Physiological activation of the nephron central command drives endogenous kidney tissue regeneration

Tissue regeneration is limited in several organs including the kidney, contributing to the high prevalence of kidney disease globally. However, evolutionary and physiological adaptive responses and the presence of renal progenitor cells suggest existing remodeling capacity. This study uncovered a novel endogenous tissue remodeling mechanism in the kidney that is activated by the loss of body fluid and salt and involves a unique niche of chief cells called macula densa (MD) that control resident progenitor cells via secreted angiogenic, growth and extracellular matrix remodeling factors, cytokines and chemokines. Serial intravital imaging, MD Wnt mouse models and transcriptome analysis provide functional and molecular characterization of this newly identified MD program for kidney regeneration complemented with human and therapeutic translation. The concept that chief cells responding to organ-specific physiological inputs control local progenitors and direct them to remodel or repair tissues may be applicable to other organs and diverse tissue regenerative therapeutic strategies.

Renal Interstitial Cells Promote Nephron Regeneration by Secreting Prostaglandin E2

In organ regeneration, progrnitor and stem cells reside in their native microenvironment, which provides dynamic physical and chemical cues essential to their survival, proliferation and differentiation. However, what kind of cells provide a native microenvironment for renal progenitor cells has not been clarified. Here, single-cell sequencing of zebrafish kidney revealed that fabp10 was a marker of renal interstitial cells (RICs), and the Tg(fabp10a:GFP) transgenic line can specifically label RICs in zebrafish kidney. The formation of RICs and nephrons are closely accompanied during nephron regeneration. RICs form a network to wrap the renal progenitor cell aggregates. RICs in close contact with cell aggregates express cyclooxygenase 2 and secrete prostaglandin 2 (PGE2). Inhibiting PGE2 production prevented nephrogenesis by reducing the proliferation and differentiation of progenitor cell aggregates. PGE2 promoted maturation of the nephron by activating the WNT signaling pathway in progenitor cell aggregates in cooperation with Wnt4a. These findings suggest that RICs provide a necessary microenvironment for rapid nephrogenesis during nephron regeneration.

Gestational Low Protein Diet Modulation on miRNA Transcriptome and Its Target During Fetal and Breastfeeding Nephrogenesis

BackgroundThe kidney ontogenesis is the most structurally affected by gestational protein restriction, reducing 28% of their functional units. The reduced nephron number is predictive of hypertension and cardiovascular dysfunctions that are generally observed in the adult age of most fetal programming models. We demonstrate miRNAs and predict molecular pathway changes associated with reduced reciprocal interaction between metanephros cap (CM) and ureter bud (UB) and a 28% decreased nephron stem cells in the 17 gestational days (17GD) low protein (LP) intake male fetal kidney. Here, we evaluated the same miRNAs and predicted targets in the kidneys of 21GD and at 7 days of life (7DL) LP offspring to elucidate the molecular modulations during nephrogenesis.MethodsPregnant Wistar rats were allocated into two groups: NP (regular protein diet- 17%) or LP (diet-6%). miRNA transcriptome sequencing (miRNA-Seq) was performed on the MiSeq platform from 21GD and 7DL male offspring kidneys using previously described methods. Among the top 10 dysfunctional regulated miRNAs, we validated 7 related to proliferation, differentiation, and apoptosis processes and investigated predicted target genes and proteins by RT-qPCR and immunohistochemistry.ResultsIn 21GD, LP fetuses were identified alongside 21 differently expressed miRNAs, of which 12 were upregulated and 9 downregulated compared to age-matched NP offspring. In 7-DL LP offspring, the differentially expressed miRNAs were counted to be 74, of which 46 were upregulated and 28 downregulated. The curve from 17-GD to 7-DL shows that mTOR was fundamental in reducing the number of nephrons in fetal kidneys where the mothers were subjected to a protein restriction. IGF1 and TGFβ curves also seemed to present the same mTOR pattern and were modulated by miRNAs 181a-5p, 181a-3p, and 199a-5p. The miRNA 181c-3p modulated SIX2 and Notch1 reduction in 7-DL but not in terms of the enhanced expression of both in the 21-GD, suggesting the participation of an additional regulator. We found enhanced Bax in 21-GD; it was regulated by miRNA 298-5p, and Bcl2 and Caspase-3 were controlled by miRNA (by 7a-5p and not by the predicted 181a-5p). The miRNA 144-3p regulated BCL6, which was enhanced, as well as Zeb 1 and 2 induced by BCL6. These results revealed that in 21GD, the compensatory mechanisms in LP kidneys led to the activation of UB ramification. Besides, an increase of 32% in the CM stem cells and a possible cell cycle halt of renal progenitor cells, which remaining undifferentiated, were observed. In the 7DL, much more altered miRNA expression was found in LP kidneys, and this was probably due to an increased maternal diet content. Additionally, we verified the activation of pathways related to differentiation and consumption of progenitor cells.

