A circulating permeability factor in focal segmental glomerulosclerosis: the hunt continues

Area of Science:

• Nephrology
• Immunology
• Pathophysiology

Background:

• Primary focal segmental glomerulosclerosis (FSGS) is a leading cause of steroid-resistant nephrotic syndrome with poor renal outcomes.
• Recurrence of FSGS post-transplantation suggests a circulating permeability factor is involved in disease pathogenesis.
• Cardiotrophin-like cytokine 1 (CLC-1) and anti-CD40 antibody have been proposed, but a definitive factor remains undiscovered.

Purpose of the Study:

• To evaluate the role of soluble urokinase-type plasminogen activator receptor (suPAR) in the pathogenesis of primary FSGS.
• To assess suPAR's potential as a diagnostic biomarker for FSGS.
• To investigate suPAR as a therapeutic target for FSGS.

Main Methods:

• Review of cohort studies examining serum suPAR levels in relation to renal function and FSGS diagnosis.
• Analysis of in vivo studies investigating the effects of suPAR upregulation on proteinuria and podocyte injury.
• Consideration of emerging hypotheses regarding different, currently unmeasurable, forms of suPAR.

Main Results:

• Serum suPAR levels show a negative association with renal function but limited ability to differentiate FSGS from other glomerular diseases.
• In vivo studies with forced suPAR upregulation did not induce proteinuria or podocyte injury, contradicting initial findings.
• A different, currently unmeasurable, form of suPAR is hypothesized to be the causative factor in FSGS.

Conclusions:

• The role of suPAR in FSGS pathogenesis is uncertain, with current assays potentially not detecting the active form.
• Further research is essential to identify the specific circulating permeability factor implicated in FSGS.
• Identifying this factor could lead to novel diagnostic biomarkers and therapeutic targets for primary and recurrent FSGS.