Mobilized human hematopoietic stem/progenitor cells promote kidney repair after ischemia/reperfusion injury

Prevention of methylmercury-triggered ROS-mediated impairment of embryo development by co-culture with adult adipose-derived mesenchymal stem cells

Methylmercury (MeHg) is a potent toxin that exerts deleterious effects on human health via environmental contamination. Significant effects of MeHg on neuronal development in embryogenesis have been reported. Recently, our group demonstrated that MeHg exerts toxic effects on pre- and post-implantation embryonic development processes from zygote to blastocyst stage. Our results showed that MeHg impairs embryo development by induction of apoptosis through reactive oxygen species (ROS) generation that triggers caspase-3 cleavage and activation, which, in turn, stimulates p21-activated kinase 2 (PAK2) activity. Importantly, ROS were identified as a key upstream regulator of apoptotic events in MeHg-treated blastocysts. Data from the current study further confirmed that MeHg exerts hazardous effects on cell proliferation, apoptosis, implantation, and pre- and post-implantation embryo development. Notably, MeHg-induced injury was markedly prevented by co-culture with adipose-derived mesenchymal stem cells (ADMSCs) in vitro. Furthermore, ADMSC injection significantly reduced MeHg-mediated deleterious effects on embryo, placenta, and fetal development in vivo. Further investigation of the regulatory mechanisms by which co-cultured ADMSCs could prevent MeHg-induced impairment of embryo development revealed that ADMSCs effectively reduced ROS generation and its subsequent downstream apoptotic events, including loss of mitochondrial membrane potential and activation of caspase-3 and PAK2. The collective findings indicate that co-culture with mesenchymal stem cells (MSCs) or utilization of MSC-derived cell-conditioned medium offers an effective potential therapeutic strategy to prevent impairment of embryo development by MeHg.

High-Salt Diet Aggravates Endothelial-to-Mesenchymal Transition in Glomerular Fibrosis in Dahl Salt-Sensitive Rats

BACKGROUND

Both diabetic and hypertensive nephropathy eventually progress to glomerulosclerosis. Previous studies revealed a potential role of endothelial-to-mesenchymal transition (EndMT) in the pathophysiology of glomerulosclerosis in diabetic rats. Therefore, we hypothesized that EndMT was also involved in the development of glomerulosclerosis in salt-sensitive hypertension. We aimed to explore the effects of high-salt diet on endothelial-to-mesenchymal transition (EndMT) in glomerulosclerosis in Dahl salt-sensitive (Dahl-SS) rats.

METHODS

Eight-week-old male rats were fed high-salt (8%NaCl; DSH group) or normal salt (0.3%NaCl; DSN group) for eight weeks, with systolic blood pressure (SBP), serum creatinine, urea, 24-hour urinary protein/sodium, renal interlobar artery blood flow, and pathological examination measured. We also examined endothelial-(CD31) and fibrosis-related protein(α-SMA) expressions in glomeruli.

RESULTS

High-salt diet increased SBP (DSH vs. DSN, 205.2 ± 8.9 vs. 135.4 ± 7.9 mm Hg, P < 0.01), 24-hour urinary protein (132.55 ± 11.75 vs. 23.52 ± 5.94 mg/day, P < 0.05), urine sodium excretions (14.09 ± 1.49 vs. 0.47 ± 0.06 mmol/day, P < 0.05), and renal interlobar artery resistance. Glomerulosclerosis increased (26.1 ± 4.6 vs. 7.3 ± 1.6%, P < 0.05), glomerular CD31 expressions decreased while α-SMA expression increased in DSH group. Immunofluorescence staining showed that CD31 and α-SMA co-expressed in glomeruli of the DSH group. The degree of glomerulosclerosis negatively correlated with CD31 expressions (r = -0.823, P < 0.01) but positively correlated with α-SMA expressions (r = 0.936, P < 0.01).

CONCLUSIONS

We demonstrated that a high-salt diet led to glomerulosclerosis involving the EndMT process, which played an essential role in glomerulosclerosis in hypertensive Dahl-SS rats.

Hepatoprotective Effects of Hyaluronic Acid-Preconditioned Bone Marrow Mesenchymal Stem Cells against Liver Toxicity via the Inhibition of Apoptosis and the Wnt/β-Catenin Signaling Pathway

BACKGROUND

Doxorubicin (DOX) is widely used to treat a variety of malignancies in both adults and children, including those of the bladder, breast, stomach, and ovaries. Despite this, it has been reported to cause hepatotoxicity. The recent discovery of bone marrow-derived mesenchymal stem cells' (BMSCs) therapeutic effects in the context of liver diseases suggests that their administration plays a part in the mitigation and rehabilitation of drug-induced toxicities.

OBJECTIVES

This study investigated whether bone BMSCs could reduce DOX-induced liver damage by blocking the Wnt/β-catenin pathway that causes fibrotic liver.

MATERIALS AND METHODS

BMSCs were isolated and treated with hyaluronic acid (HA) for 14 days before injection. Thirty-five mature male SD rats were categorized into four groups; group one (control) rats were supplemented with saline 0.9% for 28 days, group two (DOX) rats were injected with DOX (20 mg/kg), group three (DOX + BMSCs) rats were injected with 2 × 106 BMSCs after 4 days of DOX injection, group four (DOX + BMSCs + HA) rats were injected with 0.1 mL BMSCs pretreated with HA after 4 days of DOX. After 28 days the rats were sacrificed, and blood and liver tissue samples were subjected to biochemical and molecular analysis. Morphological and immunohistochemical observations were also carried out.

RESULTS

In terms of liver function and antioxidant findings, cells treated with HA showed considerable improvement compared to the DOX group (p < 0.05). Moreover, the expression of inflammatory markers (TGFβ1, iNos), apoptotic markers (Bax, Bcl2), cell tracking markers (SDF1α), fibrotic markers (β-catenin, Wnt7b, FN1, VEGF, and Col-1), and ROS markers (Nrf2, HO-1) was improved in BMSCs conditioned with HA in contrast to BMSCs alone (p < 0.05).

CONCLUSION

Our findings proved that BMSCs treated with HA exert their paracrine therapeutic effects via their secretome, suggesting that cell-based regenerative therapies conditioned with HA may be a viable alternative to reduce hepatotoxicity.

Repetitive administration of cultured human CD34+ cells improve adenine-induced kidney injury in mice

BACKGROUND

There is no established treatment to impede the progression or restore kidney function in human chronic kidney disease (CKD).

AIM

To examine the efficacy of cultured human CD34+ cells with enhanced proliferating potential in kidney injury in mice.

METHODS

Human umbilical cord blood (UCB)-derived CD34+ cells were incubated for one week in vasculogenic conditioning medium. Vasculogenic culture significantly increased the number of CD34+ cells and their ability to form endothelial progenitor cell colony-forming units. Adenine-induced tubulointerstitial injury of the kidney was induced in immunodeficient non-obese diabetic/severe combined immunodeficiency mice, and cultured human UCB-CD34+ cells were administered at a dose of 1 × 10⁶/mouse on days 7, 14, and 21 after the start of adenine diet.

RESULTS

Repetitive administration of cultured UCB-CD34+ cells significantly improved the time-course of kidney dysfunction in the cell therapy group compared with that in the control group. Both interstitial fibrosis and tubular damage were significantly reduced in the cell therapy group compared with those in the control group (P < 0.01). Microvasculature integrity was significantly preserved (P < 0.01) and macrophage infiltration into kidney tissue was dramatically decreased in the cell therapy group compared with those in the control group (P < 0.001).

CONCLUSION

Early intervention using human cultured CD34+ cells significantly improved the progression of tubulointerstitial kidney injury. Repetitive administration of cultured human UCB-CD34+ cells significantly improved tubulointerstitial damage in adenine-induced kidney injury in mice via vasculoprotective and anti-inflammatory effects.

Immunomagnetic Delivery of Adipose-Derived Endothelial Progenitor Cells for the Repair of Renal Ischemia-Reperfusion Injury in a Rat Model

Renal ischemia-reperfusion injury (IRI) is a significant cause of acute kidney injury (AKI) and usually brings severe public health consequences. Adipose-derived endothelial progenitor cell (AdEPCs) transplantation is beneficial for AKI but suffers from low delivery efficiency. This study was conducted to explore the protective effects of magnetically delivered AdEPCs on the repair of renal IRI. Two types of magnetic delivery methods, namely the endocytosis magnetization (EM) method and the immunomagnetic (IM) method were fabricated using PEG@Fe₃O₄ and CD133@Fe₃O₄, and their cytotoxicities in AdEPCs were assessed. In the renal IRI rat model, magnetic AdEPCs were injected via the tail vein and a magnet was placed beside the injured kidney for magnetic guidance. The distribution of transplanted AdEPCs, renal function, and tubular damage were evaluated. Our results suggested that CD133@Fe₃O₄ had the minimum negative effects on the proliferation, apoptosis, angiogenesis, and migration of AdEPCs compared with PEG@Fe₃O₄. Renal magnetic guidance could significantly enhance the transplantation efficiency and the therapeutic outcomes of AdEPCs-PEG@Fe₃O₄ and AdEPCs-CD133@Fe₃O₄ in the injured kidneys. However, under renal magnetic guidance, AdEPCs-CD133@Fe₃O₄ had stronger therapeutic effects than PEG@Fe₃O₄ after renal IRI. The immunomagnetic delivery of AdEPCs with CD133@Fe₃O₄ could be a promising therapeutic strategy for renal IRI.

