Effects of cytochalasin D-eluting stents on intimal hyperplasia in a porcine coronary artery model.

OBJECTIVE: To investigate whether cytochalasin D-eluting stents (CDES) suppress intimal hyperplasia in porcine coronary arteries and to compare the efficacy of paclitaxel and cytochalasin D as inhibitors of vascular smooth muscle cell (SMC) proliferation and platelet aggregation in vitro. METHODS: Rabbit platelet-rich plasma and SMC cultures derived from rabbit aortas were exposed to 10(-8)-10(-5) M cytochalasin D or paclitaxel. Stents directly coated with 2 microg cytochalasin D (low-dose CDES, n=12) and bare stents (n=12) were randomly deployed in the right and left coronary artery of 12 pigs. Six weeks later, neointima was studied using quantitative coronary angiography (QCA) and morphometry. To examine a ten-fold higher dose, polybutyl methacrylate/polyvinyl acetate-coated stents were loaded with 20 microg cytochalasin D. High-dose CDES (n=10) and polymer-only stents (n=11) were deployed in 11 pigs. RESULTS: After 7 days, cytochalasin D (IC(50) 9.9+/-0.4 10(-8) M) and paclitaxel (IC(50) 1.1+/-0.4 10(-8) M) inhibited SMC proliferation in vitro (n=4). In contrast, cytochalasin D (10(-6)-10(-5) M, n=5), but not paclitaxel, attenuated platelet shape change and aggregation induced by ADP. In vivo QCA showed less late lumen loss in low-dose CDES (0.08+/-0.07 vs. 0.32+/-0.08 mm, P=0.05), but morphometry demonstrated only a tendency toward a decreased intimal area. High-dose CDES inhibited both late lumen loss (0.31+/-0.08 vs. 0.91+/-0.06 mm, P<0.01) and intimal area (1.57+/-0.20 vs. 2.46+/-0.22 mm(2), P<0.01). Immunohistochemistry revealed that CDES suppressed peri-strut macrophage recruitment (CD68, P=0.04) and cell proliferation (Ki67, P=0.03) as compared to polymer-only stents without interfering with endothelial cell recovery or the density of alpha-SMC actin staining. Thromboses or edge effects were not observed in either study. CONCLUSIONS: CDES inhibited in-stent hyperplasia. The reduction (39%) with 20 mug CDES was equivalent to that reported for paclitaxel-eluting stents in pigs. Interference with platelet aggregation, SMC migration, SMC proliferation, and leukocyte recruitment could contribute to the benefit. The data indicate that targeting of actin microfilaments has a potential to suppress in-stent restenosis.

Glucose-mediated cross-linking of collagen in rat tendon and skin.

BACKGROUND: Cross-linking of macromolecules like collagen plays an important role in the development of complications in diabetes and ageing. One of the underlying mechanisms of this cross-linking is the formation of advanced glycation endproducts (AGEs). METHODS: In this study, we assessed the use of differential scanning calorimetry (DSC) for the determination of these cross-links and the effects of an AGE inhibitor and breaker. RESULTS: Treatment with N-phenacylthiazolium bromide (ALT-711) of diabetic rats with 2 months duration of diabetes normalized large artery stiffness, assessed by characteristic input impedance and systemic arterial compliance, but with the use of DSC, no statistical difference in cross-linking between control and treated animals could be measured. In addition, we performed in vitro incubation of collagen preparations with ribose and glucose to assess the DSC method as well as the influence of AGE breakers and inhibitors. Incubation of rat tail tendon (RTT) with 100 mmol/l glucose showed an increase in collagen cross-linking expressed as an increase in shrinkage temperature (T(s)). Addition of aminoguanidine (AG), an inhibitor of AGE formation, prior to glucose incubation showed a slower increase of the amount of glucose-derived cross-linking. Replacing glucose with ribose showed a quicker increase in cross-linking and less effect on cross-linking by adding aminoguanidine, demonstrating the higher reactivity of pentoses above hexoses. Similar experiments with rat skin samples (RSS) showed that RSS (type III collagen) are less susceptible to glucose-mediated cross-linking than RTT (type I collagen). We observed no effect of addition of ALT-711, a breaker of glucose-derived cross-links, on the extent of collagen cross-linking in both RTT and RSS. CONCLUSION: Overall, DSC is considered a useful method for assessing glucose-mediated cross-linking in vitro with nonphysiological glucose concentrations. The in vivo use in biological samples is limited due to the lack of sensitivity. However, DSC remains a quick and well-quantitated method in comparison with other methods, like enzymatic digestibility.