[Efficacy and mechanism of local delivery of rapamycin and rapamycin-loaded poly(lactic-co-glycolic) acid nanoparticles on coronary restenosis of injury-stenosis model of minipigs]

Abstract

Objective: To determine whether intramural administration of rapamycin (RPM)-loaded polylactic-polyglycolic acid (PLGA) nanoparticles (NPs) can reduce intimal thickening and affect the mRNA expressions of matrix metalloproteinase (MMP)-2, tissue inhibitor of metalloproteinase (TIMP)-2 and p27(kipl) in a coronary injury-stenosis model of minipigs.

Methods: Twenty eight minipigs were randomly separated into four groups: saline group (n=7), blank PLGA NPs group (5.0 mg/ml)(n=7), RPM group (1.0 mg/ml)(n=7), and RPM-PLGA NPs(5.0 mg/ml)group (n=7), respectively. Different treatments were intracoronary locally delivered via a Dispatch™ catheter for 10 minutes. Serial angiography was performed pre-and post-modeling 30 days and the percent stenosis degree was assessed. Hematoxylin-Eosin (HE) staining, Weigert's resorcin fuchsin staining and picric acid-sirius red staining were used for morphometric analysis. Immunohistochemistry was performed to assess the levels of proliferating cell nuclear antigen (PCNA), MMP-2, and TIMP-2 at early and late time points, respectively. The expression of p27(kip1) mRNA was detected by in situ hybridization staining.

Results: Data from 21 minipigs had been collected at the end of the experiment with 6, 4, 5, and 6 from the former mentioned 4 groups, respectively. For the instant injury index, there was no significant difference among the four groups. The percent stenosis degree of RPM-PLGA NPs group was significantly lower than that of the other three groups respectively (all P< 0.05). The neointima area, net external elastic lamina area to external elastic laminal area ratio, and proliferative index of RPM-PLGA NPs group were significantly less than those of the other three groups, with all the P values less than 0.05. The mean value of integral optical density of p27(kip1)mRNA expression of RPM-PLGA group was 0.35 ± 0.06, higher than that of blank PLGA NPs group (0.12 ± 0.05, P< 0.01), saline group (0.16 ± 0.03, P< 0.05), and RPM group (0.15 ± 0.03, P< 0.05), respectively. The MMP-2/TIMP-2 ratio and the positive expression index of PCNA in RPM-PLGA group were lower than that of the other groups (P< 0.05).

Conclusions: Locally delivered rapamycin-loaded PLGA NPs significantly reduces MMP-2/TIMP-2 ratio and PCNA expression, increases p27(kip1) mRNA expression and significantly relieves percent stenosis degree and shows excellent acute procedural results in the minipig interventional coronary artery oversized balloon injury model. The results from minipig model further support that this approach could be a potential clinical procedure for vascular proliferative disease.