Increased expression of fibroblast growth factors in segmental renal dysplasia

Aberrations in FGFR1, FGFR2, and RIP5 Expression in Human Congenital Anomalies of the Kidney and Urinary Tract (CAKUT)

This study aimed to explore the spatio-temporal expression patterns of congenital anomalies of kidney and urinary tract (CAKUT) candidate genes, Fibroblast Growth Factor Receptor 1 (FGFR1), Fibroblast Growth Factor Receptor 2 (FGFR2) and Receptor-Interacting Protein Kinase 5 (RIP5), in human fetal kidney development (CTRL) and kidneys affected with CAKUT. Human fetal kidneys from the 22nd to 41st developmental week (duplex, hypoplastic, dysplastic, and controls) were stained with antibodies and analyzed by epifluorescence microscopy and RT-qPCR. The effect of CAKUT candidate genes on kidney nephrogenesis and function is confirmed by statistically significant variations in the spatio-temporal expression patterns of the investigated markers. The nuclear localization of FGFR1, elevated expression score of FGFR1 mRNA, the increased area percentage of FGFR1-positive cells in the kidney cortex, and the overall decrease in the expression after the peak at the 27th developmental week in dysplastic kidneys (DYS), suggest an altered expression pattern and protein function in response to CAKUT pathophysiology. The RT-qPCR analysis revealed a significantly higher FGFR2 mRNA expression score in the CAKUT kidneys compared to the CTRL. This increase could be due to the repair mechanism involving the downstream mediator, Extracellular Signal-Regulated Kinase 1/2 (ERK1/2). The expression of RIP5 during normal human kidney development was reduced temporarily, due to urine production and increased later since it undertakes additional functions in the maturation of the postnatal kidney and homeostasis, while the expression dynamics in CAKUT-affected kidneys exhibited a decrease in the percentage of RIP5-positive cells during the investigated developmental period. Our findings highlight the importance of FGFR1, FGFR2, and RIP5 as markers in normal and pathological kidney development.

Biomarkers in vesicoureteral reflux: an overview

Aim: This article aimed to review the role of cytokines, chemokines, growth factors and cellular adhesion molecules as biomarkers for vesicoureteral reflux (VUR) and reflux nephropathy (RN). Methods: We reviewed articles from 1979 onward by searching PubMed and Scopus utilizing the combination of words: 'VUR' or 'RN' and each one of the biomarkers. Results: Genetic, inflammatory, fibrogenic, environmental and epigenetic factors responsible for renal scarring need to be better understood. TGF-β, IL-10, IL-6, IL-8 and TNF seem to exert a role in VUR particularly in RN based on the current literature. Serum levels of procalcitonin have been also associated with high-grade VUR and RN. These molecules should be more intensively evaluated as potential biomarkers for renal scarring in VUR. Conclusion: Further studies are necessary to define which molecules will really be of utility in clinical decisions and as therapeutic targets for VUR and RN.

Novel cystogenic role of basic fibroblast growth factor in developing rodent kidneys

Basic fibroblast growth factor (bFGF) is a heparin-binding growth factor that is accumulated in human dysplastic and cystic renal diseases. Previous studies have shown that bFGF can modulate the growth of developing renal tubules; however, its role in the pathogenesis of renal cyst formation is not clearly understood. Here, we tested the hypothesis that overexpression of bFGF in developing rodent kidneys induces cyst formation in vivo. We used two different adenoviral-mediated gene-transferring approaches to overexpress bFGF in developing rodent kidneys. Initially, metanephric kidney (MK) explants harvested from embryonic day 15 Sprague-Dawley rats were infected with adenoviral vectors (rAd) encoding human bFGF or LacZ genes and transplanted under the renal capsule of adult female rats. Subsequently, to determine whether bFGF could induce renal cysts in developing kidneys with an intact renal collecting system, we injected rAd-bFGF or LacZ vectors in the retroorbital plexus of newborn mice. Basic FGF induced a more efficient integration of the MK explants into the host kidneys and increased the vascularization and proliferation of developing tubules, leading to tubular dilatation and rapid formation of renal cysts. In addition, we successfully expressed human bFGF in the kidney of newborn mice in vivo and induced tubular dilatation and renal cysts. In contrast, mice injected with rAd-lacZ did not develop tubular dilatation or renal cysts. To the best of our knowledge, these experiments show for the first time that overexpression of bFGF in developing rodent kidneys can induce the formation of renal cysts in vivo.

Localization and functional characterization of glycosaminoglycan domains in the normal human kidney as revealed by phage display-derived single chain antibodies

Glycosaminoglycans (GAG) play an important role in renal homeostasis. They are strongly negatively charged polysaccharides that bind and modulate a myriad of proteins, including growth factors, cytokines, and enzymes. With the aid of specific phage display-derived antibodies, the distribution of heparan sulfate (HS) and chondroitin sulfate (CS) domains in the normal human kidney was studied. HS domains were specifically located in basement membranes and/or surfaces of renal cells and displayed a characteristic distribution over the nephron. A characteristic location in specific parts of the tubular system was also observed. CS showed mainly an interstitial location. Immunoelectron microscopy indicated specific ultrastructural location of domains. Only partial overlap with any of seven different proteoglycan core proteins was observed. Two HS domains, one highly sulfated (defined by antibody HS4C3) and one low sulfated (defined by antibody RB4Ea12), were studied for their cell biologic relevance with respect to the proliferative effect of FGF-2 on human mesangial cells in vitro. Fibroblast growth factor 2 (FGF-2) binding was HS dependent. Addition of purified HS4C3 antibody but not of the RB4Ea12 antibody counteracted the binding and the proliferative effect of FGF-2, indicating that the HS4C3 domain is involved in FGF-2 handling by mesangial cells. In conclusion, specific GAG domains are differentially distributed in the normal human kidney and are likely involved in binding of effector molecules such as FGF-2. The availability of tools to identify and study relevant GAG structures allows the development of glycomimetica to halt, for instance, mesangial proliferation and matrix production as seen in diabetic nephropathy.