Tissue Engineering Neovagina for Vaginoplasty in Mayer-Rokitansky-Küster-Hauser Syndrome and Gender Dysphoria Patients: A Systematic Review

Background: Vaginoplasty is a surgical solution to multiple disorders, including Mayer-Rokitansky-Küster-Hauser syndrome and male-to-female gender dysphoria. Using nonvaginal tissues for these reconstructions is associated with many complications, and autologous vaginal tissue may not be sufficient. The potential of tissue engineering for vaginoplasty was studied through a systematic bibliography search. Cell types, biomaterials, and signaling factors were analyzed by investigating advantages, disadvantages, complications, and research quantity. Search Methods: A systematic search was performed in Medline, EMBASE, Web of Science, and Scopus until March 8, 2022. Term combinations for tissue engineering, guided tissue regeneration, regenerative medicine, and tissue scaffold were applied, together with vaginoplasty and neovagina. The snowball method was performed on references and a Google Scholar search on the first 200 hits. Original research articles on human and/or animal subjects that met the inclusion (reconstruction of vaginal tissue and tissue engineering method) and no exclusion criteria (not available as full text; written in foreign language; nonoriginal study article; genital surgery other than neovaginal reconstruction; and vaginal reconstruction with autologous or allogenic tissue without tissue engineering or scaffold) were assessed. The Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) checklist, the Newcastle-Ottawa Scale, and the Gold Standard Publication Checklist were used to evaluate article quality and bias. Outcomes: A total of 31 out of 1569 articles were included. Data extraction was based on cell origin and type, biomaterial nature and composition, host species, number of hosts and controls, neovaginal size, replacement fraction, and signaling factors. An overview of used tissue engineering methods for neovaginal formation was created, showing high variance of cell types, biomaterials, and signaling factors and the same topics were rarely covered multiple times. Autologous vaginal cells and extracellular matrix-based biomaterials showed preferential properties, and stem cells carry potential. However, quality confirmation of orthotopic cell-seeded acellular vaginal matrix by clinical trials is needed as well as exploration of signaling factors for vaginoplasty. Impact statement General article quality was weak to sufficient due to unreported cofounders and incomplete animal study descriptions. Article quality and heterogenicity made identification of optimal cell types, biomaterials, or signaling factors unreliable. However, trends showed that autologous cells prevent complications and compatibility issues such as healthy cell destruction, whereas stem cells prevent cross talk (interference of signaling pathways by signals from other cell types) and rejection (but need confirmation testing beyond animal trials). Natural (orthotopic) extracellular matrix biomaterials have great preferential properties that encourage future research, and signaling factors for vascularization are important for tissue engineering of full-sized neovagina.

Prion Protein Overexpression in Adipose-Derived Mesenchymal Stem Cells (ADMSCs) Effectively Protected Rodent Kidney Against Ischemia-Reperfusion Injury Via Enhancing ATP/Mitochondrial Biogenesis-Role of ADMSC Rejuvenation and Proliferation

BACKGROUND

We tested the hypothesis that overexpression of cellular-prion-protein in adipose-derived mesenchymal stem cells (PrPCOE-ADMSCs) effectively protected the kidney against ischemia-reperfusion (IR) injury in rat.

METHODS

Part I of cell culture was categorized into A1(ADMSCs)/A2(ADMSCs+p-Cresol)/A3(PrPCOE in ADMSCs)/A4 (PrPCOE in ADMSCs+p-Cresol). Part II of cell culture was divided into B1(ADMSCs)/B2[ADMSCs+lipopolysaccharide (LPS)]/B3(PrPCOE in ADMSCs)/B4(PrPCOE in ADMSCs+LPS). Sprague-Dawley (SD) rats (n = 50) were equally categorized into groups 1 (sham-operated-control)/2 (IR)/3 (IR+ADMSCs/6.0 × 105 equally divided into bilateral-renal arteries and 6.0 × 105 intravenous administration by 1 h after IR)/4 [IR+PrPCOE-ADMSCs (identical dosage administered as group 3)]/5 [IR+silencing PRNP -ADMSCs (identical dosage administered as group 3)], and kidneys were harvested post-day 3 IR injury.

RESULTS

Part I results demonstrated that the cell viability at 24/48/72 h, BrdU uptake/number of mitDNA/APT concentration/mitochondrial-cytochrome-C+ cells and the protein expressions of ki67/PrPC at 72 h-cell culturing were significantly higher in PrPCOE-ADMSCs than in ADMSCs (all P < 0.001). The protein expressions of oxidative-stress (NOX-1/NOX2/NOX4/oxidized protein)/mitochondrial-damaged (p22-phox/cytosolic-cytochrome-C)/inflammatory (p-NF-κB/IL-1ß/TNF-α/IL-6)/apoptotic (cleaved caspase-3/cleaved-PARP) biomarkers were lowest in A1/A3 and significantly higher in A2 than in A4 (all P < 0.001). Part II result showed that the protein expressions of inflammatory (p-NF-κB/IL-1ß/TNF-α/IL-6)/apoptotic (cleaved caspase-3/cleaved-PARP) biomarkers exhibited an identical pattern of part I among the groups (all P < 0.001). The protein expressions of inflammatory (p-NF-κB/IL-1ß/TNF-α/MMP-9)/oxidative-stress (NOX-1/NOX-2/oxidized-protein)/mitochondrial-damaged (cytosolic-cytochrome-C/p22-phox)/apoptotic (cleaved caspase-3/cleaved-PARP/mitochondrial-Bx)/autophagic (beclin-1/ratio of LC3B-II/LC3B-I)/fibrotic (Smad3/TGF-ß) biomarkers and kidney-injury-score/creatinine level were lowest in group 1, highest in group 2, significantly higher in group 5 than in groups 3/4 (all P < 0.0001).

CONCLUSION

PrPCOE in ADMSCs rejuvenated these cells and played a cardinal role on protecting the kidney against IR injury.

Development of Cell Therapies for Renal Disease and Regenerative Medicine

The incidence of renal disease is gradually increasing worldwide, and this condition has become a major public health problem because it is a trigger for many other chronic diseases. Cell therapies using multipotent mesenchymal stromal cells, hematopoietic stem cells, macrophages, and other cell types have been used to induce regeneration and provide a cure for acute and chronic kidney disease in experimental models. This review describes the advances in cell therapy protocols applied to acute and chronic kidney injuries and the attempts to apply these treatments in a clinical setting.

Inhibition of histone methyltransferase G9a effectively protected the kidney against ischemia-reperfusion injury

This study examined whether BIX01294, a histone methyltransferase G9a inhibitor, effectively preserves the renal function following acute kidney ischemia-reperfusion (AKIR) injury. Adult-male-SD rats (n = 24) were equally categorized into Group 1 (sham-operated control), Group 2 (AKIR + 1.0 cc N/S I.P. injection), and Group 3 (AKIR + BIX01294/5 mg/Kg by I.P. administration at 3 h after the procedure) and the kidneys were harvested at day-3 post-IR procedure. The results showed that by day 3, the levels of creatinine and the blood urea nitrogen (BUN) were significantly higher in group 3 and more significantly higher in group 2 than in group 1 (all P < 0.0001). The protein expression of upstream (TLR-2/TLR-4/MyD88/TRAF6/p-NF-κB) and downstream (IL-1ß/IL-6/TNF-α) inflammatory signaling molecules exhibited a pattern identical to that of creatinine levels among the groups (all P < 0.0001). The protein expression of oxidative stress (NOX-1/NOX-2), MAP kinase family members (ASK1/MKK4/MKK7/JNK/p-38/p-ERK1/2), apoptosis (cleaved-caspase3/cleaved-caspase8/cleaved-PARP/mitochondrial-Bax), fibrosis (Smad3/TGF-ß), and mitochondrial-damaged markers (cyclophilin D/cytosolic-cytochrome-C) displayed a pattern identical to that of creatinine levels among the groups (all P < 0.0001). The kidney injury score, fibrosis, cellular expression of inflammation (CD68+cells), and glomerulus/renal-tubular damaged markers (Snail/KIM-1/WT-1) exhibited an identical pattern, whereas the cellular expression of podocyte component (synaptopodin) displayed an opposite pattern of creatinine levels among the groups (all P < 0.0001). Therefore, the G9a inhibitor effectively protected kidneys against IR injury.

Comprehensive insight into endothelial progenitor cell-derived extracellular vesicles as a promising candidate for disease treatment

Endothelial progenitor cells (EPCs), which are a type of stem cell, have been found to have strong angiogenic and tissue repair capabilities. Extracellular vesicles (EVs) contain many effective components, such as cellular proteins, microRNAs, messenger RNAs, and long noncoding RNAs, and can be secreted by different cell types. The functions of EVs depend mainly on their parent cells. Many researchers have conducted functional studies of EPC-derived EVs (EPC-EVs) and showed that they exhibit therapeutic effects on many diseases, such as cardiovascular disease, acute kidney injury, acute lung injury, and sepsis. In this review article, we comprehensively summarized the biogenesis and functions of EPCs and EVs and the potent role of EPC-EVs in the treatment of various diseases. Furthermore, the current problems and future prospects have been discussed, and further studies are needed to compare the therapeutic effects of EVs derived from various stem cells, which will contribute to the accelerated translation of these applications in a clinical setting.

