Routine Histology Services
Routine histology services and special histology services play a critical role in tissue-based research or diagnosis. Staining is the core of both types of services, employing different methods. By coloring otherwise transparent tissue sections, staining allows pathologists and researchers to view tissue morphology (structure) or to look for the presence or prevalence of particular cell types, structures or even micro-organisms such as bacteria.
The term “routine staining” refers to the hematoxylin and eosin stain (H&E) that is used “routinely” with all tissue specimens to reveal the underlying tissue structures and conditions. The term “special stains” is used to refer to alternative staining techniques outside of H&E routine staining to provide specific information researchers or pathologists need.
Routine histology services cover the procedures from wet tissues to formalin fixed paraffin embedded (FFPE) sections and histochemical staining (H&E) staining. These services generally include:
- Tissue trimming
- Tissue processing
- Tissue embedding in paraffin blocks
- Sectioning your paraffin-embedded tissues
- Mounting sections on positively charged slides or any other treated slides of your choice
- Routine Hematoxylin/Eosin (H&E) stain or other special staining.
- As per customer’s request, we can deliver unstained slides, stained slides or isolated DNA/RNA/Protein from FFPE samples or staining images.
Frequently Asked Questions (FAQ)
FAQ 1. How do I prepare the tissue samples for tissue processing?
- The usual fixative for paraffin embedded tissues is neutral buffered formalin (NBF). This is equivalent to 4% fresh paraformaldehyde in a buffered solution
- Where the best possible morphology is required, animals should be anesthesized and subjected to cardiac perfusion with saline, followed by a 10% formalin flush. If biochemical studies need to be performed on the tissue, a 10% formalin flush should not be used as it may interfere with subsequent analysis.
- For routine stains where perfusion is not required, tissue is sectioned and drop-fixed in a 10% formalin solution. Fixative volume should be 20 times that of tissue on a weight per volume; use 2 ml of formalin per 100 mg of tissue.
- Due to the slow rate of diffusion of formalin (0.5 mm/hr), tissue should be sectioned into 3-5 mm slices before transferring into formalin. This will ensure the best possible preservation of tissue and offers rapid uniform penetration and fixation of tissue within 3 hours.Tissue should be fixed for a minimum 48 hours at room temperature.
- After 48 hours of fixation, move tissue into 70% ethanol for long term storage.
FAQ 2. What is Hematoxylin and Eosin (H&E) stain?
Hematoxylin and Eosin (H&E) stain is the most commonly used staining system. It is an important part of VitroVivo routine histology services. H&E contains two dyes haemotoxylin and eosin. Eosin is an acidic dye: it is negatively charged (general formula for acidic dyes is: Na+dye-). It stains basic (or acidophilic) structures red or pink. This is also sometimes termed ‘eosinophilic’. Thus the cytoplasm is stained pink by H&E staining.
Hematoxylin can be considered as a basic dye (general formula for basic dyes is:dye+ Cl-). Hematoxylin is actually a dye called hematein (obtained from the log-wood tree) used in combination with aluminium ions (Al3+). It is used to stain acidic (or basophilic) structures a purplish blue. (Hematoxylin is not strictly a basic dye, but it is used with a ‘mordant’ that makes this stain act as a basic dye. The mordant (aluminium salts) binds to the tissue, and then hematoxylin binds to the mordant, forming a tissue-mordant-hematoxylin linkage.) Thus the nucleus is stained purple by H&E staining.
This means that the nucleus, and parts of the cytoplasm that contain RNA stain up in one color (purple), and the rest of the cytoplasm stains up a different color (pink)