Collagen fibrillar networks as skeletal frameworks. A demonstration by cell-maceration/scanning electron microscope method.

TLDR

Collagen fibrillar networks provide structural support and a microenvironment for cells, resisting stretch and varying by tissue type. The study uses a cell‑maceration/SEM method to demonstrate the arrangement of collagen fibrillar networks in various tissues. The method removes cellular elements by NaOH immersion and rinsing, exposing collagen fibrils that are then visualized by TEM and SEM. SEM imaging revealed a detailed three‑dimensional collagen fibril architecture, including myocyte‑sheathing fibrils that prevent cell slippage, helically arranged fibrils surrounding skeletal muscle and nerve fibers, microridge‑forming interwoven fibrils anchoring epithelial tissues, and heterogeneous pores in intestinal mucosa.

Abstract

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 3-7 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 observations of 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 meshwork 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.