Plasticity of kidney cells: role in kidney remodeling and scarring

Endothelial cell plasticity in kidney fibrosis and disease

Renal endothelial cells demonstrate an impressive remodeling potential during angiogenic sprouting, vessel repair or while transitioning into mesenchymal cells. These different processes may play important roles in both renal disease progression or regeneration while underlying signaling pathways of different endothelial cell plasticity routes partly overlap. Angiogenesis contributes to wound healing after kidney injury and pharmaceutical modulation of angiogenesis may home a great therapeutic potential. Yet, it is not clear whether any differentiated endothelial cell can proliferate or whether regenerative processes are largely controlled by resident or circulating endothelial progenitor cells. In the glomerular compartment for example, a distinct endothelial progenitor cell population may remodel the glomerular endothelium after injury. Endothelial-to-mesenchymal transition (EndoMT) in the kidney is vastly documented and often associated with endothelial dysfunction, fibrosis, and kidney disease progression. Especially the role of EndoMT in renal fibrosis is controversial. Studies on EndoMT in vivo determined possible conclusions on the pathophysiological role of EndoMT in the kidney, but whether endothelial cells really contribute to kidney fibrosis and if not what other cellular and functional outcomes derive from EndoMT in kidney disease is unclear. Sequencing data, however, suggest no participation of endothelial cells in extracellular matrix deposition. Thus, more in-depth classification of cellular markers and the fate of EndoMT cells in the kidney is needed. In this review, we describe different signaling pathways of endothelial plasticity, outline methodological approaches and evidence for functional and structural implications of angiogenesis and EndoMT in the kidney, and eventually discuss controversial aspects in the literature.

Renal intrinsic cells remodeling in diabetic kidney disease and the regulatory effects of SGLT2 Inhibitors

Diabetic kidney disease (DKD) is a prevalent complication of diabetes and a major secondary factor leading to end-stage renal disease. The kidney, a vital organ, is composed of a heterogeneous group of intrinsic cells, including glomerular endothelial cells, podocytes, mesangial cells, tubular epithelial cells, and interstitial fibroblasts. In the context of DKD, hyperglycemia elicits direct or indirect injury to these intrinsic cells, leading to their structural and functional changes, such as cell proliferation, apoptosis, and transdifferentiation. The dynamic remodeling of intrinsic cells represents an adaptive response to stimulus during the pathogenesis of diabetic kidney disease. However, the persistent stimulus may trigger an irreversible remodeling, leading to fibrosis and functional deterioration of the kidney. Sodium-glucose cotransporter 2 (SGLT2) inhibitors, a new class of hypoglycemic drugs, exhibit efficacy in reducing blood glucose levels by curtailing renal tubular glucose reabsorption. Furthermore, SGLT2 inhibitors have been shown to modulate intrinsic cell remodeling in the kidney, ameliorate kidney structure and function, and decelerate DKD progression. This review will elaborate on the intrinsic cell remodeling in DKD and the underlying mechanism of SGLT2 inhibitors in modulating it from the perspective of the renal intrinsic cell, providing insights into the pathogenesis of DKD and the renal protective action of SGLT2 inhibitors.

MCP-1/IL-12 ratio expressions correlated with adventitial collagen depositions in renal vessels and IL-4/IFN-γ expression correlated with interstitial collagen depositions in the kidneys of dogs with canine leishmaniasis

Collagen deposition is a common event in chronic inflammation, and canine Leishmaniosis (CanL) is generally associated with a long and chronic evolution. Considering that the kidney shows fibrinogenic changes during CanL, and the balance of cytokines/chemokines regulates the profibrinogenic and antifibrinogenic immune responses differently, it can be hypothesized that the balance of cytokines/chemokines can be differentially expressed in the renal tissue in order to determine the expression of collagen depositions in the kidneys. This study aimed to measure collagen deposition and to evaluate cytokine/chemokine expressions in the kidney by means of qRT-PCR in sixteen Leishmania-infected dogs and six uninfected controls. Kidney fragments were stained with hematoxylin & eosin (H&E), Masson's Trichrome, Picrosirius Red, and Gomori's reticulin. Intertubular and adventitial collagen depositions were evaluated by the morphometric approach. Cytokine RNA expressions were measured by means of qRT-PCR to identify molecules involved in chronic collagen depositions in kidneys with CanL. Collagen depositions were related to the presence of clinical signs, and more intense intertubular collagen depositions occurred in infected dogs. Adventitial collagen deposition, as morphometrically measured by the average area of the collagen, was more intense in clinically affected dogs than in subclinically infected dogs. TNF-α/TGF-β, MCP1/IL-12, CCL5/IL-12, IL-4/IFN-γ, and IL-12/TGF-β expressions were associated with clinical manifestations in dogs with CanL. The IL-4/IFN-α ratio was more commonly expressed and upregulated in clinically affected dogs, and downregulated in subclinically infected dogs. Furthermore, MCP-1/IL-12 and CCL5/IL-12 were more commonly expressed in subclinically infected dogs. Strong positive correlations were detected between morphometric values of interstitial collagen depositions and MCP-1/IL-12, IL-12, and IL-4 mRNA expression levels in the renal tissues. Adventitial collagen deposition was correlated with TGF-β, IL-4/IFN-γ, and TNF-α/TGF-β. In conclusion, our results showed the association of MCP-1/IL-12 and CCL5/IL-12 ratios with an absence of clinical signs, as well as an IL-4/IFN-α ratio with adventitial and intertubular collagen depositions in dogs with visceral leishmaniosis.

Intrarenal arterial administration of human umbilical cord-derived mesenchymal stem cells effectively preserved the residual renal function of diabetic kidney disease in rat

Background

This experimental study was designed as a preclinical study for testing the hypothesis that intrarenal arterial (IRA) transfusion of human umbilical cord-derived mesenchymal stem cells (HUCDMSCs) therapy preserved the residual renal function of diabetic kidney disease (DKD) in rat [induction by 5/6 nephrectomy of left kidney and right nephrectomy, followed by intraperitoneal administration of aminoguanidine (180 mg/kg) and streptozotocin (30 mg/kg)].

Methods

Animals (n = 24) were categorized into group 1 (sham-operated control), group 2 (DKD), group 3 [DKD + HUCDMSCs (2.1 × 10⁵/IRA injection at day 28 after CKD induction)] and group 4 [(DKD + HUCDMSCs (6.3 × 10⁵/IRA injection)].

Results

By day 60 after DKD induction, the kidneys were harvested and the result showed that the creatinine level, ratio of urine protein/urine creatinine and kidney injury score were lowest in group 1, highest in group 2 and significantly lower in group 4 than in group 3 (all p < 0.0001). The protein expressions of apoptotic (cleaved caspase-3/cleaved PARP/mitochondrial Bax), fibrotic (TGF-ß/p-Smad3), autophagic (ratio of LC3B-II/LC3B-I, Atg5/Beclin-1), oxidative stress (NOX-1/NOX-2/oxidized protein/p22phox), mitochondrial/DNA-damaged (cytosolic-cytochrome-C/DRP1/γ-H2AX) and inflammatory (MMP-9/TNF-α/p-NF-κB) biomarkers exhibited an identical pattern, whereas the protein expressions of angiogenesis factors (CD31/vWF/vascularity) exhibited an opposite pattern of creatinine level among the groups (all p < 0.0001). Histopathological findings demonstrated the renal tubular-damaged (KIM-1)/kidney fibrosis area/oxidative stress (8-OHdG + cells) expressed an identical pattern, whereas the podocyte components (ZO-1/synaptopodin/podocin) exhibited an opposite pattern of creatinine level among the groups (all p < 0.0001). No tumorigenesis or immune rejection event was identified.

