Rare
neural cell adhesion molecule (
NCAM) positive cells have been previously described within the normal human adult kidney interstitium, speculating that they could increase in the interstitium with incipient interstitial renal
fibrosis (IRF). In the present study, among 93 biopsy samples of various
kidney diseases, NCAM+ interstitial cells were detected in 62.4% cases. An increased number of NCAM+ cells was significantly observed only in incipient IRF compared to normal renal tissues and advanced IRF stages (p<0.001), independently of underlying diseases (p = 0.657). All three major
NCAM isoforms' RT-PCR bands were visible either in normal or in kidneys with incipient IRF, albeit their
mRNA expression levels measured by qRT-PCR were different. Applying qRT-PCR on pure NCAM+ cells population, obtained by
laser capture microdissection, significant
mRNA over-expression of NCAM140kD
isoform was found in NCAM+ cells within incipient IRF (p = 0.004), while NCAM120kD and NCAM180kD
isoforms were not changed significantly (p = 0.750; p = 0.704; respectively). Simultaneously, qRT-PCR also showed significant αSMA (p = 0.014) and SLUG (p = 0.004) mRNAs up-regulation within the NCAM+ cells of incipient IRF, as well as highly decreased
matrix metalloproteinases (
MMP) -2 and -9 mRNAs (p = 0.028; p = 0.036; respectively). However, using double immunofluorescence MMP-9 could still be detectable on the
protein level in rare NCAM+ cells within the incipient IRF. Further characterization of NCAM+ cells by double immunofluorescent labeling revealed their association with molecules involved in
fibrosis.
Fibroblast growth factor receptor 1 (FGFR1) and α5β1
integrin were extensively expressed on NCAM+ cells within the incipient IRF areas, whereas human epididymis protein-4 (HE4) was found to be present in few NCAM+ cells of both normal and interstitium with incipient
fibrosis. Heterogeneity of NCAM+ interstitial cells in normal and incipient IRF, concerning molecules related to
fibrosis and variable expression of
NCAM isoforms, could suggest diverse role of NCAM+ cells in homeostasis and in regulation of renal
fibrosis in diseased kidneys.