Rapamycin Improves Adipose-Derived Mesenchymal Stem Cells (ADMSCs) Renoprotective Effect against Cisplatin-Induced Acute Nephrotoxicity in Rats by Inhibiting the mTOR/AKT Signaling Pathway

Objective: Because the poor survival of transplanted cells in a hostile microenvironment limits stem cell therapy, in the current study, we investigated the effect of rapamycin (Rapa)-preactivated autophagy on the survival and homing of transplanted adipose mesenchymal stem cells (ADMSCs) in a rat model of cisplatin (Cis)-induced nephrotoxicity, as well as the possible role of the mTOR/AKT signaling pathway. Materials and methods: In vitro, ADMSCs isolated from rats were treated with 50 nmol/L rapamycin for 2 h, after which the cytoprotective and autophagy-inducing effects of Rapa were investigated. The cis-induced acute nephrotoxicity rat model was constructed in vivo. ADMSCs and Rapa-ADMSCs were administered into the tail vein before Cis therapy. At 3, 7, and 10 days after Cis injection, all animals were euthanized. The renal functions and morphology as well as autophagy response were assessed. Results: The pretreatment of cultured ADMSCs with Rapa caused a significant increase in autophagic activities and lysosome production of the cells, with a significant increase in the secretion of SDF-1, IL-10 and autophagy promoter LC3 and Beclin from these cells, while mTOR/AKT pathways were inhibited. In addition, the transplantation of Rapa-pretreated ADMSCs restored the kidney functions and morphology dramatically. Renal expression of SDF-1 and HIF1 was upregulated, while expression of IL-6, NF-kB and TGF-β1 was downregulated. Conclusions: We concluded that the preactivation of autophagy with Rapa improves the survival and differentiation of the transplanted ADMSCs by inhibiting the mTOR/AKT signaling pathway, which in turn could significantly attenuate the Cis-induced acute renal injury.

Genipin-crosslinked decellularized scaffold induces regeneration of defective rat kidneys

Objective: The purpose of this study was to improve the performance of decellularized renal scaffolds by the genipin crosslinking method to facilitate the regeneration of tissues and cells and provide better conditions for the regeneration and repair of defective kidneys. Methods: SD rats were randomly divided into three groups: normal group, uncrosslinked scaffold group and genipin-crosslinked scaffold group. Hematoxylin eosin, Masson and immunofluorescence staining was used to observe the histomorphological characteristics of the kidneys in each group. The preservation of the renal vascular structure in the three groups was observed by vascular casting. A collagenase degradation assay was used to detect the antidegradation ability of the kidney in the three groups. CCK8 assays were used to test the in vitro biocompatibility of the scaffolds. The lower 1/3 of the rat left kidney was excised, and the defect was filled with decellularized renal scaffolds to observe the effect of scaffold implantation on the regenerative ability of the defective kidney. Results: Histological images showed that the genipin-crosslinked scaffold did not destroy the structure of the scaffold, and the collagen fibers in the scaffold was more regular, and the outline of the glomerulus was clearer than uncrosslinked scaffold. The results of casting showed that the vascular structure of genipin-crosslinked scaffold was still intact. The anti-degradation ability test showed that the anti-degradation ability of genipin-crosslinked scaffold was significantly higher than that of the uncrosslinked scaffold. Cell culture experiments showed that the genipin-crosslinked scaffold had no cytotoxicity and promoted cell proliferation to some extent. In vivo scaffold transplantation experiments further demonstrated that the genipin-crosslinked scaffold had better anti-degradation and anti-inflammatory ability. Conclusion: Genipin-crosslinked rat kidney scaffold complemented kidney defects in rats can enhance scaffold-induced kidney regeneration and repair.

VEGF Receptor 1 Promotes Hypoxia-Induced Hematopoietic Progenitor Proliferation and Differentiation

Although it is well known that hypoxia incites unleashed cellular inflammation, the mechanisms of exaggerated cellular inflammation in hypoxic conditions are not known. We observed augmented proliferation of hematopoietic stem and progenitor cells (HSPC), precursors of inflammatory leukocytes, in mice under hypoxia. Consistently, a transcriptomic analysis of human HSPC exposed to hypoxic conditions revealed elevated expression of genes involved in progenitor proliferation and differentiation. Additionally, bone marrow cells in mice expressed high amount of vascular endothelial growth factor (VEGF), and HSPC elevated VEGF receptor 1 (VEGFr1) and its target genes in hypoxic conditions. In line with this, VEGFr1 blockade in vivo and in vitro decreased HSPC proliferation and attenuated inflammation. In silico and ChIP experiments demonstrated that HIF-1α binds to the promoter region of VEGFR1. Correspondingly, HIF1a silencing decreased VEGFr1 expression in HSPC and diminished their proliferation. These results indicate that VEGF signaling in HSPC is an important mediator of their proliferation and differentiation in hypoxia-induced inflammation and represents a potential therapeutic target to prevent aberrant inflammation in hypoxia-associated diseases.

Comparison of Stromal Vascular Fraction and Adipose-Derived Stem Cells for Protection of Renal Function in a Rodent Model of Ischemic Acute Kidney Injury

Aims

Few studies have compared the use of different cell types derived from adipose tissue or the optimal route for efficient and safe cell delivery in ischemic acute kidney injury (AKI). We compared the abilities of stromal vascular fraction (SVF) and adipose-derived stem cells (ADSC), injected via three different routes, to protect renal function in a rodent model of ischemic AKI.

Methods

Ninety male Sprague-Dawley rats were randomly divided into 9 groups: sham, nephrectomy control, AKI control, transaortic renal arterial SVF injection, renal parenchymal SVF injection, tail venous SVF injection, transaortic renal arterial ADSC injection, renal parenchymal ADSC injection, and tail venous ADSC injection groups. Their renal function was assessed 4 days before and 1, 2, 3, 4, 7, and 14 days after surgical procedures to induce ischemic AKI. The histomorphometric studies were performed 14 days after surgical procedures.

Results

Renal parenchymal injection of SVF notably reduced the level of serum blood urea nitrogen and creatinine elevation compared to the AKI control group. Renal parenchymal injection of SVF notably reduced the level of creatinine clearance decrease. In addition, collagen content was lower in the renal parenchymal SVF injection group, and fibrosis was reduced. Apoptosis was reduced in the renal parenchymal SVF injection group, and proliferation was increased. The expression levels of antioxidative markers such as glutathione reductase and peroxidase were higher in the renal parenchymal SVF injection group.

Conclusions

Our findings suggest that renal function is protected from ischemic AKI through renal parenchymal injection of SVF, which has enhanced antifibrotic, antiapoptotic, and antioxidative effects.

Hypoxia-Inducible Factor Protects Against Acute Kidney Injury via the Wnt/β-Catenin Signaling Pathway

Promoting adaptive repair (AR) in acute kidney injury (AKI) is an effective strategy to preventprogression from AKI to chronic kidney disease (CKD). However, the mechanisms involved in renal repair after AKI remain unclear. In this study, we investigated the role of hypoxia-inducible factor (HIF), an important regulator of ischemic and hypoxic injury, in AKI during the repair phase. We established mouse models of ischemia-reperfusion injury (IRI)-induced AKI with AR or maladaptive repair (MAR). We found that after injury, the activation of HIF in the AR group was rapid, while in the MAR group, HIF activation was relatively delayed, and its expression was significantly lower than that in the AR group during the early repair phase. To further investigate the mechanism of HIF, we regulated the expression of HIF-1α and HIF-2α in HK-2 cells and EA.hy926 cells, respectively. Silencing HIF expression reduced proliferation and increased apoptosis in cells injured by hypoxia/reoxygenation (H/R). Self-healing ability was further reduced due to the downregulation of HIF. Moreover, HIF overexpression had the opposite effect. HIF increased the expression of β-catenin and its downstream target genes. Activation of Wnt/β-catenin by the small molecule activator SKL2001 mitigated the damaging effect of HIF knockdown, while blocking β-catenin with the inhibitor IWR-1-endo reduced the protective effects of HIF. In conclusion, HIF, which is highly expressed in the early stage after AKI, promotes renal repair by interacting with the Wnt/β-catenin signaling pathway.

Integrin α5 Is Regulated by miR-218-5p in Endothelial Progenitor Cells

BACKGROUND

Endothelial cell injury is a common nidus of renal injury in patients and consistent with the high prevalence of AKI reported during the coronavirus disease 2019 pandemic. This cell type expresses integrin α5 (ITGA5), which is essential to the Tie2 signaling pathway. The microRNA miR-218-5p is upregulated in endothelial progenitor cells (EPCs) after hypoxia, but microRNA regulation of Tie2 in the EPC lineage is unclear.

METHODS

We isolated human kidney-derived EPCs (hkEPCs) and surveyed microRNA target transcripts. A preclinical model of ischemic kidney injury was used to evaluate the effect of hkEPCs on capillary repair. We used a genetic knockout model to evaluate the effect of deleting endogenous expression of miR-218 specifically in angioblasts.

RESULTS

After ischemic in vitro preconditioning, miR-218-5p was elevated in hkEPCs. We found miR-218-5p bound to ITGA5 mRNA transcript and decreased ITGA5 protein expression. Phosphorylation of 42/44 MAPK decreased by 73.6% in hkEPCs treated with miR-218-5p. Cells supplemented with miR-218-5p downregulated ITGA5 synthesis and decreased 42/44 MAPK phosphorylation. In a CD309-Cre/miR-218-2-LoxP mammalian model (a conditional knockout mouse model designed to delete pre-miR-218-2 exclusively in CD309⁺ cells), homozygotes at e18.5 contained avascular glomeruli, whereas heterozygote adults showed susceptibility to kidney injury. Isolated EPCs from the mouse kidney contained high amounts of ITGA5 and showed decreased migratory capacity in three-dimensional cell culture.