MO337UNILATERAL NEPHRECTOMY OVERCOMES PROGRESSION TO CHRONIC KIDNEY DISEASE AFTER ACUTE INJURY IN MICE BY STIMULATING PROLIFERATION OF RENAL PROGENITOR CELLS

Background and Aims Acute kidney injury (AKI) is a global health concern with an incidence of 13.3 million patients per year, and increasing. AKI is recognized as an important risk factor for the development of chronic kidney disease (CKD). A crucial aspect for successful renal recovery after AKI is an efficient proliferative response of surviving tubular epithelial cells (TECs). Recently, we established a murine model in which the functional and histological recovery of a single kidney, injured by ischemia, is enhanced by removal of the unharmed contralateral kidney; a phenomenon termed nephrectomy-induced recovery. The renal epithelial reparative response in this unique physiological model has not been investigated, yet can provide new insights in unlocking the inherent regenerative potential of the renal epithelium. Method AKI was induced in R26RtdTomato and PAX2/Confetti mice by left unilateral ischemia/reperfusion (UIRI) for 21 min at 34°C, after which either right nephrectomy (Nx) or no Nx was performed 3 days later. Mice were euthanized 6 weeks and 28 days after UIRI, respectively. At week 6, kidneys were weighted and renal function was assessed by serum creatinine. At 28 days, renal tissue of Pax2/Confetti mice was collected to perform renal progenitor cell lineage tracing experiments by immunofluorescence and confocal microscopy. Results When nephrectomy was performed after UIRI, left kidney-to-body weight ratio did not change significantly over time, whereas, when no nephrectomy was performed, left kidney-to-body weight ratio gradually declined from 7,84 ± 0,48 mg/dl at day 3 till 3,26 ± 0,51 mg/dl at week 6, indicating severe atrophy in the injured left kidney. This loss of renal mass was associated with a significant increase in serum creatinine (1,76 ± 0,13 mg/dl) as compared to control (0,21 ± 0,12 mg/dl), whereas with nephrectomy, renal function fully restored. Clonal analysis in PAX2/Confetti mice revealed that nephrectomy after UIRI led to a significant increase in proliferating (i.e. clonogenic) Pax2+ progenitor cells, resulting in more multicellular clones as compared to un-nephrectomized controls. Conclusion Nephrectomy after UIRI overcomes chronic loss of renal mass and function within the investigated 6-week time frame. This study is the first to demonstrate that nephrectomy stimulates clonal expansion of renal progenitor cells in an injured kidney, beyond that observed for spontaneous repair after UIRI. Insight in the signaling mechanisms may reveal new therapeutic approaches to incite the inherent renal regeneration potential.

