Imaging of podocyte foot processes by fluorescence microscopy

Area of Science:

• Nephrology
• Cell Biology
• Genetics

Background:

• Visualizing podocyte foot processes traditionally relies on electron microscopy, which has significant technical limitations.
• Electron microscopy requires specialized equipment and immunogold labeling, and cannot leverage advances in in vivo fluorophores.

Purpose of the Study:

• To develop a novel genetic strategy for visualizing single podocytes and their foot processes using conventional fluorescence microscopy.
• To overcome the limitations associated with electron microscopy for podocyte research.

Main Methods:

• Generated a transgenic mouse line expressing a GFP-Cre-ERT2 fusion protein under the collagen α1(I) promoter for specific podocyte expression.
• Utilized submaximal tamoxifen administration for genetic labeling of single podocytes in crossed Cre-reporter lines.
• Evaluated three reporter systems, identifying the Coll1α1GCE;Gt(ROSA)26Sor(tm9(CAG-tdTomato)) bigenic model for optimal visualization.

Main Results:

• The developed genetic labeling strategy enabled detailed visualization of podocyte foot processes, including tertiary branches, via epifluorescence microscopy.
• The Coll1α1GCE;Gt(ROSA)26Sor(tm9(CAG-tdTomato)) mouse line provided a strong, homogeneous reporter signal for clear observation.
• The method allowed for the visualization and quantification of ultrastructural changes in podocyte foot processes following injury.

Conclusions:

• This novel genetic labeling technique combined with fluorescence microscopy offers a valuable complement to electron microscopy for studying podocytes.
• The method facilitates the in vivo analysis of podocyte structure, development, and response to injury.
• This approach enhances the study of podocyte precursors and their role in kidney health and disease.