Optical Microscopy and Electron Microscopy for the Morphological Evaluation of Tendons: A Mini Review

Abstract

The morphological characteristics of tendons have been thoroughly evaluated via microscopy. Optical microscopy and electron microscopy are the most commonly used techniques for tendon tissue observation. According to the principles of both microscopy types, preparation and evaluation methods vary. Simple optical microscopy is commonly used in the observation of cells and extracellular matrix, and many stains, including hematoxylin-eosin, Van Gieson, Prussian blue, Alcian blue, and toluidine blue, are used for evaluating cells, collagen fiber arrangement, and noncollagenous proteins. Histological scoring systems have been used in many studies for semi-quantification. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) are the most commonly used electron microscopy types, and special consideration is needed for the fixation and embedding protocols. Glutaraldehyde followed by osmium is most commonly used in the chemical fixation of tendon tissue, followed by epoxy resin embedment. Longitudinal sections captured in SEM images show the arrangement of collagen fibrils and the cells and lipid drops among them, while cross sections captured in TEM images show the diameter and distribution of collagen fibrils. SEM and TEM are used together for comprehensive evaluations. This mini review is focused on the preparation methodology and related evaluation indexes for the morphological evaluation of tendons.

Effects and Mechanism of Particulate Matter on Tendon Healing Based on Integrated Analysis of DNA Methylation and RNA Sequencing Data in a Rat Model

“…Since cross-sections show the diameter and distribution of collagen fibrils, TEM analysis is a useful method for evaluating the tendon ultrastructure [ 16 ]. Here, a TEM analysis revealed the decreased mean diameter of collagen fibrils in the PM group.…”

“…To our knowledge, this is the first study to investigate the effects of PM exposure on tendon healing. Our multi-pronged histological [ 15 ], ultrastructure morphological [ 16 ], and biomechanical [ 17 ] approaches using well-established methods successfully revealed the effects of PM in an ATR rat model. The use of PM2.5, which is capable of reaching the end of the respiratory tract with airflow, and an analysis of PM circulation in the chamber using a computer simulation further improved the methodology.…”

“…We hypothesized that PM exposure may substantially influence tendon healing. Here, we performed multi-pronged histological [ 15 ], ultrastructure morphological [ 16 ], and biomechanical [ 17 ] investigations using well-established methods to reveal the effects of PM in an ATR rat model. Additionally, we performed the combined analysis of DNA methylation and RNA sequencing (RNA-seq) data to elucidate the mechanism underlying the PM-induced effects on tendon healing.…”

Sample Preparation of Atherosclerotic Plaque for SAXS/WAXS Experimentation

“…Epoxy resin embedding is often used with glutaraldehyde fixation for use in electron microscopy . A protocol was devised to embed and section large plaque samples in epoxy resin (Merck U.K.).…”

“…Epoxy resin embedding is often used with glutaraldehyde fixation for use in electron microscopy. 22 A protocol was devised to embed and section large plaque samples in epoxy resin (Merck U.K.). Samples were then sectioned to 100 μm using an IsoMet Precision Cutter (Buehler, Coventry U.K.).…”