BIASED CELL-MIGRATION OF FIBROBLASTS EXHIBITING CONTACT GUIDANCE IN ORIENTED COLLAGEN GELS

We present here the first quantitative correlation for cell contact gu idance in an oriented fibrillar network in terms of biased cell migrat ion. The correlation is between the anisotropic cell diffusion paramet er, D(A) = D(x)/D(y) and the collagen gel birefringence, DELTAn, a mea sure of axially biased collagen fibril orientation in the x-direction. The cell diffusion coefficients, D(x) and D(y), measure the dispersal of cells in the directions coincident with and normal to the axis of fibril orientation, respectively. Three essential methodological compo nents are involved: (i) exploiting the orienting effect of a magnetic field on collagen fibrils during fibrillogenesis to systematically pre pare uniform axially oriented collagen gels; (ii) using a microscope/i mage analysis workstation with precise, computer-controlled rotating a nd translating stages to automate birefringence measurement and, along with rapid ''coarse optical sectioning'' via digital image processing , to enable 3-D cell tracking of many cells in multiple samples simult aneously; and (iii) employing a rigorous statistical analysis of the c ell tracks to estimate the magnitude and precision of the direction-de pendent cell diffusion coefficients, D(x) and D(y), that define D(A). We find that this measure of biased migration in contact guidance (D(A )) increases with increasing collagen fibril orientation (DELTAn) due mainly to a rapid enhancement of migration along the axis of fibril or ientation at low levels of fibril orientation, and to a continued supp ression of migration normal to the axis of fibril orientation at high levels of fibril orientation.