The effect of alpha lipoic acid in a porcine in-stent restenosis model

Combating Ischemia-Reperfusion Injury with Micronutrients and Natural Compounds during Solid Organ Transplantation: Data of Clinical Trials and Lessons of Preclinical Findings

Although extended donor criteria grafts bear a higher risk of complications such as graft dysfunction, the exceeding demand requires to extent the pool of potential donors. The risk of complications is highly associated with ischemia-reperfusion injury, a condition characterized by high loads of oxidative stress exceeding antioxidative defense mechanisms. The antioxidative properties, along with other beneficial effects like anti-inflammatory, antiapoptotic or antiarrhythmic effects of several micronutrients and natural compounds, have recently emerged increasing research interest resulting in various preclinical and clinical studies. Preclinical studies reported about ameliorated oxidative stress and inflammatory status, resulting in improved graft survival. Although the majority of clinical studies confirmed these results, reporting about improved recovery and superior organ function, others failed to do so. Yet, only a limited number of micronutrients and natural compounds have been investigated in a (large) clinical trial. Despite some ambiguous clinical results and modest clinical data availability, the vast majority of convincing animal and in vitro data, along with low cost and easy availability, encourage the conductance of future clinical trials. These should implement insights gained from animal data.

Development of Novel Drug-Eluting Stents for Acute Myocardial Infarction

Delayed arterial healing at culprit sites after drug-eluting stent (DES) placement for acute myocardial infarction (AMI) is associated with increased risk of late stent thrombosis. The Korea Acute Myocardial Infarction Registry was established in commemoration of the 50^th anniversary of Korea Circulation Society. Between November 2005 and December 2016, more than 62,000 patients were registered from 50 primary percutaneous coronary intervention (PCI) centers in Korea. DES in AMI may be safe and effective, however, there is concern about increased stent thrombosis after DES implantation in AMI patients, requiring longer-term dual anti-platelet therapy to reduce the risk of late stent thrombosis. Device innovation is needed to overcome issues such as stent thrombosis and restenosis by using new coating materials with biocompatible polymers, different coating methods using non-polymer techniques, bioabsorbable stents and pro-healing stents. In this review article, we describe the current usage of DES in AMI in Korea and introduce novel DES uses in development for patients with AMI. We have developed many types of DES in our research laboratory. Abciximab-coated stents inhibited platelet thrombi and restenosis. Furthermore, anti-oxidants (carvedilol, probucol and alpha-lipoic acid) were used for stent coating. Currently we are developing novel DESs using polymer-free and natural binding techniques, peptide coating stents, gene-and-drug delivery, bioabsorbable stents using 3D printing, endothelial progenitor cell capturing stents to promote reendothelialization and reduce stent thrombosis. New DESs in development may be safe and effective in preventing late stent thrombosis and restenosis in patients with AMI.

Sirolimus coating on heparinized stents prevents restenosis and thrombosis

The aim of this study was to evaluate the inhibitory effect of sirolimus coating on the occurrence of restenosis and thrombosis with heparinized stents. Heparin and dopamine were conjugated by chemical bonding and anchored on the stent surface by a mussel-inspired adhesion mechanism. Subsequently, sirolimus was coated with poly lactic-glycolic acid on the heparinized stent surface. The heparin was well attached to the surface, and the surface was smooth after sirolimus coating. The smoothness of the surface was maintained after expansion of the stent. The amount of sirolimus released from the stent was 67.3% ± 4.55% within 7 days, followed by continual release up to day 28. The proliferation of smooth muscle cells was successfully arrested (51.3% ± 2.25% at 7 days of culture) by sirolimus released from the stent. Platelet adhesion was clearly prevented in the heparin-coated group (78.0 ± 8.00/1.8 cm²) compared to that in the heparin noncoated group (5.0 ± 1.00/1.8 cm²). Animal studies showed that the heparin and sirolimus-coated stent group had no obvious inflammatory response and no change in the fibrin score compared to those in the other groups. However, restenosis clearly decreased in the heparin and sirolimus-coated group (12.3% ± 3.54%) compared to the bare-metal stent group (27.5% ± 8.52%) and the heparin-coated group (25.3% ± 11.79%). These results suggest that heparinized surface-based sirolimus coating may be a useful approach for the prevention of restenosis and stent thrombosis.

