What is an Artifact in Histology?
An artifact in histology refers to any artificial alteration or distortion introduced into a tissue sample during the various stages of preparation, examination, and analysis. These artifacts can arise from chemical, mechanical, or procedural factors, and can lead to misinterpretation of the tissue's actual histological features.
Common Sources of Artifacts
Artifacts can originate from multiple sources during the histological process: Fixation: Improper fixation can cause shrinkage, swelling, or hardening of tissues.
Processing: Inadequate dehydration or clearing can result in incomplete infiltration of embedding media.
Sectioning: Uneven cutting or dull microtome blades can cause chatter or compression artifacts.
Staining: Inconsistent staining can obscure true tissue architecture.
Mounting: Air bubbles or improper mounting media can distort the view under the microscope.
How Do Fixation Artifacts Occur?
Fixation is critical for preserving tissue morphology. However, artifacts can occur if the fixation process is not done correctly. For example, using an inappropriate fixative, such as formalin, can lead to tissue shrinkage or hardening. Over-fixation can make tissues too rigid to cut, whereas under-fixation can result in autolysis and degradation.
What Are Processing Artifacts?
During tissue processing, samples undergo dehydration, clearing, and infiltration with embedding media. Incomplete dehydration can leave residual water in the tissue, which can interfere with clearing agents and embedding media, leading to poor section quality. Similarly, incomplete clearing can prevent proper infiltration of paraffin, causing uneven sections.
How Are Sectioning Artifacts Introduced?
Sectioning artifacts are often produced by the microtome. If the microtome blade is not sharp, it can cause compression artifacts, where the tissue appears squashed. Chatter artifacts, which manifest as a series of regular, parallel lines, can result from vibrations during cutting or from an improperly adjusted microtome.
What Are Staining Artifacts?
Staining is essential to differentiate various cellular components. However, inconsistent or improper staining can introduce artifacts. For example, overstaining can obscure cellular details, while understaining can make structures indistinguishable. Variations in pH and staining times can also affect the outcome, leading to non-specific staining.
How Do Mounting Artifacts Affect Analysis?
After staining, sections are mounted on slides for microscopic examination. Mounting artifacts such as air bubbles, dust, or contaminants can interfere with the visualization of the tissue. Using the wrong mounting medium can also cause the tissue to appear distorted or can affect the refractive index.
Ensure proper
fixation by using appropriate fixatives and following recommended protocols.
Optimize tissue
processing conditions to ensure complete dehydration, clearing, and infiltration.
Use sharp microtome blades and properly adjust the microtome to avoid sectioning artifacts.
Standardize
staining procedures to achieve consistent results.
Carefully mount sections to avoid air bubbles and contaminants.
Conclusion
Artifacts in histology can significantly impact the interpretation of tissue samples. Understanding their sources and implementing best practices can help minimize these artifacts, ensuring accurate and reliable histological analysis. By paying close attention to each stage of the histological process, from fixation to mounting, it is possible to reduce the introduction of artifacts and enhance the quality of microscopic examinations.
