Effects of fibinolysis on neurite growth from dorsal root ganglia cultured in two- and three-dimensional fibrin gels

The mechanism of neurite penetration of three-dimensional fibrin matrices was investigated by culturing embryonic chick dorsal root ganglia (DRGs) within fibrin gels, upon fibrin gels, and upon laminin. The length of neurites within three-dimensional matrices of fibrin was decreased in a concentration-dependent manner by agents that inhibited plasmin, e.g. aprotinin, or that inhibited plasminogen activation, e.g., epsilon-aminocaproic acid (EACA), or plasminogen antiserum. In contrast, such agents increased the length of neurites growing out from DRGs cultured upon two-dimensional substrates of fibrin and had no effect on the length of neurites growing out from DRGs cultured upon laminin. Visualization of neurites within three-dimensional fibrin matrices demonstrated that the distance between fibrin strands was much smaller than the diameter of neurites. All these data were consistent with the hypothesis that fibrinolysis localized to the region of the neurite tip is an important mechanism for neurite penetration of a physical barrier of fibrin strands arranged in a three-dimensional matrix.