Effect of stents coated with a combination of sirolimus and alpha-lipoic acid in a porcine coronary restenosis model

The aim of this study was to evaluate antiproliferative sirolimus- and antioxidative alpha-lipoic acid (ALA)-eluting stents using biodegradable polymer [poly-L-lactic acid (PLA)] in a porcine coronary overstretch restenosis model. Forty coronary arteries of 20 pigs were randomized into four groups in which the coronary arteries had a bare metal stent (BMS, n = 10), ALA-eluting stent with PLA (AES, n = 10), sirolimus-eluting stent with PLA (SES, n = 10), or sirolimus- and ALA-eluting stent with PLA (SAS, n = 10). A histopathological analysis was performed 28 days after the stenting. The ALA and sirolimus released slowly over 30 days. There were no significant differences between groups in the injury or inflammation score; however, there were significant differences in the percent area of stenosis (56.2 ± 11.78% in BMS vs. 51.5 ± 12.20% in AES vs. 34.7 ± 7.23% in SES vs. 28.7 ± 7.30% in SAS, P < 0.0001) and fibrin score [1.0 (range 1.0-1.0) in BMS vs. 1.0 (range 1.0-1.0) in AES vs. 2.0 (range 2.0-2.0) in SES vs. 2.0 (range 2.0-2.0) in SAS, P < 0.0001] between the four groups. The percent area of stenosis based on micro-computed tomography corresponded with the restenosis rates based on histopathological stenosis in different proportions in the four groups (54.8 ± 7.88% in BMS vs. 50.4 ± 14.87% in AES vs. 34.5 ± 7.22% in SES vs. 28.9 ± 7.22% in SAS, P < 0.05). SAS showed a better neointimal inhibitory effect than BMS, AES, and SES at 1 month after stenting in a porcine coronary restenosis model. Therefore, SAS with PLA can be a useful drug combination for coronary stent coating to suppress neointimal hyperplasia.

A bumpy and winding but right path to domestic drug-eluting coronary stents

Restenosis and stent thrombosis remain major concerns after percutaneous coronary intervention for the treatment of coronary artery disease. The present review was undertaken in order to highlight the various coronary stents that have been investigated in our Heart Research Center, and how far we have come from the first heparin-coated stent first used in the late 1990s. Thereafter, from the abciximab-coated stent to the current gene-delivery stent and other newer agents, our group has applied a range of techniques in this field. However, in groups similar to ours, the restenosis rates of such stents are still high for second-generation drug-eluting stents (DESs). Moreover, our nation imports almost all of these types of stents from other countries. Thus, we need to develop domestic coronary stents. Research into newer DESs are warranted in Korea so as to achieve improved safety and efficacy outcomes.

Mechanical and Histopathological Comparison between Commercialized and Newly Designed Coronary Bare Metal Stents in a Porcine Coronary Restenosis Model

The aim of this study was to compare the stent designed by Chonnam National University Hospital (designated as CNUH) with commercial cobalt-chromium coronary stent in a porcine coronary overstretch restenosis model. CNUH stent was subjected to mechanical performance tests. Pigs were randomized into two groups in which the coronary arteries (10 pigs, 10 coronaries in each group) had either CNUH stent or control commercial bare metal stent. Histopathologic analysis was assessed at 28 days after stenting. In mechanical performance tests, CNUH stent showed 2.65N, 35.1N, 0.52N, 1.94%, 4.29% in the flat plate radial compression, radial force, 3 point bending, Foreshortening and recoil test, respectively. There was no significant difference in the injury score, internal elastic lamina (IEL), lumen area, neointima area, percent area stenosis, inflammation score and fibrin score between the two groups (1.2±0.35, 4.1±0.41 mm², 2.7±0.56 mm², 1.6±0.47 mm², 36.7±11.2%, 1.2±0.62, 0.2±0.34 in CNUH stent group vs. 1.2±0.38, 3.7±0.64 mm², 2.5±0.49 mm², 1.5±0.61 mm², 36.3±12.17%, 1.1±0.12, 0.4±0.46 in commercial stent group, respectively). In the mechanical performance test, CNUH stent showed the moderated performance under the guideline of FDA. CNUH stent demonstrated similar histological reactions compared with commercial cobalt-chromium stent in a porcine coronary overstretch restenosis model.

Impact of heterogeneous overlapping drug-eluting stents on the arterial responses of rabbit iliac arteries: a comparison with overlapping bare metal stents

Background and Objectives

Although the use of heterogeneous overlapping drug-eluting stents (DES) is not uncommon in clinical practice, whether the implantation sequences of heterogeneous DES will influence the endothelialization or arterial responses differently remains unclear.

