Secreted Matrix Metalloproteinase-9 of Proliferating Smooth Muscle Cells as a Trigger for Drug Release from Stent Surface Polymers in Coronary Arteries

Abstract

Cardiovascular diseases are the leading causes of death in industrialized countries. Atherosclerotic coronary arteries are commonly treated with percutaneous transluminal coronary intervention followed by stent deployment. This treatment has significantly improved the clinical outcome. However, triggered vascular smooth muscle cell (SMC) proliferation leads to in-stent restenosis in bare metal stents. In addition, stent thrombosis is a severe side effect of drug eluting stents due to inhibition of endothelialization. The aim of this study was to develop and test a stent surface polymer, where cytotoxic drugs are covalently conjugated to the surface and released by proteases selectively secreted by proliferating smooth muscle cells. Resting and proliferating human coronary artery smooth muscle cells (HCASMC) and endothelial cells (HCAEC) were screened to identify an enzyme exclusively released by proliferating HCASMC. Expression analyses and enzyme activity assays verified selective and exclusive activity of the matrix metalloproteinase-9 (MMP-9) in proliferating HCASMC. The principle of drug release exclusively triggered by proliferating HCASMC was tested using the biodegradable stent surface polymer poly-l-lactic acid (PLLA) and the MMP-9 cleavable peptide linkers named SRL and AVR. The specific peptide cleavage by MMP-9 was verified by attachment of the model compound fluorescein. Fluorescein release was observed in the presence of MMP-9 secreting HCASMC but not of proliferating HCAEC. Our findings suggest that cytotoxic drug conjugated polymers can be designed to selectively release the attached compound triggered by MMP-9 secreting smooth muscle cells. This novel concept may be beneficial for stent endothelialization thereby reducing the risk of restenosis and thrombosis.

Design, Synthesis, and Characterization of a Paclitaxel Formulation Activated by Extracellular MMP9

“…36 However, we chose this molecule due to its high lipophilicity and the possibility to form an amphiphilic prodrug, when linking to a hydrophilic moiety. The particular peptide (NH 2 -Ahx-SRLSLPGC-COOH) used in the synthesis of PH8 was previously investigated for MMP9 triggered release of paclitaxel from stent surfaces by Gliesche et al 37 and from polymersomes by Porta et al 38 The cleavage of this peptide by MMP9 was verified in a cell-free assay and reflected the herein measured MMP9 content in the supernatant of cultured LN-18, U87 MG, and A549 cells. Inhibition of the enzymatic activity by addition of the MMP9 inhibitor revealed the contribution of MMP9 to the release.…”

Synthesis and Characterization of PDMS–PMOXA-Based Polymersomes Sensitive to MMP-9 for Application in Breast Cancer

“…However, comparing the applicability of the above-mentioned peptides (AVR and SRL) in primary human coronary artery muscle cells, we observed that in this cellular system, where only MMP-9 activity was detected, the SRL-peptide was much more likely cleaved, releasing paclitaxel from a modified surface, than if the AVR peptide was used as the linker. Our finding suggested that there is a higher affinity of MMP-9 toward the SRL-peptide …”

“…toward the SRL-peptide. 51 In general, the diameter of rigid spherical polymersomes should be between 120 and 200 nm to prevent clearance in capillary beds or lymph nodes, splenic filtration, and entrapment in the space of Disse and hepatic parenchyma. 52 Assessing the hydrodynamic diameter of the unloaded polymersomes suggested no significant change in the average 48 However, the size distribution was significantly changed after loading with paclitaxel, and the surface crosslinking of loaded polymersomes even resulted in a loss of the Gaussian distribution, as determined by DLS.…”

Spun Biotextiles in Tissue Engineering and Biomolecules Delivery Systems

“…This fibrous system was designed for potential applications in coronary stents [122]. Drug loaded PLLA has also been conjugated with the two ends of the matrix metalloproteinase-9 (MMP-9) for a selective drug release, beneficial for stent endothelialization, thereby decreasing the risk of restenosis and thrombosis [123]. Tyrosine kinase inhibitor (ST638) was encapsulated onto prototype Igaki-Tamai stents and implanted in porcine coronary arteries.…”