Endothelialization of Sacrificial Polymer-Derived Vascular Channels: Advancement towards the Creation of Surgically Relevant Tissue Replacements

Background: Attempts to fabricate clinically translatable bioengineered tissues have been encumbered by an inability to fabricate constructs containing inflow and outflow macrochannels that are in continuity with a microchannel network. We have developed an innovative technique whereby sacrificial polymers are embedded within a polymer construct of opposite polarity, and then dissolved, resulting in an internal channel network. The objective of this initial study was to create a biodegradable construct that contained an endothelialized channel.

Methods: 4% alginate solution (polar-soluble) in syringes were mixed with 2% w/v calcium sulfate in 2:1 ratio via 4-way stopcock and injected into custom-designed molds pierced with 2 mm diameter fibers of poly-lactic acid (PLA; non-polar-soluble). After one hour, calcium chloride solution was poured into the molds. Once removed from molds, PLA was sacrificed by flushing the constructs with chloroform (non-polar solvent), leaving a patent longitudinal 2 mm channel that was subsequently coated with RGD peptide to increase cellular adhesiveness. Both ends of the channel were cannulated, injected with media containing 10⁵ cells/ml fluorescently-labeled HUVECs, and clamped. The construct was rotated for 4h to optimize circumferential cell deposition within the channel, after which time media was changed daily until the constructs were imaged with fluorescent microscopy. At the same time of seeding, alginate films (RGD-modified and unmodified) were also seeded as controls.

Results: The resultant construct contained a patent internal channel lined by endothelial cells, and its structural integrity was unaffected by the dissolution process. The endothelium was viable; the lumen was patent for the duration of the study (a total of 5 days). The alginate films confirmed our findings further with cell proliferation on RGD-modified films and no cell adhesion on unmodified films.

Conclusion: Our novel technique results in the fabrication of biodegradable hydrogel constructs that contain endothelialized channels. This process is simple, inexpensive, and easily customized to fabricate three-dimensional channel-containing constructs of any scale and design. This technique represents a significant advancement in the creation of engineered replacement tissues.