Cell orientation influences the biaxial mechanical properties of fibroblast populated collagen vessels

Bioartificial tissues, composed of cells in a collagen matrix, can be fabricated with preferred cell orientations to mimic the histologic arrangement of biologic tissues. The influence of preferred cell orientations on the biaxial mechanical behavior of bioartificial tissues is unknown. Characterizing the biaxial mechanical behavior is necessary for better predicting the in vivo behavior of bioartificial tissues. Fibroblast populated collagen vessels (FPCVs) were fabricated with two different cell orientations by controlling the mechanical constraints during incubation. The cell orientation was verified by confocal microscopy and the collagen fiber organization was examined by confocal reflection and scanning electron microscopy (SEM). Pressure-diameter, force-length tests were performed to determine the influence of cell orientation on the biaxial mechanical behavior. FPCVs were more extensible in the direction perpendicular to the preferred cell orientation, than in the direction parallel to the cell orientation. Biaxial tests were also performed in the presence of Cytochalasin D (Cyto D) to minimize the mechanical contribution of the cells. After Cyto D treatment, the FPCVs remained more extensible in the direction perpendicular to the cell orientation, even though a preferred collagen fiber orientation was not observed in the microscopy images.