WT1 and Pax2 re-expression is required for epithelial-mesenchymal transition in 5/6 nephrectomized rats and cultured kidney tubular epithelial cells

Molecular architecture of proliferative lupus nephritis as elucidated using 50-plex imaging mass cytometry proteomics

Due to unique advantages that allow high-dimensional tissue profiling, we postulated imaging mass cytometry (IMC) may shed novel insights on the molecular makeup of proliferative lupus nephritis (LN). This study interrogates the spatial expression profiles of 50 target proteins in LN and control kidneys. Proliferative LN glomeruli are marked by podocyte loss with immune infiltration dominated by CD45RO+, HLA-DR+ memory CD4 and CD8 T-cells, and CD163+ macrophages, with similar changes in tubulointerstitial regions. Macrophages are the predominant HLA-DR expressing antigen presenting cells with little expression elsewhere, while macrophages and T-cells predominate cellular crescents. End-stage sclerotic glomeruli are encircled by an acellular fibro-epithelial Bowman's space surrounded by immune infiltrates, all enmeshed in fibronectin. Proliferative LN also shows signs indicative of epithelial to mesenchymal plasticity of tubular cells and parietal epithelial cells. IMC enabled proteomics is a powerful tool to delineate the spatial architecture of LN at the protein level.

Cyclin-dependent kinase 4-related tubular epithelial cell proliferation is regulated by Paired box gene 2 in kidney ischemia-reperfusion injury

Paired box 2 (Pax2) is a transcription factor essential for kidney development and is reactivated in proximal tubular epithelial cells (PTECs) during recovery from kidney injury. However, the role of Pax2 in this process is still unknown. Here the role of Pax2 reactivation during injury was examined in the proliferation of PTECs using an ischemia-reperfusion injury (IRI) mouse model. Kidney proximal tubule-specific Pax2 conditional knockout mice were generated by mating kidney androgen-regulated protein-Cre and Pax2 flox mice. The degree of cell proliferation and fibrosis was assessed and a Pax2 inhibitor (EG1) was used to evaluate the role of Pax2 in the hypoxic condition of cultured PTECs (O₂ 5%, 24 hours). The number of Pax2-positive cells and Pax2 mRNA increased after IRI. Sirius red staining indicated that the area of interstitial fibrosis was significantly larger in knockout mice 14 days after IRI. The number of Ki-67-positive cells (an index of proliferation) was significantly lower in knockout than in wild-type mice after IRI, whereas the number of TUNEL-positive cells (an index of apoptotic cells) was significantly higher in knockout mice four days after IRI. Expression analyses of cell cycle-related genes showed that cyclin-dependent kinase 4 (CDK4) was significantly less expressed in the Pax2 knockout mice. In vitro data showed that the increase in CDK4 mRNA and protein expression induced by hypoxia was attenuated by EG1. Thus, Pax2 reactivation may be involved in PTEC proliferation by activating CDK4, thereby limiting kidney fibrosis.

Müllerian duct cyst: Case report with updates in cellular origin, corresponding immunohistochemistry, and contrast to prostatic utricle cyst

A 20-year-old male presented to the emergency department with lower abdominal pain, urinary retention, and constipation. Computed tomography (CT) revealed a large cyst on the posterior aspect of the prostate gland; he was ultimately diagnosed with a Müllerian duct cyst (MDC). Although much has been written on the radiologic diagnosis of such cysts, there is a paucity of recent literature concerning the pathological diagnosis. While older studies debated the Müllerian origin of a midline cyst abutting the poster prostate, we believe that with the advent of monoclonal PAX8 (which was positive in this lesion) and monoclonal PAX2 (which was negative), we have strong evidence that the present cyst is indeed of Müllerian origin. Further, there is debate in the literature as to whether MDC is synonymous or distinct from prostatic utricle cyst. We present an interdisciplinary analysis as to the merits and weaknesses of both sides of the debate and how data gathered from the current case could be used in a future, larger study to arrive at a more definitive conclusion.

