Distribution of exogenous complement factor H in mice in vivo.

Area of Science:

• Immunology
• Nephrology
• Biochemistry

Background:

• Factor H (FH) is a critical regulator of complement system activation.
• Dysfunctional FH causes kidney diseases like atypical hemolytic uremic syndrome (aHUS) and C3 glomerulopathy.
• FH fragments are being explored as potential therapeutic agents for these conditions.

Purpose of the Study:

• To investigate the in vivo distribution of exogenous full-length mouse FH (mFH) and its fragments (mFH1-5, mFH18-20) in mice.
• To understand the biodistribution and kidney localization mechanisms of FH constructs for potential therapeutic applications.

Main Methods:

• Radiolabelling of full-length mFH, mFH1-5, and mFH18-20 fragments.
• In vivo distribution studies in wild-type (WT), FH knockout (FH-/-), and FH/C3 double knockout (FH-/- C3-/-) mice.
• Whole-body scintigraphy and organ-level analysis to track radiolabelled FH distribution.

Main Results:

• Accumulation of radioactivity observed in the abdomen, thyroid, and urinary bladder.
• Both mFH fragments localized to the kidneys and were excreted in urine.
• mFH18-20 specifically localized to proximal tubules, requiring C3 fragment deposition for kidney concentration, not glomerular binding alone.

Conclusions:

• Glomerular glycosaminoglycans and sialic acids alone do not suffice for FH kidney accumulation.
• C3 fragment deposition is necessary for FH localization in the kidneys.
• Therapeutic strategies for aHUS must account for the simultaneous recognition of C3 fragments and glomerular components by FH.