in patients with newly diagnosed nonvalvular atrial fibrillation at risk of stroke. Phase 2 began when dabigatran, the first non\u2013vitamin K antagonist oral anticoagulant (NOAC), became available. Objectives This study sought to describe phase 2 baseline data and compare these with the pre-NOAC era collected during phase 1. Methods During phase 2, 15,641 consenting patients were enrolled (November 2011 to December 2014); 15,092 were eligible. This pre-specified cross-sectional analysis describes eligible patients\u2019 baseline characteristics. Atrial fibrillation disease characteristics, medical outcomes, and concomitant diseases and medications were collected. Data were analyzed using descriptive statistics. Results Of the total patients, 45.5% were female; median age was 71 (interquartile range: 64, 78) years. Patients were from Europe (47.1%), North America (22.5%), Asia (20.3%), Latin America (6.0%), and the Middle East/Africa (4.0%). Most had high stroke risk (CHA2DS2-VASc [Congestive heart failure, Hypertension, Age  6575 years, Diabetes mellitus, previous Stroke, Vascular disease, Age 65 to 74 years, Sex category] score  652; 86.1%); 13.9% had moderate risk (CHA2DS2-VASc = 1). Overall, 79.9% received oral anticoagulants, of whom 47.6% received NOAC and 32.3% vitamin K antagonists (VKA); 12.1% received antiplatelet agents; 7.8% received no antithrombotic treatment. For comparison, the proportion of phase 1 patients (of N = 1,063 all eligible) prescribed VKA was 32.8%, acetylsalicylic acid 41.7%, and no therapy 20.2%. In Europe in phase 2, treatment with NOAC was more common than VKA (52.3% and 37.8%, respectively); 6.0% of patients received antiplatelet treatment; and 3.8% received no antithrombotic treatment. In North America, 52.1%, 26.2%, and 14.0% of patients received NOAC, VKA, and antiplatelet drugs, respectively; 7.5% received no antithrombotic treatment. NOAC use was less common in Asia (27.7%), where 27.5% of patients received VKA, 25.0% antiplatelet drugs, and 19.8% no antithrombotic treatment. Conclusions The baseline data from GLORIA-AF phase 2 demonstrate that in newly diagnosed nonvalvular atrial fibrillation patients, NOAC have been highly adopted into practice, becoming more frequently prescribed than VKA in Europe and North America. Worldwide, however, a large proportion of patients remain undertreated, particularly in Asia and North America. (Global Registry on Long-Term Oral Antithrombotic Treatment in Patients With Atrial Fibrillation [GLORIA-AF]; NCT01468701

Targeting Heparin to Collagen within Extracellular Matrix Significantly Reduces Thrombogenicity and Improves Endothelialization of Decellularized Tissues

Thrombosis within small-diameter vascular grafts limits the development of bioartificial, engineered vascular conduits, especially those derived from extracellular matrix (ECM). Here we describe an easy-to-implement strategy to chemically modify vascular ECM by covalently linking a collagen binding peptide (CBP) to heparin to form a heparin derivative (CBP–heparin) that selectively binds a subset of collagens. Modification of ECM with CBP–heparin leads to increased deposition of functional heparin (by ∼7.2-fold measured by glycosaminoglycan composition) and a corresponding reduction in platelet binding (>70%) and whole blood clotting (>80%) onto the ECM. Furthermore, addition of CBP–heparin to the ECM stabilizes long-term endothelial cell attachment to the lumen of ECM-derived vascular conduits, potentially through recruitment of heparin-binding growth factors that ultimately improve the durability of endothelialization in vitro. Overall, our findings provide a simple yet effective method to increase deposition of functional heparin on the surface of ECM-based vascular grafts and thereby minimize thrombogenicity of decellularized tissue, overcoming a significant challenge in tissue engineering of bioartificial vessels and vascularized organs

Albumin Hydrogels Formed by Electrostatically Triggered Self-Assembly and Their Drug Delivery Capability

Biological hydrogels are fundamentally biocompatible and have intrinsic similarities to extracellular matrices in medical applications and drug delivery systems. Herein we demonstrate the ability to form drug-eluting protein hydrogels using a novel mechanism that involves the electrostatically triggered partial denaturation and self-assembly of the protein via changes in pH. Partial denaturation increases the protein’s solvent exposed hydrophobic surface area, which then drives self-assembly of the protein into a hydrogel within 10 min at 37 °C. We describe the properties of an albumin hydrogel formed by this mechanism. Intrinsic drug binding properties of albumin to all-trans retinoic acid (atRA) are conserved through the partial denaturation process, as confirmed by fluorescence quenching. atRA released from the hydrogel inhibited smooth muscle cell migration as per an in vitro scratch wound assay. Atomistic molecular dynamics and potential of mean force calculations show the preservation and potential creation of new atRA binding sites with a binding energy of −41 kJ/mol. The resulting hydrogel is also biocompatible and exhibits rapid postgelation degradation after its implantation in vivo. This interdisciplinary work provides a new tool for the development of biocompatible protein hydrogel drug delivery systems

Bone morphogenetic protein-9 effectively induces osteogenic differentiation of reversibly immortalized calvarial mesenchymal progenitor cells

AbstractCritical-sized craniofacial defect repair represents a significant challenge to reconstructive surgeons. Many strategies have been employed in an effort to achieve both a functionally and cosmetically acceptable outcome. Bone morphogenetic proteins (BMPs) provide a robust osteoinductive cue to stimulate bony growth and remodeling. Previous studies have suggested that the BMP-9 isoform is particularly effective in promoting osteogenic differentiation of mesenchymal progenitor cells. The aim of this study is to characterize the osteogenic capacity of BMP-9 on calvarial mesenchymal progenitor cell differentiation. Reversibly immortalized murine calvarial progenitor cells (iCALs) were infected with adenoviral vectors encoding BMP-9 or GFP and assessed for early and late stages of osteogenic differentiation in vitro and for osteogenic differentiation via in vivo stem cell implantation studies. Significant elevations in alkaline phosphatase (ALP) activity, osteocalcin (OCN) mRNA transcription, osteopontin (OPN) protein expression, and matrix mineralization were detected in BMP-treated cells compared to control. Specifically, ALP activity was elevated on days 3, 7, 9, 11, and 13 post-infection and OCN mRNA expression was elevated on days 8, 10, and 14 in treated cells. Additionally, treatment groups demonstrated increased OPN protein expression on day 10 and matrix mineralization on day 14 post-infection relative to control groups. BMP-9 also facilitated the formation of new bone in vivo as detailed by gross, microcomputed tomography, and histological analyses. Therefore, we concluded that BMP-9 significantly stimulates osteogenic differentiation in iCALs, and should be considered an effective agent for calvarial tissue regeneration