Short and dysfunctional telomeres sensitize the kidneys to develop fibrosis

Accumulation of short telomeres is a hallmark of aging. Mutations in telomerase or telomere-binding proteins lead to telomere shortening or dysfunction and are at the origin of human pathologies known as 'telomere syndromes', which are characterized by loss of the regenerative capacity of tissues and fibrotic pathologies. Here, we generated two mouse models of kidney fibrosis, either by combining telomerase deficiency to induce telomere shortening and a low dose of folic acid, or by conditionally deleting Trf1, a component of the shelterin telomere protective complex, from the kidneys. We find that short telomeres sensitize the kidneys to develop fibrosis in response to folic acid and exacerbate the epithelial-to-mesenchymal transition (EMT) program. Trf1 deletion in kidneys led to fibrosis and EMT activation. Our findings suggest that telomere shortening or dysfunction may contribute to pathological, age-associated renal fibrosis by influencing the EMT program.

Analysis of wt1a reporter line expression levels during proepicardium formation in the zebrafish

The epicardium is the outer mesothelial layer of the heart. It covers the myocardium and plays important roles in both heart development and regeneration. It is derived from the proepicardium (PE), groups of cells that emerges at early developmental stages from the dorsal pericardial layer (DP) close to the atrio-ventricular canal and the venous pole of the heart-tube. In zebrafish, PE cells extrude apically into the pericardial cavity as a consequence of DP tissue constriction, a process that is dependent on Bmp pathway signaling. Expression of the transcription factor Wilms tumor-1, Wt1, which is a leader of important morphogenetic events such as apoptosis regulation or epithelial-mesenchymal cell transition, is also necessary during PE formation. In this study, we used the zebrafish model to compare intensity level of the wt1a reporter line epi:GFP in PE and its original tissue, the DP. We found that GFP is present at higher intensity level in the PE tissue, and differentially wt1 expression at pericardial tissues could be involved in the PE formation process. Our results reveal that bmp2b overexpression leads to enhanced GFP level both in DP and in PE tissues.

Proliferating Infantile Hemangioma Tissues and Primary Cell Lines Express Markers Associated with Endothelial-to-Mesenchymal Transition

Supplemental Digital Content is available in the text.

Background:

We have previously shown that the endothelium of the microvessels of infantile hemangioma (IH) exhibits a hemogenic endothelium phenotype and proposed its potential to give rise to mesenchymal stem cells, similar to the development of hematopoietic cells. This endothelial-to-mesenchymal transition (Endo-MT) process involves the acquisition of a migratory phenotype by the endothelial cells, similar to epithelial-to-mesenchymal transition that occurs during neural crest development. We hypothesized that proliferating IH expresses Endo-MT–associated proteins and investigated their expression at the mRNA, protein, and functional levels.

Methods:

Immunohistochemical staining of paraffin-embedded sections of proliferating IH samples from 10 patients was undertaken to investigate the expression of the Endo-MT proteins Twist1, Twist2, Snail1, and Slug. Transcriptional analysis was performed for the same markers on proliferating IH tissues and CD34⁺ and CD34⁻ cells from proliferating IH-derived primary cell lines. Adipogenic and osteogenic differentiation plasticity was determined on the CD34-sorted fractions.

Results:

The endothelium of the microvessels and the cells within the interstitium of proliferating IH tissues expressed Twist1, Twist2, and Slug proteins. Twist1 was also expressed on the pericyte layer of the microvessels, whereas Snail1 was not expressed. Both CD34⁺ and CD34⁻ populations from the IH-derived primary cell lines underwent adipogenic and osteogenic differentiation.

Conclusions:

The expression of Endo-MT–associated proteins Twist1, Twist2, and Slug by both the endothelium of the microvessels and cells within the interstitium, and Twist1 on the pericyte layer of the microvessels of proliferating IH, suggest the presence of a process similar to Endo-MT. This may enable a tightly controlled primitive endothelium of proliferating IH to acquire a migratory mesenchymal phenotype with the ability to migrate away, providing a plausible explanation for the development of a fibrofatty residuum observed during involution of IH.

