Neonatal nephron loss during active nephrogenesis results in altered expression of renal developmental genes and markers of kidney injury

Preterm neonates are at a high risk for nephron loss under adverse clinical conditions. Renal damage potentially collides with postnatal nephrogenesis. Recent animal studies suggest that nephron loss within this vulnerable phase leads to renal damage later in life. Nephrogenic pathways are commonly reactivated after kidney injury supporting renal regeneration. We hypothesized that nephron loss during nephrogenesis affects renal development which in turn impairs tissue repair after secondary injury. Neonates prior to 36 weeks of gestation show an active nephrogenesis. In rats, nephrogenesis is ongoing until day 10 after birth. Mimicking the situation of severe nephron loss during nephrogenesis, male pups were uninephrectomized at day 1 of life (UNXd1). A second group of males was uninephrectomized at postnatal day 14 (UNXd14), after terminated nephrogenesis. Age-matched controls were sham operated. Three days after uninephrectomy transcriptional changes in the right kidney were analyzed by RNA-sequencing, followed by functional pathway analysis. In UNXd1 1182 genes were differentially regulated, but only 143 genes showed a regulation both in UNXd1 and UNXd14. The functional groups "renal development" and "kidney injury" were among the most differentially regulated groups and revealed distinctive alterations. Reduced expression of candidate genes concerning renal development (Bmp7, Gdnf, Pdgf-B, Wt1) and injury (nephrin, podocin, Tgf-β1) were detected. The downregulation of Bmp7 and Gdnf persisted until day 28. In UNXd14 Six2 was upregulated and Pax2 downregulated. We conclude that nephron loss during nephrogenesis affects renal development and induces a specific regulation of genes which might hinder tissue repair after secondary kidney injury.

Protective Role of Poria Cocos Polysaccharide Induced Differentiation of Bone Marrow Mesenchymal Stem Cells in Chronic Kidney Disease

The progressive loss of renal function and accumulation of collagen leads to CKD. Human BM-MSCs are considered as an ideal therapeutic strategy for renal regeneration in the CKD. Polysaccharides extracted from Poria cocos, an edible medicinal mushroom, have been in use in the traditional Chinese herbal medicine as they exhibit antidiabetic, antioxidative, antitumor, and other pharmacological effects. Whether the polysaccharides of P. cocos could ameliorate the CKD via induction of BM-MSC differentiation remains to be explored. The data presented here show that the polysaccharides of P. cocos not only induced BM-MSC proliferation and differentiation, but also reduced the levels of proinflammatory cytokines and improved renal morphology.

Effects of Toxicity Induced by Gentamicin on the Kidney of Killifish Aphaniops hormuzensis and the Role of Wt1 and MMP9 Genes in Response to This Toxicity

Background: Aminoglycoside antibiotics such as gentamicin are used to cure bacterial infections in humans and other animals, but they can cause nephritic damage, as well. Nephrotoxicity is one of the side effects of gentamicin. Objectives: The objective of this study was to investigate the effects of toxicity induced by gentamicin on the kidney of killifish Aphaniops hormuzensis. Also, we aimed to study the expression pattern of Wt1 and MMP9 genes by real-time PCR in response to this toxicity. Methods: First, 10 µg/g (sub-lethal dose) gentamicin was given to adult fish. The kidney tissues were dissected and preserved in 10% formalin for a 24-hour; then, they underwent standard histological procedures. The sections were prepared at 3 μm and stained with Haematoxylin & Eosin (H&E). The slide microphotography process was done by an Olympus CH2 microscope. The RNA was isolated, and cDNA was synthesized with a standard protocol, and the expression patterns of Wt1 and MMP9 genes were examined by real-time PCR. Results: Nephrotoxicity occurred 10 hours after the injection of gentamicin, and the injury was detected in the epithelium of kidney tubules. The kidney tubule regenerated itself within 10 days post-injection (dpi). On 7 dpi, the nephrogenic body formation occurred and was differentiated into renal nephrons. The Wt1 gene was upregulated (two-fold) on 5 dpi after kidney damage and then had a down-regulation on 7 dpi when the kidney began to regenerate. The MMP9 gene showed increased expression in comparison with the control sample in the study days, and this expression increased on 7 dpi by 6.6 folds. Conclusions: The results of this study, for the first time, highlighted that nephritic damage appears in the kidney of A. hormuzensis after toxicity induced by gentamicin and that changes in the expression of the examined genes are consistent with their roles in the process of renal regeneration in this species.

