Biomedical subjects

R Riessen

Publications and source records attributed to R Riessen.

27 records · Page 2Linked to original sources

PubMed1994

Prospects for site-specific delivery of pharmacologic and molecular therapies.

The local delivery of therapeutic agents to the arterial wall represents a new strategy for the treatment of vascular diseases, including restenosis. Approaches for local, intravascular, site-specific delivery include 1) direct deposition of therapeutic agents into the vessel wall through an intravascular delivery system; 2) systemic administration of inactive agents followed by local activation; and 3) systemic administration of fusion toxins that have a specific affinity to proliferating smooth muscle cells at the angioplasty site. In addition to conventional drugs, new therapeutic agents based on molecular mechanisms, including recombinant genes and antisense oligonucleotides, are now under investigation. Although development of intravascular drug delivery devices, including those tailored to accommodate novel therapeutic agents, offers new treatment options for restenosis and other vascular diseases, certain issues that currently limit the safety and efficacy of these approaches remain to be addressed.

Blood Vessels↗

PubMed1994

Increased gene expression after liposome-mediated arterial gene transfer associated with intimal smooth muscle cell proliferation. In vitro and in vivo findings in a rabbit model of vascular injury.

Arterial gene transfer represents a novel strategy that is potentially applicable to a variety of cardiovascular disorders. Attempts to perform arterial gene transfer using nonviral vectors have been compromised by a low transfection efficiency. We investigated the hypothesis that cellular proliferation induced by arterial injury could augment gene expression after liposome-mediated gene transfer. Nondenuded and denuded rabbit arterial strips were maintained in culture for up to 21 d, after which transfection was performed with a mixture of the plasmid encoding firefly luciferase and cationic liposomes. In non-denuded arteries, the culture interval before transfection did not affect the gene expression. In contrast, denuded arteries cultured for 3-14 d before transfection yielded 7-13-fold higher expression (vs. day 0; P < 0.005). Transfection was then performed percutaneously to the iliac arteries of live rabbits with or without antecedent angioplasty. Gene expression increased when transfection was performed 3-7 d postangioplasty (P < 0.05). Proliferative activity of neointimal cells assessed in vitro by [3H]thymidine incorporation, and in vivo by immunostaining for proliferating cell nuclear antigen, increased and declined in parallel with gene expression. These findings thus indicate that the expression of liposome-mediated arterial gene transfer may be augmented in presence of ongoing cellular proliferation.

Animals↗

PubMed1994

Regional differences in the distribution of the proteoglycans biglycan and decorin in the extracellular matrix of atherosclerotic and restenotic human coronary arteries.

Proteoglycans are important constituents of blood vessels and accumulate in various forms of vascular disease. Little is known concerning the proteoglycan composition of restenotic lesions formed after angioplasty and whether the proteoglycan composition of these lesions differs from that of primary atherosclerosis. Accordingly, we sought to characterize the distribution of two proteoglycans, biglycan and decorin, in primary atherosclerotic and restenotic lesions of human coronary arteries. Restenosis (n = 37) and primary (n = 11) lesions obtained from 48 patients by directional atherectomy of human coronary arteries were stained with antibodies against biglycan and decorin. To further characterize the extracellular matrix of restenotic tissues, we studied the co-distribution of these proteoglycans with collagen types I, III, and IV. The loose fibroproliferative tissue seen predominantly in restenosis lesions consistently stained positively for biglycan in patterns of deposition ranging from disseminated to homogeneous. The density and intensity of biglycan staining was correlated with the density of collagen type I and III fiber networks, both of which were observed to interweave among the loose fibroproliferative tissue. The compact connective tissue of primary atherosclerotic plaque was characterized by strong biglycan staining which co-localized with intense collagen type I and III staining. Only basement membrane-like structures rich in collagen type IV demonstrated negative biglycan staining. In contrast, loose fibroproliferative tissue exhibited no significant staining for decorin. Strong immunostaining for decorin, however, was found in primary atherosclerotic plaque. There are thus regional differences in the distribution of extracellular matrix proteoglycans of restenotic and primary human atherosclerotic lesions; these observations suggest that differences established for the biological roles of biglycan and decorin in other organ systems may extend as well to pathologically altered human coronary arteries.

Angioplasty, Balloon↗

PubMed1993

Arterial gene transfer using pure DNA applied directly to a hydrogel-coated angioplasty balloon.

