Mohammad F. Kiani

Infarct scar as living tissue.

Abstract. Infarct scar tissue has long been considered inert (acellular, composed simply of fibrillar collagen) and whose function is simply to restore structural integrity to infarcted myocardium and to provide tensile strength that prevents tissue rupture. Technologies of cellular and molecular biology have altered this perspective. Infarct scar is now recognized as living tissue: composed of a persistent population of fibroblast-like cells whose ongoing activity includes a regulation of collagen turnover and scar tissue contraction and which are nourished by a neovasculature. Herein we briefly review these various components of the infarct scar that provide for its dynamic nature and which is relevant to todays interest in preventing heart failure through a rebuilding (regrowing) of myocardial tissue at the infarct size.

Leukocyte-inspired biodegradable particles that selectively and avidly adhere to inflamed endothelium in vitro and in vivo

We exploited leukocyte–endothelial cell adhesion chemistry to generate biodegradable particles that exhibit highly selective accumulation on inflamed endothelium in vitro and in vivo. Leukocyte–endothelial cell adhesive particles exhibit up to 15-fold higher adhesion to inflamed endothelium, relative to noninflamed endothelium, under in vitro flow conditions similar to that present in blood vessels, a 6-fold higher adhesion to cytokine inflamed endothelium relative to non-cytokine-treated endothelium in vivo, and a 10-fold enhancement in adhesion to trauma-induced inflamed endothelium in vivo due to the addition of a targeting ligand. The leukocyte–inspired particles have adhesion efficiencies similar to that of leukocytes and were shown to target each of the major inducible endothelial cell adhesion molecules (E-selectin, P-selectin, vascular cell adhesion molecule 1, and intercellular adhesion molecule 1) that are up-regulated at sites of pathological inflammation. The potential for targeted drug delivery to inflamed endothelium has significant implications for the improved treatment of an array of pathologies, including cardiovascular disease, arthritis, inflammatory bowel disease, and cancer.

Radiation-induced permeability and leukocyte adhesion in the rat blood–brain barrier: modulation with anti-ICAM-1 antibodies

We assessed the acute effects of radiation on the rat blood-brain barrier. A cranial window model and intravital microscopy were used to measure changes in permeability and leukocyte adhesion in pial vessels after a localized, single dose of 20 Gy. Permeability was assessed using five sizes of fluorescein isothiocyanate (FITC)-dextran molecules (4.4-, 10-, 38.2-, 70-, and 150-kDa) with measurements performed before and 2, 24, 48, 72 and 96 h after irradiation for the 4.4 and 38.2-kDa molecules and before and 24 h after irradiation for the other three molecules. To demonstrate the nature of blood-brain barrier permeability, we concurrently studied the permeability of microvessels in the cremaster muscle. In both tissues, permeability to FITC-dextran was significantly greater 24 h after irradiation than before (P<0.05). The exception was that radiation did not affect the permeability of pial vessels to the 150-kDa molecule. The particle-size dependence of the permeability changes in the brain were indicative of altered integrity of endothelial tight junctions and occurred concomitantly with an increase in cell adhesion which was determined by fluorescent labeling of leukocytes with rhodamine 6G. An early inflammatory response to irradiation was apparent in the brain 2 h after irradiation. The numbers of rolling and adherent leukocytes increased significantly and peaked at 24 h. Injection with the anti-ICAM-1 mAb significantly reduced leukocyte adhesion and permeability thereby linking the two processes. These findings provide a target to reduce radiation-related permeability and cell adhesion and potentially the side effects of radiation in the CNS.

Expression and Functional Significance of Adhesion Molecules on Cultured Endothelial Cells in Response to Ionizing Radiation

Objective: Upregulation of adhesion molecules on endothelial cells following irradiation has been shown, but the functional significance of this upregulation in various endothelial cell lines is not clear. We have developed an in vitro flow model to study the functional consequences of the radiation‐induced upregulation of E‐selectin and intercellular adhesion molecule (ICAM‐1).

Targeting microparticles to select tissue via radiation induced upregulation of endothelial cell adhesion molecules

AbstractPurpose. Certain endothelial cell adhesion molecules are up regulated in tissue that has been irradiated for therapeutic purposes. This up-regulation of adhesion molecules provides a potential avenue for targeting drugs to select tissues.nMethods. Microspheres were coated with a mAb to ICAM-1 and the level of adhesion of the anti-ICAM-1 microspheres to irradiated tissue in vitro and in vivo was quantified.nResults. Under in vitro flow conditions, the number of adherent microspheres on irradiated HUVEC was 4.8 ± 0.9 times that of control; the adhesion of anti-ICAM-1 microspheres on irradiated HUVEC could be enhanced by more than 170% in the presence of RBC (20% hematocrit) in the medium. In vivo in a rat cranial window model, the number of adherent anti-ICAM-1 microspheres in locally irradiated cerebral tissue was 8 and 13 times that of IgG microspheres at 24 h and 48 h post-irradiation, respectively and returned to baseline 7 days post-irradiation. In locally irradiated animals, the number of adhering microspheres in unirradiated tissue remained at the basal level.nConclusions. Radiation-induced up-regulation of endothelial cell adhesion molecules may be exploited to target drugs and/or genes to select segments of the endothelium.

Aldosteronism in heart failure: a proinflammatory/fibrogenic cardiac phenotype. Search for biomarkers and potential drug targets.

