UVB-activated psoralen reduces luminal narrowing after balloon dilation because of inhibition of constrictive remodeling

Robust quantitative assessment of collagen fibers with picrosirius red stain and linearly polarized light as demonstrated on atherosclerotic plaque samples

Collagen is an important component in maintaining structural integrity and functionality of tissues and is modulated in various biological processes. Its visualization and possible quantification using histopathological stains can be important for understanding disease progression or therapeutic response. Visualization of collagen fiber with the histological stain picrosirius red (PSR) is enhanced with polarized light and quantitative analysis is possible using circular polarizers. However, linear polarizers are more commonly available and easier to optically align. The objective of the present study is to demonstrate a novel image acquisition technique and analysis method using linearly polarized light. The proposed imaging technique is based on image acquisition at multiple slide rotation angles, which are co-registered to form a composite image used for quantitative analysis by pixel intensity or pixel counting. The technique was demonstrated on multiple human coronary samples with varying histopathologies and developed specifically to analyze cap collagen in atherosclerotic plaque. Pixel counting image analysis was found to be reproducible across serial tissue sections and across different users and sufficiently sensitive to detect differences in cap structural integrity that are likely relevant to prediction of rupture risk. The benefit of slide rotation angle under linear polarization to acquire images represents a feasible and practical implementation for expanding the general utility of PSR for quantitative analysis.

Design, Development, In Vitro and Preliminary In Vivo Evaluation of a Novel Photo-Angioplasty Device: Lumi-Solve

PURPOSE

Paclitaxel (PTX)-coated drug eluting balloon catheters (DEBc) used in the management of neointimal hyperplasia (NIH) have been associated with safety concerns. Alternative coating agents and targeted delivery systems may improve safety and DEBc efficacy. Utilizing a multi-platform approach we designed, developed and evaluated Lumi-Solve, a novel DEBc, coated with ultraviolet (UV) 365 nm-activated caged metacept-3 (c-MCT-3), an epigenetic agent from the histone deacetylase inhibitor (HDACi) class.

METHODS

In vitro catheter and contrast media transmission of UV365nm was evaluated spectroscopically. UV365nm conversion of c-MCT-3 to MCT-3 was evaluated chromatographically. Cellular toxicity and HDACi activity of c-MCT-3 ∓UV365nm was evaluated in vitro. In vivo UV365nm conversion of c-MCT-3 to MCT-3 was evaluated in an ovine carotid artery model.

RESULTS

Catheter material and dilute contrast media did not attenuate UV365nm transmission or c-MCT-3 activation. c-MCT-3 demonstrated less cellular toxicity than MCT-3 and PTX. UV365nm-activated c-MCT-3 demonstrated HDACi activity. In vivo activation of c-MCT-3 produced MCT-3.

CONCLUSIONS

Lumi-Solve, a novel DEBc device developed utilizing a combination of chemical, fibre-optic and catheter based technology platforms, demonstrated potential for targeted delivery of bioactive HDACi to the blood vessel wall supporting direct application to the management of NIH and warranting additional in vivo studies.

Effectiveness of narrow-band ultraviolet-B phototherapy for prevention of intimal hyperplasia in a rat carotid balloon injury model

BACKGROUND AND OBJECTIVE

Narrow-band ultraviolet-B light (NBUVB) (313 nm) is known to have anti-proliferative effects, implying a potential treatment for intimal hyperplasia, but it remains to be ascertained. We assessed the effects of NBUVB irradiation for prevention of intimal hyperplasia.

STUDY DESIGN/MATERIALS AND METHODS

The rat carotid arteries were irradiated with NBUVB after balloon injury (BI), and the degree of intimal hyperplasia was histopathologically assessed. The anti-proliferative effects using cultured human smooth muscle cells were evaluated by flow cytometry and immunoblot analysis.

RESULTS

NBUVB (0.3-4.5 J/cm(2)) irradiation immediately after BI reduced the degree of intimal hyperplasia at 14 and 28 days after BI (P<0.001) without any obvious complications. Neither an increase in the number of medial cells nor upregulation of proliferating cell nuclear antigen was observed in the irradiated arteries. NBUVB irradiation at 2 or 14 days after BI significantly suppressed further intimal hyperplasia (P<0.01). NBUVB-irradiated cultured cells showed inhibited proliferation involved with G(1) and G(2)/M arrests. Increased expression of p53 and inhibition of retinoblastoma protein (pRB) phosphorylation were also seen in the NBUVB-irradiated cells.

CONCLUSIONS

These data suggest that NBUVB irradiation is an effective method for preventing intimal hyperplasia. The anti-proliferative effect is partly due to the cell cycle arrest caused by p53 expression and inhibited pRB phosphorylation.

Increase in Collagen Turnover But Not in Collagen Fiber Content Is Associated with Flow-Induced Arterial Remodeling

BACKGROUND

Degradation and synthesis of collagen are common features in arterial geometrical remodeling. Previous studies described an association between arterial remodeling and an increase in collagen fiber content after balloon injury. However, this does not exclude that the association between collagen content and remodeling depends on arterial injury since the association of collagen fiber content and arterial remodeling, without arterial injury, has not been investigated. The aim of the present study was to study the relation between flow-induced arterial geometrical remodeling, without arterial injury, and collagen synthesis and degradation, collagen fiber content and cell-migration-associated moesin levels.