CONCLUSIONS

These results demonstrate the critical regulatory role of miR-218-5p in kidney EPC migration, a finding that may inform efforts to treat microvascular kidney injury via therapeutic cell delivery.

SIRT3 deficiency exacerbates early-stage fibrosis after ischaemia-reperfusion-induced AKI

BACKGROUND

Sirtuin 3 (SIRT3) is a crucial regulator of mitochondrial function and is associated with injury and repair in acute kidney injury (AKI). To investigate whether mitochondrial damage and early renal fibrosis are associated with decreased renal SIRT3 levels, we established an in vivo model.

METHODS

In vivo, we established ischaemia-reperfusion-induced AKI (IR-AKI) models in wild-type (WT) and SIRT3-knockout (SIRT3-KO) mice. Serum creatinine (Scr) and blood urea nitrogen (BUN) were measured by an automatic biochemical analyser, and renal pathological changes were examined by haematoxylin and eosin (HE) staining. Renal fibrosis in mice was assessed by Masson's trichrome staining. The expression of SIRT3, renal fibrosis-related markers (FN and α-SMA), and mitochondrial markers (DRP1, FIS1, OPA1, and MFN1) was measured by Western blotting. Morphological changes in mitochondria in renal tubular epithelial cells were analysed by transmission electron microscopy (TEM).

RESULTS

The levels of Scr and BUN were elevated with severe renal pathological damage in the IR-AKI model, especially in SIRT3-KO mice. In the IR-AKI model, the obvious increases in FN and α-SMA protein levels suggested that there was severe fibrosis in the kidney tissue, OPA1 and MFN1 protein levels were reduced while DRP1 and FIS1 protein levels were greatly increased. TEM photomicrographs showed that mitochondrial fragmentation was increased in the renal tubular epithelial cells of mice with IR injury. SIRT3-KO mice exhibited exacerbated changes.

CONCLUSION

Our findings indicate that SIRT3 plays a significant role in early-stage fibrosis after IR-AKI by regulating mitochondrial dynamics and that SIRT3 deficiency exacerbates renal dysfunction and renal fibrosis.

Molecular Mechanisms of Kidney Injury and Repair

Chronic kidney disease (CKD) will become the fifth global cause of death by 2040, thus emphasizing the need to better understand the molecular mechanisms of damage and regeneration in the kidney. CKD predisposes to acute kidney injury (AKI) which, in turn, promotes CKD progression. This implies that CKD or the AKI-to-CKD transition are associated with dysfunctional kidney repair mechanisms. Current therapeutic options slow CKD progression but fail to treat or accelerate recovery from AKI and are unable to promote kidney regeneration. Unraveling the cellular and molecular mechanisms involved in kidney injury and repair, including the failure of this process, may provide novel biomarkers and therapeutic tools. We now review the contribution of different molecular and cellular events to the AKI-to-CKD transition, focusing on the role of macrophages in kidney injury, the different forms of regulated cell death and necroinflammation, cellular senescence and the senescence-associated secretory phenotype (SAPS), polyploidization, and podocyte injury and activation of parietal epithelial cells. Next, we discuss key contributors to repair of kidney injury and opportunities for their therapeutic manipulation, with a focus on resident renal progenitor cells, stem cells and their reparative secretome, certain macrophage subphenotypes within the M2 phenotype and senescent cell clearance.

Overexpression of miR-19a and miR-20a in iPS-MSCs preserves renal function of chronic kidney disease with acute ischaemia-reperfusion injury in rat

This study tested the hypothesis that therapy with double overexpression of miR‐19a‐3p and miR‐20a‐5p (miR^DOE) to human inducible pluripotent stem cell–derived mesenchymal stem cells (iPS‐MSCs) was superior to iPS‐MSCs alone for preserving renal function in rat with pre‐existing chronic kidney disease (CKD), followed by ischaemia‐reperfusion (IR) injury. In vitro study demonstrated that the protein expressions of oxidative stress (NOX‐1/NOX‐2/NOX4/oxidized protein/p22phox), inflammatory downstream signalling (TLR2&4/MyD88/TRAF6/IKK‐ß/p‐NFκB/IL‐1ß/IL‐6/MMP‐9) and cell apoptosis/death signalling (cleaved caspase‐3/mitochondrial Bax/p‐ERKs/p‐JNK/p‐p38) at time‐points of 24‐hour/48‐hour cell cultures were significantly increased in p‐Cresol‐treated NRK‐52E cells than in the control that was significantly reversed by miR‐19a‐3p‐transfected iPS‐MSC (all P < .001). Animals were categorized into group 1 (sham‐operated control), group 2 (CKD‐IR), group 3 (CKD‐IR + oligo‐miR^DOE of iPS‐MSCs/6.0 ×10⁵/intra‐renal artery transfusion/3 hours after IR procedure), group 4 (CKD‐IR + iPS‐MSCs) and group 5 (CKD‐IR + miR^DOE of iPS‐MSCs/6.0 ×10^5/intra‐renal artery transfusion/3 hour after IR procedure). By day 35, the creatinine/BUN levels were lowest in group 1, highest in group 2 and significantly lower in group 5 than in groups 3 and 4 (all P < .0001) but they showed no difference between the latter two groups. The protein expressions of oxidative stress, inflammatory downstream signalling and cell apoptosis/death signalling exhibited an identical pattern of creatinine level among the five groups (all P < .00001). Also, the microscopic findings demonstrated that the kidney injury score/fibrotic area/number of inflammatory cells (CD14+/CD68+) exhibited an identical pattern of creatine level (all P < .0001). The miR^DOE of iPS‐MSCs was superior to iPS‐MSCs for preserving the residual kidney function and architecture in CKD‐IR rat.

Stem/progenitor cell in kidney: characteristics, homing, coordination, and maintenance

Renal failure has a high prevalence and is becoming a public health problem worldwide. However, the renal replacement therapies such as dialysis are not yet satisfactory for its multiple complications. While stem/progenitor cell-mediated tissue repair and regenerative medicine show there is light at the end of tunnel. Hence, a better understanding of the characteristics of stem/progenitor cells in kidney and their homing capacity would greatly promote the development of stem cell research and therapy in the kidney field and open a new route to explore new strategies of kidney protection. In this review, we generally summarize the main stem/progenitor cells derived from kidney in situ or originating from the circulation, especially bone marrow. We also elaborate on the kidney-specific microenvironment that allows stem/progenitor cell growth and chemotaxis, and comment on their interaction. Finally, we highlight potential strategies for improving the therapeutic effects of stem/progenitor cell-based therapy. Our review provides important clues to better understand and control the growth of stem cells in kidneys and develop new therapeutic strategies.

Peritubular Capillary Rarefaction: An Underappreciated Regulator of CKD Progression

Peritubular capillary (PTC) rarefaction is commonly detected in chronic kidney disease (CKD) such as hypertensive nephrosclerosis and diabetic nephropathy. Moreover, PTC rarefaction prominently correlates with impaired kidney function and predicts the future development of end-stage renal disease in patients with CKD. However, it is still underappreciated that PTC rarefaction is a pivotal regulator of CKD progression, primarily because the molecular mechanisms of PTC rarefaction have not been well-elucidated. In addition to the established mechanisms (reduced proangiogenic factors and increased anti-angiogenic factors), recent studies discovered significant contribution of the following elements to PTC loss: (1) prompt susceptibility of PTC to injury, (2) impaired proliferation of PTC, (3) apoptosis/senescence of PTC, and (4) pericyte detachment from PTC. Mainly based on the recent and novel findings in basic research and clinical study, this review describes the roles of the above-mentioned elements in PTC loss and focuses on the major factors regulating PTC angiogenesis, the assessment of PTC rarefaction and its surrogate markers, and an overview of the possible therapeutic agents to mitigate PTC rarefaction during CKD progression. PTC rarefaction is not only a prominent histological characteristic of CKD but also a central driving force of CKD progression.

Erythropoietin Preconditioning Mobilizes Endothelial Progenitor Cells to Attenuate Nephron-Sparing Surgery-Induced Ischemia-Reperfusion Injury

The purpose of this study was to examine the role of endothelial progenitor cells (EPCs) in protection against ischemic-reperfusion injury (IRI) in a nephron-sparing surgery (NSS) rat model using erythropoietin (EPO) preconditioning. Fifty-four male Sprague-Dawley rats were randomly divided into 3 groups for right kidney nephrectomy treatment: sham group (exposure without clamp treatment), NSS group (3 days of peritoneal phosphate buffered saline [PBS] injection before renal blood vessels were clamped for 40 mins and NSS was performed), and EPO group (3 days of EPO abdomen injections prior to renal blood vessel clamping for 40 min before NSS was performed). After 12, 24, and 72 hours, inferior vena cava blood and renal tissues were harvested. The extent of renal injury was assessed, along with EPC number, cell proliferation, angiogenesis, and vascular growth factor expression. EPO preconditioning significantly improved renal function and histologic morphology, indicated by reduced blood urea nitrogen (BUN) ([33.12 ± 1.88] vs [16.03 ± 0.91], P < .05) and serum creatinine (Scr) ([190.2 ± 20.23] vs [77.23 ± 5.82], P < .05) levels and histologic injury scores ([3.20 ± 0.78] vs [1.70 ± 0.67], P < .05). Angiogenesis in peritubular capillaries markedly increased in the EPO group. EPC numbers increased in the kidneys at 24 hours following reperfusion in the EPO group, compared to the NSS group. Furthermore, EPO preconditioning also increased SDF-1α and CXCR7 expression at 24 hours following reperfusion relative to the NSS group. These findings suggest that EPO pretreatment can reduce renal injury in rats caused by IRI. Mechanistically, this may be related to EPC mobilization and recruitment to injured renal tissues by SDF-1α and CXCR7.

