WT1 and kidney progenitor cells

Making immortalized cell lines from embryonic mouse kidney

Immortalized cell lines derived from embryonic mouse kidneys are useful tools for exploring signaling pathways, morphogenetic mechanisms, and gene function in renal development: they also provide a means for efficient first-round screening of panels of small molecules intended to combat renal pathologies such as the development of cysts, and such cell line-based screening can allow a valuable reduction in the numbers of animals needed for a given line of research. This chapter presents a simple method for generating cell lines from the "Immortomouse," which carries a temperature-sensitive SV40 antigen, under the control of an interferon-regulated promoter.

Molecular characterization of Wilms' tumor from a resource-constrained region of sub-Saharan Africa

Sub-Saharan African children have an increased incidence of Wilms' tumor (WT) and experience alarmingly poor outcomes. Although these outcomes are largely due to inadequate therapy, we hypothesized that WT from this region exhibits features of biological aggressiveness that may warrant broader implementation of high-risk therapeutic protocols. We evaluated 15 Kenyan WT (KWT) for features of aggressive disease (blastemal predominance and Ki67/cellular proliferation) and treatment resistance (anaplasia and p53 immunopositivity). To explore the additional biological features of KWT, we determined the mutational status of the CTNNB1/β-catenin and WT1 genes and performed immunostaining for markers of Wnt pathway activation (β-catenin) and nephronic progenitor cell self-renewal (WT1, CITED1 and SIX2). We characterized the proteome of KWT using imaging mass spectrometry (IMS). The results were compared to histology- and age-matched North American WT (NAWT) controls. For patients with KWT, blastemal predominance was noted in 53.3% and anaplasia in 13%. We detected increased loss to follow-up (p = 0.028), disease relapse (p = 0.044), mortality (p = 0.001) and nuclear unrest (p = 0.001) in patients with KWT compared to controls. KWT and NAWT showed similar Ki67/cellular proliferation. We detected an increased proportion of epithelial nuclear β-catenin in KWT (p = 0.013). All 15 KWT specimens were found to harbor wild-type CTNNB1/β-catenin, and one contained a WT1 nonsense mutation. WT1 was detected by immunostaining in 100% of KWT, CITED1 in 80% and SIX2 in 80%. IMS revealed a molecular signature unique to KWT that was distinct from NAWT. The African WT specimens appear to express markers of adverse clinical behavior and treatment resistance and may require alternative therapies or implementation of high-risk treatment protocols.

MUC1 in mesenchymal-to-epithelial transition during human nephrogenesis: changing the fate of renal progenitor/stem cells?

BACKGROUND

The development of the human kidney is a complex process requiring interactions between epithelial and mesenchymal cells. The condensed cap mesenchyme is hypothesized to generate a population of stem/progenitor cells that undergo mesenchymal-epithelial transition (MET) originating nephrons. Few immunohistochemical markers are available for detecting cap mesenchymal cells in the early phases of MET.

METHODS

The expression of MUC1 was evaluated in the kidneys, of 4 human foetuses and 2 newborns.

RESULTS

MUC1 immunoreactivity was detected in all the examined kidneys in the cap mesenchyme and in the renal vesicles. Immunostaining for MUC1 in cap mesenchymal cells changed from one nodule to the next: some mesenchymal nodules were negative, some showed MUC1 reactivity in scattered cells, whereas in others, positive cells revealed the presence of a roundish developing epithelial structure.

CONCLUSIONS

Our data clearly indicates, for the first time to the best of our knowledge, immunohistochemical evidence of MUC1 expression during human kidney development. We focused on MUC1 reactivity in the cap mesenchyme. On the basis of these preliminary data, we speculate that MUC1 may be involved in human nephrogenesis and may play a relevant role in MET from the cap mesenchyme to the renal vesicle, changing the fate of renal stem/progenitor cells.

Expression of WT1 during normal human kidney development

Wilms Tumor 1 (WT1) is a zinc finger protein, expressed by human podocytes in the adult kidney, which plays a relevant role in different phases of nephrogenesis in experimental animals. Since no data are available for specific role in the human fetal kidney, this study aimed at investigating the expression of WT1 during the different phases of nephrogenesis. To this end, the expression of WT1 was evaluated in the kidneys, from four human fetuses and two newborns. WT1 immunoreactivity was detected in all the examined kidneys, but not in the kidneys of the newborn at term. Immunostaining for WT1 was observed in podocytes of the glomeruli and in the subcapsular regions, in areas of active glomerulogenesis. The extent and the intensity of immunoreactivity for WT1 changed from one case to the next according to the different gestational age. This study confirms in human kidney the relevant role played by WT1 during nephrogenesis. Its expression pattern suggests a main role in the regulation of the process of Mesenchimal-Epithelial-Transition and in the development and maturation of podocytes. Further studies are needed to verify the correlation between the expression pattern of WT1 and that of other genes products involved in nephrogenesis, in order to better understand their relationship at protein level.