Heart failure is a major health problem of epidemic proportions. Irrespective of its etiologic origins, a dysfunction of this normally efficient muscular pump is associated with systemic consequences, a progressive downhill clinical course and poor prognosis. Ventricular dysfunction is ultimately accompanied by neurohormonal system activation that accounts for: the congestive heart failure syndrome; an induction of oxi/nitrosative stress; adverse vascular remodeling; and activation of the immune system that contributes to a wasting syndrome known as cardiac cachexia. Circulating effector hormones of the renin-angiotensin-aldosterone system are an integral feature of this neurohormonal activation; they have systemic consequences. Insights into the pathophysiology of heart failure will identify improved methods of prevention, including biomarkers to aid in its detection and identification of risk, and to the development of specific drug targets. Herein we address one aspect of the neurohormonal profile of heart failure, namely that related to aldosteronism. Our focus is directed at the link between aldosteronism and its adverse influence on coronary vasculature structure, a proinflammatory/fibrogenic cardiac phenotype, which is based on an immunostimulatory state that includes activated peripheral blood mononuclear cells.

Should direct measurements of tumor oxygenation relate to the radiobiological hypoxic fraction of a tumor

PURPOSEnNumerous previous studies have attempted to relate the radiobiological hypoxic fraction (HF) to direct measures of tumor oxygenation such as HbO2 saturations, tumor pO2 levels, or hypoxic cell labeling. Although correlations have been found within tumor lines, no overall relationships were seen across tumor lines. The current objective was to examine the effect on HF of changes in the fractions of the oxygenated and anoxic tumor cells that remain clonogenic.nnnMETHODS AND MATERIALSnA mathematical model was developed that relates the HF to direct measures of tumor oxygenation. The primary assumptions were that: (a) the tumor is divided into distinct compartments of either fully oxygenated or fully anoxic cells, and (b) the survival of the oxygenated cells is negligible compared to that of the anoxic cells. Based on these assumptions, the HF is plotted as a function of the fractions of clonogenic or nonclonogenic, and oxygenated or anoxic cells.nnnRESULTSnIf all cells are clonogenic, then the HF equals the fraction of anoxic cells. If a higher fraction of anoxic than oxygenated cells are nonclonogenic, then the HF will be overestimated by the fraction of the tumor measured to be anoxic using direct measuring techniques. If a higher fraction of the oxygenated than anoxic cells are nonclonogenic, the HF will be underestimated by the fraction of anoxic cells.nnnCONCLUSIONnCorrelations between the HF and direct measures of tumor oxygenation have been described within tumor lines evaluated under different physiological condition. However, such relationships can be totally unpredictable between different tumors if the fraction of the anoxic cells that is clonogenic varies substantially. Clearly, if tumor anoxia cannot be detected using direct measures, this is an accurate indication that the tumor is well oxygenated. When tumor anoxia is present, however, the conclusions are ambiguous. Even when a small fraction of the tumor is measured as anoxic, direct measures of tumor oxygenation may not be representative of the HF if a substantial proportion of nonclonogenic cells is present.

Observations on the Accuracy of Photometric Techniques Used to Measure Some In Vivo Microvascular Blood Flow Parameters

Objective: The accuracy of optical methods used to measure in vivo microvascular blood flow parameters is investigated using measurements made in all vessels of microvascular networks of the rat mesentery.

A ''Geographic Information Systems'' Based Technique for the Study of Microvascular Networks

AbstractAn automated system (ANET) has been developed to construct interactive maps of microvascular networks, calculate blood flow parameters, and simulate microvascular network blood flow using the geographic information systems (GIS) technology. ANET enables us to automatically collect and display topological, structural, and functional parameters and simulate blood flow in microvascular networks. The user-definable programming interface was used for the manipulation of drawings and data. Visual enhancement techniques such as color can be used to display useful information within a network. In ANET the network map becomes a graphical interface through which network information is stored and retrieved and simulations of microvascular network blood flow are carried out. We have used ANET to study the effects of ionizing radiation on normal tissue microvascular networks. Our results indicate that while vessel diameters significantly increased with age in control animals they decreased in irradiated animals. The tortuosity of irradiated vessels (16.3 ± 1.1 mean±standard error of the mean) was significantly different from control vessels (10.0 ± 1.3) only at 7 days postirradiation. Average red blood cell transit time was significantly different between control (1.6 ± 0.6 s) and irradiated (10.7 ± 5.7 s) microvascular networks at 30 days postirradiation. ANET provides an effective tool for handling the large volume of complex data that is usually obtained in microvascular network studies and for simulating blood flow in microvascular networks.

Effects of ionizing radiation on the adhesive interaction of human tumor and endothelial cells in vitro

A centrifugation assay was used to determine the effects of ionizing radiation on the adhesive interaction of A549 human lung adenocarcinoma tumor cells and human umbilical vein endothelial cells (HUVEC). The tumor cells were fluorescently labeled and divided into control (sham-irradiated) and irradiated groups. The irradiated groups were exposed to irradiation levels ranging from 5 to 20 Gy using a Cs source. A specified number of these A549 tumor cells were then delivered into each well of 96-well cell culture plates containing confluent monolayers of human umbilical cord vein endothelial cells (HUVEC), and were given time to adhere to the endothelial cells. The wells were then sealed and were exposed to an acceleration field varying from 1 to 42 g (0-500 rpm) for 10 min. Finally, the wells were drained, and the number of tumor cells adhering to the endothelial monolayer were counted using a fluorescent microscope system. Our results indicate that the irradiation of A549 tumor cells significantly increased their adhesive interaction with endothelial cells (number of adhering irradiated cells/number of adhering control cells = 1.0, 1.3, 1.9, 2.2 for 0, 5, 10, 20 Gy respectively). In contrast, when endothelial cells were irradiated, rather than tumor cells, adhesive interaction decreased with an increase in the radiation dose (irradiated/control = 1.0, 0.9, 0. 8, 0.5 for 0, 5, 10, 20 Gy respectively). Simultaneous irradiation of both the tumor cells and the endothelial cells did not alter their adhesive interaction significantly. These findings may have important implications for the metastatic ability of irradiated tumor cells.