Conclusion

IRA injection of xenogeneic MSCs was safe and effectively protected the residual renal function and architectural integrity in DKD rat.

Identification of functional pathways for regenerative bioactivity of selected renal cells

Background

Selected renal cells (SRC) are in Phase II clinical trials as a kidney-sourced, autologous, tubular epithelial cell-enriched cell-based therapy for chronic kidney disease (CKD). In preclinical studies with rodent models of CKD, SRC have been shown to positively modulate key renal biomarkers associated with development of the chronic disease condition.

Methods

A comparative bioinformatic analysis of transcripts specifically enriched or depleted in SRC component sub-populations relative to the initial, biopsy-derived cell source was conducted.

Results

Outcomes associated with therapeutically relevant bioactivity from a systematic, genome-wide transcriptomic profiling of rodent SRC are reported. Key transcriptomic networks and concomitant signaling pathways that may underlie SRC mechanism of action as manifested by reparative, restorative, and regenerative bioactivity in rodent models of chronic kidney disease are identified. These include genes and gene networks associated with cell cycle control, transcriptional control, inflammation, ECM–receptor interaction, immune response, actin polymerization, regeneration, cell adhesion, and morphogenesis.

Conclusions

These data indicate that gene networks associated with development of the kidney are also leveraged for SRC regenerative bioactivity, providing evidence of potential mechanisms of action.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-02713-6.

Ectodomain shedding by ADAM proteases as a central regulator in kidney physiology and disease

Besides its involvement in blood and bone physiology, the kidney's main function is to filter substances and thereby regulate the electrolyte composition of body fluids, acid-base balance and toxin removal. Depending on underlying conditions, the nephron must undergo remodeling and cellular adaptations. The proteolytic removal of cell surface proteins via ectodomain shedding by A Disintegrin and Metalloproteases (ADAMs) is of importance for the regulation of cell-cell and cell-matrix adhesion of renal cells. ADAM10 controls glomerular and tubule development in a Notch1 signaling-dependent manner and regulates brush border composition. ADAM17 regulates the renin angiotensin system and is together with ADAM10 involved in calcium phosphate homeostasis. In kidney disease ADAMs, especially ADAM17 contribute to inflammation through their involvement in IL-6 trans-signaling, Notch-, epithelial growth factor receptor-, and tumor necrosis factor α signaling. ADAMs are interesting drug targets to reduce the inflammatory burden, defective cell adhesion and impaired signaling pathways in kidney diseases.

Xenoestrogen exposure and kidney function in the general population: Results of a community-based study by laboratory tests and questionnaire-based interviewing

BACKGROUND

Chronic kidney disease (CKD) is a growing concern worldwide. Exposure to xenoestrogens (XEs), such as phthalates, parabens, and phenols, lead to CKD. However, kidney function and its complex relationship with XEs, lifestyle, and dietary habits are not well understood.

METHODS

In the present cross-sectional community-based cohort study, we enrolled 887 subjects for a questionnaire-based interview and laboratory tests. XE exposure concerning lifestyle/dietary habits were evaluated using questionnaires. Urinary levels of 17XE metabolites were measured in 60 subjects with high exposure risk scores and 60 subjects with low exposure risk scores.

RESULTS

Univariate and multivariate linear regression showed that a high exposure score (β ± SE: 4.226 ± 1.830, P = 0.021) was independently negatively associated with eGFR in 887 subjects. Univariate and multivariate linear regression to urinary XEs and urine albumin creatinine excretion ratio (UACR) in 120 subjects indicated that ethylparaben (EP) (β: 1.934, 95% CI: 0.135-3.733, P = 0.035) was significantly associated with increased UACR. Multivariate regression analyses of the CKD subgroup (n = 38), after adjusting for age, showed that higher levels of mono-(2-ethylhexyl) phthalate (MEHP), EP, nonylphenol (NP), and benzophenone-3 (BP-3) were significantly associated with lower estimated glomerular filtration rate (eGFR). Higher urinary levels of MEHP (OR: 3.037, 95% CI: 1.274-7.241) were more likely associated with high exposure scores (>5 points), after adjusting for diabetes, gender, eGFR, age, Na, Ca, albumin, vitamin D, systolic blood pressure (SBP), white blood cell count, total bilirubin, aspartate transaminase, and heart rate. MEHP (β ± SE: 0.033 ± 0.009, P < 0.001) was also significantly positively associated with total exposure scores after applying multivariate linear regression analyses.

CONCLUSION

XE exposure scores obtained from the questionnaires were negatively associated with kidney function. Urinary metabolites of XEs, including EP, NP, BP-3, and MEHP, are potential risk factors for microalbuminuria and decline in kidney function. MEHP seemed to have the strongest correlation with high exposure scores and decline in kidney function.

Renal Mononuclear Phagocytes in Lupus Nephritis

Renal mononuclear phagocytes are a highly pleiotropic group of immune cells of myeloid origin that play multiple protective and pathogenic roles in tissue homeostasis, inflammation, repair, and fibrosis. Infiltration of kidneys with these cells is a hallmark of lupus nephritis and is associated with more severe disease and with increased risk of progression to end‐stage renal disease. This review presents current knowledge of the diversity of these cells and their involvement in kidney inflammation and resolution and describes how they contribute to the chronic inflammation of lupus nephritis. A better understanding of the subset heterogeneity and diverse functions of mononuclear phagocytes in the lupus nephritis kidney should provide fertile ground for the development of new therapeutic approaches that promote the differentiation and survival of protective subsets while targeting pathogenic cell subsets that cause inflammation and fibrosis.

Intrarenal Renin–Angiotensin System Involvement in the Pathogenesis of Chronic Progressive Nephropathy—Bridging the Informational Gap Between Disciplines

Chronic progressive nephropathy (CPN) is the most commonly encountered spontaneous background finding in laboratory rodents. Various theories on its pathogenesis have been proposed, but there is a paucity of data regarding specific mechanisms or physiologic pathways involved in early CPN development. The current CPN mechanism of action for tumorigenesis is largely based on its associated increase in tubular cell proliferation without regard to preceding subcellular degenerative changes. Combing through the published literature from multiple biology disciplines provided insight into the preceding cellular events. Mechanistic pathways involved in the progressive age-related decline in rodent kidney function and several key inflexion points have been identified. These critical pathway factors were then connected using data from renal models from multiple rodent strains, other species, and mechanistic work in humans to form a cohesive picture of pathways and protein interactions. Abundant data linked similar renal pathologies to local events involving hypoxia (hypoxia-inducible factor 1α), altered intrarenal renin–angiotensin system (RAS), oxidative stress (nitric oxide), and pro-inflammatory pathways (transforming growth factor β), with positive feedback loops and downstream effectors amplifying the injury and promoting scarring. Intrarenal RAS alterations seem to be central to all these events and may be critical to CPN development and progression.

