Fibrillar pattern of self-assembled and cell-assembled collagen: resemblance and analogy.

The geometrical characteristics of fibrillar organizations are studied by electron microscopy in structures obtained in vitro in cell-free assembled collagen gels, and in vivo in dermal tracts of anuran skin. We analyze several characteristics of the fibrils including the diameter, the outline, the curvature and the extrafibrillar space. We analyze also the variation of fibrillar orientation (twist) in longitudinal and transverse thin sections of these structures. The results are compared in the Discussion to determine to what extent these fibrillar patterns are similar to liquid crystalline organizations and to what extent they result from a self-assembly or a cell-assembly process.