Collagen Fibrillar Networks as Skeletal Frameworks: A Demonstration by Cell-Maceration/Scanning Electron Microscope Method

A cell-maceration/scanning electron microscope (SEM) method was employed to demonstrate the arrangement of the collagen fibrillar network of various tissues. Immersion of fixed tissues in NaOH (25°C) for 37 days, followed by rinsing in distilled water successfully removed the cellular elements, exposing collagen fibrils which were identified as such by transmission electron microscopy in their natural locations. SEM observationsof the preparations are able to demonstrate the three-dimensional architecture of collagen fibrils much more precisely than other methods, including the silver impregnation method. Collagen fibrils, forming sheaths for housing individual cardiac myocytes, fused together, thus ensuring an equal stretch of contiguous myocytes and preventing the slippage of adjacent cells. Individual skeletal muscle fibers and nerve fibers were ensheathed by the mesh-work of collagen fibrils running in two opposite helices. Such structures seem to play an important role in resisting the stretching impetus. At the epithelial-connective tissue junction of the tongue and fingertip skin, interwoven collagen fibrils formed numerous microridges which probably provide a broad anchorage for the epithelium. In the intestinal mucosa, the collagen fibrillar network immediately below the basal laminae of the villous epithelium possessed heterogeneous pores. As the collagen fibrillar network shows morphological features specific to individual organs and tissues, it is suggested that such formations not only constitute the skeletal framework but also provide those cells which are housed there with a microenvironment suitable for their activities.