Sitagliptin and shock wave-supported peripheral blood derived endothelial progenitor cell therapy effectively preserves residual renal function in chronic kidney disease in rat-role of dipeptidyl peptidase 4 inhibition

This study tested whether sitagliptin and shock wave (SW)-assisted circulatory-derived autologous endothelial progenitor cell (EPC) therapy would effectively preserve residual renal function in chronic kidney disease (CKD) induced by 5/6 left-nephrectomy/remove right kidney plus daily feeding high-protein diet (H^PD) in rat. Adult-male SD rats (n = 40) were categorized into group 1 (sham-operated control with H^PD), group 2 (H^PD-CKD), group 3 [H^PD-CKD + EPC (1.2 × 10⁶ cell)/intra-vessel administration by day 14 after CKD-induction], group 4 [H^PD-CKD + SW (0.12 mJ/mm²/180 shorts) at days 14/21/28 after CKD-induction by ultrasound-guided application] and group 5 [H^PD-CKD + SW + EPC + sitagliptin (Sita; 600 mg/kg/day since day 14 after CKD induction)]. All animals were euthanized by day 60. By day 60, renal blood flow (RBF) was highest in group 1 and progressively increased from groups 2 to 5, whereas the levels of creatinine/BUN/proteinuria exhibited an opposite pattern of RBF among the five groups (all p < 0.001). The circulating levels of GLP-1/SDF-1α and protein levels of angiogenesis (VEGF/SDF-1α/CXCR4) and GLP-1R in kidney were progressively increased from groups 1 to 5, whereas circulating DPP4 activity exhibited an opposite pattern of SDF-1α among the groups (all p < 0.0001). The protein expressions of oxidative-stress (NOX-1/NOX-2/oxidized protein), apoptosis (Bax/caspase-3/PARP), fibrosis (Smad3/TGF-ß) and inflammation (TNF-α/NF-κB/MMP-2) and kidney injury score displayed an opposite pattern, whereas the protein expressions of TMP2, endothelial-cell markers (CD31/eNOS) and podocyte integrity biomarkers (podocin/ZO-1/synaptopodin) exhibited an identical pattern of RBF among the groups (all p < 0.001). In conclusion Sita associated SW-assisted EPC effectively protected residual renal function in CKD.

Glomeruli from patients with nephrin mutations show increased number of ciliated and poorly differentiated podocytes

BACKGROUND

Podocytes are postmitotic, highly specialized cells which maintain the glomerular filtration barrier (GFB). Their injury is characterized by foot processes effacement and change in protein expression leading to proteinuria and end-stage kidney disease.

METHODS

Our study focuses on the morphological and immunohistochemical changes of human podocytes during normal development and postnatal period, compared to congenital nephrotic syndrome of the Finnish type (CNF). Kidney tissues taken from 17 human conceptuses 8th-38th weeks old, two healthy and three CNF kidneys were embedded in paraffin for immunohistochemical or double immunofluorescence methods, or were embedded in resin for electron microscopy. Paraffin sections were stained with markers for proliferation (Ki-67), proteins nephrin and nestin, and alpha-tubulin. Quantification of positive cells were performed using Mann Whitney and Kruskal-Wallis test.

RESULTS

Tissue analysis showed that proliferation of podocytes gradually decreased during development and disappeared in postnatal period. Decrease in number of ciliated glomerular cells and visceral podocytes (from 47% to 3%), and parietal epithelial cells (from 32% to 7%) characterized normal development. Nestin and nephrin co-expressed in developing podocytes in different cellular compartments. During development, nephrin expression increased (from 17% to 75%) and postnatally changed its pattern, while nestin positive glomerular cells decreased from 98% to 40%. CNF glomeruli displayed increased number of immature ciliated podocytes (6%) and parietal epithelial cells (9%).

CONCLUSION

Changes in cytoplasmic alpha-tubulin expression and reduced nephrin expression (20%) indicating association of incomplete podocyte maturation with failure of GFB function and appearance of prenatal proteinuria in CNF patients.

Phenotypic plasticity of mesenchymal stem cells is crucial for mesangial repair in a model of immunoglobulin light chain-associated mesangial damage

Mesangiopathies produced by glomerulopathic monoclonal immunoglobulin light chains (GLCs) acting on the glomerular mesangium produce two characteristic lesions: AL-amyloidosis (AL-Am) and light chain deposition disease (LCDD). In both cases, the pathology is centered in the mesangium, where initial and progressive damage occurs. In AL-Am the mesangial matrix is destroyed and replaced by amyloid fibrils and in LCDD, the mesangial matrix is increased and remodeled. The collagen IV rich matrix is replaced by tenascin. In both conditions, mesangial cells (MCs) become apoptotic as a direct effect of the GLCs. MCs were incubated in-vitro with GLCs and animal kidneys were perfused ex-vivo via the renal artery with GLCs, producing expected lesions, and then mesenchymal stem cells (MSCs) were added to both platforms. Each of the two platforms provided unique information that when put together created a comprehensive evaluation of the processes involved. A "cocktail" with growth and differentiating factors was used to study its effect on mesangial repair. MSCs displayed remarkable phenotypic plasticity during the repair process. The first role of the MSCs after migrating to the affected areas was to dispose of the amyloid fibrils (in AL-Am), the altered mesangial matrix (in LCDD) and apoptotic MCs/debris. To accomplish this task, MSCs transformed into facultative macrophages acquiring an abundance of lysosomes and endocytotic capabilities required to engage in phagocytic functions. Once the mesangial cleaning was completed, MSCs transformed into functional MCs restoring the mesangium to normal. "Cocktail" made the repair process more efficient.

KIFC1, a novel potential prognostic factor and therapeutic target in hepatocellular carcinoma

Kinesin family member C1 (KIFC1, also known as HSET) is a minus end-directed motor protein, which is critical in centrosome clustering. The present study investigated the expression of KIFC1 in paired hepatocellular carcinoma (HCC) tissues and adjacent non-cancerous tissues from 91 patients by immunohistochemical analysis; clinical data were concomitantly collected. KIFC1 was expressed at high levels in HCC tissues, compared with that in peritumoral tissues (54.9 vs. 14.3%; P<0.01), and its expression correlated with tumor emboli, metastasis, recurrence and time of recurrence. Kaplan-Meier analysis showed that the expression of KIFC1 was significantly associated with tumor-free survival rates. In addition, multivariate analyses revealed that the overexpression of KIFC1was an independent predictive marker in patients with HCC. Consistently, data derived from GEPIA was in agreement with the results. In vitro, KIFC1 knockdown effectively decreased HCC cell viability, and induced apoptosis and cell death. KIFC1 knockdown also significantly suppressed tumor cell migration and invasion in vitro. Mechanistically, the apoptosis-related protein, B-cell lymphoma-2 (Bcl-2), was downregulated in KIFC1 small interfering RNA-treated groups, whereas thee levels of Bcl-2-associated X protein and p53 were upregulated. In addition, the expression levels of phosphorylated phosphoinositide 3-kinase and phosphorylated AKT were decreased significantly when KIFC1 was silenced. The epithelial-mesenchymal transition-related proteins, N-cadherin, matrix metalloproteinase-2 (MMP-2), β-catenin, Slug, and Zinc finger E-box-binding homeobox 1, were downregulated, whereas the expression of E-cadherin was upregulated. The overexpression of KIFC1 was correlated closely with the progression of HCC and poor prognosis, and suggested that the expression levels of KIFC1 are a potential prognostic biomarker and therapeutic target in HCC.

