Association between thrombotic microangiopathy and activated alternative complement pathway in malignant...

Area of Science:

• Nephrology
• Immunology
• Genetics

Background:

• Malignant nephrosclerosis, a severe form of hypertensive renal microangiopathy, can lead to end-stage renal disease.
• Activation of the complement alternative pathway (AP) is implicated in malignant nephrosclerosis pathogenesis, though genetic links remain debated.

Purpose of the Study:

• To investigate AP activation and genetic complement defects in malignant nephrosclerosis.
• To correlate these findings with renal microangiopathy, clinical features, and patient prognosis.

Main Methods:

• Analysis of renal biopsies from 50 malignant nephrosclerosis patients and 25 controls.
• Immunohistochemistry for complement deposits (C5b-9, C3a, C5a, C4d, MBL) and confocal microscopy for C5b-9/CD34 co-localization.
• ELISA for plasma and urinary complement factors (FB, FP, FD, FH, C3a, C5a) and whole-exome sequencing for genetic abnormalities.

Main Results:

• Renal biopsies showed features similar to atypical hemolytic uremic syndrome with C5b-9, C3a, and C5a deposition.
• Elevated urinary AP components and decreased FH levels were observed in patients.
• Urinary AP levels correlated with renal function and prognosis, and mutations in MCP, CFB, CFH, and CFHR5 genes were found in 8/20 patients.

Conclusions:

• Aberrant complement AP dysregulation is associated with malignant nephrosclerosis activity, severity, and renal outcomes.
• Screening for complement defects is recommended for potential therapeutic strategies using complement regulators.
• Further research is needed to elucidate the precise role of AP in the disease's pathogenesis.