Combined Therapy With Hyperbaric Oxygen and Melatonin Effectively Reduce Brain Infarct Volume and Preserve Neurological Function After Acute Ischemic Infarct in Rat

This study tested the hypothesis that combined hyperbaric oxygen (HBO) and melatonin (Mel) was superior to either one for protecting the brain functional and parenchymal integrity from acute ischemic stroke (IS) injury. Adult-male Sprague-Dawley rats were divided into groups 1 (sham-operated control), 2 (IS), 3 (IS + HBO), 4 (IS + Mel), and 5 (IS + HBO-Mel). By day 28 after IS, the brain infarct area (BIA) was lowest in group 1, highest in group 2, significantly higher in groups 3 and 4 than in group 5, but not different between groups 3 and 4. The neurological function at day 7, 14, and 28 exhibited an opposite pattern to BIA among the 5 groups. The protein expressions of inflammatory (IL-1β/IL-6/iNOS/TNF-α/p-NF-κB), apoptotic (cleaved-caspase3/cleaved-PARP/mitochondrial Bax), mitochondrial/DNA-damaged (cytochrome-C/γ-H2AX), oxidative stress (NOX-1/NOX-2), and autophagy (i.e. ratio of CL3B-II/CL3B-I) biomarkers displayed an identical pattern of BIA among 5 groups. Cellular expressions of inflammation (F4/80+/GFAP+) and DNA-damaged biomarker (γ-H2AX+) exhibited an identical pattern, whereas the integrities of myelin sheath/neuron (MPB+/NeuN+), endothelial cell (CD31+/vWF+), and number of small vessels exhibited an opposite pattern of BIA among the 5 groups. Combined HBO-Mel therapy offered an additional benefit in protecting the brain against IS injury.

Lgr5-positive endothelial progenitor cells occupy a tumor and injury prone niche in the kidney vasa recta

The Wnt pathway co-receptor, Leucine Rich Repeat Containing G Protein-Coupled Receptor 5 (LGR5), labels tumor-prone stem cell populations in certain types of tissue. In this study, we show that ARID1A and PIK3CA mutations in LGR5⁺ cells result in renal angiosarcomas in adult mice. The tumors originate in the renal medulla. We further show that LGR5 labels SOX17⁺/CD31⁺/CD34⁺/CD133⁺/AQP1⁺/CD146⁺ endothelial progenitor cells within the descending vasa recta or straight arterioles of the kidney, which are specialized capillaries that maintain medullary osmotic gradients necessary for water reabsorption and the production of concentrated urine. LGR5⁺ endothelial progenitor cells are tightly associated with contractile pericytes within the descending vasa recta. Long-term in vivo lineage tracing revealed that LGR5⁺ cells give rise to renal medullary vasculature. We further show that LGR5⁺ cells are activated in response to ischemic kidney injury. Our findings uncover a physiologically relevant endothelial progenitor cell population within the kidney vasa recta.

Rat Mesenchymal Stromal Cell Sheets Suppress Renal Fibrosis via Microvascular Protection

Renal fibrosis is one of the largest global health care problems, and microvascular (MV) injury is important in the development of progressive fibrosis. Although conventional cell therapy suppresses kidney injury via the role of vasoprotective cytokines, the effects are limited due to low retention of administered cells. We recently described that transplantation of hepatocyte growth factor (HGF)‐transgenic mesothelial cell sheets showed a remarkable cell survival and strong therapeutic effects in a rat renal fibrosis model. Due to the translational hurdles of transgenic cells, we here applied this technique for allogeneic transplantation using rat bone marrow mesenchymal stromal cells (MSCs). MSC sheets were transplanted onto the kidney surface of a rat renal ischemia–reperfusion‐injury model and the effects were compared between those in untreated rats and those receiving intravenous (IV) administration of the cells. We found that donor‐cell survival was superior in the cell sheet group relative to the IV group, and that the cell sheets secreted HGF and vascular endothelial growth factor (VEGF) up to day 14. Transplantation of cell sheets increased the expression of activated HGF/VEGF receptors in the kidney. There was no evidence of migration of transplanted cells into the kidney parenchyma. Additionally, the cell sheets significantly suppressed renal dysfunction, MV injury, and fibrosis as compared with that observed in the untreated and IV groups. Furthermore, we demonstrated that the MSC sheet protected MV density in the whole kidney according to three‐dimensional microcomputed tomography. In conclusion, MSC sheets strongly prevented renal fibrosis via MV protection, suggesting that this strategy represents a potential novel therapy for various kidney diseases. stem cells translational medicine2019;8:1330&1341

Rat bone marrow mesenchymal stromal cell sheets were transplanted onto the kidney surface. In ischemia–reperfusion‐injury, microvascular density loss caused by endothelial injury resulted in progressive renal fibrosis. Mesenchymal stromal cell sheets remained long‐term on the kidney surface and protected the microvasculature, which resulted in suppression of progressive fibrosis. The therapeutic effects were partially explained by the role of hepatocyte growth factor/vascular endothelial growth factor secreted from mesenchymal stromal cell sheets.

Nephroprotective effect of losartan in IgA model rat

Objective

This study was performed to investigate the possible nephroprotective effects of losartan in a rat model of experimental IgA nephropathy (IgAN).

Methods

Thirty male Sprague–Dawley rats were randomly divided into three groups. The rats in the model group were treated with bovine serum albumin (oral gavage), lipopolysaccharide (tail vein injection), and carbon tetrachloride (subcutaneous injection); rats in the losartan group received treatments similar to those of the model group, and were orally gavaged with losartan; and rats in the control group received phosphate-buffered saline alone (both orally and intravenously).

Results

Losartan treatment lowered the 24-hour urinary protein, serum blood urea nitrogen, and serum creatinine levels. Proliferating mesangial cells with a variable increase in the mesangial matrix were detected in the model group, whereas injury in the losartan group was significantly attenuated. Immunohistochemistry revealed that the expression levels of transforming growth factor (TGF)-β1 and α-smooth muscle actin were significantly elevated in the model group but reduced in the losartan group. The expression levels of TGF-β1 and monocyte chemoattractant protein-1 were minimal in the control group, significantly increased in the model group, and reduced in the losartan group.

Conclusion

Losartan has a protective effect against tubulointerstitial injury in IgAN.

Preactivated and disaggregated shape-changed platelets protect kidney against from ischemia-reperfusion injury in rat through attenuating inflammation reaction

This study tested the hypothesis that preactivated and disaggregated shape-changed platelet (PreD-SCP) therapy significantly protected rat kidney from ischemia-reperfusion (IR) injury. Adult-male Sprague-Dawley rats (n = 24) were equally categorized into Groups 1 (sham-operated control [SC]), 2 (SC + PreD-SCP), 3 (IR only), and 4 (IR + PreD-SCP). By 72 hr after IR procedure, the circulatory levels of creatinine, blood urine nitrogen and inflammatory biomarkers (interleukin [IL]-6/tumor necrosis factor [TNF]-α), and ratio of urine protein to urine creatinine were significantly higher in Group 3 than in other groups and significantly higher in Group 4 than in Groups 1 and 2, but they showed no different between Groups 1 and 2 (all p < .001). The microscopic findings showed that the expressions of kidney injury score, cellular inflammation (MMP-9/CD14//F4/80), and fibrotic area were identical to the circulatory inflammation, whereas the integrity of podocyte components (ZO-1/synaptopodin/podocin) exhibited an opposite to circulatory inflammation among the four groups (all p < .0001). The protein expressions of inflammatory (TNF-α/IL-1ß/NF-κB/iNOS/TRAF6/MyD88/TLR-4), apoptotic/cell death (mitochondrial Bax/cleaved caspase-3/p-53), oxidized protein, mitogen-activated protein kinase family (p-38/p-JNK/p-c-JUN), and mitochondrial-damaged biomarkers displayed a similar pattern, whereas the antiapoptotic (Bcl-2/Bcl-XL) and integrity of mitochondrial biomarkers followed an opposite trend to circulatory inflammation among the four groups (all p < .001). PreD-SCP therapy effectively protected the kidney against IR injury.

Flow Cytometric Analysis of Hematopoietic Populations in Rat Bone Marrow. Impact of Trauma and Hemorrhagic Shock

Severe injury and hemorrhagic shock (HS) result in multiple changes to hematopoietic differentiation, which contribute to the development of immunosuppression and multiple organ failure (MOF). Understanding the changes that take place during the acute injury phase may help predict which patients will develop MOF and provide potential targets for therapy. Obtaining bone marrow from humans during the acute injury phase is difficult so published data are largely derived from peripheral blood samples, which infer bone marrow changes that reflect the sustained inflammatory response. This preliminary and opportunistic study investigated leucopoietic changes in rat bone marrow 6 h following traumatic injury and HS. Terminally anesthetized male Porton Wistar rats were allocated randomly to receive a sham operation (cannulation with no injury) or femoral fracture and HS. Bone marrow cells were flushed from rat femurs and immunophenotypically stained with specific antibody panels for lymphoid (CD45R, CD127, CD90, and IgM) or myeloid (CD11b, CD45, and RP-1) lineages. Subsequently, cell populations were fluorescence-activated cell sorted for morphological assessment. Stage-specific cell populations were identified using a limited number of antibodies, and leucopoietic changes were determined 6 h following trauma and HS. Myeloid subpopulations could be identified by varying levels CD11b expression, CD45, and RP-1. Trauma and HS resulted in a significant reduction in total CD11b + myeloid cells including both immature (RP-1(-)) and mature (RP-1+) granulocytes. Multiple B-cell lymphoid subsets were identified. The total percentage of CD90+ subsets remained unchanged following trauma and HS, but there was a reduction in the numbers of maturing CD90(-) cells suggesting movement into the periphery. © 2019 The Authors. Cytometry Part A published by Wiley Periodicals, Inc. on behalf of International Society for Advancement of Cytometry.