Investigated the safety of intra-renal arterial transfusion of autologous CD34+ cells and time courses of creatinine levels, endothelial dysfunction biomarkers and micro-RNAs in chronic kidney disease patients-phase I clinical trial

This was a phase I clinical trial to investigate the safety of autologous peripheral-blood-derived CD34+ cell therapy for patients with chronic kidney disease (CKD-treatment) (i.e., at Stages III and IV). Between November 2014 and October 2015, a total of 10 study patients were prospectively enrolled into this phase I trial. Patients who failed to enroll into the trial in the initial state of eligibility assessment were served as CKD-control group (n = 9). The health-control group was composed of 10 volunteers for the purposes of comparing (1) circulation level of endothelial progenitor cells (EPCs), (2) angiogenesis ability, and (3) anti-apoptotic miRNAs between healthy subjects and CKD patients. CD34+ cells (5.0 x 107) were transfused into right-renal artery after subcutaneous G-CSF injection (5μg/kg/twice a day for 4 days). Circulating EPC number, angiogenesis capacity (i.e., Matrigel assay) and anti-apoptotic miRNAs (miR-374a-5p/miR-19a-3p/ miR-106b-5p/miR-26b-5p/ miR-20a-5p) were significantly lower in CKD patients than in healthy subjects (all p < 0.001). Flow-cytometric analysis of renal-vein blood samplings (i.e., at 0/5/10/30 mins after cell transfusion) showed the EPC level was significantly progressively increased (p < 0.001). Procedural safety was 100% with all patients uneventfully discharged and one-year survival rate was 100%. The paired-t test showed serum creatinine maintained the same level between the baseline and at the end of one-year follow-up (all p > 0.4), whereas the net increase between initial and final creatinine level was higher in CKD-control than in CKD-treatment. In conclusion, CD34+ cell therapy was safe and maintained the renal function in stationary state at the end of study period.

Liraglutide Reduces Both Atherosclerosis and Kidney Inflammation in Moderately Uremic LDLr-/- Mice

Chronic kidney disease (CKD) leads to uremia. CKD is characterized by a gradual increase in kidney fibrosis and loss of kidney function, which is associated with a progressive increase in risk of atherosclerosis and cardiovascular death. To prevent progression of both kidney fibrosis and atherosclerosis in uremic settings, insight into new treatment options with effects on both parameters is warranted. The GLP-1 analogue liraglutide improves glucose homeostasis, and is approved for treatment of type 2 diabetes. Animal studies suggest that GLP-1 also dampens inflammation and atherosclerosis. Our aim was to examine effects of liraglutide on kidney fibrosis and atherosclerosis in a mouse model of moderate uremia (5/6 nephrectomy (NX)). Uremic (n = 29) and sham-operated (n = 14) atherosclerosis-prone low density lipoprotein receptor knockout mice were treated with liraglutide (1000 μg/kg, s.c. once daily) or vehicle for 13 weeks. As expected, uremia increased aortic atherosclerosis. In the remnant kidneys from NX mice, flow cytometry revealed an increase in the number of monocyte-like cells (CD68⁺F4/80^-), CD4⁺, and CD8⁺ T-cells, suggesting that moderate uremia induced kidney inflammation. Furthermore, markers of fibrosis (i.e. Col1a1 and Col3a1) were upregulated, and histological examinations showed increased glomerular diameter in NX mice. Importantly, liraglutide treatment attenuated atherosclerosis (~40%, p < 0.05) and reduced kidney inflammation in NX mice. There was no effect of liraglutide on expression of fibrosis markers and/or kidney histology. This study suggests that liraglutide has beneficial effects in a mouse model of moderate uremia by reducing atherosclerosis and attenuating kidney inflammation.

Podocyte injury and its consequences

Podocytes maintain the glomerular filtration barrier, and the stability of this barrier depends on their highly differentiated postmitotic phenotype, which also defines the particular vulnerability of the glomerulus. Recent podocyte biology and gene disruption studies in vivo indicate a causal relationship between abnormalities of single podocyte molecules and proteinuria and glomerulosclerosis. Podocytes live under various stresses and pathological stimuli. They adapt to maintain homeostasis, but excessive stress leads to maladaptation with complex biological changes including loss of integrity and dysregulation of cellular metabolism. Podocyte injury causes proteinuria and detachment from the glomerular basement membrane. In addition to "sick" podocytes and their detachment, our understanding of glomerular responses following podocyte loss needs to address the pathways from podocyte injury to sclerosis. Studies have found a variety of glomerular responses to podocyte dysfunction in vivo, such as disruption of podocyte-endothelial cross talk and activation of podocyte-parietal cell interactions, all of which help us to understand the complex scenario of podocyte injury and its consequences. This review focuses on the cellular aspects of podocyte dysfunction and the adaptive or maladaptive glomerular responses to podocyte injury that lead to its major consequence, glomerulosclerosis.

Pathogenesis of Type 2 Epithelial to Mesenchymal Transition (EMT) in Renal and Hepatic Fibrosis

Epithelial to mesenchymal transition (EMT), particularly, type 2 EMT, is important in progressive renal and hepatic fibrosis. In this process, incompletely regenerated renal epithelia lose their epithelial characteristics and gain migratory mesenchymal qualities as myofibroblasts. In hepatic fibrosis (importantly, cirrhosis), the process also occurs in injured hepatocytes and hepatic progenitor cells (HPCs), as well as ductular reaction-related bile epithelia. Interestingly, the ductular reaction contributes partly to hepatocarcinogenesis of HPCs, and further, regenerating cholangiocytes after injury may be derived from hepatic stellate cells via mesenchymal to epithelia transition, a reverse phenomenon of type 2 EMT. Possible pathogenesis of type 2 EMT and its differences between renal and hepatic fibrosis are reviewed based on our experimental data.

High‑mobility group box 1 has a prognostic role and contributes to epithelial mesenchymal transition in human hepatocellular carcinoma

High‑mobility group box 1 (HMGB1), a member of the high‑mobility group protein family, was originally characterized as a non‑histone, nuclear DNA‑binding protein. While the roles of HMGB1 in inflammation and cell differentiation have been previously reported, its role in tumor cell migration and invasion, particularly in hepatocellular carcinoma (HCC), has remained elusive. The present study reported that the expression of HMGB1 in HCC tissues was significantly higher than that in matched tumor‑adjacent tissues (P<0.05). HMGB1 was expressed at significantly elevated levels in tumors of patients with large tumor size, high histological grade and advanced tumor‑node‑metastasis stage (P<0.05). The positive expression of HMGB1 correlated with a poor three‑year overall and disease‑free survival of HCC patients (P<0.05). In addition, HMGB1 was an independent factor for predicting the three‑year overall and disease‑free survival of HCC patients (P<0.05). An in vitro experiment revealed that knockdown of HMGB1 inhibited cell migration and invasion in the HCC cell lines Huh7 and MHCC97H (P<0.05). Furthermore, western blot analysis showed that HMGB1 knockdown markedly inhibited epithelial mesenchymal transition in Huh7 and MHCC97H cells. These results suggested that HMGB1 may be utilized as an independent prognostic marker in HCC and may promote tumor progression by promoting cell migration and invasion.

Novel approach for the detection of tubular cell migration into the interstitium during renal fibrosis in rats

Background

The process of epithelial-mesenchymal transition (EMT), which is generally defined by phenotypic changes of injured tubules such as loss of epithelial markers or acquisition of mesenchymal markers, implies various activating steps, including proliferation, migration, and ability to produce extracellular matrix proteins. We established here a novel approach for the detection of tubular cell migration into the interstitium during renal fibrosis in vivo.

