VEGF: Potential therapy for renal regeneration

Interleukin-2/anti-interleukin-2 immune complex attenuates cold ischemia-reperfusion injury after kidney transplantation by increasing renal regulatory T cells

BACKGROUND

Cold ischemia-reperfusion injury (IRI) is an unavoidable complication of kidney transplantation. We investigated the role of regulatory T cells (Treg) in cold IRI and whether the interleukin (IL)-2/anti-IL-2 antibody complex (IL-2C) can ameliorate cold IRI.

METHODS

We developed a cold IRI mouse model using kidney transplantation and analyzed the IL-2C impact on cold IRI in acute, subacute and chronic phases.

RESULTS

Treg transfer attenuated cold IRI, while Treg depletion aggravated cold IRI. Next, IL-2C administration prior to IRI mitigated acute renal function decline, renal tissue damage and apoptosis and inhibited infiltration of effector cells into kidneys and pro-inflammatory cytokine expression on day 1 after IRI. On day 7 after IRI, IL-2C promoted renal regeneration and reduced subacute renal damage. Furthermore, on day 28 following IRI, IL-2C inhibited chronic fibrosis. IL-2C decreased reactive oxygen species-mediated injury and improved antioxidant function. When IL-2C was administered following IRI, it also increased renal regeneration with Treg infiltration and suppressed renal fibrosis. In contrast, Treg depletion in the presence of IL-2C eliminated the positive effects of IL-2C on IRI.

CONCLUSION

Tregs protect kidneys from cold IRI and IL-2C inhibited cold IRI by increasing the renal Tregs, suggesting a potential of IL-2C in treating cold IRI.

KEY POINTS

Interleukin (IL)-2/anti-IL-2 antibody complex attenuated acute renal injury, facilitated subacute renal regeneration and suppressed chronic renal fibrosis after cold ischemia-reperfusion injury (IRI) by increasing the renal Tregs. IL-2/anti-IL-2 antibody complex decreased reactive oxygen species-mediated injury and improved antioxidant function. This study suggests the therapeutic potential of the IL-2/anti-IL-2 antibody complex in kidney transplantation-associated cold IR.

Bi-functional KIT-PR1P peptides combine with VEGF to protect ischemic kidney in rats by targeting to Kim-1

Introduction

Acute kidney injury (AKI) was a disease with a high mortality mainly caused by renal ischemia/reperfusion injury (I/R). Although the current non-targeted administration of vascular endothelial growth factor (VEGF) for AKI had been revealed to facilitate the recovery of renal I/R, how to targeted deliver VEGF and to retain it efficiently in the ischemic kidney was critical for its clinical application.

Methods

In present study, bi-functional KIT-PR1P peptides were constructed which bond VEGF through PR1P domain, and targeted ischemic kidney through KIT domain to interact with biomarker of AKI-kidney injury molecule-1 (Kim-1). Then the targeted and therapeutic effects of KIT-PR1P/VEGF in AKI was explored in vitro and in vivo.

Results

The results showed KIT-PR1P exhibited better angiogenic capacity and targeting ability to hypoxia HK-2 cells with up-regulated Kim-1 in vitro. When KIT-PR1P/VEGF was used for the treatment of renal I/R through intravenous administration in vivo, KIT-PR1P could guide VEGF and retain its effective concentration in ischemic kidney. In addition, KIT-PR1P/VEGF promoted angiogenesis, alleviated renal tubular injury and fibrosis, and finally promoted functional recovery of renal I/R.

Conclusion

These results indicated that the bi-functional KIT-PR1P peptides combined with VEGF would be a promising strategy for the treatment of AKI by targeting to Kim-1.

Nicotine increased VEGF and MMP2 levels in the rat eye and kidney

Chronic cigarette smoking affects many tissues negatively. Nicotine in tobacco has negative effects on tissues, kidneys, and eyes especially, where microcirculation is vitally important for the survival and functioning. It is known that appropriate vascular endothelial growth factor (VEGF) and (matrix metalloproteinase 2) MMP2 levels are required for suitable vascularity and enough microcirculation. The aim of this study was to investigate the effect of nicotine on VEGF and MMP2 levels in kidney and eyes, where microcirculation is very important for their function. The nicotine was given into drinking water, to male and female rats for 6 weeks. During the first 2 weeks, the nicotine concentration was 10 mg/L, then was given at a fixed dose of 20 mg/L until the end of the experiment. The VEGF and MMP2 levels were increased in kidney tissue of both genders as a result of given nicotine. MMP2 levels were also increased in the eye tissue for both genders similarly. However, VEGF levels increased in the eye tissue with nicotine in males, whereas it did not change in females. The use of nicotine made VEGF and MMP2 levels increase in kidney tissue in both genders of rats. This increase in VEGF was observed only in male eye tissue, not in females. According to our findings, it can be suggested that nicotine has negative effects on microvascular circulation by increasing VEGF and MMP2 levels. In addition, it should be pointed out that estrogen might have protective effects on female eye tissue. Further studies are necessary to understand the complex relationship between the role of nicotine and estrogen on eye and kidney tissues.