Novel repair mechanisms in a renal ischaemia/reperfusion model: Subsequent saxagliptin treatment modulates the pro-angiogenic GLP-1/cAMP/VEGF, ANP/eNOS/NO, SDF-1α/CXCR4, and Kim-1/STAT3/HIF-1α/VEGF/eNOS pathways

The reno-protective effects of antidiabetic dipeptidyl peptidase (DPP)-4 inhibitors have been studied regarding their antioxidant and anti-inflammatory properties. However, the potential ability of saxagliptin to ameliorate renal injury by enhancing neovascularization has not been elucidated. To address this issue, saxagliptin (10 and 30 mg/kg) was administered to Wistar rats after the induction of renal ischaemia/reperfusion (I/R). Our results showed that saxagliptin operated through different axes to ameliorate I/R injury. By inhibiting DPP-4, saxagliptin maintained stromal cell-derived factor-1α expression and upregulated its chemokine receptor CXCR4 to trigger vasculogenesis through the enhanced migration of endothelial progenitor cells (EPCs). Additionally, this compound rescued the levels of glucagon-like peptide-1 and its downstream mediator cAMP to increase vascular endothelial growth factor (VEGF) and CXCR4 levels. Moreover, saxagliptin stimulated atrial natriuretic peptide/endothelial nitric oxide synthase to increase nitric oxide levels and provoke angiogenesis and renal vasodilation. In addition to inhibiting DPP-4, saxagliptin increased the renal kidney injury molecule-1/pY705-STAT3/hypoxia-inducible factor-1α/VEGF pathway to enhance angiogenesis. Similar to other gliptins, saxagliptin exerted its anti-inflammatory and antioxidant effects by suppressing the renal contents of p (S536)-nuclear factor-κB p65, tumour necrosis factor-α, monocyte chemoattractant protein-1, myeloperoxidase, and malondialdehyde while boosting the glutathione content. These events improved the histological structure and function of the kidney, as evidenced by decreased serum creatinine, blood urea nitrogen, and cystatin C and increased serum albumin. Accordingly, in addition to its anti-inflammatory and antioxidant activities, saxagliptin dose-dependently ameliorated I/R-induced renal damage by enhancing neovascularization through improved tissue perfusion and homing of bone marrow-derived EPCs to mediate repair processes.

Loss of Renal Peritubular Capillaries in Hypertensive Patients Is Detectable by Urinary Endothelial Microparticle Levels

Hypertension, an important cause of chronic kidney disease, is characterized by peritubular capillary (PTC) loss. Circulating levels of endothelial microparticles (EMPs) reflect systemic endothelial injury. We hypothesized that systemic and urinary PTC-EMPs levels would reflect renal microvascular injury in hypertensive patients. We prospectively measured by flow cytometry renal vein, inferior vena cava, and urinary levels of EMPs in essential (n=14) and renovascular (RVH; n=24) hypertensive patients and compared them with peripheral blood and urinary levels in healthy volunteers (n=14). PTC-EMPs were identified as urinary exosomes positive for the PTC marker plasmalemmal-vesicle-associated protein. In 7 RVH patients, PTC and fibrosis were also quantified in renal biopsy, and in 18 RVH patients, PTC-EMPs were measured again 3 months after continued medical therapy with or without stenting (n=9 each). Renal vein and systemic PTC-EMPs levels were not different among the groups, whereas their urinary levels were elevated in both RVH and essential hypertension versus healthy volunteers (56.8%±12.7% and 62.8%±10.7% versus 34.0%±17.8%; both P≤0.001). Urinary PTC-EMPs levels correlated directly with blood pressure and inversely with estimated glomerular filtration rate. Furthermore, in RVH, urinary PTC-EMPs levels correlated directly with stenotic kidney hypoxia, histological PTC count, and fibrosis and inversely with cortical perfusion. Three months after treatment, the change in urinary PTC-EMPs levels correlated inversely with a change in renal function ( r=-0.582; P=0.011). Therefore, urinary PTC-EMPs levels are increased in hypertensive patients and may reflect renal microcirculation injury, whereas systemic PTC-EMPs levels are unchanged. Urinary PTC-EMPs may be useful as novel biomarkers of intrarenal capillary loss.

Genetic communication by extracellular vesicles is an important mechanism underlying stem cell-based therapy-mediated protection against acute kidney injury

Stem cell-based therapy appears to be a promising new candidate for acute kidney injury (AKI) management. Traditionally, it has been accepted that the mechanism underlying the regenerative effect of stem cells is based on their paracrine/endocrine activity, including release of bioactive factors that act on injured renal cells and presentation of proangiogenic, antiapoptotic, antioxidative, and immunomodulatory effects. Recently, multiple studies have confirmed that extracellular vesicles (EVs) are a kind of vesicle rich in a broad variety of biologically active molecules, including lipids, proteins, and, in particular, nucleic acids. EVs are able to transfer genetic information to target cells, alter target gene regulatory networks, and exert biological effects. Stem cell-derived EVs (SC-EVs) are emerging as potent genetic information sources that deliver mRNAs and miRNAs to injured renal cells and exert renoprotective effects during AKI. On the other hand, EVs originating from injured renal cells also contain genetic information that is believed to be able to influence phenotypic and functional changes in stem cells, favoring renal recovery. In this review, we summarize studies providing evidence of genetic communication during the application of stem cells in preclinical AKI models, aiming to clarify the mechanism and describe the therapeutic effects of stem cell-based therapy in AKI patients.

Induced pluripotent stem cell-derived endothelial progenitor cells attenuate ischemic acute kidney injury and cardiac dysfunction

Background

Renal ischemia–reperfusion (I/R) injury is a major cause of acute kidney injury (AKI), which is associated with high morbidity and mortality. AKI is a serious and costly medical condition. Effective therapy for AKI is an unmet clinical need, and molecular mechanisms underlying the interactions between an injured kidney and distant organs remain unclear. Therefore, novel therapeutic strategies should be developed.

Methods

We directed the differentiation of human induced pluripotent stem (iPS) cells into endothelial progenitor cells (iEPCs), which were then applied for treating mouse AKI. The mouse model of AKI was induced by I/R injury.

Results

We discovered that intravenously infused iEPCs were recruited to the injured kidney, expressed the mature endothelial cell marker CD31, and replaced injured endothelial cells. Moreover, infused iEPCs produced abundant proangiogenic proteins, which entered into circulation. In AKI mice, blood urea nitrogen and plasma creatinine levels increased 2 days after I/R injury and reduced after the infusion of iEPCs. Tubular injury, cell apoptosis, and peritubular capillary rarefaction in injured kidneys were attenuated accordingly. In the AKI mice, iEPC therapy also ameliorated apoptosis of cardiomyocytes and cardiac dysfunction, as indicated by echocardiography. The therapy also ameliorated an increase in serum brain natriuretic peptide. Regarding the relevant mechanisms, indoxyl sulfate and interleukin-1β synergistically induced apoptosis of cardiomyocytes. Systemic iEPC therapy downregulated the proapoptotic protein caspase-3 and upregulated the anti-apoptotic protein Bcl-2 in the hearts of the AKI mice, possibly through the reduction of indoxyl sulfate and interleukin-1β.

Conclusions

Therapy using human iPS cell-derived iEPCs provided a protective effect against ischemic AKI and remote cardiac dysfunction through the repair of endothelial cells and the attenuation of cardiomyocyte apoptosis.

Electronic supplementary material

The online version of this article (10.1186/s13287-018-1092-x) contains supplementary material, which is available to authorized users.

Hypoxic Preconditioned Mesenchymal Stromal Cell Therapy in a Rat Model of Renal Ischemia-reperfusion Injury: Development of Optimal Protocol to Potentiate Therapeutic Efficacy

Although previous and ongoing clinical studies have used stromal cells during renal ischemia-reperfusion injury (IRI), there is little consensus regarding the optimal protocol. We aimed to optimize the protocol for hypoxic preconditioned human bone marrow-derived mesenchymal stromal cell (HP-hBMSC) therapy in a rat model of renal IRI. We determined the optimal injection route (renal arterial, renal parenchymal, and tail venous injection), dose (low-dose: 1×10⁶, moderate-dose: 2×10⁶, and high-dose: 4×10⁶), and injection period (pre-, concurrent-, and post-IRI). During optimal injection route study, renal arterial injections significantly reduced the decreasing glomerular filtration rate (GFR), as compared to GFRs for the IRI control group, 2 and 4 days after IRI. Therapeutic effects and histological recoveries were the greatest in the group receiving renal arterial injections. During the dose finding study, high-dose injections significantly reduced the decreasing GFR, as compared to GFRs for the IRI control group, 3 days after IRI. Therapeutic effects and histological recoveries were the greatest in the high-dose injection group. While determining the optimal injection timing study, concurrent-IRI injection reduced elevated serum creatinine levels, as compared to those of the IRI control group, 1 day after IRI. Pre-IRI injection significantly reduced the decreasing GFR, as compared with GFRs for the IRI control group, 1 day after IRI. Therapeutic effects and histological recoveries were the greatest in the concurrent-IRI group. In conclusion, the concurrent-IRI administration of a high dose of HP-hBMSC via the renal artery leads to an optimal recovery of renal function after renal IRI.

