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

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.

Elastin-like recombinamers in collagen-based tubular gels improve cell-mediated remodeling and viscoelastic properties

“…The cell metabolic activity was monitored along the two weeks of experiment to first confirm their viability and to evaluate their proliferation. The metabolic function was expressed in relation to the condition of 0% ELR at Day 1, since pure collagen gel has an inherent biocompatibility (51), which has previously been reported for the reconstituted collagen used in this work (52). Results ( Figure 3A) showed no significant difference in the cell metabolic function among all conditions within each time point.…”

Injectable Scaffolds Enriched with Silver to Inhibit Bacterial Invasion in Tissue Regeneration

“…Nevertheless, we think that according to previous results on alginate, largely studied as drug delivery system and/or as cell carrier and recently also for gene immobilization, it is able to provide a sustained release of Ag, as it gradually degrades for several months [13]. This is also valid for collagen according to our previous works that proposed its use in different applications [24,41,42].…”

Biomaterials for Sequestration of Growth Factors and Modulation of Cell Behavior

“…As an additional advantage, heparin also increased the hemocompatibility of the gels, improving their eventual usefulness for endothelialization in vascular bypass grafts. [99] Alternatively, heparin can be covalently crosslinked into the gel network, leading to a more stable incorporation. For example, N-3-dimethylaminopropyl-N′-ethylcarbodiimide (EDC) and NHS chemistry have been used to graft N-(3-aminopropyl) methacrylamide (NAPMAAm) onto heparin, to allow free radical polymerization along with PEG diacrylate (PEGDA).…”

“…As an additional advantage, heparin also increased the hemocompatibility of the gels, improving their eventual usefulness for endothelialization in vascular bypass grafts. [ 99 ]…”