In the histopathological evaluation of kidney tissue, not only the morphology of the cells but also the structure of the basal membranes surrounding the glomeruli and tubules provides important information. In particular, revealing changes in the thickness, continuity, and contour of the glomerular basal membrane in renal biopsies is a crucial component of light microscopic evaluation.
While hematoxylin and eosin (H&E) provide basic information about general tissue architecture and cellular morphology, specialized histochemical stains are used in renal histopathology to highlight certain structural details. PAS, trichrome, and silver-based methods are among the main stains used for this purpose.
From these methods Periodic Acid–Silver Methenamine (PASM), commonly Jones methenamine silver or briefly Jones paint It is known as and is used especially in the detailed representation of basal membranes.
The basic principle of PASM/Jones staining
The PASM/Jones method is a histochemical reaction based on the oxidation of certain carbohydrate-containing tissue components with periodic acid, followed by the reduction of silver ions.
In the first stage, periodic acid oxidizes the appropriate carbohydrate groups in the tissue, leading to the formation of aldehyde groups. Subsequently, when the section reacts with a silver-methenamine-containing solution, silver ions are reduced in these regions, resulting in the deposition of metallic silver.
As a result, basal membranes and some other reacting structures are visible under the microscope. between dark brown and black It becomes apparent.
This high contrast facilitates the examination of glomerular capillary walls and basal membrane contours in particular.
Why is it important in renal histopathology?
The glomeruli of the kidney are highly specialized structures responsible for blood filtration. One of the key components of the glomerular filtration barrier is... glomerular basement membrane (GBM).
In various renal diseases, changes can occur in the structure of the glomerular basement membrane. The basement membrane may thicken, become irregular, be damaged segmentally, or different morphological patterns may appear along the capillary wall.
PASM/Jones staining reveals basal membranes with strong contrast, which helps in evaluating these changes under light microscopy.
Therefore, this method is particularly important in the histopathological evaluation of renal biopsies.
What structures does Jones paint represent?
PASM/Jones staining specifically:
- glomerular basement membranes,
- tubular basement membranes,
- Bowman capsule,
- some vascular basement membranes,
- specific components of the mesangial matrix
It can make it more noticeable.
Structures that react with silver appear dark, while the counterstain used makes it easier to distinguish the surrounding cellular structures.
This feature allows for a more detailed assessment of the complex microscopic architecture of renal tissue.
Membranous nephropathy and "spike" appearance
One of the classic examples of using Jones paint. membranous nephropathy It is a histopathological evaluation.
In membranous nephropathy, subepithelial immune complex deposits can occur along the glomerular capillary wall. New formations of basal membrane material may appear around these deposits.
In silver plating, these changes are characteristic along the capillary wall. “spike-like protrusions It can be seen in this way.
Jones methenamine silver stain enhances this basal membrane material, making these morphological changes easier to see under a light microscope.
However, the evaluation of renal disease is not based solely on a single histochemical stain. Findings are assessed using other stains such as H&E, PAS, and trichrome, as well as immunofluorescence and electron microscopic examinations when necessary.
Basement membrane double contours
Another morphological feature for which PASM/Jones staining is useful. It is the formation of a double contour in the glomerular capillary walls..
In some glomerular diseases, changes in the basement membrane and capillary wall structure can result in parallel or double-contour-like appearances instead of a single, smooth contour.
Because silver stains clearly mark the basal membrane, these changes can be easily detected under a light microscope.
Therefore, the value of Jones dye is not simply that it "colors the basal membrane black." Its real value lies in..., Its purpose is to make subtle changes in the architecture of the basal membrane visible.
Are PAS and PASM/Jones the same thing?
Because both methods use periodic acid, PAS and PASM/Jones can sometimes be considered closely related. However, their reaction mechanisms and the microscopic appearances they produce are not the same.
PAS (Periodic Acid–Schiff) During dyeing, aldehyde groups formed as a result of oxidation react with Schiff's reagent to produce the characteristic magenta color.
PASM/Jones In this method, a silver-methenamine system is used after oxidation, and the target structures appear dark brown-black due to the deposition of metallic silver.
In renal histopathology, the two stains are not direct alternatives to each other, but often complementary methodsIt can be considered as such.
While PAS contributes to a general assessment of the mesangial matrix and basal membranes, PASM/Jones is particularly useful in highlighting basal membrane contours and some subtle structural changes.
Factors affecting dyeing quality
Silver impregnation methods can be sensitive to technical conditions. Therefore, controlled execution of the staining procedure is important for reliable and reproducible results.
Factors such as the purity of the water used, the cleanliness of the glassware, the preparation of the reagents, the incubation conditions, and the control of the reaction time can affect the dyeing result.
Insufficient reaction can cause basal membranes to appear weak, while excessive reaction can lead to increased background staining and masking of fine morphological details.
Therefore, in silver-based methods such as PASM/Jones, it is not only the quality of the reagents that matters, standardized laboratory procedures and appropriate quality control It is also important.
A single dye is not sufficient for renal biopsies.
Renal pathology is one of the fields where different histological and molecular methods are evaluated together.
While H&E shows general tissue and cell morphology, PAS provides information specifically about basal membranes and the mesangial matrix. Trichrome stainings contribute to the evaluation of fibrosis and collagen-containing structures, while PASM/Jones can reveal basal membrane architecture in more detail.
Immunofluorescence imaging can demonstrate the distribution of immunoglobulins, complement components, and other targets within tissues. Electron microscopy, on the other hand, allows for the examination of ultrastructural changes that cannot be assessed with light microscopy.
Therefore, while PASM/Jones staining is an important tool in the evaluation of renal biopsy, It is just one of the methods that make up the entirety of histopathological evaluation.
BioGnost PASM / Jones Kit
In the SpesBio histology and cytology portfolio BioGnost PASM / Jones Kit, Stabilized It is located.
The kit is a seven-reagent staining system specifically designed for the visualization of renal glomerular basement membranes and other argentaffin structures.
The method involves a silver-methenamine reaction following periodic acid oxidation. Tinting with gold chloride enhances the contrast of the target structures, while sodium thiosulfate is used to remove unbound silver compounds. The Nuclear Fast Red counterstain creates a contrast between the darkly stained target structures and surrounding tissue structures, causing them to appear in red tones.
According to the manufacturer's technical specifications, the kit is formulated to be stable at room temperature and is offered in different test capacities.
As with all histochemical methods, it is important for the laboratory to verify PASM/Jones staining according to its own sample preparation, staining, and quality control procedures.
Conclusion
PASM/Jones staining is one of the important specialized staining methods in renal histopathology that allows for detailed examination of the basement membranes and especially the glomerular capillary wall architecture.
Thanks to its high-contrast imaging based on silver impregnation, the contour, thickness, and some structural changes of the glomerular basement membrane can be made more visible under a light microscope.
However, the true value of the method lies not only in showing certain structures in dark color, It contributes to the evaluation of subtle morphological changes in the architecture of renal tissue, together with other histological and auxiliary methods. He is lying down.
To inform: This content has been prepared using scientific literature and reliable technical sources. It is intended for general scientific information purposes only and does not constitute diagnostic or treatment advice. Histochemical methods should be evaluated according to the sample used, laboratory procedure, and verified study conditions.