Umbilical cord-derived mesenchymal stem cell transplantation in vaginal replacement in vitro and in a rat model

Cell transplantation strategies represent a potential therapeutic approach towards repair of congenital vaginal agenesis. In this study, the efficacy and mechanisms of action of treatment with human umbilical cord-derived mesenchymal stem cells (UC-MSCs) on vaginal regeneration was explored. UC-MSC transplantation alone, small intestinal submucosal (SIS) grafting alone, and a combination of UC-MSC transplantation/SIS grafting were performed with a vaginal defect rat model. Histological analyses of tissue sections were subsequently performed. UC-MSCs promoted the recovery of keratinizing squamous epithelium and papillae to nearly the same levels as in normal tissue. Of the treatments tested, UC-MSC transplantation showed optimal performance in inhibiting collagen deposition and accelerating the synthesis of elastin to maintain tissue elasticity. UC-MSC treatment also increased Cyclin D1, Ki67, and CD31 expression as assessed by immunohistochemistry. We also investigated the effects of UC-MSC secretions on keratinocytes in a co-culture model. UC-MSCs significantly stimulated vaginal tissue repair by promoting vaginal epithelium regeneration via paracrine factors but not by exploiting their keratinocyte differentiation potential. Further, UC-MSCs facilitated epithelial cell viability and promoted cell cycle progression via the AKT/GSK3β/Cyclin D1 pathway. These results indicate that UC-MSC transplantation is a feasible approach for vaginal tissue regeneration.

Human Peripheral Blood Mononuclear Cells Incubated in Vasculogenic Conditioning Medium Dramatically Improve Ischemia/Reperfusion Acute Kidney Injury in Mice

Acute kidney injury (AKI) is a major clinical problem that still has no established treatment. We investigated the efficacy of cultured human peripheral blood mononuclear cells (PBMNCs) for AKI. Ischemia/reperfusion injury (IRI) was used to induce AKI in male nonobese diabetic (NOD/severe combined immunodeficiency) mice aged 7 to 8 wk. PBMNCs were isolated from healthy volunteers and were subjected to quality and quantity controlled (QQc) culture for 7 d in medium containing stem cell factor, thrombopoietin, Flt-3 ligand, vascular endothelial growth factor, and interleukin 6. IRI-induced mice were divided into 3 groups and administered (1) 1 × 10⁶ PBMNCs after QQc culture (QQc PBMNCs group), (2) 1 × 10⁶ PBMNCs without QQc culture (non-QQc PBMNCs group), or (3) vehicle without PBMNCs (IRI control group). PBMNCs were injected via the tail vein 24 h after induction of IRI, followed by assessment of renal function, histological changes, and homing of injected cells. Blood urea nitrogen and serum creatinine (Cr) 72 h after induction of IRI in the QQc PBMNCs group dramatically improved compared with those in the IRI control and the non-QQc PBMNCs groups, accompanied by the improvement of tubular damages. Interstitial fibrosis 14 d after induction of IRI was also significantly improved in the QQc PBMNCs group compared with the other groups. The renoprotective effect noted in the QQc PBMNCs group was accompanied by reduction of peritubular capillary loss. The change of PBMNCs’ population (increase of CD34+ cells, CD133+ cells, and CD206+ cells) and increased endothelial progenitor cell colony-forming potential by QQc culture might be one of the beneficial mechanisms for restoring AKI. In conclusion, an injection of human QQc PBMNCs 24 h after induction of IRI dramatically improved AKI in mice.

Ischemia-Reperfusion Injury Reduces Long Term Renal Graft Survival: Mechanism and Beyond

Ischemia-reperfusion injury (IRI) during renal transplantation often initiates non-specific inflammatory responses that can result in the loss of kidney graft viability. However, the long-term consequence of IRI on renal grafts survival is uncertain. Here we review clinical evidence and laboratory studies, and elucidate the association between early IRI and later graft loss. Our critical analysis of previous publications indicates that early IRI does contribute to later graft loss through reduction of renal functional mass, graft vascular injury, and chronic hypoxia, as well as subsequent fibrosis. IRI is also known to induce kidney allograft dysfunction and acute rejection, reducing graft survival. Therefore, attempts have been made to substitute traditional preserving solutions with novel agents, yielding promising results.

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Ischaemia reperfusion injury (IRI) potentiates delayed renal graft function and causes reduction in renal graft survival

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IRI causes innate immune system activation, hypoxic injury, inflammation and graft vascular disease

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Reducing prolonged cold ischaemic time improves graft survival

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Novel protective strategies include mesenchymal stem cells, machine perfusion, and ex vivo preservation solution saturated with gas.

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Further studies are needed to investigate the long-term effects of novel ex vivo preservation agents

Endothelial colony-forming cells and pro-angiogenic cells: clarifying definitions and their potential role in mitigating acute kidney injury

Acute kidney injury (AKI) represents a significant clinical concern that is associated with high mortality rates and also represents a significant risk factor for the development of chronic kidney disease (CKD). This article will consider alterations in renal endothelial function in the setting of AKI that may underlie impairment in renal perfusion and how inefficient vascular repair may manifest post-AKI and contribute to the potential transition to CKD. We provide updated terminology for cells previously classified as 'endothelial progenitor' that may mediate vascular repair such as pro-angiogenic cells and endothelial colony-forming cells. We consider how endothelial repair may be mediated by these different cell types following vascular injury, particularly in models of AKI. We further summarize the potential ability of these different cells to mitigate the severity of AKI, improve perfusion and maintain vascular structure in pre-clinical studies.

Extendin-4 protects kidney from acute ischemia-reperfusion injury through upregulation of NRF2 signaling

This study tested the hypothesis that exendin-4 (Ex4) protects kidneys against ischemia-reperfusion (IR) injury mainly through upregulation of nuclear-factor erythroid 2-related factor 2 (Nrf2) signaling and downregulation of oxidative stress. Male-adult Sprague-Dawley rats (n=24) were equally divided into group 1 (sham-operated control), group 2 [IR only, ischemia (1 h)/reperfusion (72 h)] and group 3 (IR-Ex4, 10 μg/kg at 30 min, 24 h, 48 h after IR procedure). The in vitro study demonstrated that the protein expressions of phosphorylated (p)-Akt and Nrf2 were significantly progressively increased at time points of 0/0.5/1/3 h and 0/0.5/1/3/6/12/24 h, respectively in NRK-52E cells co-cultured with Ex4 (20 nM) (all P<0.0001). Additionally, the protein expressions of NOX-1/NOX2 were significantly increased, whereas p-Akt was significantly decreased in NRK-52E cells co-cultured with P-cresol (200 μM) that were significantly reversed after Ex4 treatment (all P<0.0001). As compared with baseline, the creatinine level, left/right kidney weight and MCP-1-positively stained area in the kidney parenchyma were significantly increased at 24 h after the IR procedure and significantly progressively decreased after that (all P<0.0001). By 27 h after IR, creatinine level/MCP-1 + area was significantly higher in group 2 than in groups 1 and 3, and significantly higher in group 3 than in group 1 (all P<0.0001). The numbers of Nrf2 +/NQO-1 + cells/SOD activity in kidney parenchyma were significantly lower in group 2 than in groups 1 and 3, and significantly lower in group 1 than in group 3 (all P<0.0001). In conclusion, Ex4 protected kidney from IR injury through upregulating antioxidants and downregulating inflammation/oxidative stress.

Harnessing CXCR4 antagonists in stem cell mobilization, HIV infection, ischemic diseases, and oncology

CXCR4 antagonists (e.g., Plerixafor^TM ) have been successfully validated as stem cell mobilizers for peripheral blood stem cell transplantation. Applications of the CXCR4 antagonists have heralded the era of cell-based therapy and opened a potential therapeutic horizon for many unmet medical needs such as kidney injury, ischemic stroke, cancer, and myocardial infarction. In this review, we first introduce the central role of CXCR4 in diverse cellular signaling pathways and discuss its involvement in several disease progressions. We then highlight the molecular design and optimization strategies for targeting CXCR4 from a large number of case studies, concluding that polyamines are the preferred CXCR4-binding ligands compared to other structural options, presumably by mimicking the highly positively charged natural ligand CXCL12. These results could be further justified with computer-aided docking into the CXCR4 crystal structure wherein both major and minor subpockets of the binding cavity are considered functionally important. Finally, from the clinical point of view, CXCR4 antagonists could mobilize hematopoietic stem/progenitor cells with long-term repopulating capacity to the peripheral blood, promising to replace surgically obtained bone marrow cells as a preferred source for stem cell transplantation.