METHODS AND RESULTS

In 23 New Zealand White rabbits an arteriovenous shunt (AV shunt) was created in the carotid and femoral artery to induce a structural diameter increase or a partial ligation (n = 27 rabbits) to induce a diameter decrease. In both models, arterial remodeling was accompanied by increased procollagen synthesis, reflected by increased procollagen mRNA or Hsp47 protein levels. In both models, however, no changes were detected in collagen fiber content. Active MMP-2 and moesin levels were increased after AV shunting.

CONCLUSIONS

Collagen synthesis and MMP-2 activation were associated with arterial remodeling. However, a change in collagen fiber content was not observed. These results suggest that, during flow-induced geometrical arterial remodeling, increases in collagen synthesis are used for matrix collagen turnover and cell migration but not to augment collagen fiber content.

Matrix metalloproteinase inhibition reduces intimal hyperplasia in a porcine arteriovenous-graft model

BACKGROUND

The patency of arteriovenous (AV) polytetrafluoroethylene grafts for hemodialysis is impaired by intimal hyperplasia (IH) at the venous outflow tract. IH mainly consists of vascular smooth muscle cells, fibroblasts, and extracellular matrix proteins. Because matrix metalloproteinases (MMPs) are enzymes able to degrade extracellular matrix proteins such as elastin and collagen and also stimulate migration of vascular smooth muscle cells, we hypothesized that BB2983 (a broad-spectrum MMP inhibitor) could reduce IH in AV grafts.

METHODS

In 12 pigs, AV grafts were created bilaterally between the carotid artery and the jugular vein. Six pigs received the oral MMP inhibitor (MMPi), and six pigs served as a control. Four weeks after AV shunting, the grafts and adjacent vessels were excised and underwent histologic analysis. Quantification of elastin content was performed on Elastin von Gieson-stained sections.

RESULTS

At the venous outflow tract, IH was strongly inhibited after MMPi when compared with the control group (1.02 +/- 0.26 mm(2) vs 2.14 +/- 0.38 mm(2); P =.027). The medial area did not differ significantly. In the control group elastin density decreased compared with nonoperated veins. This decrease was not observed in the MMPi group (nonoperated, 6.3% +/- 0.4%; MMPi, 7.2% +/- 0.7% vs untreated, 3.6% +/- 0.5%; P =.0004). Outward remodeling of the vein was not influenced by MMP inhibition.

CONCLUSION

MMPi reduces IH formation at the venous outflow tract of AV grafts in pigs, probably by inhibiting elastin degradation. These data suggest that MMP inhibitors might be useful for minimizing IH in AV grafts, thus prolonging patency rates of AV grafts in patients on hemodialysis.

Function and structure of pressurized and perfused porcine carotid arteries: effects of in vitro balloon angioplasty

In this report we describe the application of an in vitro pressure-perfusion system for study of functional/structural changes after in vitro balloon dilation injury. Pig carotid arteries were perfused at P = 100 mm Hg and Q = 100 ml/min, balloon angioplastied (BA), and cultured under these hemodynamic conditions for 4 or 8 days (n = 5 BA and 6 controls for each time point). To assess endothelial function, outer diameter changes in response to bradykinin (BK) were measured daily. Remodeling was determined from the shift in pressure-passive diameter relation, as obtained after papaverine addition. Arterial samples were processed for histology. Control arteries showed spontaneous tone, BK-induced relaxation, and inward remodeling that was more pronounced at day 8 (ratio end-to-start passive diameter at P = 100 mm Hg, 0.69 +/- 0.04; P < 0.001) than at day 4 (0.85 +/- 0.03, P = 0.03). Intimal hyperplasia was detectable in these control vessels at day 8 with accumulation of alpha-smooth muscle actin-positive cells around the lumen. Angioplasty caused ruptures and dissections and abolished tone that returned after 5 days of perfusion along with BK-dependent relaxation. No significant inward remodeling or intimal hyperplasia was observed at day 8 after angioplasty. Thus, BA inhibits remodeling, which occurs after in vitro perfusion of conductance arteries.

Rapid, arteriovenous graft failure due to intimal hyperplasia: a porcine, bilateral, carotid arteriovenous graft model

BACKGROUND

The loss of patency constitutes the major complication of arteriovenous (AV) polytetrafluoroethylene hemodialysis grafts. In most cases, this graft failure is due to intimal hyperplasia at the venous outflow tract, including proliferation of vascular, smooth muscle cells and fibroblasts with deposition of extracellular matrix proteins. Thus far, procedures developed for improving patency have proven unsuccessful, which can be partly explained by the lack of relevant animal models. For this purpose, we developed a porcine model for AV graft failure that will allow the assessment of promising therapeutic strategies in the near future.

MATERIALS AND METHODS

In 14 pigs, AV grafts were created bilaterally between the carotid artery and the jugular vein using expanded polytetrafluoroethylene. Two, 4 or 8 weeks after AV shunting, the grafts and adjacent vessels were excised and underwent histologic analysis.

RESULTS

From 2 weeks onwards, a thick neo-intima developed at the venous anastomosis, predominantly consisting of alpha-actin-positive vascular smooth muscle cells (VSMC). Intimal area increased over time, coinciding with a decreased graft flow. Grafts remained patent for at least 4 weeks. At 8 weeks, patency rates declined to less than 50% due to thrombus formation superimposed on progressive neo-intima formation.

CONCLUSIONS

Implantation of an AV graft between the carotid artery and jugular vein in pigs causes a rapid neo-intimal response, accompanied by a loss of patency of 50% at 8 weeks after surgery. This model offers a suitable tool to study local interventions aimed at the improvement of AV graft patency rates.