Alterations on a key nephrogenic/cardiogenic gene expression linked to hypertension development

The elevation of blood pressure produces specific organic lesions, including kidney and cardiac damage. On the other hand, cardiovascular disease usually leads to the development of hypertension. Thus, hypertension could be both a cause and a consequence of cardiovascular disease. Previous studies linked the lack of nitric oxide to cardiovascular abnormalities, including hypertension, arteriosclerosis, myocardial infarction, cardiac hypertrophy, diastolic heart failure, and reduced endothelium-derived hyperpolarizing factor responses, with shorter survival. The lack of this gas also leads to renal/cardiac abnormalities. It is widely known that nephrogenic deficiency is a risk factor for kidney disease. Besides, recent evidence suggests that alterations in WT-1, a key nephrogenic factor, could contribute to the development of hypertension. Moreover, some genes involved in the development of hypertension depend on WT-1. This knowledge makes it essential to investigate and understand the mechanisms regulating the expression of these genes during renal/cardiac development, and hypertension. As a consequence, the most in-depth knowledge of the complex aetiopathogenic mechanism responsible for the hypertensive disease will allow us to propose novel therapeutic tools.

CP-31398 inhibits the progression of cervical cancer through reversing the epithelial mesenchymal transition via the downregulation of PAX2s

CP-31398, a styrylquinazoline, emerges from a screen for therapeutic agents that restore the wild-type DNA-binding conformation of mutant p53 to suppress tumors in vivo, but its effects on cervical cancer (CC) remain unknown. Hence, this study aimed to explore the effects CP-31398 has on the CC cells and to investigate whether it is associated with paired box 2 (PAX2) expression. CC cells were treated with different concentrations of CP-31398 (1, 2, 4, 6, 8, and 10 μg/ml) to determine the optimum concentration using fluorometric microculture cytotoxicity assay. After constructing the sh-PAX2 vector, CC cells were transfected with sh-PAX2 or treated with CP-31398. The effects of CP-31398 or PAX2 silencing on CC cell proliferation, apoptosis, invasion, and migration were evaluated. Epithelial mesenchymal transition (EMT)-related genes such as E-cadherin, vimentin, N-cadherin, snail, and twist in CC cells were detected. Tumor formation experiment in nude mice was performed to observe tumor growth. The optimum concentration of CP-31398 was 2 μg/ml. PAX2 was overexpressed in CC cells. CC cells treated with CP-31398 or treated with sh-PAX2 inhibited proliferation, invasion, and migration but promoted apoptosis with decreased PAX2 expression. The EMT process in CC cells was also reversed after treatment with CP-31398 or sh-PAX2. Moreover, the tumor formation experiment in nude mice revealed the inhibitory activity of CP-31398 in CC tumor in nude mice by suppressing PAX2. Our results provide evidence that CP-31398 could inhibit EMT and promote apoptosis of CC cells to curb CC tumor growth by downregulating PAX2.

PAX2 may induce ADAM10 expression in renal tubular epithelial cells and contribute to epithelial-to-mesenchymal transition

Purpose

We sought to investigate the role of PAX2 in renal epithelial-to-mesenchymal transition (EMT), examining the influence of PAX2 on ADAM10 expression during renal EMT and ADAM10 expression in fibrotic kidneys.

Methods

A rat renal tubular epithelial cell line, NRK52E, was transfected with lentivirus carrying PAX2, and E-cadherin and α-SMA expressions were measured. The influence of PAX2 on ADAM10 promoter activity was evaluated using chromatin immunoprecipitation (CHIP) and dual-luciferase reporter assay. We also treated NRK52E with ADAM10-specific over-expression vector and inhibitors and measured E-cadherin and α-SMA expression. In vivo, Wistar rats (n = 36) were subjected to unilateral ureteral obstruction (UUO) (n = 18) or sham surgery (n = 18), with tissues from post-operative day 3, 7, and 14 days examined, and PAX2/ADAM10 activity measured. ADAM10 expression was also assessed in kidneys from patients with chronic kidney disease (CKD).

Results

In NRK52E overexpressing PAX2, ADAM10 and α-SMA levels were increased, while E-cadherin levels were decreased. CHIP and dual-luciferase reporter assay showed that PAX2 directly bound to a specific site within the ADAM10 promoter, and over-expression of PAX2 significantly activated ADAM10 transcription. NRK52E with ADAM10 over-expression also significantly decreased E-cadherin and increased α-SMA levels. In the fibrotic kidneys of rats with UUO, E-cadherin levels were increased and α-SMA levels were decreased, and expression of PAX2 and ADAM10 increased. ADAM10 expression also elevated in the renal tissues of CKD patients.