Results

Using an osmotic pump, bromodeoxyuridine (BrdU) was continuously given to 7-week-old Wistar rats for 4 weeks, and BrdU-positive cells were detected by immunostaining. BrdU-positive cells were present in aquaporin-1-positive proximal tubules, but not in the interstitium of BrdU-treated rat kidneys. After unilateral ureteral obstruction (UUO), some BrdU-positive tubular cells protruded from the basement membrane and migrated into the interstitium. Interstitial BrdU-positive cells were co-localized with alpha-smooth muscle actin, fibroblast specific protein-1, vimentin, and type I collagen, but not with CD68 or CD3. No BrdU-positive cells were observed in the interstitium of sham-operated kidneys. The number of BrdU-positive cells migrating into the interstitium significantly increased and peaked at 8 days after UUO.

Conclusions

Long-term BrdU labeling marked some of the proximal tubular cells and enabled us to detect tubular cell migration into the interstitium after UUO. This simple method might be useful to detect EMT in vivo.

Pharmacological inhibition of galectin-3 protects against hypertensive nephropathy

Galectin-3 activation is involved in the pathogenesis of renal damage and fibrogenesis. Limited data are available to suggest that galectin-3-targeted intervention is a potential therapeutic candidate for the prevention of chronic kidney disease. Homozygous TGR(mREN)27 (REN2) rats develop severe high blood pressure (BP) and hypertensive end-organ damage, including nephropathy and heart failure. Male REN2 rats were treated with N-acetyllactosamine [galectin-3 inhibitor (Gal3i)] for 6 wk; untreated REN2 and Sprague-Dawley rats served as controls. We measured cardiac function with echocardiogram and invasive hemodynamics before termination. BP and proteinuria were measured at baseline and at 3 and 6 wk. Plasma creatinine was determined at 6 wk. Renal damage was assessed for focal glomerular sclerosis, glomerular desmin expression, glomerular and interstitial macrophages, kidney injury molecule-1 expression, and α-smooth muscle actin expression. Inflammatory cytokines and extracellular matrix proteinases were quantified by quantitative real-time PCR. Systolic BP was higher in control REN2 rats, with no effect of Gal3i treatment. Plasma creatinine and proteinuria were significantly increased in control REN2 rats; Gal3i treatment reduced both. Renal damage (focal glomerular sclerosis, desmin, interstitial macrophages, kidney injury molecule-1, α-smooth muscle actin, collagen type I, and collagen type III) was also improved by Gal3i. All inflammatory markers (CD68, IL-68, galectin-3, and monocyte chemoattractant protein-1) were elevated in control REN2 rats and attenuated by Gal3i. Markers of extracellular matrix turnover were marginally altered in untreated REN2 rats compared with Sprague-Dawley rats. In conclusion, galectin-3 inhibition attenuated hypertensive nephropathy, as indicated by reduced proteinuria, improved renal function, and decreased renal damage. Drugs binding to galectin-3 may be therapeutic candidates for the prevention of chronic kidney disease.

Cordyceps sinensis polysaccharide CPS-2 protects human mesangial cells from PDGF-BB-induced proliferation through the PDGF/ERK and TGF-β1/Smad pathways

CPS-2, a Cordyceps sinensis polysaccharide, has been demonstrated to have significant therapeutic activity against chronic renal failure. However, little is known about the underlying molecular mechanism. In this study, we found that CPS-2 could inhibit PDGF-BB-induced human mesangial cells (HMCs) proliferation in a dose-dependent manner. In addition, CPS-2 notably suppressed the expression of α-SMA, PDGF receptor-beta (PDGFRβ), TGF-β1, and Smad 3 in PDGF-BB-treated HMCs. Furthermore, PDGF-BB-stimulated ERK activation was significantly inhibited by CPS-2, and this inhibitory effect was synergistically potentiated by U0126. CPS-2 could prevent the PDGFRβ promoter activity induced by PDGF-BB, and return expression of PDGFRβ, TGF-β1, and TGFβRI to normal levels while cells were under PDGFRβ and ERK silencing conditions and transfected with DN-ERK. Taken together, these findings demonstrated that CPS-2 reduces PDGF-BB-induced cell proliferation through the PDGF/ERK and TGF-β1/Smad pathways, and it may have bi-directional regulatory effects on the PDGF/ERK cellular signaling pathway.

Serum-free culture of rat proximal tubule cells with enhanced function on chitosan

The proximal tubule performs a variety of important renal functions and is the major site for nutrient reabsorption. The purpose of this study is to culture rat renal proximal tubule cells (PTCs) on chitosan without serum to maintain a transcellular pathway to transport water and ions effectively without loss of highly differentiated cell function. The effect of chitosan, which is structurally similar to glycosaminoglycans, in the absence of serum on the primary cultured PTCs was compared that of collagen with or without serum. Two days after seeding, more tubule fragments and higher PTC viability were observed on chitosan than on collagen with or without serum. Proliferation marker Ki-67 immunostaining and phosphorylated extracellular-regulated kinase (ERK) expression results displayed similar proliferation capability of PTCs established on chitosan without serum and collagen with 2% fetal bovine serum after 4 days of incubation. When grown to confluence, PTCs formed a monolayer with well-organized tight junctions and formation of domes on chitosan without serum. Moreover, evaluation of the transepithelial electrical resistance showed that both chitosan and serum were involved in the modification of water and ion transport in confluent cells. By showing the direct suppression of PTC growth and dome formation treated with heparinase, we demonstrated that the interaction between cell surface heparin sulfate proteoglycan and chitosan played an important role in PTC proliferation and differentiation. A successful primary culture of PTCs has now been produced on chitosan in serum-free culture condition, which offers potential applications for chitosan in renal tissue engineering.

Suppression of XBP1S mediates high glucose-induced oxidative stress and extracellular matrix synthesis in renal mesangial cell and kidney of diabetic rats

Recent evidences suggest that endoplasmic reticulum (ER) stress was involved in multi pathological conditions, including diabetic nephropathy (DN). X-box binding protein 1(XBP1), as a key mediator of ER stress, has been proved having the capability of preventing oxidative stress. In this study, we investigated the effects of spliced XBP1 (XBP1S), the dominant active form of XBP1, on high glucose (HG)-induced reactive oxygen species (ROS) production and extracellular matrix (ECM) synthesis in cultured renal mesangial cells (MCs) and renal cortex of STZ-induced diabetic rats. Real time PCR and Western blot were used to evaluate the mRNA and protein levels respectively. Transfection of recombinant adenovirus vector carrying XBP1S gene (Ad-XBP1S) was used to upregulate XBP1S expression. XBP1S siRNA was used to knockdown XBP1S expression. ROS level was detected by dihydroethidium (DHE) fluorescent probe assay. The results showed that HG treatment significantly reduced XBP1S protein and mRNA level in the cultured MCs while no obvious change was observed in unspliced XBP1 (XBP1U). In the mean time, the ROS production, collagen IV and fibronectin expressions were increased. Diphenylene-chloride iodonium (DPI), a NADPH oxidase inhibtor, prevented HG-induced increases in ROS as well as collagen IV and fibronectin expressions. Transfection of Ad-XBP1S reversed HG-induced ROS production and ECM expressions. Knockdown intrinsic XBP1S expression induced increases in ROS production and ECM expressions. Supplementation of supreoxide reversed the inhibitory effect of Ad-XBP1S transfection on ECM synthesis. P47phox was increased in HG-treated MCs. Ad-XBP1S transfection reversed HG-induced p47phox increase while XBP1S knockdown upregulated p47phox expression. In the renal cortex of diabetic rats, the expression of XBP1S was reduced while p47phox, collagen IV and fibronectin expression were elevated. These results suggested that XBP1S pathway of ER stress was involved in HG-induced oxidative stress and ECM synthesis. A downstream target of XBP1S in regulating ROS formation might be NADPH oxidase.