Direct arterial gene transfer has been previously achieved using double-balloon catheters and perforated balloons, in most cases facilitated by the use of cationic liposomes or viral vectors. These gene delivery systems, however, have been compromised by issues relating to efficacy and/or safety, and furthermore require that angioplasty be performed independent of gene transfer. We investigated the possibility that arterial gene transfer might be performed during balloon angioplasty by delivery of naked genetic material from a thin coat of hydrogel polymer applied to a standard angioplasty balloon. Transfections with luciferase DNA applied to a hydrogel balloon were performed in rabbit arteries. Luciferase expression 3 days after transfection was tested in three different models: (i) an organ culture model (n = 10); (ii) surgically exposed carotid arteries (n = 14); and (iii) external iliac arteries using a percutaneous approach (n = 13). Supplementary transfections (n = 3), intended to identify the site of arterial transfection, were performed using the gene encoding for nuclear-specific beta-galactosidase (beta-gal). All rabbit arteries transfected with the luciferase gene (37/37; 100%) expressed luciferase activity. Gene expression achieved in vivo, either in the surgically exposed carotid arteries or in the external iliac arteries transfected percutaneously, was quantitatively similar to that achieved in the organ culture model. Reduction in the duration of inflation from 30 min to 1 min had no statistically significant impact on transfection efficiency. Gene expression was documented to persist up to 14 days post percutaneous transfection. Analysis of arteries transfected with nuclear-specific beta-gal showed the presence of the transgene in intimal and subintimal sites. These results demonstrate that vascular gene transfer can be performed successfully without liposomes or viral vectors using DNA applied to a standard angioplasty catheter balloon coated with hydrogel. Percutaneous transfection with a hydrogel-coated balloon permits gene transfer coincident with the angioplasty procedure itself, even with inflations as short as 1 min.

Angioplasty, Balloon↗

PubMed1993

Respiratory failure after cerebral injury.

Pulmonary dysfunction is a common complication of severe head injury. The degree of initial hypoxemia that develops appears to correspond with the location and magnitude of the head injury. If unrecognized and not aggressively treated, the hypoxic insult will magnify the cerebral insult. A severe postinjury hypermetabolic state also develops and, if unrecognized and not managed aggressively with nutritional support, can also lead to severe catabolism, increased infection, and further lung dysfunction. Although supportive care is the major treatment at present, pharmacologic manipulation of the increased catecholamine activity, which is considered to be causative, may be effective in controlling both the impaired gas exchange and the hypermetabolic state. A knowledge of the various lung dysfunction states that occur in the head-injured patient population is required to optimize recovery and minimize complications.

Craniocerebral Trauma↗

PubMed1992

Vascular injury and time course of smooth muscle cell proliferation after experimental holmium laser angioplasty.

BACKGROUND: In vitro experiments have shown that holmium laser energy can effectively ablate even calcified plaque in human arterial vessels. Because high-energy densities from holmium lasers can easily be transmitted through quartz fibers, this solid-state laser has been suggested as an alternative intraluminal treatment of atherosclerotic plaque. METHODS AND RESULTS: To develop an intimal plaque, 35 New Zealand White rabbits underwent electrical stimulation of their right carotid artery for 28 days. Subsequently, in 25 rabbits, holmium laser angioplasty (wavelength, 2.12 microns; pulse duration, 150 microseconds; energy density, 350 mJ/mm2) was performed. To study the morphological results, the vessels were excised after 7, 14, 28, and 42 days. Cross sections were analyzed in regard to laser-specific injury. Staining of alpha-actin was used to identify smooth muscle cells (SMCs). After bromodeoxyuridine labeling, the extent of proliferation (number of cells undergoing DNA synthesis) was determined by using a monoclonal antibody. Holmium laser ablation resulted in an initial decrease of the numbers of intimal cell layers in the early group (7 days after treatment: 5 +/- 1 cell layers with 76 +/- 39 microns; control: 13 +/- 3 cell layers with 144 +/- 44 microns). Quantification of SMCs undergoing DNA synthesis in the intima (control: 51 +/- 19 cells/mm2) showed a significant increase of labeled cells after 7 (216 +/- 74 cells/mm2, p = 0.003) and 14 days (281 +/- 139 cells/mm2, p = 0.011). Integrity of the internal elastic lamina was disrupted in all animals after intervention. Seven and 14 days after treatment, a considerable reduction of medial cell nuclei was found in 10 of 12 animals. SMC proliferation in the medial layer was increased within the first 2 weeks after laser ablation (168 +/- 113 cells/mm2; control: 8 +/- 4 cells/mm2; p = 0.023). Six weeks after holmium laser angioplasty, SMC proliferation had returned to control levels in the intima and remained increased in the medial layer. This proliferative response resulted in a significant increase of intimal thickening within 6 weeks after laser ablation (30 +/- 6 cell layers, 375 +/- 97 microns resp.; p = 0.001 each). CONCLUSIONS: Holmium laser treatment leads to considerable vessel wall injury and results in SMC proliferation in the intimal and medial layer with a maximum of proliferative activity within the first 2 weeks. Subsequently, this results in considerable intimal and medial hyperplasia within 6 weeks after treatment.

