The Expression Profile of Complement Components in Podocytes

Area of Science:

• Nephrology
• Immunology
• Molecular Biology

Background:

• Podocytes are crucial for the glomerular filtration barrier and are implicated in proteinuric kidney diseases.
• Emerging evidence suggests podocytes synthesize complement components involved in glomerular disease pathogenesis.
• The precise profile and extent of complement expression in podocytes are not well-defined.

Purpose of the Study:

• To comprehensively examine the complement expression profile in podocytes under both physiological and injury-induced conditions.
• To identify specific complement factors synthesized by podocytes.
• To investigate how podocyte injury stimuli affect complement gene expression.

Main Methods:

• Conventional RT-PCR was used to screen for complement component expression in podocytes.
• Tandem mass spectrometry confirmed the presence of specific complement proteins (C3, Crry, C1q-binding protein).
• Fluorescence confocal microscopy visualized representative complement components.
• Primary cultured and immortalized podocytes were treated with injury factors like puromycin aminonucleoside (PAN), angiotensin II (Ang II), interleukin-6 (IL-6), and transforming growth factor-β (TGF-β).

Main Results:

• Out of 32 complement components, 23 were detected in podocytes via RT-PCR.
• Seventeen specific complement factors (including C1q, C3, and Crry) were consistently expressed in both primary and immortalized podocytes.
• Nine complement factors (including C4, C5, and C9) were not detected.
• Podocyte complement gene expression levels were significantly modulated by PAN, Ang II, IL-6, and TGF-β treatments.
• Key complement components like C3 and Crry were validated at the protein level.

Conclusions:

• Primary podocytes express a wide array of complement components at both mRNA and protein levels.
• Podocyte complement expression is dynamic and responsive to various injury-inducing stimuli.
• These findings highlight the intrinsic role of podocytes in the renal complement system and their potential contribution to glomerular diseases.