Clinical significance of fibroblast-specific protein-1 expression on podocytes in patients with focal segmental glomerulosclerosis

Backgrounds/Aims: We previously reported that fibroblast-specific protein 1 (FSP1) is a marker of epithelial-mesenchymal transition (EMT) in tubulointerstitial fibrosis. The EMT-like changes observed in podocytes are reportedly associated with podocyte detachment which may cause focal glomerulosclerosis. Methods: In cross-sectional studies, we analyzed podocyte expression of FSP1 immunohistochemically using renal biopsy specimens from 31 patients with focal segmental glomerulosclerosis (FSGS) and 39 patients with minimal change disease (MCD). We also semiquantitatively analyzed glomerular expression of FSP1 mRNA using laser capture microdissection and real-time PCR. Results: We found that FSP1 was localized to podocytes in both FSGS and MCD patients; however, the number of FSP1+ podocytes per glomerular profile was significantly higher in patients with FSGS than in those with MCD, and there was a corresponding difference in the levels of FSP1 mRNA. FSP1+ podocyte counts per glomerular profile in FSGS patients correlated significantly with the prevalence of glomerulosclerosis and the extent of interstitial type-I collagen-positive areas. Conclusion: Taken together, these data suggest that podocyte expression of FSP1 could shed light on the potential linkage between EMT-like changes, detachment of podocytes from the glomerular basal membrane and the pathophysiology underlying FSGS.