What are Preparation Artifacts?
Preparation artifacts refer to distortions or alterations in tissue samples that occur during the preparation process for histological examination. These artifacts can affect the interpretation of the tissue morphology and lead to misdiagnosis or erroneous conclusions.
Types of Preparation Artifacts
Fixation Artifacts
Fixation is a critical step that preserves tissue morphology and prevents autolysis. However, improper fixation can lead to artifacts such as shrinkage, swelling, and formalin pigment. For instance, if tissues are fixed in formalin for too long, it can cause a brown pigment known as
formalin pigment to form.
Dehydration Artifacts
During dehydration, tissues are passed through a series of alcohol solutions. Rapid dehydration or prolonged exposure to alcohol can lead to tissue shrinkage and hardening, making the tissues brittle and more prone to tearing during sectioning.
Embedding Artifacts
Embedding involves infiltrating tissues with a medium such as paraffin wax. Incomplete infiltration or overheating of the wax can cause tissue distortion and the formation of vacuoles or cracks within the tissue sections.
Sectioning Artifacts
Sectioning artifacts occur when tissues are cut into thin sections using a microtome. Common sectioning artifacts include knife marks, chatter (vibrations), and compression. These artifacts can obscure cellular details and make it difficult to interpret the tissue morphology accurately.
Staining Artifacts
Staining is essential for visualizing tissue structures under a microscope. However, uneven staining, overstaining, or understaining can lead to artifacts that obscure the true nature of the tissues. For example, overstaining with
hematoxylin and
eosin (H&E) can make it difficult to distinguish between different cellular components.
Proper Fixation: Use the appropriate fixative and fixation time for the tissue type. Ensure that tissues are adequately penetrated by the fixative.
Controlled Dehydration: Gradually dehydrate tissues using a graded series of alcohols to avoid rapid shrinkage or hardening.
Optimal Embedding: Ensure complete infiltration of embedding medium and avoid overheating the medium.
Careful Sectioning: Use a sharp microtome blade and adjust the cutting speed and angle to minimize sectioning artifacts.
Consistent Staining: Follow standardized staining protocols and use fresh reagents to ensure even and accurate staining.
Unnatural Tissue Morphology: Look for unusual shapes, sizes, or arrangements of cells and tissues that do not match normal histology.
Presence of Foreign Material: Identify any extraneous substances such as dust, fibers, or air bubbles that may have been introduced during preparation.
Irregular Staining Patterns: Note areas with uneven staining or unexpected color intensities that may indicate staining artifacts.
Conclusion
Preparation artifacts are a common challenge in histology that can impact the accuracy of tissue analysis. By understanding the causes and types of artifacts, and by implementing strategies to minimize them, histologists can improve the quality of tissue preparation and enhance the reliability of histological examinations. Recognizing and addressing these artifacts is essential for accurate diagnosis and research outcomes.