A novel role of HIF-1α/PROX-1/LYVE-1 axis on tissue regeneration after renal ischaemia/reperfusion in mice

Context: Renal ischaemia reperfusion (I/R) is a common clinical condition with a high morbidity and mortality rate. To date, I/R-induced renal injury remains an ineffective treatment. Objective: We hypothesis that angiogenesis and lymphangiogenesis markers, prospero homeobox-1 (PROX-1) and lymphatic endothelial hyaluronan receptor-1 (LYVE-1), are critical during I/R. Material and methods: Kunming mice were subjected to I/R and observed for the following eight consecutive days. Pathology analysis and protein distribution were detected by H&E staining, immunohistochemistry and immunofluorescence confocal analysis. Results: After I/R treatment, renal pathology was changed. HIF-1α was induced in the early stage and colocalisation with PROX-1 mainly in the renal tubular region, whereas PROX-1 and LYVE-1 were colocalised in the glomerulus of the endothelial region. Conclusions: In this study, we revealed HIF-1α/PROX-1/LVYE-1 axis dynamic changes in different regions after I/R and demonstrated for the first time it activates during I/R repair.

Low-energy extracorporeal shock wave ameliorates ischemic acute kidney injury in rats

BACKGROUND

Low-energy extracorporeal shock wave (SW) improves ventricular function in ischemic cardiomyopathy through the upregulation of vascular endothelial growth factor (VEGF). VEGF is known to play important roles in acute kidney injury (AKI), and the present study investigates the efficacy of SW for AKI by renal ischemia-reperfusion (I/R) injury.

METHODS

Male 8-week-old Sprague-Dawley rats were divided into the following groups: SW-treated I/R group (I/R-SW), untreated I/R group (I/R), and Sham group. To induce I/R, the left renal pedicles were clamped for 45 min. The I/R-SW group was treated with SW to both kidneys on the immediate postoperative period (day 0), days 1, 2, 7, 8, 9, 14, 15, and 16. Rats were killed on day 2 and day 20 to determine histology, renal function, and Vegf family mRNA expression.

RESULTS

Plasma creatinine on day 2 was significantly lower in the I/R-SW group than in the I/R group. Light microscopy revealed significantly lower tubular injury scores for the outer medulla in the I/R-SW group than in the I/R group. Podoplanin-positive lymphatic vessels were significantly increased in the left (affected side) outer medulla in the I/R-SW group on day 20. The expression levels of Vegf in the right (intact side) cortex were significantly higher in the I/R-SW group than in the I/R group on day 2.

CONCLUSION

Shock wave ameliorated renal tubular injury and renal function in AKI model, through the stimulation of Vegf family expression and lymphangiogenesis. SW may be effective as a non-invasive treatment for ischemic AKI.

EPCs enhance angiogenesis in renal regeneration

Decellularized renal scaffolds have previously been used for renal regeneration following partial nephrectomy, in which angiogenesis played a key role. In this study, rats underwent partial nephrectomy and repaired with decellularized renal scaffolds. Subsequently, the labeled EPCs were intravenously injected into rats in EPCs group, and the control group received an equal amount of phosphate-buffer saline (PBS). We chose 1, 2 and 4 weeks post operation as time point. Average microvascular density (aMVD) analyses revealed higher angiogenesis in EPCs group compared with the control group. The expression of angiogenic growth factors including vascular endothelial growth factor (VEGF), platelet derived growth factor (PDGF) and hypoxia-inducible factors 1-alpha (HIF-1α), was generally higher in the EPCs group in all weeks (1, 2 and 4), and peaked in week 2. EPCs were observed to home into renal injury site, promoting angiogenesis across the renal parenchyma-scaffold interface to be potentially used as bridges for EPCs to migrate into the implanted scaffolds. Administration of exogenous EPCs promotes angiogenesis and vasculogenesis in decellularized renal scaffolds-mediated renal regeneration, providing adequate microenvironment for kidney recovery post renal injury.

A Maternally Sequestered, Biopolymer-Stabilized Vascular Endothelial Growth Factor (VEGF) Chimera for Treatment of Preeclampsia

BACKGROUND

Preeclampsia is a hypertensive syndrome that complicates 3% to 5% of pregnancies in the United States. Preeclampsia originates from an improperly vascularized and ischemic placenta that releases factors that drive systemic pathophysiology. One of these factors, soluble fms-like tyrosine kinase-1, is believed to sequester vascular endothelial growth factor (VEGF), leading to systemic endothelial dysfunction and hypertension. With the goal of targeting soluble fms-like tyrosine kinase-1 while simultaneously preventing fetal exposure to VEGF, we fused VEGF to elastin-like polypeptide, a biopolymer carrier that does not cross the placental barrier (ELP-VEGF).