Conclusions

PAX2 directly increased expression of ADAM10, the presence of which contributed to EMT in renal tubular epithelia and hence plays an important role in renal fibrosis.

MicroRNA-141-3p/200a-3p target and may be involved in post-transcriptional repression of RNA decapping enzyme Dcp2 during renal development

The RNA decapping enzyme Dcp2 is a crucial enzyme involved in the process of RNA turnover, which can post-transcriptionally regulate gene expression. Dcp2 has been found to be highly expressed in embryonic, but not adult, kidneys. Here we showed that Dcp2 mRNA was expressed, but Dcp2 proteins were absent, in mouse kidneys after postnatal day 10 (P10). In kidneys of adult Dcp2-IRES-EGFP knock-in mice, Dcp2 was undetectable but EGFP was expressed, indicating that Dcp2 mRNA was not completely silenced in adult kidneys. Using luciferase reporter assays, we found that miR-141-3p/200a-3p directly targeted the 3' UTR of Dcp2 mRNA. Overexpression of miR-141-3p and miR-200a-3p downregulated endogenous Dcp2 protein expression. Furthermore, miR-141-3p and miR-200a-3p expression was low in embryonic kidneys but increased dramatically after P10 and was negatively correlated with Dcp2 protein expression during renal development. These results suggest miR-141-3p/200a-3p may be involved in post-transcriptional repression of Dcp2 expression during renal development.

ABBREVIATIONS

IRES: internal ribosome entry site; EGFP: enhanced green fluorescent protein; UTR: untranslated region.

Snail and kidney fibrosis

Snail family zinc finger 1 (SNAI1) is a transcription factor expressed during renal embryogenesis, and re-expressed in various settings of acute kidney injury (AKI). Subjected to tight regulation, SNAI1 controls major biological processes responsible for renal fibrogenesis, including mesenchymal reprogramming of tubular epithelial cells, shutdown of fatty acid metabolism, cell cycle arrest and inflammation of the microenvironment surrounding tubular epithelial cells. The present review describes in detail the interactions of SNAI1 with AKI-associated signalling pathways. We also discuss how this central factor has been iteratively (and promisingly) targeted in a number of animal models in order to prevent or slow down renal fibrogenesis.

Heat shock protein 70/nitric oxide effect on stretched tubular epithelial cells linked to WT-1 cytoprotection during neonatal obstructive nephropathy

BACKGROUND

Mechanical stress is a key pathogenic driver of apoptosis in the tubular epithelium in obstructive nephropathy. Heat shock protein 70 (Hsp70) and Wilms' tumor (WT-1) have been proposed to represent linked downstream effectors of the cytoprotective properties of NO. In the present study, we sought to evaluate whether the cytoprotective effects of L-arginine in neonatal obstructive nephropathy may be associated with NO-dependent increases in WT-1 and Hsp70 expression.

METHODS

Neonatal Wistar-Kyoto rats were submitted to complete unilateral ureteral obstruction (UUO) and treated thereafter with vehicle, L-NAME or L-arginine by daily gavage for 14 days to block or augment NO levels, respectively. Normal rat kidney epithelial cells by NRK-52E were exposed to mechanical stress in vitro in the presence or absence of L-NAME, L-arginine, sodium nitroprusside (SNP), L-arginine + SNP or L-arginine/L-NAME. Induction of apoptosis and the mRNA expression of WT-1 and Hsp70 genes were assessed.

RESULTS

WT-1 and Hsp70 genes expression decreased in the presence of L-NAME and following UUO coincident with increased tubular apoptosis. L-arginine treatment increased NO levels, reduced apoptosis and restored expression levels of WT-1 and Hsp70 to control levels. L-arginine treatment in vitro reduced basal apoptotic rates and prevented apoptosis in response to mechanical strain, an effect enhanced by SNP co-incubation. L-NAME increased apoptosis and prevented the anti-apoptotic action of L-arginine.

