Heparin-Modified Collagen Gels for Controlled Release of Pleiotrophin: Potential for Vascular Applications.

Francesco Copes,Caroline Loy,Pascale Chevallier,Daniele Pezzoli,Francesca Boccafoschi,Diego Mantovani

doi:10.3389/fbioe.2019.00074

Francesco Copes, Caroline Loy + Show 4 more

Open Access

https://doi.org/10.3389/fbioe.2019.00074

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Abstract

A fast re-endothelialization, along with the inhibition of neointima hyperplasia, are crucial to reduce the failure of vascular bypass grafts. Implants modifications with molecules capable of speeding up the re-endothelialization process have been proposed over the last years. However, clinical trials of angiogenic factor delivery have been mostly disappointing, underscoring the need to investigate a wider array of angiogenic factors. In this work, a drug release system based on a type I collagen hydrogel has been proposed for the controlled release of Pleiotrophin (PTN), a cytokine known for its pro-angiogenetic effects. Heparin, in virtue of its ability to sequester, protect and release growth factors, has been used to better control the release of PTN. Performances of the PTN drug delivery system on endothelial (ECs) and smooth muscle cells (SMCs) have been investigated. Structural characterization (mechanical tests and immunofluorescent analyses of the collagen fibers) was performed on the gels to assess if heparin caused changes in their mechanical behavior. The release of PTN from the different gel formulations has been analyzed using a PTN-specific ELISA assay. Cell viability was evaluated with the Alamar Blue Cell Viability Assay on cells directly seeded on the gels (direct test) and on cells incubated with supernatant, containing the released PTN, obtained from the gels (indirect test). The effects of the different gels on the migration of both ECs and SMCs have been evaluated using a Transwell migration assay. Hemocompatibility of the gel has been assessed with a clotting/hemolysis test. Structural analyses showed that heparin did not change the structural behavior of the collagen gels. ELISA quantification demonstrated that heparin induced a constant release of PTN over time compared to other conditions. Both direct and indirect viability assays showed an increase in ECs viability while no effects were noted on SMCs. Cell migration results evidenced that the heparin/PTN-modified gels significantly increased ECs migration and decreased the SMCs one. Finally, heparin significantly increased the hemocompatibility of the collagen gels. In conclusion, the PTN-heparin-modified collagen here proposed can represent an added value for vascular medicine, able to ameliorate the biological performance, and integration of vascular grafts.

Highlights

Every year is estimated that around 17.9 million of people die of cardiovascular diseases, mainly heart attacks and strokes, making them the first cause of death in the world (WHO1)
The stress/relaxation unconfined compression tests were performed on CTRL gels and on the modified gels to evaluate if the addition of heparin or PTN to the gel mix caused any changes in the mechanical properties of the gels
The equilibrium elastic modulus of the four gels composition has been analyzed: no significant differences in the equilibrium elastic modulus of the gel compositions were detected (Figure 1A)

Summary

Introduction

Every year is estimated that around 17.9 million of people die of cardiovascular diseases, mainly heart attacks and strokes, making them the first cause of death in the world (WHO1). Most of the time the root of these diseases can be found in atherosclerosis, a progressive pathology in which a plaque made of lipids, cholesterol, foamy cells, cellular debris, and calcium builds up in the walls of the arteries (Association). Most of the time the root of these diseases can be found in atherosclerosis, a progressive pathology in which a plaque made of lipids, cholesterol, foamy cells, cellular debris, and calcium builds up in the walls of the arteries (Association2) Overtime, this plaque hardens and narrows the lumen of the affected artery, reducing the blood flow and leading to the aforementioned conditions. The gold standard is the use of autologous vessels, such as saphenous vein, internal mammary arteries, and radial artery (MartínezGonzález et al, 2017) These options are not always available because of patients’ condition. Clinical trials of proendothelialization enrichment of vascular grafts have been mostly unsatisfactory, the need to investigate new approaches (Springer, 2006) for this application

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