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RENAL EXPRESSION OF COMPLEMENT FACTOR H (CFH) AND FACTOR HRELATED PROTEINS (CFHRs)
Vernon, K¹, Botto, M¹, Cook, T², Pickering, M¹
¹Rheumatology Section and ²Department of Histopathology, Imperial College, London
INTRODUCTION: CFH is the major regulator of the complement alternative pathway (AP), and
CFH dysfunction is associated with dense deposit disease (DDD) and atypical haemolytic uraemic
syndrome (aHUS). The predominant site of CFH synthesis is the liver, but a diverse range of cell
types can synthesize CFH. Renal synthesis of CFH has been demonstrated for human mesangial cells
and rodent podocytes. In addition to CFH, the CFH protein family also includes the complement
factor H-related proteins (CFHRs). Three CFHRs have been reported in mice (CFHR-A, -B & -C),
whilst in humans there are five CFHRs (CFHR1-5). CFHR5 and recently CFHR1 have been
demonstrated to act as complement regulators in vitro. A mutation in CFHR5 has also been associated
with C3 glomerulonephritis. Importantly, local complement synthesis may have a major impact on
tissue pathophysiology, as has been demonstrated for renal-derived C3 in cold-ischaemia renal injury
and allogeneic renal transplantation. We hypothesised that an analogous situation may exist for renalderived CFH and CFHRs.
AIM: To characterize the expression of CFH and the CFHRs in mouse and human liver and kidney
tissue.
METHODS: Mouse liver, whole mouse kidney, and human liver and kidney tissue were
homogenized in liquid nitrogen, and RNA extracted using RNA-Bee isolation reagent (Amsbio,
Abingdon, UK). Human renal biopsy tissue immediately placed in RNAlater®, was also used to
extract RNA using the RNAqueous®-4PCR kit. cDNA was then synthesized using oligo(dT)12-18
primers and Superscript™ II Reverse Transcriptase (Invitrogen, Paisley, UK). The cDNA for CFH
and the CFHRs was then amplified using specific primers.
RESULTS: (A) Murine CFH and CFHR expression. CFH transcript was detected in both liver and
whole kidney tissue. Liver expression of all three CFH-related proteins (CFHR-A, -B and -C) was
easily detected and the intensity of all three transcripts was greater than that of CFH. Whole kidney
expression of CFHR-B was readily detectable whilst that of both CFHR-A and -C was very weak. (B)
Human CFH and CFHR expression. CFH was detected in both liver and kidney tissue. CFHR1, 2, 3
and 4 transcripts were detectable in the liver. In contrast, low levels of expression of CFHR1, 3 and 4
were seen variably in renal tissue, whilst CFHR2 was not identified in any of the samples tested.
Expression of CFHR5 is in progress.
CONCLUSION: CFH is expressed by both the liver and kidney in mice and humans. Our
preliminary results show liver and kidney expression of all three CFHRs in the mouse. Expression of
CFHR1-4 in human renal tissue however was variable. Further work to define the relative expression
of these proteins in the liver and kidney, both in healthy and disease states, is in progress. Given the
deposition of complement seen in glomerular inflammation, understanding the local expression of
these proteins may help explain the pathophysiological mechanisms underlying disease.