CONCLUSIONS

L-arginine treatment in experimental neonatal UUO reduces apoptosis coincident with restoration of WT-1 and Hsp70 expression levels and directly inhibits mechanical strain-induced apoptosis in an NO-dependent manner in vitro. This potentially implicates an NO-Hsp70-WT-1 axis in the cytoprotective effects of L-arginine.

Molecular cloning of canine Wilms' tumor 1 for immunohistochemical analysis in canine tissues

Wilms’ tumor 1 (WT1) expression has been investigated in various human cancers as a target molecule for cancer immunotherapy. However, few studies have focused on WT1 expression in dogs. Firstly, cDNA of canine WT1 (cWT1) was molecularly cloned from normal canine kidney. The cross-reactivity of the anti-human WT1 monoclonal antibody (6F-H2) with cWT1 was confirmed via Western blotting using cells overexpressing cWT1. Immunohistochemical staining revealed that cWT1 expression was detected in all canine lymphoma tissues and in some normal canine tissues, including the kidney and lymph node. cWT1 is a potential immunotherapy target against canine cancers.

Emerging Transcriptional Mechanisms in the Regulation of Epithelial to Mesenchymal Transition and Cellular Plasticity in the Kidney

Notwithstanding controversies over the role of epithelial to mesenchymal transition in the pathogenesis of renal disease, the last decade has witnessed a revolution in our understanding of the regulation of renal cell plasticity. Significant parallels undoubtedly exist between ontogenic processes and the initiation and propagation of damage in the diseased kidney as evidenced by the reactivation of developmental programmes of gene expression, in particular with respect to TGFβ superfamily signaling. Indeed, multiple signaling pathways converge on a complex transcriptional regulatory nexus that additionally involves epigenetic activator and repressor mechanisms and microRNA regulatory networks that control renal cell plasticity. It is becoming increasingly apparent that differentiated cells can acquire an undifferentiated state akin to “stemness” which is leading us towards new models of complex cell behaviors and interactions. Here we discuss the latest findings that delineate new and novel interactions between this transcriptional regulatory network and highlight a hitherto poorly recognized role for the Polycomb Repressive Complex (PRC2) in the regulation of renal cell plasticity. A comprehensive understanding of how external stimuli interact with the epigenetic control of gene expression, in normal and diseased contexts, establishes a new therapeutic paradigm to promote the resolution of renal injury and regression of fibrosis.

PAX4 Defines an Expandable β-Cell Subpopulation in the Adult Pancreatic Islet

PAX4 is a key regulator of pancreatic islet development whilst in adult acute overexpression protects β-cells against stress-induced apoptosis and stimulates proliferation. Nonetheless, sustained PAX4 expression promotes β-cell dedifferentiation and hyperglycemia, mimicking β-cell failure in diabetic patients. Herein, we study mechanisms that allow stringent PAX4 regulation endowing favorable β-cell adaptation in response to changing environment without loss of identity. To this end, PAX4 expression was monitored using a mouse bearing the enhanced green fluorescent protein (GFP) and cre recombinase construct under the control of the islet specific pax4 promoter. GFP was detected in 30% of islet cells predominantly composed of PAX4-enriched β-cells that responded to glucose-induced insulin secretion. Lineage tracing demonstrated that all islet cells were derived from PAX4⁺ progenitor cells but that GFP expression was confined to a subpopulation at birth which declined with age correlating with reduced replication. However, this GFP⁺ subpopulation expanded during pregnancy, a state of active β-cell replication. Accordingly, enhanced proliferation was exclusively detected in GFP⁺ cells consistent with cell cycle genes being stimulated in PAX4-overexpressing islets. Under stress conditions, GFP⁺ cells were more resistant to apoptosis than their GFP^- counterparts. Our data suggest PAX4 defines an expandable β-cell sub population within adult islets.

