Vascular Biology and Hypertension

Targeted thrombolysis

Fibrinolysis has been proven to be very beneficial in patients with acute myocardial infarction, vein thrombosis, pulmonary embolism, and stroke. However, limitations in thrombolytic efficacy and bleeding complications have caused an ongoing search for improved thrombolytic drugs.

Targeting of thrombolytic drugs to clots by monoclonal antibodies is a promising alternative approach to create fibrinolytic agents with enhanced thrombolytic potency and less bleeding problems and may thus represent a potential way out of the current stagnation in thrombolysis.

We have generated single-chain antibodies, which are small antibody fragments derived from full IgG antibodies and are a newly emerging basis for therapeutic agents, that allow targeting of fibrinolytics to the clot. The target of these antibodies is the activated GP IIb/IIIa receptor on platelets. This epitope is highly specific and at the same time highly abundant at the clot and therefore presents an ideal target for accumulating agents to arterial clots, which are typically rich in platelets.

The ability of the activation-specific anti-GP IIb/IIIa single-chain antibodies to inhibit fibrinogen binding provides the unique opportunity to combine a new type of activation-specific anti-platelet therapy with clot-targeted fibrinolysis. In addition, the recombinant nature of the single-chain antibody constructs allows the combination with a third component, clot-targeted anticoagulation in a single molecule.

Single-chain antibodies for directed stem cell homing and targeting of effector cells in vascular disease

Stem cell therapy has attracted major scientific and public interest and promises substantial medical advances in various fields, including therapeutic approaches for atherosclerosis and heart failure following myocardial infarction. One of the major hurdles to date has been the poor efficiency of stem cell delivery to sites where their effect is needed.

Our project aims to develop novel biotechnological approaches that are based on our single-chain antibodies. The biological effects of this novel cell targeting approach will be evaluated in a mouse model of advanced atherosclerosis. Haematopoietic progenitor cells and regulatory T cells will be targeted: The first cell type for their potential to restore endothelial integrity, and the second cell type for their potential to suppress effector T cells, attenuating the development of atherosclerosis.

Several different systems will be explored: The display of antibodies on the surface of cells using adenoviral gene transfer with a mammalian expression vector inserting the anchoring domain of platelet-derived growth factor receptor as well as lipid anchors to display antibodies on the cell surface. This will be done by chemical coupling of the single-chain antibody to an unsaturated lipid oleyl chain polyethylene glycol membrane anchor and by recombinant fusion to bacterial lipoproteins.

This project is highly significant in two regards. Firstly, we will develop several cell-based strategies of potential therapeutic benefit for the growing number of patients with atherosclerosis and its associated clinical complications. Secondly, we will develop methods that might be generally applicable in regenerative cell therapies for many areas of human diseases.

MRI-nanoparticles for non-invasive diagnosis of vascular diseases

We have generated conformation-specific single-chain antibodies that can selectively target specific markers associated with unstable atherosclerotic plaques and thrombosis. We have demonstrated that these antibodies can be used as selective imaging agents using iron oxide particles as contrast providing components.

For this project, we aim to generate unique imaging agents by conjugating our conformation-specific single-chain antibodies to dendrimers loaded with gadolinium. In contrast to ferric oxide ("black contrast", the MRI properties provided by gadolinium ("white contrast") allow intravascular imaging by providing contrast against circulating blood and the vessel wall.

After ligation of the antibody and dendrimer fragments, in vitro tests will ensure that conjugation does not affect specificity. In vivo testing in animal models of atherosclerosis and thrombosis using magnetic resonance imaging will prove the ability for the early detection of unstable atherosclerotic lesions, thrombosis and difficult to diagnose vessel occlusions, such as pulmonary embolism.