Optimal dosing of intravascular low-power red laser light as an adjunct to coronary stent implantation: insights from a porcine coronary stent model.

BACKGROUND: It is believed that restenosis following coronary interventions is the result of endothelial denudation that leads to thrombus formation, vascular remodeling, and smooth muscle cell proliferation. Low-power red laser light (LPRLL) irradiation enhances endothelial cell growth in vitro and in vivo, and reduces restenosis in animal models. The present study investigated the optimal dose of intravascular LPRLL therapy in the prevention of in-stent stenosis in a porcine coronary stent model. METHODS AND RESULTS: Selected right coronary artery segments were pretreated with a LPRLL balloon, delivering a dose of 0 mW during 1 min (group 1, n = 10), 50 mW during 1 min (group II, n = 10), or 100 mW during 1 min (group III, n = 10) before stenting. Quantitative coronary analysis of the stented vessel was performed before stenting, immediately after stenting, and at 6 weeks follow-up. The pigs were sacrificed, and histologic and morphometric analyses were conducted. At 6 weeks, minimal luminal stent diameter was significantly narrower in the control group compared to the 50-mW dose group (p < 0.05). These results were confirmed by morphometric analysis. Neointimal area was also significantly decreased in the 50-mW dose group. CONCLUSIONS: Intravascular LPRLL contributes to reduction of angiographic in-stent restenosis and neointimal hyperplasia in this animal model. The optimal dose using the LPRLL balloon system seems to be approximately 5 mW delivered during 1 min.

Effect of short pulsed nonablative infrared laser irradiation on vascular cells in vitro and neointimal hyperplasia in a rabbit balloon injury model.

BACKGROUND: Neointimal hyperplasia after PTCA is an important component of restenosis. METHODS AND RESULTS: Cultures of rabbit endothelial cells and smooth muscle cells (SMCs) were irradiated with different doses of nonablative infrared (1064-nm) radiation. Normalized viability index detected with nondestructive Alamar Blue assay and direct cell count were studied. Our experiments demonstrated dose-dependent cytostatic or cytotoxic effects of laser irradiation. We also evaluated the long-term effect of endoluminal nonablative infrared laser irradiation on neointimal hyperplasia in a rabbit balloon injury model. PTCA of both iliac arteries of 23 New Zealand White rabbits was performed. One iliac artery was subjected to intra-arterial subablative infrared irradiation via a diffuse tip fiber. The contralateral vessel served as control. The diet was supplemented with 0.25% cholesterol and 2% peanut oil for 10 days before and 60 days after PTCA. Morphometry after 60 days showed that intimal areas were 0.76+/-0.18 and 1.85+/-0.30 mm(2) in the laser and control arteries, respectively (P=2.2x10(-11)). CONCLUSIONS: We conclude that nonablative infrared laser inhibited neointimal hyperplasia after PTCA in cholesterol-fed rabbits for up to 60 days.

Low-power helium: neon laser irradiation enhances production of vascular endothelial growth factor and promotes growth of endothelial cells in vitro.

BACKGROUND AND OBJECTIVE: Numerous reports suggest that low-power laser irradiation (LPLI) is capable of affecting cellular processes in the absence of significant thermal effect. The objective of the present study was to determine the effect of LPLI on secretion of vascular endothelial growth factor (VEGF) and proliferation of human endothelial cells (EC) in vitro. STUDY DESIGN/MATERIALS AND METHODS: Cell cultures were irradiated with single different doses of LPLI (Laser irradiance from 0.10 to 6.3 J/cm(2)) by using a He:Ne continuous wave laser (632 nm). VEGF secretion by smooth muscle cells (SMC) and fibroblasts was quantified by sandwich enzyme immunoassay technique. The endothelial cell proliferation was measured by Alamar Blue assay. VEGF and transforming growth factor beta (TGF-beta) expression by cardiomyocytes was studied by reverse transcription-polymerase chain reaction (RT-PCR). RESULTS: We observed that (1) LPLI of vascular and cardiac cells results in a statistically significant increase of VEGF secretion in culture (1.6-fold for SMC and fibroblasts and 7-fold for cardiomyocytes) and is dose dependent (maximal effect was observed with LPLI irradiance of 0.5 J/cm(2) for SMC, 2.1 J/cm(2) for fibroblasts and 1.05 J/cm(2) for cardiomyocytes). (2) Significant stimulation of endothelial cell growth was obtained with LPLI-treated conditioned medium of SMC (maximal increase was observed with LPLI conditioned medium with irradiance of 1.05 J/cm(2) for SMC and 2.1 J/cm(2) for fibroblasts. CONCLUSIONS: Our studies demonstrate that low-power laser irradiation increases production of VEGF by SMC, fibroblasts, and cardiac myocytes and stimulates EC growth in culture. These data may have significant importance leading to the establishment of new methods for endoluminal postangioplasty vascular repair and myocardial photoangiogenesis.