Shear Stress-Induced Alteration of Epithelial Organization in Human Renal Tubular Cells

Tubular epithelial cells in the kidney are continuously exposed to urinary fluid shear stress (FSS) generated by urine movement and recent in vitro studies suggest that changes of FSS could contribute to kidney injury. However it is unclear whether FSS alters the epithelial characteristics of the renal tubule. Here, we evaluated in vitro and in vivo the influence of FSS on epithelial characteristics of renal proximal tubular cells taking the organization of junctional complexes and the presence of the primary cilium as markers of epithelial phenotype. Human tubular cells (HK-2) were subjected to FSS (0.5 Pa) for 48h. Control cells were maintained under static conditions. Markers of tight junctions (Claudin-2, ZO-1), Par polarity complex (Pard6), adherens junctions (E-Cadherin, β-Catenin) and the primary cilium (α-acetylated Tubulin) were analysed by quantitative PCR, Western blot or immunocytochemistry. In response to FSS, Claudin-2 disappeared and ZO-1 displayed punctuated and discontinuous staining in the plasma membrane. Expression of Pard6 was also decreased. Moreover, E-Cadherin abundance was decreased, while its major repressors Snail1 and Snail2 were overexpressed, and β-Catenin staining was disrupted along the cell periphery. Finally, FSS subjected-cells exhibited disappeared primary cilium. Results were confirmed in vivo in a uninephrectomy (8 months) mouse model where increased FSS induced by adaptive hyperfiltration in remnant kidney was accompanied by both decreased epithelial gene expression including ZO-1, E-cadherin and β-Catenin and disappearance of tubular cilia. In conclusion, these results show that proximal tubular cells lose an important number of their epithelial characteristics after long term exposure to FSS both in vitro and in vivo. Thus, the changes in urinary FSS associated with nephropathies should be considered as potential insults for tubular cells leading to disorganization of the tubular epithelium.

Epigenetic repression of Krüppel-like factor 4 through Dnmt1 contributes to EMT in renal fibrosis

Krüppel-like factor 4 (KLF4) is a transcription factor which plays divergent roles in a number of physiological or pathological process. However, the expression and role of KLF4 in renal fibrosis remain undetermined. The aim of the present study was to determine the epigenetic alterations of KLF4 and its potential role and mechanisms of action in epithelial-to-mesenchymal transition (EMT) in renal fibrosis. The hypermethylation of the KLF4 promoter accompanied by a decrease in KLF4 expression were observed in mice subjected to unilateral ureteral obstruction (UUO) and in HK-2 cells stimulated with transforming growth factor (TGF)-β1. However, treatment with 5-aza-2'-deoxycytidine attenuated the TGF-β1-induced downregulation of KLF4 and E-cadherin and the upregulation of α-smooth muscle actin (α-SMA) in the HK-2 cells. DNA methyltransferase 1 (Dnmt1) participated in the TGF-β1-mediated hypermethylation of the KLF4 promoter in the HK-2 cells. In addition, functional analysis demonstrated that the overexpression of KLF4 led to an increase in the expression of E-cadherin and zonula occludens-l (ZO-1), and a decrease in the expression of α-SMA and fibroblast-specific protein 1 (FSP-1), thus reversing the effects of the suppression of KLF4. These data suggest that KLF4 inhibits the progression of EMT in renal epithelial cells. In conclusion, our findings demonstrate that KLF4 is downregulated during EMT in renal fibrosis in vivo and in vitro; thus, KLF4 functions as a suppressor of renal fibrogenesis. The hypermethylation of KLF4 directly mediated by Dnmt1 contributes to the progression of EMT in renal epithelial cells. KLF4 promoter methylation may thus be a promising diagnostic marker or therapeutic target in renal fibrosis.

Pax genes: regulators of lineage specification and progenitor cell maintenance

Pax genes encode a family of transcription factors that orchestrate complex processes of lineage determination in the developing embryo. Their key role is to specify and maintain progenitor cells through use of complex molecular mechanisms such as alternate RNA splice forms and gene activation or inhibition in conjunction with protein co-factors. The significance of Pax genes in development is highlighted by abnormalities that arise from the expression of mutant Pax genes. Here, we review the molecular functions of Pax genes during development and detail the regulatory mechanisms by which they specify and maintain progenitor cells across various tissue lineages. We also discuss mechanistic insights into the roles of Pax genes in regeneration and in adult diseases, including cancer.