TDAG51 mediates epithelial-to-mesenchymal transition in human proximal tubular epithelium

Epithelial-to-mesenchymal transition (EMT) contributes to renal fibrosis in chronic kidney disease. Endoplasmic reticulum (ER) stress, a feature of many forms of kidney disease, results from the accumulation of misfolded proteins in the ER and leads to the unfolded protein response (UPR). We hypothesized that ER stress mediates EMT in human renal proximal tubules. ER stress is induced by a variety of stressors differing in their mechanism of action, including tunicamycin, thapsigargin, and the calcineurin inhibitor cyclosporine A. These ER stressors increased the UPR markers GRP78, GRP94, and phospho-eIF2α in human proximal tubular cells. Thapsigargin and cyclosporine A also increased cytosolic Ca2+ concentration and T cell death-associated gene 51 (TDAG51) expression, whereas tunicamycin did not. Thapsigargin was also shown to increase levels of active transforming growth factor (TGF)-β1 in the media of cultured human proximal tubular cells. Thapsigargin induced cytoskeletal rearrangement, β-catenin nuclear translocation, and α-smooth muscle actin and vinculin expression in proximal tubular cells, indicating an EMT response. Subconfluent primary human proximal tubular cells were induced to undergo EMT by TGF-β1 treatment. In contrast, tunicamycin treatment did not produce an EMT response. Plasmid-mediated overexpression of TDAG51 resulted in cell shape change and β-catenin nuclear translocation. These results allowed us to develop a two-hit model of ER stress-induced EMT, where Ca2+ dysregulation-mediated TDAG51 upregulation primes the cell for mesenchymal transformation via Wnt signaling and then TGF-β1 activation leads to a complete EMT response. Thus the release of Ca2+ from ER stores mediates EMT in human proximal tubular epithelium via the induction of TDAG51.

Continuing exposure to low-dose nonylphenol aggravates adenine-induced chronic renal dysfunction and role of rosuvastatin therapy

Background

Nonylphenol (NP), an environmental organic compound, has been demonstrated to enhance reactive-oxygen species (ROS) synthesis. Chronic exposure to low-dose adenine (AD) has been reported to induce chronic kidney disease (CKD).

Methods

In this study, we tested the hypothesis that chronic exposure to NP will aggravate AD-induced CKD through increasing generations of inflammation, ROS, and apoptosis that could be attenuated by rosuvastatin. Fifty male Wistar rats were equally divided into group 1 (control), group 2 (AD in fodder at a concentration of 0.25%), group 3 (NP: 2 mg/kg/day), group 4 (combined AD & NP), and group 5 (AD-NP + rosuvastatin: 20 mg/kg/day). Treatment was continued for 24 weeks for all animals before being sacrificed.

Results

By the end of 24 weeks, serum blood urea nitrogen (BUN) and creatinine levels were increased in group 4 than in groups 1–3, but significantly reduced in group 5 as compared with group 4 (all p < 0.05). Histopathology scorings of renal-parenchymal and tubular damages were significantly higher in group 4 than in groups 1–3, but remarkably lower in group 5 compared with group 4 (all p < 0.01). Both gene and protein levels of inflammation, oxidative stress, ROS, and cellular apoptosis were remarkably higher in group 4 compared with groups 1–3, but lowered in group 5 than in group 4 (all p < 0.001). Conversely, both gene and protein levels of anti-oxidants, anti-inflammation and anti-apoptosis were markedly increased in group 5 compared with group 4 (all p < 0.001).

Conclusion

NP worsened AD-induced CKD that could be reversed by rosuvastatin therapy.

Nephroprotective effects of subcapsular transplantation of metanephric mesenchymal cells on gentamicin-induced acute tubular necrosis in rats

BACKGROUND

The subcapsular transplantation of metanephric mesenchymal cells (MMCs) may be a new therapeutic approach for the treatment of acute tubular necrosis (ATN). To investigate this hypothesis and provide evidence for its possible use in the clinic, we evaluated the nephroprotective effects of transplanting MMCs into the renal subcaspsule of rats with ATN induced by gentamicin.

METHODS

MMCs were expanded in culture. After gentamicin-induced ATN was established, fluorescently-labeled cells were transplanted and traced in kidney tissues by fluorescence microscopy. Serum creatinine (Cr), urea nitrogen (BUN), and N-acetyl-b-D-glucosaminidase (NAG) levels were determined at different time points. Kidney pathology was studied by hematoxylin-eosin staining. Apoptosis was examined by the TUNEL assay.

RESULTS

In the MMCs-treated group, the mortality rate decreased; BUN, Cr, and NAG levels peaked at 8 days, and were significantly lower than those in the other groups at 11 and 14 days. RIMM-18 cells locally recruited through precise tropism to sites of injury had the ability to migrate into the tubuli from the renal subcapsule. Damage to the cell-treated kidneys was reduced. The pathologic lesion scores of tubular damage reached the highest values at 8 days in the treated kidneys and 11 days in the untreated ones. The apoptotic index showed that the peaks of apoptosis occurred at earlier stages of the injury process in cell-treated than in untreated kidney and thereafter declined in a time-dependent manner.

CONCLUSION

The subcapsular transplantation of MMCs could ameliorate renal function and repair kidney injury.

Glomerular parietal epithelial cells of adult murine kidney undergo EMT to generate cells with traits of renal progenitors

Glomerular parietal epithelial cells (GPECs) are known to revert to embryonic phenotype in response to renal injury. However, the mechanism of de-differentiation in GPECs and the underlying cellular processes are not fully understood. In the present study, we show that cultured GPECs of adult murine kidney undergo epithelial-mesenchymal transition (EMT) to generate cells, which express CD24, CD44 and CD29 surface antigens. Characterization by qRT-PCR and immunostaining of these clonogenic cells demonstrate that they exhibit metastable phenotype with co-expression of both epithelial (cytokeratin-18) and mesenchymal (vimentin) markers. Transcript analysis by qRT-PCR revealed high expression of metanephric mesenchymal (Pax-2, WT-1, Six-1, Eya-1, GDNF) and uteric bud (Hoxb-7, C-Ret) genes in these cells, indicating their bipotent progenitor status. Incubation of GPECs with EMT blocker Prostaglandin E2, resulted in low expression of renal progenitor markers reflecting the correlation between EMT and acquired stemness in these cells. Additional in vitro renal commitment assays confirmed their functional staminality. When injected into E13.5 kidney rudiments, the cells incorporated into the developing kidney primordia and co-culture with E13.5 spinal cord resulted in branching and tubulogenesis in these cells. When implanted under renal capsule of unilaterally nephrectomized mice, these cells differentiated into immature glomeruli and vascular ducts. Our study demonstrates that EMT plays a major role in imparting plasticity to terminally differentiated GPECs by producing metastable cells with traits of kidney progenitors. The present study would improve our understanding on epithelial cell plasticity, furthering our knowledge of its role in renal repair and regeneration.

Effects of Huanshuai Recipe Oral Liquid on restructuring glomerular microvasculature and expression of vascular endothelial growth factor in subtotal nephrectomized rats

OBJECTIVES

To explore the effects and significance of Huanshuai Recipe Oral Liquid (, HSR), a formula with supplementing qi, nourishing blood and activating blood on restructuring glomerular microvasculature and expression of vascular endothelial growth factor (VEGF) in subtotal nephrectomized (SNX) rats.