Long-term follow-up after coronary stenting and intravascular red laser therapy.

A high restenosis rate remains a limiting factor for coronary angioplasty and stenting. Recently, use of intravascular red light therapy (IRLT) has been shown to be effective in different animal models and in humans in reducing the restenosis rate. Sixty-eight patients were treated with IRLT in conjunction with coronary stenting procedures. Mean age was 64 +/- 9 years. Treated lesions were type A (11), type B (42), and type C (18) with a mean lesion length of 16.5 +/- 2.4 mm. Reference vessel diameter and minimal lumen diameter (MLD) before therapy were 2.90 +/- 0.15 and 1.12 +/- 0.36 mm, respectively. After stenting and laser irradiation, MLD was 2.76 +/- 0.39 mm. No procedural complications or in-hospital adverse events occurred. All patients were followed up as depicted in the protocol. Sixty-one patients underwent angiographic restudy, which revealed restenosis in 9 patients (14.7%). Observed restenosis rate by artery size was > 3 mm (n = 21, 0%), 2.5 to 3.0 mm (n = 28, 14.2%), and <2.5 mm (n = 12, 41.6%). We conclude that IRLT is safe and feasible and reduces the expected restenosis rate in patients after coronary stenting in arteries of >2.5 mm.

Endoluminal reconstruction of the arterial wall with endothelial cell/glue matrix reduces restenosis in an atherosclerotic rabbit.

OBJECTIVES: The objectives of this study were 1) to improve the attachment of reimplanted endothelial cells (EC) using a fibrin glue, and 2) to assess the impact of endothelial reseeding on restenosis eight weeks after balloon angioplasty. BACKGROUND: A possible mechanism contributing to restenosis after balloon angioplasty is the loss of the EC lining. Previous attempts to reseed EC had little effect due to rapid loss of the seeded cells. METHODS: Twelve atherosclerotic rabbits were subjected to angioplasty of iliac arteries and reseeding procedure. One iliac artery was subjected to EC/glue reconstruction and a contralateral site to EC seeding without glue. The animals were sacrificed after 4 h. In another series 12 rabbits were treated in the same fashion and were restudied at eight weeks. Additionally, in 10 animals one iliac was subjected to glue treatment, and another served as control. RESULTS: Histological examination demonstrated the ability of this method to reattach the EC/glue matrix circumferentially to 68.0 +/- 6.7% of the arterial wall in comparison with 13.5 +/- 3.9% reattachment after EC seeding. Morphometry at eight weeks showed that the lumen area was significantly greater in the EC/glue group (1.23 +/- 0.35 mm2) than in the EC seeding alone (0.65 +/- 0.02 mm2) and 0.72 +/- 0.41 mm2 in the glue group. This was principally accounted for by the statistically significant differences in the intimal area (0.76 +/- 0.18 mm vs. 1.25 +/-0.26 mm2 and 1.01 +/- 0.53 mm2, respectively). CONCLUSIONS: The attachment of EC after angioplasty can be greatly improved with fibrin glue matrix. The near 70% endothelial coverage achieved by this method resulted in a significant reduction of restenosis in atherosclerotic rabbit.

Angiogenesis in the latissimus dorsi muscle using different regimens of electrical stimulation and pharmaceutical support.

It is our contention that the prevention of ischemia-reperfusion injuries immediately after latissimus dorsi muscle (LDM) mobilization and enhancement of angiogenesis will be effective in improving cardiomyoplasty results. The investigations were performed on adult sheep. Three hours after LDM mobilization, various stages of leukocyte-endothelium interaction were revealed: leukocytes binding to the endothelium, leukocyte destruction of endothelium, and leukocytes leaving capillaries through gaps in the endothelium. Fifty-six days after mobilization various stages of necrosis were discernible. The area occupied by capillaries was 3.45 +/- 0.26% vs. 3.99 +/- 0.24% in control muscle; most of the endothelial cells exhibited morphologic degeneration. Electrical stimulation with 60 CPM actually decreased the capillary density to 2.15 +/- 0.7%, and most of the endothelial cells were damaged, with disrupted plasma membranes. Muscle subjected to 15 CPM increased the percent of capillaries to 5.01 +/- 0.56%, and endothelial cells appeared normal in ultrastructure. Pharmaceutical support prevented muscle damage and accelerated revascularization. After 56 days of autologous biological glue (ABG) application, the area occupied by capillaries was 5.57 +/- 0.24%. This increased to 8.47 +/- 0.72% when aprotinin (proteinase inhibitor) was added to ABG, and to 9.40 +/- 1.24% with pyrrolostatin (free radical scavenger). Both ABG application with aprotinin and electrical stimulation at 15 CPM prevent the LDM from postmobilization damage, and increase angiogenic potential.