Materials and Methods

Twenty-one rabbits were randomized to receive overlapping stents in the iliac artery for 3 months {distal sirolimus-eluting stent (SES, Cypher™)+proximal paclitaxel-eluting stent (PES, Taxus™) (C+T, n=7), distal Taxus+proximal Cypher (T+C, n=7) and bare metal stent (BMS)+BMS (B+B, n=7)}. Endothelial function was evaluated by the acetylcholine provocation test during follow-up angiography. Histopathological changes in proximal, overlapped, and distal stented segments were evaluated.

Results

Although the overall angiographic outcomes were comparable, late loss (mm) in the distal stented segment was higher in the B+B (0.39±0.07) and C+T (0.40±0.20) than that in the T+C (0.06±0.02) group (p<0.001). The incidence of acetylcholine-induced spasm was higher in the DES groups compared with BMS, regardless of the implantation sequences (85.7% in C+T vs. 14.3% in B+B vs. 71.4% in T+C, p=0.017). Notably, only the distal Cypher implantation group (C+T) had three cases of stent fracture. A histopathological analysis showed that despite similar arterial injury scores, Taxus and Cypher stents had higher inflammatory reactions at the overlapped and distal segments compared with those of BMS.

Conclusion

Despite similar arterial injury, higher inflammatory reactions were observed in overlapping DES segments regardless of the implantation sequence compared with that of BMS. Moreover, DES was associated with impaired endothelial function on the adjacent non-stented segments.

Chlamydia pneumoniae heat shock protein 60 is associated with apoptotic signaling pathway in human atheromatous plaques of coronary artery disease patients

BACKGROUND

Chlamydia pneumoniae heat shock protein (HSP) 60 is known to contribute to the activation of inflammation. In addition, there are contradictory reports on C. pneumoniae and their role in activation of pathways (apoptotic/antiapoptotic/necrosis) in coronary artery disease (CAD). Hence, more studies are required to know the actual role of C. pneumoniae in activation of apoptotic/antiapoptotic/necrosis pathways.

METHODS AND RESULTS

In this study, two sets of patient groups (cHSP60 positive and cHSP60 negative) were included and gene expression was studied by cDNA micro array and real time polymerase chain reaction arrays. Expression of Caspase-3, 8, 9, c-FLIP, PPAR-γ, PGC-1α, and Gsk-3b were also evaluated at protein level by immunoblotting. In cHSP60 positive CAD patients significantly higher (p<0.001) mRNA expression was found for CCL4, CXCL4, CXCL9, IL-8, CD40LG, CD8, TGFβ1, TGFβ2, APOE, EGR1, CTGF, APOB, LDLR, LPA, and LPL, whereas significantly lower (p<0.001) mRNA expression was detected for CD4, IL1F10, IFNA2, and IL-10 as compared to cHSP60 negative CAD patients. Additionally, at protein level expression of Caspase-3 (p=0.027), 8 (p=0.028), and 9 (p=0.037) were higher and c-FLIP (p=0.028) and PPAR-γ (p=0.95) expression were comparable in cHSP60 positive CAD patients compared to cHSP60 negative CAD patients.

CONCLUSION

Genes/proteins of pre-apoptotic caspase dependent/independent pathways, chemokines, and inflammatory cytokines receptors were significantly up-regulated in human atheromatous plaques of cHSP60 positive CAD patients suggesting an association of cHSP60 with CAD.

Effect of a dual drug-coated stent with abciximab and alpha-lipoic Acid in a porcine coronary restenosis model

Background and Objectives

The aim of this study was to examine the anti-proliferative and anti-inflammatory effects of a stent coated with abciximab and alpha-lipoic acid (ALA) in a porcine coronary overstretch restenosis model.

Materials and Methods

A total of 10 pigs were randomized into two groups (10 pigs, 10 coronaries in each group) in which the coronary arteries were stented with a dual-coated stent and a bare metal stent (control) by randomization. Stents were deployed with oversizing (stent/artery ratio 1.3 : 1) in the porcine coronary arteries, and histopathology was assessed 28 days after stenting.

Results

There was no significant difference in the injury score between the two groups. In the neointima, the lymphohistiocyte count was significantly lower in dual-coat stent group compared with the control stent group (120±85 cells vs. 159±80 cells, p=0.048). There was no significant difference in the fibrin score between the two groups (0.16±0.34 in the dual-coated stent group vs. 0.25±0.48 in the control stent group, p=0.446). The neointima area was not significantly different between both groups (1.55±0.8 mm² in dual-coated stent group vs. 1.40±0.86 mm² in the control stent group, p=0.447).

Conclusion

Although the dual-coated stent with abciximab and ALA showed no significant difference in inhibition of neointimal hyperplasia when compared with the bare metal stent, it was associated with a reduced inflammatory reaction when compared with the control stent in a porcine coronary restenosis model.