Cell atavistic transition: Paired box 2 re-expression occurs in mature tubular epithelial cells during acute kidney injury and is regulated by Angiotensin II

The regeneration of tubular epithelial cells (TECs) after acute kidney injury (AKI) is crucial for the recovery of renal structure and function. The mechanism by which quiescent TECs re-obtain a potential to regenerate remains unknown. In this study, we observed a transient re-expression of embryonic gene Paired box 2 (Pax2) in adult rat TECs in vivo during ischemia-reperfusion induced AKI and most Pax2 positive TECs co-expressed kidney injury molecule-1 (KIM-1), a tubular injury marker. The re-expression of Pax2 was accompanied by increased levels of intrarenal Angiotensin II, which is a crucial injury factor of AKI. Furthermore, we also found a temporary re-expression of Pax2 in NRK-52E cells under the stimulation of Angiotensin II. This stimulatory effect could be blocked by PD123319 (Angiotensin II type 2 receptor (AT2R) inhibitor) and AG490 (Janus Kinase 2 (JAK2) inhibitor). As Pax2 is essential for the phenotypic conversion from mesenchymal stem cells to TECs during kidney development, we proposed that the re-expression of Pax2 in mature TECs may be an indicator of “atavistic” transition which mimics but reverses the processes of development of TECs. This could be proved by that a progenitor marker, CD24, was also found to be transiently expressed shortly after the expression of Pax2 in NRK-52E cells stimulated with Angiotensin II. The expression of CD24 was also suppressed by PD123319 and AG490. Moreover, knockdown of Pax2 by RNA interference could significantly reduce the expression of CD24 in NRK-52E cells stimulated with Angiotension II. Those findings suggest that mature TECs can trans-differentiate into progenitor-like cells by “atavistic transition”, which may participate in the recovery of tissue structure and Pax2 may play a pivotal role in this process. That might have important implications for further understanding of tubular regeneration after injury.

Less expression of prohibitin is associated with increased paired box 2 (PAX2) in renal interstitial fibrosis rats

Prohibitin (PHB) and paired box 2 (PAX2) are associated with the development of renal interstitial fibrosis (RIF). This study was performed to investigate whether or not the PHB could regulate the PAX2 gene expression in unilateral ureteral obstruction (UUO) in rats. Eighty Wistar male rats were randomly divided into two groups: sham operation group (SHO) and model group subjected to unilateral ureteral obstruction (GU), n = 40, respectively. The model was established by left ureteral ligation. Renal tissues were collected at 14-day and 28-day after surgery. RIF index, protein expression of PHB, PAX2, transforming growth factor-βl (TGF-β1), α-smooth muscle actin (α-SMA), collagen-IV (Col-IV), fibronectin (FN) or cleaved Caspase-3, and cell apoptosis index in renal interstitium, and mRNA expressions of PHB, PAX2 and TGF-β1 in renal tissue were detected. When compared with those in SHO group, expression of PHB (mRNA and protein) was significantly reduced, and expressions of PAX2 and TGF-β1 (protein and mRNA) were markedly increased in the GU group (each p < 0.01). Protein expressions of α-SMA, Col-IV, FN and cleaved Caspase-3, and RIF index or cell apoptosis index in the GU group were markedly increased when compared with those in the SHO group (each p < 0.01). The protein expression of PHB was negatively correlated with protein expression of PAX2, TGF-β1, α-SMA, Col-IV, FN or cleaved Caspase-3, and RIF index or cell apoptosis index (all p < 0.01). In conclusion, less expression of PHB is associated with increased PAX2 gene expression and RIF index in UUO rats, suggesting that increasing the PHB expression is a potential therapeutic target for prevention of RIF.

PAX Genes in Cancer; Friends or Foes?

PAX genes have been shown to be critically required for the development of specific tissues and organs during embryogenesis. In addition, PAX genes are expressed in a handful of adult tissues where they are thought to play important roles, usually different from those in embryogenesis. A common theme in adult tissues is a requirement for PAX gene expression in adult stem cell maintenance or tissue regeneration. The connections between adult stem cell PAX gene expression and cancer are intriguing, and the literature is replete with examples of PAX gene expression in either situation. Here we systematically review the literature and present an overview of postnatal PAX gene expression in normal and cancerous tissue. We discuss the potential link between PAX gene expression in adult tissue and cancer. In addition, we discuss whether persistent PAX gene expression in cancer is favorable or unfavorable.