Biodesign of a skeletal muscle flap as a model for cardiac assistance.

In using autologous muscles for cardiac assistance, it is crucial to reduce ischemia-reperfusion injury in the surgically traumatized skeletal muscle. In adult sheep, we developed a simple model of surgically designed 2 latissimus dorsi muscle leaflets by modifying the vascular supply to these leaflets. Three pockets with graded injury were established, and muscle morphology and vascular remodeling were monitored in 3 experimental groups: muscle leaflets without any treatment (Group 1, n = 6) that served as controls; muscle leaflets integrated with a fibrin interlayer (Group 2, n = 6); and leaflets integrated with fibrin and entrapped pyrrolostatin (Group 3, n = 6). We applied the fibrinogen and thrombin solutions, which polymerize to form a three-dimensional meshwork joining the tissues, creating a provisional matrix for angiogenesis, and acting as a delivery depot for agents aimed at minimizing ischemia-reperfusion lesion formation. After 2 months, the muscle leaflets biointegrated with the fibrin interface showed none of the signs of necrosis or ischemia-reperfusion lesions seen in the controls. Although no angiogenic factors were incorporated, the fibrin interlayer rapidly (<2 weeks) became a densely vascularized tissue replete with a voluminous capillary network. In contrast, controls showed poor bonding between the tissues, muscle fiber deterioration, and a compromised vascular network. Muscle structure was best preserved and angiogenesis was greatest when pyrrolostatin, a free radical scavenger, was added to the fibrin meshwork to reduce damage caused by overproduction of free radicals. This newly designed model will be useful to study many current approaches in cardiovascular biology, from pharmaceuticals to gene therapy, which might prove advantageous in muscle-designed cardiac assistance.

Low-power laser irradiation increases cyclic GMP synthesis in penile smooth muscle cells in vitro.

OBJECTIVE: The objective of the present study was to determine the effect of low-power laser irradiation (LPLI) on cyclic guanosine monophosphate (cGMP) produced by human corpus cavernosum smooth muscle cells (HCC SMC) in vitro. BACKGROUND DATA: Numerous reports suggest that LPLI is capable of affecting cellular processes in the absence of significant thermal effect METHODS: HCC SMC cultures were irradiated with single-dose LPLI using a He-Ne continuous wave laser (632 nm) with different energy densities (0.52-2.1 J/cm2). Assessment of effect on cell viability was performed utilizing Alamar Blue assay. Effect of LPLI on cGMP production was studied by radioimmunoassay. RESULTS: We observed that: (1) LPLI of HCC SMC results in a statistically significant increase of cGMP synthesis in culture and is dose dependent (maximal effect was observed with LPLI irradiance of 1.57 J/cm2. (2) There were no changes in Normalized Viability Index (NVI) immediately after and 24 h following laser irradiation. CONCLUSION: Our studies demonstrate that LPLI irradiation stimulates elevation of cGMP in vitro.

Influence of different stent materials on endothelialization in vitro.

The objective of our study was to investigate the influence of different stent materials on endothelialization in vitro. Using the non-destructive Alamar Blue assay and scanning electron microscopy, we compared long-term growth and morphology of vascular cells on disks of three prospective stent materials, i.e., 316 L stainless steel, 18 K, and 24 K gold. Our results demonstrate superior human EC proliferative capacity on gold surfaces compared to that on 316 L stainless steel. Thus, both the hyperplasia and thrombotic complications which often follow stenting might be minimized by employing gold stents, which have a greater capacity than steel in supporting a functional neo-endothelium.

Photoremodeling of arterial wall reduces restenosis after balloon angioplasty in an atherosclerotic rabbit model.