Angioplasty, Laser↗

PubMed1990

Oxygen partial pressure distribution within skeletal muscle: indicator of whole body oxygen delivery in patients?

Simultaneously with determination of cardiac output, the distribution of oxygen partial pressure within biceps muscle was measured during and after open heart surgery in 29 patients. During extracorporeal circulation (ECC) mean muscular oxygen partial pressure (MPO2m) decreased from 25 mmHg to 14 mmHg with an increase of MPO2 values below 5 mmHg from 4% to 20%. Sustained decrease of MPO2m (greater than 1h) did not occur after ECC. Before ECC and in the postoperative period, MPO2m was lineary correlated (r = 0.85) to whole body oxygen delivery (Ox. offer) suggesting that local oxygen delivery within biceps muscle was sufficiently indicated only by systemic parameters of oxygen transport which require determination of cardiac output. Particularly with regard to relative changes, MPO2m might be used for estimation of whole body oxygen offer clinically.

Adult↗

PubMed1990

Pulmonary dysfunction after cerebral injury.

Pulmonary dysfunction is a common complication of severe head injury. The degree of initial hypoxemia which develops appears to correspond with the location and magnitude of the head injury. If unrecognized and not aggressively treated, the hypoxic insult will magnify the cerebral insult. A severe postinjury hypermetabolic state also develops and, if unrecognized and not managed aggressively with nutritional support, can also lead to severe catabolism, increased infection, and further lung dysfunction. Although supportive care is the major treatment at present, pharmacologic manipulation of the increased catecholamine activity, which is considered to be causative, may be effective in controlling both the impaired gas exchange and the hypermetabolic state. A knowledge of the various lung dysfunction states which occur in the head-injured patient population is required to optimize recovery and minimize complications.

Craniocerebral Trauma↗

PubMedDate not supplied

Toxicity, uptake kinetics and efficacy of new transfection reagents: increase of oligonucleotide uptake.

Human arterial smooth muscle cell (haSMC) proliferation is stimulated by platelet-derived growth factor (PDGF) release of human arterial endothelial cells (haEC) whereas transforming growth factor-beta(1) (TGF-beta(1)) secretion by haSMC promotes extracellular matrix formation. Inhibitory concepts with antisense oligonucleotides (ASO) against those growth factors might be promising, requiring, however, sufficient transfection efficacy. Thus, toxicity and efficacy of new transfection reagents were examined. MTT tests showed that high doses >1.6 microg/ml of the liposome Cytofectin GSV((R)) (CF) and the dendrimer SuperFect (SF) reduced mitochondrial activity of haEC after > or =4 h transfection whereas viability of haSMC was not influenced. DAC-30((R)) showed significant toxic effects on haEC and haSMC at each dose after > or =4 h and Lipofectin((R)) (LF) caused complete detachment of haEC and haSMC in medium containing 10% serum. Uptake studies demonstrated that 'naked' ASO were not incorporated intracellularly whereas transfection within CF or SF resulted in a strong cytoplasmic and nuclear labeling after 2-5 h. With DAC-30, only a slight cytoplasmic fluorescence was found. SF caused an unexpected stimulation of endothelial PDGF-AB synthesis. Thus, CF was favored for inhibition studies. ELISA, Western and Northern blotting showed a significant inhibition of endothelial PDGF-B and smooth muscle TGF-beta(1) mRNA expression and synthesis after transfection for 3-5 h using 0.1-1.0 microM ASO versus control oligonucleotides. We conclude that Cytofectin GSV is superior to the other transfection reagents, predominantly at haEC, showing an improved efficacy and less toxicity than the classical liposome Lipofectin. Cytofectin GSV might offer a promising tool for antisense strategies in the treatment of vascular disorders.

Blood Vessels↗