Dynamic Culturing of Smooth Muscle Cells in Tubular Poly(Trimethylene Carbonate) Scaffolds for Vascular Tissue Engineering

Porous, tubular, flexible, and elastic poly(trimethylene carbonate) (PTMC) scaffolds (length 8 cm and inner diameter 3mm) for vascular tissue engineering were prepared by means of a dip-coating and particulate leaching procedure. Using NaCl as porogen, scaffolds with an average pore size of 110 mm and a porosity of 85% were obtained. Before leaching the salt, the structures were made creep-resistant by means of crosslinking at 25 kGy gammairradiation. To increase the efficiency of cell seeding, the scaffolds were provided with a microporous outer layer of 0.2mm with an average pore size of 28 mm and a porosity of 65% (total wall thickness 1 mm). Human smooth muscle cells (SMCs) were seeded in these scaffolds with an efficiency of 43%, as determined after 24 h cell adhesion. SMCs were cultured in the scaffolds up to 14 days under stationary conditions or under pulsatile flow conditions in a bioreactor (pressure 70-130 mmHg, 69 pulsations/min, and average wall shear rate 320 s(-1)). Although SMCs proliferated under both conditions, cell numbers were three to five times higher in case of dynamic culturing. This was qualitatively confirmed by means of histology. Also, in terms of mechanical properties, the dynamically cultured constructs performed better than the statically cultured constructs. After culturing for 14 days, the maximum tensile strengths of the constructs, determined in the radial direction, had increased from 0.16 MPa (unseeded scaffold) to 0.48MPa (dynamic culturing) and 0.38 MPa (static culturing). The results of this study indicate that a potentially useful medial layer for tissue-engineered vascular grafts can be prepared by dynamic culturing of human SMCs seeded in porous tubular poly(trimethylene carbonate) scaffolds.