Three-dimensional microchannels in biodegradable polymeric films for control orientation and phenotype of vascular smooth muscle cells

The poor mechanical strength and vasoactivity of current small-diameter tissue engineered blood vessels (TEBVs) remain unsolved problems. Given the plasticity of smooth muscle cells (SMCs), 1 of the main limitations of current scaffolding techniques is the difficulty in controlling SMC phenotype shifts in vitro. A synthetic phenotype allows the cells to rapidly proliferate and produce extracellular matrix (ECM), whereas a shift to contractile phenotype with organized ECM ultimately provides a functional blood vessel. In this study, 3D deep (65 μm) and wide microchannels separated by high-aspect ratio (8) microwalls were successfully ultraviolet (UV) microembossed using a liquid UV polymerizable biodegradable macromer (poly(ε-caprolactone-r-L-lactide-r- glycolide) diacrylate) and the in vitro guidance effects of varying channel width (40-160 μm) on SMCs were verified. The results show that SMCs cultured in the wider microchannels (80-160 μm wide) switch from fibroblast morphology and random orientation to spindle-shaped morphology, and align along the direction of the microchannel nearing confluence achieved with similar cell density to unpatterned film. Further, an enhanced expression of smooth muscle α-actin of SMCs grown on micropatterns was found nearing confluence, which demonstrates a phenotype shift to a more contractile phenotype. These films are flexible and can be folded into tubular and lamellar structures for tissue engineering of small-diameter TEBVs as well as other organs such as esophagus or intestine. These results suggest that these micropatterned synthetic biodegradable scaffolds may be useful for guiding SMCs to grow into functional, small-diameter vascular grafts.