I concentrate on two different research areas, which are the exploration into the mechanisms of thrombosis in animals and mechanisms of cancer metastasis in humans and animals. These two research areas are linked by a common theme of hemostasis, i.e. I am specifically looking at the role of coagulation in thrombosis and cancer metastasis.

Thrombosis in animals

Thrombosis is a serious complication of various diseases in animals, including sepsis, neoplasia, cardiac disease and inflammation. When thrombi develop in blood vessels, the tissues supplied by these vessels undergo hypoxic injury, causing cell death, organ dysfunction and even failure. The consequence of this tissue damage can be devastating to the patient, resulting in prolonged illness and even death. Thrombi are thought to form through three major pathways called Virchows's triad: endothelial injury, abnormalities in blood flow (stasis) and hypercoagulability. Hypercoagulability, which is defined as an abnormally activated coagulation cascade, is the research focus in my laboratory. I am particularly interested in the role of tissue factor (coagulation factor III or tissue thromboplastin) in mediating hypercoagulability and, consequently, thrombosis in animals.

Figure 1: Tissue factor, in complex with factor FVIIa (FVIIa), activates factor X (FX). FXa, in the presence of calcium and factor V, cleaves prothrombin to thrombin. Thrombin amplifies its own production by activating coagulation factors (factor FIX) and cofactors (factor VIII, factor V) of the intrinsic and common pathways. This generates a large burst of thrombin, which then cleaves fibrinogen to fibrin and activates factor XIII, which crosslinks fibrin forming an insoluble fibrin clot.

Tissue factor is the main trigger of the complex coagulation cascade. It is a transmembrane protein that is constitutively expressed on the surface of fibroblasts and smooth muscles, which underly the endothelium in blood vessels. The coagulation cascade is normally activated when endothelial cells are injured. This injury exposes extravascular tissue factor to its circulating ligand, plasma factor VII (FVII). Once bound to tissue factor, FVII becomes activated and together the two proteins form an enzymatic complex, which binds to and activates another coagulation factor, factor X (FX). FX is the lead protein of the common pathway of coagulation, whose end-result is the generation of the potent enzyme, thrombin from prothrombin (factor II). Thrombin is the ultimate enzyme responsible for clot or thrombus formation, since it is directly responsible for converting fibrinogen into fibrin, which forms the basis of thrombi (Figure 1).
In disease conditions, tissue factor may be aberrantly expressed on endothelium, circulating monocytes or cancer cells. This aberrant tissue factor expression is the current focus of my research studies into mechanisms of thrombosis in animals. I am investigating the thrombosis pathogenesis in two diseases in animals:

1. Immune-mediated hemolytic anemia (IMHA) in dogs.
   Dogs with this hematologic disorder develop severe anemia when their body starts to destroy its own erythrocytes. During this disease, thrombi form in multiple blood vessels, such as the lungs. This thrombosis is a major cause of death in dogs with IMHA.
2. Herpes virus myeloencephalopathy in horses.
   Some horses infected with equine herpes virus type-1 develop a severe neurologic syndrome characterized by paresis, paralysis and recumbency. Thrombosis in spinal cord vessels is a characteristic pathologic feature of this disorder and contributes to the spinal cord injury and clinical signs seen in affected horses.

Both of these studies are currently supported by grants funded by the Morris Animal Foundation.

Cancer metastasis

Figure 2: Endothelial cells grown within a fabricated microfluidic channel (arrowheads). The endothelial cells are confluent within the channel as shown by linear red immunostaining of vascular-endothelial cadherin (arrows), a marker of inter-endothelial junctions.

My interest in this area arose from my professional diagnostic service responsibilities, in which I frequently make a diagnosis of cancer from aspirates of tissues of animals. My desire to understand the biology of cancer and to help animals led to this research focus in my laboratory. I am studying the role of tissue factor in cancer metastasis in humans and animals. Tissue factoris upregulated in cancer cells and is thought to be a marker of oncogenic transformation. Activation of coagulation, with thrombus formation, is a common consequence of cancer in people. To facilitate my studies on how tissue factor helps cancer cells metastasize, I have established a collaboration with the Department of Biomedical Engineering at Cornell University. We have developed a unique microfluidic device, consisting of small (<70 um) semi-cylindrical "vascular" channels fabricated into a synthetic transparent polymer. Endothelial cells can be grown within the channels and can be exposed to fluid shear forces, similar to what they experience in blood (Figure 2). We are using this device to explore how cancer cells interact with endothelial cells to form metastatic tumors as well as to answer specific questions related to endothelial biology in the microvasculature. These studies are supported by Consolidated grants from the College of Veterinary Medicine and a Nanobiotechnology Center grant from Cornell University.

Clinical pathology-related research

I am a veterinary clinical pathologist and am dedicated to advancing my field through investigative studies. Anything clinical pathology-related is fair research game, as can be seen from my varied research publications. My main clinical pathologic interests are hemostatic disorders and hematopoietic neoplasia.

Panel A: Wright's-stained smear of a bone marrow aspirate from a dog with acute megakaryocytic leukemia. Most of the cells in the aspirate are abnormal megakaryocytes (red arrows).	Panel B: Wright's stained smear of a bone marrow aspirate from a dog with Leishmania. A macrophage containing Leishmania amastigotes is visible in the center (red arrow).	Panel C: Bone marrow smear from a cat with acute lymphoid leukemia. The marrow is dominated by large blasts, with only a few small lymphocytes (L). Normal hematopoietic cells were absent.