mTOR Signaling in Kidney Diseases

The mammalian target of rapamycin (mTOR), a serine/threonine protein kinase, is crucial in regulating cell growth, metabolism, proliferation, and survival. Under physiologic conditions, mTOR signaling maintains podocyte and tubular cell homeostasis. In AKI, activation of mTOR signaling in tubular cells and interstitial fibroblasts promotes renal regeneration and repair. However, constitutive activation of mTOR signaling in kidneys results in the initiation and progression of glomerular hypertrophy, interstitial fibrosis, polycystic kidney disease, and renal cell carcinoma. Here, we summarize the recent studies about mTOR signaling in renal physiology and injury, and discuss the possibility of its use as a therapeutic target for kidney diseases.

Regenerating tubular epithelial cells of the kidney

Acute tubular injury accounts for the most common intrinsic cause for acute kidney injury. Normally, the tubular epithelium is mitotically quiescent. However, upon injury, it can show a brisk capacity to regenerate and repair. The scattered tubular cell (STC) phenotype was discovered as a uniform reaction of tubule cells triggered by injury. The STC phenotype is characterized by a unique protein expression profile, increased robustness during tubular damage and increased proliferation. Nevertheless, the exact origin and identity of these cells have been unveiled only in part. Here, we discuss the classical concept of renal regeneration. According to this model, surviving cells dedifferentiate and divide to replace neighbouring lost tubular cells. However, this view has been challenged by the concept of a pre-existing and fixed population of intratubular progenitor cells. This review presents a significant body of previous work and animal studies using lineage-tracing methods that have investigated the regeneration of tubular cells. We review the experimental findings and discuss whether they support the progenitor hypothesis or the classical concept of renal tubular regeneration. We come to the conclusion that any proximal tubular cell may differentiate into the regenerative STC phenotype upon injury thus contributing to regeneration, and these cells differentiate back into tubular cells once regeneration is finished.

In vivo two-photon microscopy reveals the contribution of Sox9+ cell to kidney regeneration in a mouse model with extracellular vesicle treatment

Mesenchymal stem cell (MSC)–derived extracellular vesicles (EVs) have been shown to stimulate regeneration in the treatment of kidney injury. Renal regeneration is also thought to be stimulated by the activation of Sox9+ cells. However, whether and how the activation mechanisms underlying EV treatment and Sox9+ cell–dependent regeneration intersect is unclear. We reasoned that a high-resolution imaging platform in living animals could help to untangle this system. To test this idea, we first applied EVs derived from human placenta–derived MSCs (hP-MSCs) to a Sox9-CreERT2; R26mTmG transgenic mouse model of acute kidney injury (AKI). Then, we developed an abdominal imaging window in the mouse and tracked the Sox9+ cells in the inducible Sox9-Cre transgenic mice via in vivo lineage tracing with two-photon intravital microscopy. Our results demonstrated that EVs can travel to the injured kidneys post intravenous injection as visualized by Gaussia luciferase imaging and markedly increase the activation of Sox9+ cells. Moreover, the two-photon living imaging of lineage-labeled Sox9+ cells showed that the EVs promoted the expansion of Sox9+ cells in kidneys post AKI. Histological staining results confirmed that the descendants of Sox9+ cells contributed to nephric tubule regeneration which significantly ameliorated the renal function after AKI. In summary, intravital lineage tracing with two-photon microscopy through an embedded abdominal imaging window provides a practical strategy to investigate the beneficial functions and to clarify the mechanisms of regenerative therapies in AKI.

