ENGINEERED ALIGNMENT IN MEDIA EQUIVALENTS - MAGNETIC PREALIGNMENT ANDMANDREL COMPACTION

We predicted and measured the evolution of smooth muscle cell (SMC) or ientation in media-equivalents (MEs) for four fabrication conditions ( F-, M-, F+, M+) under Free or Mandrel compaction (F/M) with and withou t magnetic prealignment of the collagen fibrils in the circumferential direction (+/-). Mandrel compaction refers to SMC-induced compaction of the ME that is constrained by having a nonadhesive mandrel placed i n the ME lumen. Predictions were made using our anisotropic biphasic t heory (ABT) for tissue-equivalent mechanics. Successful prediction of trends of the SMC orientation data for all four fabrication cases was obtained: maintenance of the initial isotropic state for F-, loss of i nitial circumferential alignment for F+, development of circumferentia l alignment for M-, and enhancement of initial circumferential alignme nt for M+. These results suggest two mechanisms by which the presence of the mandrel leads to much greater mechanical stiffness in the circu mferential direction reported for mandrel compacted MEs relative to fr ee compacted MEs : (I) by inducing an increasing circumferential align ment of the SMC and collagen, and (2) by inducing a large sb ess on th e SMC, resulting in secretion and accumulation of stiffening component s.