What is the Difference Between Podocytes and Mesangial Cells

The main difference between podocytes and mesangial cells is that podocytes are the cells that wrap around the capillaries of the glomerulus, whereas mesangial cells are specialized cells that form the mesangium of the glomerulus. 

Podocytes and mesangial cells are two cell types that occur in the glomerulus. They have functions in controlling the filtration of blood.

Key Areas Covered

1. What are Podocytes
– Definition, Structure, Function
2. What are Mesangial Cells
– Definition, Structure, Function
3. Similarities Between Podocytes and Mesangial Cells
– Outline of Common Features
4. Difference Between Podocytes and Mesangial Cells
– Comparison of Key Differences

Key Terms 

Mesangial Cells, Podocytes

What are Podocytes

Podocytes are specialized cells that wrap around the capillaries and the neighboring cells of the glomerulus. They play a key role in preventing the entry of plasma protein to the glomerular filtrate. They form a barrier in the filtration slits and foot processes. Also, they form a dynamic network of cellular extensions. The foot processes of podocytes form a narrow network with uniform gaps. By that, they allow the passage of small solutes, retaining blood cells. Also, it is less permeable to large solutes like albumin. In addition, cytoskeletal dynamics and the podocytes’ structural plasticity are important for proper renal function.

Figure 1: Podocytes

Furthermore, podocytes are terminally differentiated cells consisting of the cell body and major processes extending from the cell body. Major processes form interdigitated foot processes that wrap the capillaries of the glomerulus. Further, major processes contain microtubules and intermediate filaments. In contrast, foot processes contain a cytoskeleton containing actin. Additionally, the foot processes contain a thick glycocalyx coat that is negatively charged. The negative charge on the foot processes repels the foot process from each other. 

What are Mesangial Cells

Mesangial cells are supporting cells of the podocytes that occur in the basement membrane of the glomerulus. The components of the glomerulus prevent the entry of large plasma proteins into the glomerular filtrate, only filtering water and small molecules. Importantly, mesangium occurs in close proximity to the podocytes in the glomerulus. Mesangial cells are one of the three types of cells that make up the glomerulus. The other cell types include podocytes and endothelial cells. 30-40% of the cell population of the glomerulus contain mesangial cells. They occur between the capillary loops in the mesangial matrix.

Figure 2: Glomerulus

Moreover, mesangial cells resemble smooth muscle cells, and they possess immune cell-like characteristics. They possess phagocytic and scavenging properties. Mesangial cells remove trapped residues and aggregated proteins. Therefore, it keeps the glomerular filtrate free of debris. 

Similarities Between Podocytes and Mesangial Cells

• Podocytes and mesangial cells are two cell types in the glomerulus.
• Their function is to control the filtration of blood in the glomerulus.
• They contain actin, giving contractile properties to the cells. 

Difference Between Podocytes and Mesangial Cells

Definition

Podocytes refer to specialized epithelial cells that coat the outer walls of glomerular capillaries. In contrast, mesangial cells refer to irregularly shaped cells that extend processes from their cell body towards the glomerular basement membrane (GBM).

Significance

Podocytes are the cells that wrap around the capillaries of the glomerulus, while mesangial cells are specialized cells that form the mesangium of the glomerulus. 

Structure

Podocytes consist of a cell body, major processes that extend outward from their cell body, forming interdigitated foot processes (FPs) that enwrap the glomerular capillaries. In contrast, mesangial cells have irregular shapes with flattened-cylinder-like cell bodies and processes at both ends containing actin, myosin, and actinin, giving them contractile properties.

Function

Podocytes prevent the entry of plasma proteins into the glomerular filtrate, while mesangial cells are important in clearing the glomerulus of pathogens and deposited extra-glomerular material. 

Conclusion

In brief, podocytes and mesangial cells are two types of cells that occur in the glomerulus. Podocytes wrap around the capillaries of the glomerulus. They have interdigitated foot processes that enwrap the glomerular capillaries. They prevent the entry of plasma proteins into the glomerular filtrate. In comparison, mesangial cells form the mesangium of the glomerulus. Their cell bodies are flattened, cylinder-like cell bodies that have contractility. They are important in clearing glomerular pathogens and depositing extra-glomerular material. Therefore, the main difference between podocytes and mesangial cells is their structure and function. 

References:

1. Reiser J, Altintas MM. Podocytes. F1000Res. 2016 Jan 28;5:F1000 Faculty Rev-114. doi: 10.12688/f1000research.7255.1. PMID: 26918173; PMCID: PMC4755401.
2. Ebefors K, Bergwall L, Nyström J. The Glomerulus According to the Mesangium. Front Med (Lausanne). 2022 Jan 26;8:740527. doi: 10.3389/fmed.2021.740527. PMID: 35155460; PMCID: PMC8825785.

Image Courtesy:

1. “Glomerulum of mouse kidney in Scanning Electron Microscope, magnification 5,000x” By SecretDisc – Own work (CC-BY SA 3.0) via Commons Wikimedia
2. “Renal corpuscle-en” By Shypoetess – Own Work (CC-BY SA 4.0) via Commons Wikimedia