Sybille Hanke

Inhibition of cellular proliferation after experimental balloon angioplasty by low-molecular-weight heparin.

Background The proliferative response induced by balloon angioplasty is known to be an important factor in the development of restenosis after successful coronary angioplasty. Methods and Results To study the effects of low-molecular-weight heparin (LMWH) on cellular proliferation after experimental balloon angioplasty, LMWH (3.9 kd, 400 anti-Xa units/kg/day) was given to 20 male New Zealand White rabbits. After an intimal fibromuscular plaque was induced by electrical stimulation in the right carotid artery, LMWH was applied during the 7 days after balloon dilatation. As the control group, 20 other rabbits underwent balloon angioplasty without application of LMWH. The vessels were excised 3, 7, 14, and 28 days after balloon treatment. During the final 18 hours before the rabbits were killed, bromodeoxyuridine was applied. Intimal wall thickness increased from 13±5 cell layers (preangioplasty control group) to 20±6 cell layers in the LMWH-treated group at 28 days (p < 0.05). In contrast, histological examination of control animals 28 days after angioplasty revealed a significant increase to 35±15 cell layers (p < 0.01). Immunohistological quantification showed a significant increase (p < 0.001) of cells undergoing DNA synthesis at 3 (10.2±4.2%) and 7 (7.7±4.8%) days after balloon dilatation in control animals. In contrast, at 3 and 7 days after balloon treatment, the percentage of cells undergoing DNA synthesis in LMWH-treated rabbits was lower (3 days, 2.7±1.8%; 7 days, 1.9±0.3%) than the corresponding untreated controls but showed a significant increase (p < 0.01) compared with the preangioplasty controls. The differences between the two groups were statistically significant, however (3 days, p < 0.01; 7 days, p < 0.05). As early as 14 days after angioplasty, the extent of cellular proliferation was normalized and was comparable to the preintervention levels in both groups. Conclusions Our data indicate that the proliferative response after balloon angioplasty can be reduced in vivo by early treatment with LMWH and thus encourage further clinical investigations.

Morphological changes and smooth muscle cell proliferation after experimental excimer laser treatment.

BackgroundLittle is known about the mechanism(s) in the development of restenosis after excimer laser angioplasty. Thus, the rationale of this study was to determine the time course of intimal and medial smooth muscle cell (SMC) proliferation and histomorphological changes after experimental excimer laser treatment. Methods and ResultsLaser ablation was performed in the right carotid artery of 34 New Zealand White rabbits after development of a fibromuscular plaque by repeated weak electrical stimulations. The vessels were excised 3, 7, 14, 21, 28, and 42 days after excimer laser treatment. Staining of a-actin was used to identify SMCs. In five rabbits (15%), a stenosis of more than 50% of luminal area was due to intimal proliferation of SMCs, and in four other rabbits, a total occlusion was due to organized thrombi. After the initial ablation of the preformed plaque (13±6 intimal SMC layers) a continuous increase of intimal wall thickness was found from 7 + 6 SMC layers at 7 days to 28±5 intimal SMC layers at 28 days after excimer laser ablation (p < 0.01). After 42 days, no additional increase of intimal thickening occurred. After bromodeoxyuridine labeling, the extent of cell proliferation (percent of cells undergoing DNA synthesis) in the intima and media was determined using a monoclonal antibody against bromodeoxyuridine. Immunohistological quantification of SMC proliferation in the intima revealed a significant increase of cells undergoing DNA synthesis at 3 (p <0.05) and 14 (p <0.01) days after laser treatment. Medial proliferation of SMCs was delayed and had a significant increase 7 days (p < 0.05) after intervention. Twenty-one days after laser treatment, SMC proliferation in the intima as well as in the media was normalized. ConclusionsThe proliferative response of SMCs after experimental excimer laser treatment will occur as a dynamic process with a maximum of SMCs undergoing DNA synthesis during 14 days after laser ablation, resulting in an increase of intimal thickening within 4 weeks after laser treatment. The extent of intimal hyperplasia due to SMC proliferation after excimer laser treatment is comparable with the effect of transluminal balloon angioplasty in this experimental model.

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

BackgroundIn 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 ResultsTo 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 pm; pulse duration, 150 jasec; 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 α-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 μm; control: 13±3 cell layers with 144±44 μm). 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 μm resp.; p=0.001 each). ConclusionsHolmium 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.

Aortic Plaque Size and Endometrial Response in Cholesterol-Fed Rabbits Treated With Estrogen Plus Continuous or Sequential Progestin