OBJECTIVES: This study evaluated the long-term impact of endoluminal low power red laser light (LPRLL) on restenosis in an atherosclerotic rabbit model. BACKGROUND: Despite widespread application of balloon angioplasty for treatment of coronary artery disease, restenosis limits its clinical benefits. Restenosis is a complex process and may be partly attributed to the inability of the vascular endothelium to regenerate and cover the denuded area at the site of arterial injury. We previously demonstrated that LPRLL stimulates endothelial cell proliferation in vitro and contributes to rapid endothelial regeneration after balloon injury in nonatherosclerotic rabbits. METHODS: Rabbit abdominal aortas (n = 12) were treated in separate zones with balloon dilation and balloon dilation plus laser illumination. Endoluminal laser therapy was performed using a laser-balloon catheter delivering a single dose of 10 mW for 3 min from a helium-neon laser (632 nm). Angiography was performed before and after treatment and was repeated 8 weeks before harvesting the aortas. RESULTS: Quantitative angiographic analysis demonstrated no differences in the minimal lumen diameter (MLD) between the two zones before treatment; an increase in the MLD in both zones after balloon angioplasty and a significant versus slight reduction of the MLD in the balloon treatment versus balloon plus laser zones at 8 weeks. Histologic examination showed a very high level of myointimal hyperplasia in the balloon treatment zones but a minimal level in the LPRLL-treated zones. Morphometric analysis revealed a statistically significant difference in the lumen area, intimal area and intima/media ratio between the balloon versus balloon plus laser treatment sites. CONCLUSIONS: Our experimental data indicate that endoluminal irradiation with LPRLL prevents restenosis after balloon angioplasty in an atherosclerotic rabbit model.

Percutaneous Application of Fibrin Sealant to Achieve Hemostasis Following Arterial Catheterization.

OBJECTIVES: The present study sought to investigate the safety and efficacy of a new fibrin sealant using percutaneous delivery techniques. BACKGROUND: The femoral approach has become the preferred means of access for percutaneous diagnostic and interventional procedures. Control of access site bleeding following catheterization, however, remains a significant problem in interventional cardiology. METHODS: Adult mongrel dogs were used in this study. Series 1 compared the effectiveness of fibrin sealant vs. manual compression alone in the presence of anticoagulants, thrombolytic, and antiplatelet agents. Series 2 assessed fibrin sealant safety. Series 3 examined fibrin sealant performance under elevated blood pressure levels. RESULTS: Series 1: Hemostasis was achieved in all fibrin sealant sites in significantly less time (8.5 +/- 4.3 min) with no major complications compared to manual compression sites (65.2 +/- 19.3 min) accompanied by serious complications. For all adjunctive agents employed, hemostasis was achieved in fibrin sealant sites in significantly less time (warfarin 9.9 +/-.2, urokinase 11.2 +/- 5.6, ReoProª 10.5 +/- 6.3 min) than for manual compression sites (warfarin 86.5 +/- 21.4, urokinase 89.8 +/- 36.3, ReoPro 77.9 +/- 26.5 min). Series 2: I25 iodine-labeled fibrinogen sealant was applied to puncture sites with no traces of circulating radioactivity observed over a one-hour period. Series 3: hemostasis was achieved under elevated blood pressure conditions in all animals. Histologic studies showed complete re-absorption of fibrin sealant 28 days post-procedure with no evidence of foreign body reaction. CONCLUSIONS: Percutaneous application of fibrin sealant to achieve hemostasis following catheterization appears to be a simple, safe, and highly effective procedure in a canine model.

GTSF-2: a new, versatile cell culture medium for diverse normal and transformed mammalian cells.

The aim of this study was to test the versatility of a new basal cell culture medium, GTSF-2. In addition to traditional growth-factors, GTSF-2 contains a blend of three sugars (glucose, galactose, and fructose) at their physiological levels. For these studies, we isolated normal endothelial cells from human, bovine, and rat large blood vessels and microvessels. In addition, GTSF-2 was also tested as a replacement for high-glucose-containing medium for PC12 pheochromocytoma cells and for other, transformed cell lines. The cell growth characteristics were assessed with a novel cell viability and proliferation assay, which is based on the bioreduction of the fluorescent dye, Alamar Blue. After appropriate calibration, the Alamar Blue assay was found to be equivalent to established cell proliferation assays. Alamar Blue offers the advantage that cell proliferation can be measured in the same wells over an extended period of time. For some of the cell types (e.g., endothelial cells isolated from the bovine aorta, the rat adrenal medulla, or the transformed cells), proliferation in unmodified GTSF-2 was equivalent to that in the original culture media. For others cell types (e.g., human umbilical vein endothelial cells and PC12 cells), GTSF-2 proved to be a superior growth medium, when supplemented with simple additives, such as endothelial cell growth supplement (bFGF) or horse serum. Our results suggest that GTSF-2 is a versatile basal medium that will be useful for studying organ-specific differentiation in heterotypic coculture studies.