Insulin-like growth factor-1 expression in reflux nephropathy

BACKGROUND

Reflux nephropathy (RN) is recognised as a major cause of end-stage renal failure in children and young adults. Insulin-like growth factor-1 (IGF-1), a peptide growth factor produced by collecting ducts, and its receptor, insulin-like growth factor-1 receptor (IGF-1R), are present in the glomeruli and basolateral membrane of renal proximal tubular cells. Exogenous IGF-1 has been shown to enhance proliferation and reduce apoptosis of tubular cells following renal injury.

METHODS

We designed this study to investigate the expression of IGF-1 in RN. The kidney specimens from 15 children with RN were obtained at the time of nephrectomy. Control material included normal kidney specimens obtained from adult patients during partial nephrectomy for an incidentaloma. Single-label immunofluorescence histochemistry was carried out using polyclonal antibodies to IGF-1 and IGF-1R employing laser scanning confocal microscopy. Double-label immunofluorescence histochemistry was carried out using monoclonal antibodies to vimentin and clusterin to assess tubulointerstitial fibrosis. IGF-1 and IGF-1R gene expression were evaluated by in situ hybridisation (ISH). The TUNEL method was utilised to assess tubular apoptosis.

RESULTS

In the normal kidney there was strong IGF-1 and IGF-1R immunoreactivity in the proximal tubules, whereas IGF-1 and IGF-1R immunoreactivity was markedly reduced in RN specimens. Strong IGF-1 and IGF-1R mRNA expression was observed in the proximal tubules in normal kidneys, whereas IGF-1 and IGF-1R mRNA expression was undetectable in RN. Renal tubulointerstitial expression of vimentin and clusterin was markedly increased in RN kidneys. Decreased IGF-1 and IGF-1R expression in RN strongly correlated with severity of tubular apoptosis in RN compared with controls.

CONCLUSION

These data suggest that the downregulation of IGF-1 and IGF-1R may play an important role in the pathogenesis of RN, at least in part by increasing interstitial collagen deposition and tubular apoptosis.

Epidermal growth factor and monocyte chemotactic peptide-1 expression in reflux nephropathy

OBJECTIVES

Reflux nephropathy (RN) is recognised as a major cause of end stage renal failure in children and young adults. The histological findings of RN are tubular atrophy and interstitial monocyte infiltration. Epidermal growth factor (EGF) produced by tubular cells playing a pivotal role in the modulation of tubular cell growth, while monocyte chemotactic peptide-1 (MCP-1) is a powerful and specific chemotactic and activating factor for monocytes. It has been suggested that the modulation of local EGF production is directly involved in the pathogenesis of tubular damage. We designed this study to investigate the expression of EGF and MCP-1 in severe reflux nephropathy in order to further understand the pathogenesis of reflux nephropathy.

METHODS

The kidney specimens from 12 children with severe reflux nephropathy were obtained at the time of nephrectomy. Control material included normal kidney specimens obtained from three adult patients during partial nephrectomy for an incidentaloma. Single-label immunofluorescence histochemistry was carried out using polyclonal antibodies to EGF and MCP-1 employing laser scanning confocal microscopy. EGF and MCP-1 gene expression were evaluated by in situ hybridization (ISH). TUNEL method was utilized to assess tubular apoptosis.

RESULTS

In the normal kidney there was strong EGF immunoreactivity in the proximal tubules compared to the reflux nephropathy where there was lack of immunoreactivity in the proximal tubules. Normal kidney demonstrated lack of MCP-1 immunoreactivity, whereas reflux nephropathy kidney showed strong MCP-1 immunoreactivity in the proximal tubules and tubulointerstitial space. In the normal kidney there was marked EGF mRNA expression in the proximal tubules whereas EGF mRNA expression was undetectable in reflux nephropathy kidney. MCP-1 mRNA expression was undetectable in normal kidney, whereas there was strong MCP-1 mRNA expression at the tubulointerstitial level in reflux nephropathy kidney. Decreased EGF expression and increased MCP-1 expression at the tubulointerstitial levels in reflux nephropathy strongly correlated with severity of apoptosis in reflux nephropathy compared with controls.

CONCLUSIONS

Our data suggests that the downregulation of EGF with simultaneous upregulation of MCP-1 may be involved in the pathogenesis of tubulointerstitial damage in reflux nephropathy.

Increased c-Met tyrosine kinase expression in segmental renal dysplasia

Renal dysplasia (RD) is a disorganized development of renal parenchyma that results in a deficit of functional renal tissue. It has been suggested in the animal model that increased expression of HGF receptor, c-Met tyrosine kinase in the epithelial cells during kidney development may induce a growth of dysplastic epithelia and result in RD. The aim of this study was to investigate the immunoreactivity of c-Met tyrosine kinase in the dysplastic kidney in order to further understand the pathogenesis of RD. Specimens of dysplastic upper pole kidney were obtained from 19 patients during upper pole partial nephrectomy for non-functioning upper moiety of duplex kidney. In the dysplastic kidney, there was strong c-Met immunoreactivity in the epithelium of primitive tubules. In contrast, c-Met immunoreactivity was barely detectable in the normal kidney. Markedly increased expression of HGF receptor, c-Met tyrosine kinase in renal dysplasia suggests that HGF may be involved in the development of renal dysplasia.