ERT is associated with a reduced incidence of coronary risk and cardiac events in postmenopausal women, but increases the risk of endometrial hyperplasia and carcinoma. Combined estrogen and progestin therapy protects the endometrium; however, its effects on heart disease risk factors are not completely known. In our study, 56 ovariectomized New Zealand White rabbits in 7 groups received a 0.5% cholesterol diet for 12 weeks. Controls were not treated with hormones. All other animals received (per kilogram body weight per week) intramuscular injections of either 0.3 mg estrogen (estradiol valerate) alone, 8.3 mg progestin (hydroxyprogesterone caproate) alone, estrogen and progestin continuously in 3 different dosages (0.3 and 8.3 mg; 1 and 8.3 mg; or 1 and 2.8 mg; estrogen and progestin, respectively), or 1 mg estrogen with 25 mg progestin sequentially in 2-week cycles. Eight non-ovariectomized animals served as further controls for endometrial analysis. Morphometric analysis of plaque size in the aortic arch showed that estrogen monotherapy, and the 3 combined therapies with 1 mg estrogen, significantly reduced intimal thickening (P<0.05). The application of progestin alone had no effect on plaque size. The endometrium was enlarged by 3-fold after estrogen treatment, and was decreased by half after progestin treatment, compared with control uteri (P<0.05). In all groups with combined hormone regimens, endometrial size was not significantly different from control uteri. However, these uteri showed more inflammatory reactions, especially when higher doses of hormones were given. In this animal model, doses of progestin that are able to successfully reduce the proliferative effect of estrogen on endometrium do not diminish the desirable antiatherosclerotic properties of estrogen.

EFFECT OF THE ANTIOXIDANT NICANARTINE ON THE PROLIFERATIVE AND INFLAMMATORY RESPONSE AFTER EXPERIMENTAL BALLOON ANGIOPLASTY

BackgroundAntioxidant treatment seems to reduce the development of restenosis after percutaneous transluminal angioplasty. In this study, the effect of Nicanartine, a new antioxidant drug with both antiproliferative and lipid-lowering properties, on the proliferative and inflammatory response after balloon angioplasty was investigated in a rabbit model of restenosis. MethodsTo induce pre-interventional plaques in the common carotid artery of 48 New Zealand White rabbits, electrostimulation was carried out for 28 days. After a break of 7 days, balloon angioplasty was performed in 36 animals, of which 18 received Nicanartine at a dose of 120 mg/kg body weight; the other 18 served as a control group. The vessels were excised by day 7 and 28 after balloon angioplasty and examined for intimal plaque size, macrophage content and proliferative activity. Bromodeoxyuridine labeling was used to determine proliferating cells in the dilated segment; macrophages were detected using the RAM-11 antibody. ResultsIn the Nicanartine-treated group, immunohistological quantification 7 days after intervention showed a statistically significant (P < 0.05) reduction of both cells undergoing DNA synthesis (1.6 ± 1.4% versus 3.7 ± 2.2%) and intimal macrophages (0.7 ± 1.2% versus 1.3 ± 0.6%). Twenty-eight days after balloon angioplasty, proliferative activity in both groups was decreased to a level comparable to the non-dilated control groups. A clear trend towards smaller plaques could be seen in the Nicanartine group (0.146 ± 0.077 mm2 versus 0.255 ± 0.174 mm2). Total cholesterol levels did not differ significantly between the groups. ConclusionUnder treatment with Nicanartine a clear reduction in the proliferative and inflammatory response after balloon angioplasty was observed. Antioxidant treatment, especially with compounds having antiproliferative and lipid-lowering properties, appears to be an effective secondary preventive strategy after interventional treatment in patients with coronary artery disease.

Effect of low molecular weight heparin on intimal smooth muscle cell proliferation after experimental balloon angioplastyEffekt von niedermolekularem Heparin auf die Proliferation glatter Muskelzellen nach experimenteller Angioplastie

Die Entwicklung von Restenosen nach primar erfolgreicher perkutaner transluminaler Koronarangioplastie (PICA) stellt auch weiterhin das ungeloste Problem dieser invasiven kardiologischen Therapie dar [7].

Effekt von niedermolekularem Heparin auf die Proliferation glatter Muskelzellen nach experimenteller Angioplastie

Die Entwicklung von Restenosen nach primar erfolgreicher perkutaner transluminaler Koronarangioplastie (PICA) stellt auch weiterhin das ungeloste Problem dieser invasiven kardiologischen Therapie dar [7].

Effect of low molecular weight heparin on intimal smooth muscle cell proliferation after experimental balloon angioplasty

Die Entwicklung von Restenosen nach primar erfolgreicher perkutaner transluminaler Koronarangioplastie (PICA) stellt auch weiterhin das ungeloste Problem dieser invasiven kardiologischen Therapie dar [7].

In-vivo holmium laser angioplasty

Holmium laser angioplasty was performed in the atheromatous carotid artery of 10 rabbits to evaluate this mid-infrared laser as an alternative energy source for angioplasty. An additional 10 rabbits served as a control group. The laser emitted light at a wavelength of 2120 nm with pulse durations of 150 microsecond(s) . The energy density was 17.5 J/cm2. Cross sections were analyzed in regard to laser specific injury 7 and 14 days following laser irradiation. Staining of (alpha) -actin was used to identify smooth muscle cells (SMC), and bromodesoxyuridine labeling was carried out to determine the extent of proliferating cells. Integrity of the lamina elastica interna fibers was disrupted in 6 of 10 animals. In all animals, loss of medial SMCs was observed 7 and 14 days after treatment. Quantification of SMCs undergoing DNA synthesis in the intima and media showed a significant increase of labelled cells following laser irradiation. This proliferative response resulted in a significant increase of intimal thickening after laser ablation.