Biologic glue increases capillary ingrowth after cardiomyoplasty in an ischemic cardiomyopathy model.

The authors investigated the multi-step mechanism of healing after cardiomyoplasty, focusing on the process of angiogenesis. The authors contend that enhancement of angiogenesis and prevention of ischemia-reperfusion injuries immediately after muscle mobilization will be effective in improving cardiomyoplasty results. After cardiomyoplasty, autologous biologic glue (ABG) was administered between the latissimus dorsi muscle (LDM) and myocardium. By 2 months, a new pseudo interlayer was present that bridged the gap between the LDM and myocardium. Neovascularization was visible in the form of numerous small capillaries. Marked degeneration of the LDM was noted, possibly caused by muscle ischemia-reperfusion damage after mobilization. Pockets were created of ischemic and nonischemic LDM to test for angiogenesis. One was left free of ABG (control); one received ABG only; one received ABG and pyrrolostatin. Some of the capillaries were large and had erythrocytes inside. biopsy samples showed 9.4 +/- 1.9% of the sample was occupied by blood vessels (compared with 3.6 +/- 0.7% in control muscle). These preliminary studies prove the feasibility of the authors' concept and provide evidence that angiogenesis can accelerate the healing process and provide an organic bridge between the LDM and myocardium after cardiomyoplasty.

In vitro testing of endothelial cell monolayers under dynamic conditions inside a beating ventricular prosthesis.

Thromboembolic complications remain a major problem associated with the long-term clinical use of cardiac prostheses. A promising approach toward resolving this predicament is lining the blood contacting surfaces with a functional monolayer of endothelial cells (EC). In developing an endothelialized cardiac prosthesis, the authors in the past focused on establishing a confluent EC monolayer on the luminal surface of ventricular blood sacs. In this study, the authors concentrated on exposing the post confluent monolayers to the dynamic conditions inside a beating ventricle. The cells, derived from either bovine aortae or jugular veins, were grown to post confluence inside fully assembled ventricles on fibronectin or plasma cryoprecipitate coated, textured surfaces. After 11 days of culturing under static conditions, the endothelialized ventricles were connected to a mock loop that was run for 6 and 24 hr at 60 bpm and mean flow rate of 3.2 L/min. The status of the monolayer was evaluated by Alamar Blue assay before and after each run, and the extent of surface coverage was determined visually using bright field microscopic study after cell staining with KMnO4 and toluidine blue. In addition, morphometric information on cells/polyurethane surface was obtained with a scanning electron microscope. After 6 hr of pumping, cell staining revealed signs of moderate cell loss in fibronectin coated blood sacs, whereas in cryoprecipitate coated bladders the signs of denudation were marginal. In seven ventricles operated for 24 hr, Alamar Blue measurements indicated 35 +/- 16% of cell loss from monolayers established on fibronectin coating, but only 4.8 +/- 6.25% on cryoprecipitate. Thus, the current study demonstrates the feasibility of maintaining an intact endothelial surface in a beating ventricular prosthesis and indicates that the integrity of the endothelial lining is dependent upon a proper choice of surface macrostructure and protein coating.

A new method for continual quantitation of viable cells on endothelialized polyurethanes.

Many of the segmented polyurethanes currently used in cardiovascular prostheses undergo either modification of their surface structure or are lined with a confluent monolayer of endothelial cells to improve their hemocompatibility. During the establishment of an endothelial cell lining on these biopolymers it is necessary to continually monitor the number of viable cells that are covering the substrate. Yet, not all of the conventional cell enumeration techniques are suitable for assessing the growth of endothelial cells on polyurethanes. Methods, such as direct cell counting, dye uptake, or DNA or protein staining require either a transparent scaffold or lead to termination of the culturing process prior to measurement. In addition, some of the spectroscopic assays are often hampered by interaction of the dyes and/or solubilizers with the various constituents (e.g., catalyzers, antioxidants) and/or functional groups in the polyurethane formulations. In addressing these problems, we adapted a novel, highly reproducible fluorescent assay which is based on reduction by viable cells of an electrochemically sensitive compound, Alamar Blue. The bioreduced product is soluble and stable in culture media and noncytotoxic. In addition, the assay is independent of the geometry or physicochemical properties of the polymeric surfaces. In the present study we focus on the implementation of this assay to monitoring attachment and growth of various endothelial cell types on segmented polyurethanes.