METHODS

A total of 76 male Wistar rats were randomly divided into four groups: 16 in the sham-operated group and fed with tap water 10 mL/kg per day; 20 in the model group were operated with 5/6 SNX and fed with tap water 10 mL/ kg per day; 20 SNX rats in the HSR group were treated with HSR 10 mL/kg per day; 20 SNX rats in the losartan group were treated with losartan 40 mg/kg per day. Serum creatinine (SCr) and urinary protein excretion (Upro) were examined at the 2nd, 4th, 8th, and 12th weeks of the treatment, and the remnant kidneys were harvested. Changes in histological microstructure were evaluated using light microscopy, and the expression of VEGF was detected by using ELISA.

RESULTS

Upro, microvasculature injury and glomerulosclerosis were found to be alleviated in HSR and Losartan groups, respectively. The change of VEGF expression showed positive correlation with glomerular capillary area and peritubular capillary number (r=0.448, r=0.422, P<0.01), but negative correlation with that of SCr and Upro (r=-0.592, r=-0.481, P<0.01).

CONCLUSIONS

HSR could regulate the VEGF expression, reduce the loss of microvasculature, which demonstrated similar renal protective effects to losartan in SNX rats. Examination of Chinese herbal medicine influence on VEGF signaling and restructuring renal microvasculature may elucidate the molecular mechanism of renal protection to a certain degree.

Risk factors for end-stage renal disease in a community-based population: 26-year follow-up of 25,821 men and women in eastern Finland

BACKGROUND AND OBJECTIVE

There are very few European cohort studies assessing the risk factors of end-stage renal disease (ESRD) in a community-based population. This study investigated the predictors of ESRD in Finland.

DESIGN

Prospective cohort study.

SETTING

Eastern Finland.

SUBJECTS

A random sample of 25,821 men and women aged 25-64 years from the national population register participating in three independent cross-sectional population surveys in 1972, 1977 and 1982. Only the subjects without diagnosis of ESRD or chronic kidney disease based on the national register data were included in the study.

MAIN OUTCOME MEASURE

Initiation of renal replacement therapy (dialysis or kidney transplantation) identified from the Finnish Registry for Kidney Diseases through December 31, 2006.

RESULTS

A total of 94 cases with ESRD were identified during a mean follow-up period of 26.5 years. In a multivariate proportional subdistribution hazard regression analysis, taking into account death as a competing risk event, diabetes (hazard ratio [HR] 4.76, 95% confidence interval [CI] 2.32-9.79), hypertension (HR 2.21, 95% CI 1.19-4.12), obesity defined as body mass index > or =30 kg m(-2) (HR 2.02, 95 %CI 1.10-3.71) and male gender (HR 1.68, 95% CI 1.19-4.12) were independent risk factors for ESRD.

CONCLUSION

The findings of the present study confirm that modifiable risk factors play a major role in the development of ESRD in the North-European population. People with diabetes, hypertension or obesity should be considered as the target groups when planning preventive measures to control the future epidemic of ESRD.

Changes in glomerular mesangium in kidneys with congenital nephrotic syndrome of the Finnish type

Congenital nephrotic syndrome of the Finnish type (NPHS1, CNF) is an autosomal recessive disease caused by mutations in a major podocyte protein, nephrin. NPHS1 is associated with heavy proteinuria and the development of glomerular scarring. We studied the cellular and molecular changes affecting the glomerular mesangium in NPHS1 kidneys. Marked hyperplasia of mesangial cells (MC) was mainly responsible for the early mesangial expansion in NPHS1 glomeruli. The levels of the proliferation marker, mindbomb homolog 1 and the major MC mitogen, platelet-derived growth factor, and its receptors, however, were quite normal. Only a small number of cells were positive for CD68 (marker for phagocytic cells) and CD34 (marker for mesenchymal precursor cells) in the NPHS1 mesangium. MCs strongly expressed alpha-smooth muscle actin, indicating myofibloblast transformation. The expression levels of the profibrotic mediators osteopontin and transforming growth factor beta were up-regulated in NPHS1 glomeruli by 3.2 and 1.6-fold, respectively, compared to the controls. The synthesis by MCs of the typical fibroblast products collagen I, fibronectin, and tenascin, however, was low, and the extracellular matrix increase was caused by the accumulation of a normal MC product, collagen IV. The results indicate that severe glomerular sclerosis can develop without major qualitative cellular or molecular changes in the mesangium.

High glucose activates HIF-1-mediated signal transduction in glomerular mesangial cells through a carbohydrate response element binding protein

High glucose evokes a variety of signals in mesangial cells that alter cellular functions responsible for the development of diabetic glomerulopathy. The hypoxia-inducible factor-1alpha (HIF-1alpha) regulates cellular homeostasis under hypoxic conditions, but it also has pleiotropic effects in response to cellular stresses at normoxia. Here we determined whether HIF-1alpha has a role in the regulation of mesangial cells in hyperglycemia. In the streptozotocin-induced diabetic mouse model, glomerular mesangial cells had a significant increase in HIF-1alpha expression in the nucleus. In cultured mesangial cells, high glucose enhanced the expression of HIF-1alpha and its target genes known to be involved in the development of diabetic glomerulopathy. A glucose-responsive carbohydrate response element binding protein (ChREBP) was found to have a critical role in the transcriptional upregulation of HIF-1alpha and downstream gene expression in mesangial cells exposed to high glucose. Knockdown of HIF-1alpha or ChREBP in mesangial cells abrogated the high glucose-mediated perturbation of gene expression. Our results show that ChREBP and HIF-1alpha mediate gene regulation in mesangial cells. Further studies will be needed to find out whether these findings are relevant to the development of the diabetic nephropathy.

Peptide corresponding to the C terminus of tissue factor pathway inhibitor inhibits mesangial cell proliferation and activation in vivo

Mesangial cells (MsCs) are one of the resident cell types in the glomerulus and are important with respect to its function and structure. The activation and proliferation of MsCs occur in several types of glomerulonephritis, particularly proliferative glomerulonephritis, producing a series of protein factors and matrix components that impair the normal structure and function of the glomerulus. To inhibit proliferation or induction of apoptosis is considered to be one mechanism that can be used to treat these diseases. In previous studies, we found that the tissue factor pathway inhibitor (TFPI) induces the apoptosis of cultured rat MsCs. Here, we expressed a series of TFPI fragments as fusion proteins to maltose binding protein (MBP-TFPI(162-188), MBP-TFPI(187-241), MBP-TFPI(240-276), MBP-TFPI(162-241), MBP-TFPI(187-276) and MBP-TFPI(162-276)) and applied them to cultured rat mesangial cells. The C terminus of TFPI, a peptide corresponding to residues 240-276 of TFPI, was confirmed to induce apoptosis of MsCs in vitro. To observe the effect of this peptide on MsCs in vivo, we performed intramuscular gene transfer treatment on a rat model of proliferative glomerulonephritis with a plasmid containing the gene for the C terminus of TFPI. This revealed that the C terminus of TFPI exhibited suppressive effects on the activation and proliferation of MsCs and, thereby, improved renal function. Our data indicate that the C terminus of TFPI could be used in the treatment of proliferative glomerulonephritis.