Stem Cell Cure for Kidney Injury: Therapy to Solve Most Complex Issues in Renal System

Renal failure is a major health problem. The mortality rate remain high despite of several therapies. The most complex of the renal issues are solved through stem cells. In this review, different mechanism for cure of chronic kidney injury along with cell engraftment incorporated into renal structures will be analysed. Paracrine activities of embryonic or induced Pluripotent stem cells are explored on the basis of stem cell-induced kidney regeneration. Several experiments have been conducted to advance stem cells to ensure the restoration of renal functions. More vigour and organised protocols for delivering stem cells is a possibility for advancement in treatment of renal disease. Also there is a need for pressing therapies to replicate the tissue remodelling and cellular repair processes suitable for renal organs. Stem cells are the undifferentiated cells that have the ability to multiply into several cell types. In vivo experiments on animal’s stem cells have shown significant improvements in the renal regeneration and functions of organs. Nevertheless more studies show several improvements in the kidney repair due to stem cell regeneration.

5/6 nephrectomy: renal tissue regeneration and condition of brain microcirculation

THE AIM. To find out if the level of regeneration of renal tissue after nephrectomy 5/6 kidney mass is sufficient to prevent pathological deterioration of microcirculation in the cerebral cortex. MATERIAL AND METHODS. The method of intravital microscopy was used to study the density of the microvascular network of the pial sheath of the cerebral cortex in Wistar rats 4 months after the removal of 5/6 of the renal tissue mass. At the same time, the level of perfusion and oxygen saturation (SO2) were measured in the cortical tissue using laser Doppler flowmetry. To assess the degree of kidney regeneration after resection, a morphological study of kidney tissue was carried out when staining with hematoxylin-eosin and Masson. RESULTS. It was shown that 4 months after nephrectomy in the pial membrane, the density of the microvascular network decreased by an average of 1.3 times compared with falsely operated animals, and the number of arterial vessels by 1.5 times. The level of tissue perfusion (on average by 20%) and SO2 (on average from 95 to 91%) decreased statistically significantly. On morphological preparations, there were no signs of true regeneration; revealed glomerular hypertrophy, the development of fibrosis, deformation of blood vessels, and tubular structures. CONCLUSION. Renal regeneration 4 months after nephrectomy 5/6 kidney mass is insufficient to normalize its function, and therefore does not prevent the cerebrovascular accident. Significant microcirculation disorders are observed in rat cerebral cortex: a decrease in the density of the microvascular network, a decrease in the rate of cerebral blood flow and tissue oxygen saturation, which are signs of the formation of lacunar strokes.

P0524PERICYTE IS ESSENTIAL FOR RENAL TUBULAR CELL REGENERATION AFTER ACUTE KIDNEY INJURY

Background and Aims Pericyte-myofibroblast transition is activated after acute kidney injury (AKI) and is the major mechanism of ensuing chronic kidney disease (CKD). Nevertheless, the role of pericyte in renal regeneration after AKI has not been deeply investigated. Many studies have shown that pericyte can secret growth factors such as fibroblast growth factor 1 and 7 (FGF-1, FGF-7) and is essential for structure support and vascular integrity in normal kidney. We supposed that the ablation or inhibition of pericytes during AKI would retard renal repair. Method Our study demonstrated that activated pericytes/myofibroblast was beneficial for renal regeneration after AKI. We here performed pericyte ablation and pericyte inhibition after ischemia-reperfusion renal injury by using transgenic mice such as Gli1-CreERT2;iDTR mice and blockade of platelet-derived growth factor receptor β (PDGFRβ), respectively. Results Renal injury was more severe and renal recovery was worse in groups of pericyte ablation or inhibition compared to control groups. Ki67 positive tubular cells which indicated renal regeneration were much more in control groups than that in groups of pericyte ablation or inhibition. We also found higher macrophage number as well as higher inflammatory factor including tumor necrosis factor-α and interleukin-1β which indicated more severe inflammation in groups of pericyte ablation or inhibition. Conclusion These studies suggest that pericytes play a beneficial role during renal recovery after AKI. These findings delineate the adequate timing when we target on pericyte/myofibroblast to ameliorate renal fibrosis and avoid to impede renal regeneration at the same time. Further research is still needed to clarify the change of specific gene and signalling pathway after pericyte ablation or inhibition. These are promising findings that provide opportunities to develop new targets to promote AKI recovery and to ameliorate renal fibrosis.