The Comparison of the Podocyte Expression of Synaptopodin, CR1 and Neprilysin in Human Glomerulonephritis: Could the Expression of CR1 be Clinically Relevant?

Podocytes are considered as the most important cells that determine loss of structure and function of the glomerular filter. We compared the expression of three podocyte markers, i.e.: synaptopodin (SYN), CR1 and neprilysin (NEP) in 107 patients with different forms of glomerulonephritis (GN) and 5 normal kidneys (NK). A quantitative immunohistochemistry was applied to evaluate the expression of podocyte proteins. The results were related with serum creatinine (Scr), estimated glomerular filtration rate (eGFR) and urinary protein. We observed the reduction in the podocyte expression of NEP, SYN and CR1 in proliferative and non-proliferative forms of GN. Interestingly, in mesangial proliferative GN (MesPGN), the expression of SYN and CR1 was lower in IgA-MesPGN than in non-IgA-MesPGN (p<0.005 and p<0.02, respectively). In all the patients, the expression of NEP and SYN was positively related (r=0.53, p=0.02) as that of NEP and CR1 (r=0.39, p=0.04). Yet, clinical correlations with Scr (r=-0.33, p=0.03) and eGFR (r=0.26, p=0.05) were obtained only with respect to CR1. In conclusion, SYN, CR1 and NEP may be used as markers of podocyte loss in patients with GN. However, in agreement with previous studies, the clinical relevance draws a special attention to the expression of CR1.