Angiotensin II disrupts the cytoskeletal architecture of human urine-derived podocytes and results in activation of the renin-angiotensin system

High blood pressure is one of the major public health problems which causes severe disorders in several tissues including the human kidney. One of the most important signaling pathways associated with the regulation of blood pressure is the renin-angiotensin system (RAS), with its main mediator angiotensin II (ANGII). Elevated levels of circulating and intracellular ANGII and aldosterone lead to pro-fibrotic, -inflammatory and -hypertrophic milieu that causes remodelling and dysfunction in cardiovascular and renal tissues. Furthermore, ANGII has been recognized as major risk factor for the induction of apoptosis in podocytes, ultimately leading to chronic kidney disease (CDK).In the past, disease modeling of kidney-associated malignancies was extremely difficult, as the derivation of kidney originated cells is very challenging. Here we describe a differentiation protocol for reproducible differentiation of SIX2-positive urine derived renal progenitor cells (UdRPCs) into mature podocytes bearing typical foot processes. The UdRPCs-derived podocytes show the ability to execute Albumin endocytosis and the activation of the renin-angiotensin system by being responsive to ANGII stimulation. Our data reveals the ANGII dependent downregulation ofNPHS1andSYNPO, resulting in the disruption of the complex podocyte cytoskeletal architecture, as shown by immunofluorescence-based detection of α–ACTININ. In the present manuscript we confirm and propose UdRPCs as a unique cell type useful for studying nephrogenesis and associated diseases. Furthermore, the responsiveness of UdRPCs-derived podocytes to ANGII implies potential applications in nephrotoxicity studies and drug screening.

Infection by Zika Vírus in human cells alters the expression profile of miRNA-15 and activation of apoptotic caspases

Objective: Evaluate the miRNA-15 expression profile involved in cellular apoptotic regulation factors. Methodology: We used the H818308 Asian strain of ZIKV without neurological damage. The inoculations occurred in human embryonic kidney cells (HEK-293). After inoculation, samples were extracted for RT-qPCR quantification of viral RNA and miR-15. The level of activation of caspases 1, 3/7 and 8 of cells was performed using chemofluorescence. Results: The ZIKV infection alters the expression of genes and their regulators, affecting several cellular physiological processes such as apoptosis. Conclusion: Therefore, it is important to emphasize that renal progenitor cells (HEK-293) are susceptible to VZIK infection. The genetic deregulation resulting from infection directly affects important cellular processes such as apoptosis from the disordered miRNA-15 expression during the infection period.

Therapeutic potential of human induced pluripotent stem cells and renal progenitor cells in experimental chronic kidney disease

Background Chronic kidney disease (CKD) is a global public health problem. Cell therapy using pluripotent stem cells represents an attractive therapeutic approach for the treatment of CKD. Methods We transplanted mitomycin C (MMC)-treated human induced pluripotent stem cells (hiPSCs) and renal progenitor cells (RPCs) into a CKD rat model system. The RPC and hiPSC cells were characterized by immunofluorescence and qRT-PCR. Untreated 5/6 nephrectomized rats were compared to CKD animals receiving the same amount of MMC-treated hiPSCs or RPCs. Renal function, histology, and immunohistochemistry were evaluated 45 days post-surgery. Results We successfully generated hiPSCs from peripheral blood and differentiated them into RPCs expressing renal progenitor genes (PAX2, WT1, SIX2, and SALL1) and podocyte-related genes (SYNPO, NPHS1). RPCs also exhibited reduced OCT4 expression, confirming the loss of pluripotency. After cell transplantation into CKD rats, the body weight change was significantly increased in both hiPSC and RPC groups, in comparison with the control group. Creatinine clearance (CCr) was preserved only in the hiPSC group. Similarly, the number of macrophages in the kidneys of the hiPSC group reached a statistically significant reduction, when compared to control rats. Both treatments reduced positive staining for the marker α-smooth muscle actin. Histological features showed decreased tubulointerstitial damage (interstitial fibrosis and tubular atrophy) as well as a reduction in glomerulosclerosis in both iPSC and RPC groups. Conclusions In conclusion, we describe that both MMC-treated hiPSCs and RPCs exert beneficial effects in attenuating CKD progression. Both cell types were equally efficient to reduce histological damage and weight loss caused by CKD. hiPSCs seem to be more efficient than RPCs, possibly due to a paracrine effect triggered by hiPSCs. These results demonstrate that the use of MMC-treated hiPSCs and RPCs improves clinical and histological CKD parameters, avoided tumor formation, and therefore may be a promising cell therapy strategy for CKD. Graphical abstract