Systems biology of autosomal dominant polycystic kidney disease (ADPKD): computational identification of gene expression pathways and integrated regulatory networks

To elucidate the molecular pathways that modulate renal cyst growth in ADPKD, we performed global gene profiling on cysts of different size (<1 ml, n = 5; 10-20 ml, n = 5; >50 ml, n = 3) and minimally cystic tissue (MCT, n = 5) from five PKD1 human polycystic kidneys using Affymetrix HG-U133 Plus 2.0 arrays. We used gene set enrichment analysis to identify overrepresented signaling pathways and key transcription factors (TFs) between cysts and MCT. We found down-regulation of kidney epithelial restricted genes (e.g. nephron segment-specific markers and cilia-associated cystic genes such as HNF1B, PKHD1, IFT88 and CYS1) in the renal cysts. On the other hand, PKD1 cysts displayed a rich profile of gene sets associated with renal development, mitogen-mediated proliferation, cell cycle progression, epithelial-mesenchymal transition, hypoxia, aging and immune/inflammatory responses. Notably, our data suggest that up-regulation of Wnt/beta-catenin, pleiotropic growth factor/receptor tyrosine kinase (e.g. IGF/IGF1R, FGF/FGFR, EGF/EGFR, VEGF/VEGFR), G-protein-coupled receptor (e.g. PTGER2) signaling was associated with renal cystic growth. By integrating these pathways with a number of dysregulated networks of TFs (e.g. SRF, MYC, E2F1, CREB1, LEF1, TCF7, HNF1B/ HNF1A and HNF4A), our data suggest that epithelial dedifferentiation accompanied by aberrant activation and cross-talk of specific signaling pathways may be required for PKD1 cyst growth and disease progression. Pharmacological modulation of some of these signaling pathways may provide a potential therapeutic strategy for ADPKD.

The effects of ACE inhibitor and angiotensin receptor blocker on clusterin and apoptosis in the kidney tissue of streptozotocin-diabetic rats

Our first aim was to determine the effects of secreted clusterin (sCLU) and nuclear clusterin (nCLU) in diabetic nephropathy. We also aimed to investigate the post-effects of angiotensin II blockage treatment on clusterin expression and to compare these with apoptosis. Five groups of Wistar albino rats were used: First group consisted of healthy controls; the second group included the untreated STZ-diabetics; 30 days of irbesartan or perindopril treated STZ-diabetics formed the third and the fourth groups, respectively; while the subjects receiving a combined treatment with irbesartan and perindopril for 30 days consisted the fifth group. TUNEL method for apoptosis and immunohistochemical staining for TGF-beta1, alpha-SMA, clusterin-beta and clusterin-alpha/beta antibodies were performed. Apoptotic cells especially increased in the kidney tubuli of untreated diabetic group and on the contrary, a significant decrease was observed in the group that received a combined drug treatment. While sCLU was increased in the glomeruli and tubuli of the untreated diabetic group, it was decreased in all the treated groups. An increase in the nCLU immunoreactivity was observed in the podocytes, mesangial cells, and the injured tubule cells of the untreated diabetic group. nCLU immunopositive cells were decreased in all treated diabetic groups. In addition to this, the distribution of nCLU was similar to the distribution of apoptotic cells in the diabetic groups. Our results indicate that sCLU expression in diabetic nephropathy was induced due to renal tissue damage, and the nCLU expression increase in renal tubuli was related to apoptosis. Although irbesartan and perindopril prevented further renal injury in diabetes, a combined application of low-dose ACEI and AT1R blockers revealed more efficient measures, by means of renal damage prevention.

What is the significance of CD34 immunostaining in the extraglomerular and intraglomerular mesangium?

CD34, traditionally a marker of hematopoietic stem cells (HSCs), was found on endothelial cells and fibroblasts as well. At the level of the extraglomerular or intraglomerular mesangium, CD34 may signal either the presence of HSCs or, conversely, may be a marker of transdifferentiation. CD34-positive cells of the extraglomerular mesangium could migrate into the intraglomerular mesangium and participate in reparative processes at this level. The aim of our study was to analyze the presence of CD34 at the level of the extraglomerular and intraglomerular mesangium and its relationship with histological markers of activity and chronicity, as well as with other immunohistochemical markers in glomerulonephritis (GN). A cross-sectional study of 36 patients with GN was conducted. Conventional stains: hematoxylin-eosin, periodic acid Schiff, and Trichrome Gömöri, as well as immunohistochemistry: CD34, alpha smooth muscle actin (alpha SMA), vimentin, and proliferating cell nuclear antigen (PCNA) were employed. Activity and chronicity of GN were evaluated according to a scoring system initially used for lupus nephritis and antineutrophil-cytoplasmic-antibody-associated vasculitis. Immunohistochemistry was assessed using a semiquantitative score. The mean age was 46.44 +/- 12.97 years; 22 were male and 14 were female. The extraglomerular mesangium was visible on specimens in 30 patients. CD34 was present in the extraglomerular mesangium in 15 patients: 11 of these patients showed concomitant intraglomerular and extraglomerular mesangial CD34 immunostaining, while four showed only extraglomerular mesangial immunostaining. In three patients, CD34 immunostaining was present only in the intraglomerular mesangium. Twelve patients showed negative immunostaining in both the extraglomerular and the intraglomerular mesangium. Overall, there was a fair degree of relationship, which did not reach statistical significance between CD34 in the extraglomerular mesangium and CD34 in the intraglomerular mesangium across the 36 patients. In the intraglomerular mesangium, CD34 did not significantly correlate with mesangial alpha SMA, vimentin, PCNA, and activity or chronicity index. In the extraglomerular mesangium, CD34 did not show a significant correlation with alpha SMA, vimentin, or PCNA. The activity index and the chronicity index showed a good correlation with serum creatinine. Mesangial cell proliferation correlated well with the mesangial matrix increase, while interstitial vimentin showed a good correlation with interstitial alpha SMA. We demonstrated the presence of CD34 in the extraglomerular mesangium, which could be related to transdifferentiated mesangial cells or to HSCs in the absence of blood vessels at this level. Our study shows the value of histological indices for evaluating GN but cannot assign significance to CD34 immunolabeling for the assessment of GN.

Epithelial-to-mesenchymal transition in early transplant tubulointerstitial damage

It is unknown whether epithelial-to-mesenchymal transition (EMT) leads to tubulointerstitial fibrosis in renal transplants. In this study, interstitial fibrosis and markers of EMT were followed in protocol transplant biopsies in 24 patients. Tubulointerstitial damage (TID) increased from 34 to 54% between 1 and 3 mo after transplantation. Detection of EMT depended on the marker used; low levels of alpha-smooth muscle actin were found in 61% of biopsies, but the less specific marker S100 calcium binding protein-A4 (also known as Fsp1) suggested a higher incidence of EMT. The presence or development of TID did not correlate with EMT but instead significantly correlated with subclinical immune activity (P < 0.05). Among biopsies showing TID, microarray analysis revealed differential regulation of 127 genes at 1 mo and 67 genes at 3 mo compared with baseline; these genes were predominantly associated with fibrosis, tissue remodeling, and immune response. Of the 173 EMT-associated genes interrogated, however, only 8.1% showed an expression pattern consistent with EMT at 1 mo and 6.3% at 3 mo. The remainder were not differentially altered, or their changes in expression were opposite those expected to promote EMT. Quantitative reverse transcriptase-PCR revealed that the expression pattern of 12 EMT-associated genes was inconsistent over time, opposite that expected, or consistent with subclinical rejection or inflammation. In conclusion, EMT does not seem to play a significant role in the development of early allograft fibrosis.