Hyperactive FOXO1 results in lack of tip stalk identity and deficient microvascular regeneration during kidney injury

Loss of the microvascular (MV) network results in tissue ischemia, loss of tissue function, and is a hallmark of chronic diseases. The incorporation of a functional vascular network with that of the host remains a challenge to utilizing engineered tissues in clinically relevant therapies. We showed that vascular-bed-specific endothelial cells (ECs) exhibit differing angiogenic capacities, with kidney microvascular endothelial cells (MVECs) being the most deficient, and sought to explore the underlying mechanism. Constitutive activation of the phosphatase PTEN in kidney MVECs resulted in impaired PI3K/AKT activity in response to vascular endothelial growth factor (VEGF). Suppression of PTEN in vivo resulted in microvascular regeneration, but was insufficient to improve tissue function. Promoter analysis of the differentially regulated genes in KMVECs suggests that the transcription factor FOXO1 is highly active and RNAseq analysis revealed that hyperactive FOXO1 inhibits VEGF-Notch-dependent tip-cell formation by direct and indirect inhibition of DLL4 expression in response to VEGF. Inhibition of FOXO1 enhanced angiogenesis in human bio-engineered capillaries, and resulted in microvascular regeneration and improved function in mouse models of injury-repair.

DPP-4 enzyme deficiency protects kidney from acute ischemia-reperfusion injury: role for remote intermittent bowel ischemia-reperfusion preconditioning

We analyzed the effects of acute ischemia-reperfusion (KIR) injury on the status of kidney function and architecture in dipeptidyl peptidase4-difficient (DPP4^D) rats and the effect of remote small bowel ischemia-reperfusion (BIR) preconditioning. DPP4-deficient (DPP4^D) and normal Fischer344 (F344) rats were divided into 6 groups: (1) sham-F344, (2) sham-DPP4^D, (3) KIR-F344 (4) KIR-DPP4^D, (5) DPP4^D-KIR-extendin-9-39 and (6) BIR-KIR-F344. Blood creatinine and urea nitrogen levels and the urinary protein-to-creatinine ratio was higher in KIR-F344 rats than BIR-KIR-F344 or KIR-DPP4^D rats 72 h after acute KIR. Conversely, the circulating glucagon-like peptide 1 (GLP-1) levels were higher in BIR-KIR-F344 and KIR-DPP4^D than KIR-F344 rats after acute KIR. KIR-F344 rats showed greater inflammation, oxidative stress, apoptosis, DNA damage and kidney injury than other rat groups. Damage to the kidney architecture in KIR-F344 rats was greater than in BIR-KIR-F344 or KIR-DPP4^D rats. Expression of antioxidant proteins and GLP-1 receptor was higher in kidneys from KIR-DPP4^D and BIR-KIR-F344 than KIR-F344 rats, which suggests better intrinsic responses. We therefore suggest that elevated circulating GLP-1 levels due to DPP4 deficiency and BIR preconditioning protect kidney function and architecture during acute IR injury.

Advances in the Knowledge about Kidney Decellularization and Repopulation

End-stage renal disease (ESRD) is characterized by the progressive deterioration of renal function that may compromise different tissues and organs. The major treatment indicated for patients with ESRD is kidney transplantation. However, the shortage of available organs, as well as the high rate of organ rejection, supports the need for new therapies. Thus, the implementation of tissue bioengineering to organ regeneration has emerged as an alternative to traditional organ transplantation. Decellularization of organs with chemical, physical, and/or biological agents generates natural scaffolds, which can serve as basis for tissue reconstruction. The recellularization of these scaffolds with different cell sources, such as stem cells or adult differentiated cells, can provide an organ with functionality and no immune response after in vivo transplantation on the host. Several studies have focused on improving these techniques, but until now, there is no optimal decellularization method for the kidney available yet. Herein, an overview of the current literature for kidney decellularization and whole-organ recellularization is presented, addressing the pros and cons of the actual techniques already developed, the methods adopted to evaluate the efficacy of the procedures, and the challenges to be overcome in order to achieve an optimal protocol.

Multiple Mechanisms are Involved in Salt-Sensitive Hypertension-Induced Renal Injury and Interstitial Fibrosis

Salt-sensitive hypertension (SSHT) leads to kidney interstitial fibrosis. However, the potential mechanisms leading to renal fibrosis have not been well investigated. In present study, Dahl salt-sensitive (DS) rats were divided into three groups: normal salt diet (DSN), high salt diet (DSH) and high salt diet treated with hydrochlorothiazide (HCTZ) (DSH + HCTZ). A significant increase in systolic blood pressure (SBP) was observed 3 weeks after initiating the high salt diet, and marked histological alterations were observed in DSH rats. DSH rats showed obvious podocyte injury, peritubular capillary (PTC) loss, macrophage infiltration, and changes in apoptosis and cell proliferation. Moreover, Wnt/β-catenin signaling was significantly activated in DSH rats. However, HCTZ administration attenuated these changes with decreased SBP. In addition, increased renal and urinary Wnt4 expression was detected with time in DSH rats and was closely correlated with histopathological alterations. Furthermore, these alterations were also confirmed by clinical study. In conclusion, the present study provides novel insight into the mechanisms related to PTC loss, macrophage infiltration and Wnt/β-catenin signaling in SSHT-induced renal injury and fibrosis. Therefore, multi-target therapeutic strategies may be the most effective in preventing these pathological processes. Moreover, urinary Wnt4 may be a noninvasive biomarker for monitoring renal injury after hypertension.

Recovery of renal function after administration of adipose-tissue-derived stromal vascular fraction in rat model of acute kidney injury induced by ischemia/reperfusion injury

Acute kidney injury (AKI) induced by ischemia/reperfusion (I/R) injury is a major challenge in critical care medicine. The purpose of this study is to determine the therapeutic effects of the adipose-tissue-derived stromal vascular fraction (SVF) and the optimal route for SVF delivery in a rat model of AKI induced by I/R injury. Fifty male Sprague-Dawley rats were randomly divided into five groups (10 animals per group): sham, nephrectomy control, I/R injury control, renal arterial SVF infusion and subcapsular SVF injection. To induce AKI by I/R injury, the left renal artery was clamped with a nontraumatic vascular clamp for 40 min, and the right kidney was removed. Rats receiving renal arterial infusion of SVF had a significantly reduced increase in serum creatinine compared with the I/R injury control group at 4 days after I/R injury. The glomerular filtration rate of the renal arterial SVF infusion group was maintained at a level similar to that of the sham and nephrectomy control groups at 14 days after I/R injury. Masson's trichrome staining showed significantly less fibrosis in the renal arterial SVF infusion group compared with that in the I/R injury control group in the outer stripe (P < 0.001). TUNEL labeling showed significantly decreased apoptosis in both the renal arterial SVF infusion and subcapsular SVF injection groups compared with the I/R injury control group in the outer stripe (P < 0.001). Thus, renal function is effectively rescued from AKI induced by I/R injury through the renal arterial administration of SVF in a rat model.

Endothelial colony-forming cells ameliorate endothelial dysfunction via secreted factors following ischemia-reperfusion injury

Damage to endothelial cells contributes to acute kidney injury (AKI) by leading to impaired perfusion. Endothelial colony-forming cells (ECFC) are endothelial precursor cells with high proliferative capacity, pro-angiogenic activity, and in vivo vessel forming potential. We hypothesized that ECFC may ameliorate the degree of AKI and/or promote repair of the renal vasculature following ischemia-reperfusion (I/R). Rat pulmonary microvascular endothelial cells (PMVEC) with high proliferative potential were compared with pulmonary artery endothelial cells (PAEC) with low proliferative potential in rats subjected to renal I/R. PMVEC administration reduced renal injury and hastened recovery as indicated by serum creatinine and tubular injury scores, while PAEC did not. Vehicle-treated control animals showed consistent reductions in renal medullary blood flow (MBF) within 2 h of reperfusion, while PMVEC protected against loss in MBF as measured by laser Doppler. Interestingly, PMVEC mediated protection occurred in the absence of homing to the kidney. Conditioned medium (CM) from human cultured cord blood ECFC also conveyed beneficial effects against I/R injury and loss of MBF. Moreover, ECFC-CM significantly reduced the expression of ICAM-1 and decreased the number of differentiated lymphocytes typically recruited into the kidney following renal ischemia. Taken together, these data suggest that ECFC secrete factors that preserve renal function post ischemia, in part, by preserving microvascular function.

Human vascular progenitor cells derived from renal arteries are endothelial-like and assist in the repair of injured renal capillary networks

Vascular progenitor cells show promise for the treatment of microvasculature endothelial injury. We investigated the function of renal artery progenitor cells derived from radical nephrectomy patients, in animal models of acute ischemic and hyperperfusion injuries. Present in human adventitia, CD34positive/CD105negative cells were clonal and expressed transcription factors Sox2/Oct4 as well as surface markers CXCR4 (CD184)/KDR(CD309) consistent with endothelial progenitor cells. Termed renal artery-derived vascular progenitor cells (RAPC), injected cells were associated with decreased serum creatinine after ischemia/reperfusion, reduced albuminuria after hyperperfusion, and improved blood flow in both models. A small population of RAPC integrated with the renal microvasculature following either experimental injury. At a cellular level, RAPC promoted local endothelial migration in co-culture. Profiling of RAPC microRNA identified high levels of miRNA 218; also found at high levels in exosomes isolated from RAPC conditioned media after cell contact for 24 hours. After hydrogen peroxide-induced endothelial injury, RAPC exosomes harbored Robo-1 transcript; a gene known to be regulated by mir218. Such exosomes enhanced endothelial cell migration in culture in the absence of RAPC. Thus, our work shows the feasibility of pre-emptive pro-angiogenic progenitor cell procurement from a targeted patient population and potential therapeutic use in the form of autologous cell transplantation.