METHODS AND RESULTS

ELP-VEGF restored in vitro endothelial cell tube formation in the presence of plasma from placental ischemic rats. Long-term administered ELP-VEGF in pregnant rats accumulated in maternal kidneys, aorta, liver, and placenta, but the protein was undetectable in the pups when administered at therapeutic doses in dams. Long-term administration of ELP-VEGF in a placental ischemia rat model achieved dose-dependent attenuation of hypertension, with blood pressure equal to sham controls at a dose of 5 mg/kg per day. ELP-VEGF infusion increased total plasma soluble fms-like tyrosine kinase-1 levels but dramatically reduced free plasma soluble fms-like tyrosine kinase-1 and induced urinary excretion of nitrate/nitrite, indicating enhanced renal nitric oxide signaling. ELP-VEGF at up to 5 mg/kg per day had no deleterious effect on maternal or fetal body weight. However, dose-dependent adverse events were observed, including ascites production and neovascular tissue encapsulation around the minipump.

CONCLUSIONS

ELP-VEGF has the potential to treat the preeclampsia maternal syndrome, but careful dosing and optimization of the delivery route are necessary.

Matrix Metalloproteinase-2 Knockout and Heterozygote Mice Are Protected from Hydronephrosis and Kidney Fibrosis after Unilateral Ureteral Obstruction

Matrix Metalloproteinase-2 (Mmp2) is a collagenase known to be important in the development of renal fibrosis. In unilateral ureteral obstruction (UUO) the obstructed kidney (OK) develops fibrosis, while the contralateral (CL) does not. In this study we investigated the effect of UUO on gene expression, fibrosis and pelvic remodeling in the kidneys of Mmp2 deficient mice (Mmp2-/-), heterozygous animals (Mmp2+/-) and wild-type mice (Mmp2+/+). Sham operated animals served as controls (Cntrl). UUO was prepared under isoflurane anaesthesia, and the animals were sacrificed after one week. UUO caused hydronephrosis, dilation of renal tubules, loss of parenchymal thickness, and fibrosis. Damage was most severe in Mmp2+/+ mice, while both Mmp2-/- and Mmp2+/- groups showed considerably milder hydronephrosis, no tubular necrosis, and less tubular dilation. Picrosirius red quantification of fibrous collagen showed 1.63±0.25% positivity in OK and 0.29±0.11% in CL (p<0.05) of Mmp2+/+, Mmp2-/- OK and Mmp2-/- CL exhibited only 0.49±0.09% and 0.23±0.04% (p<0.05) positivity, respectively. Mmp2+/- OK and Mmp2+/- CL showed 0.43±0.09% and 0.22±0.06% (p<0.05) positivity, respectively. Transcriptomic analysis showed that 26 genes (out of 48 examined) were differentially expressed by ANOVA (p<0.05). 25 genes were upregulated in Mmp2+/+ OK compared to Mmp2+/+ CL: Adamts1, -2, Col1a1, -2, -3a1, -4a1, -5a1, -5a2, Dcn, Fbln1, -5, Fmod, Fn1, Itga2, Loxl1, Mgp, Mmp2, -3, Nid1, Pdgfb, Spp1, Tgfb1, Timp2, Trf, Vim. In Mmp2-/- and Mmp2+/- 18 and 12 genes were expressed differentially between OK and CL, respectively. Only Mmp2 was differentially regulated when comparing Mmp2-/- OK and Mmp2+/- OK. Under stress, it appears that Mmp2+/- OK responds with less Mmp2 upregulation than Mmp2+/+ OK, suggesting that there is a threshold level of Mmp2 necessary for damage and fibrosis to occur. In conclusion, reduced Mmp2 expression during UUO protects mice against hydronephrosis and renal fibrosis.

Obesity and renovascular disease

Obesity remains a prominent public health concern. Obesity not only contributes greatly to cardiovascular events but has also been identified to initiate and affect the progression of preexisting chronic kidney disease. The prevalence of renal artery stenosis is growing world-wide, especially in the elderly population and in individuals with atherosclerotic risk factors such as obesity. Prolonged renovascular disease causes inflammation and microvascular remodeling within the post-stenotic kidney, which promote tissue scarring and may account for irreversible renal damage. Obesity has been shown to aggravate kidney damage via several pathways, including exacerbation of microvascular regression and renal cell injury mediated by adipocytes and insulin resistance, thereby worsening the structural and functional outcomes of the kidney in renovascular disease. Dietary modification and inhibition of the renin-angiotensin-aldosterone system have been shown to alleviate obesity-induced tissue injury and remodeling. Possibly, angiogenic factors may boost microvascular repair in the ischemic kidney in the obesity milieu. Novel therapeutic interventions targeting deleterious pathways that are activated by obesity and responsible for kidney damage need to be explored in future studies.

Renal primordia activate kidney regenerative events in a rat model of progressive renal disease

New intervention tools for severely damaged kidneys are in great demand to provide patients with a valid alternative to whole organ replacement. For repairing or replacing injured tissues, emerging approaches focus on using stem and progenitor cells. Embryonic kidneys represent an interesting option because, when transplanted to sites such as the renal capsule of healthy animals, they originate new renal structures. Here, we studied whether metanephroi possess developmental capacity when transplanted under the kidney capsule of MWF male rats, a model of spontaneous nephropathy. We found that six weeks post-transplantation, renal primordia developed glomeruli and tubuli able to filter blood and to produce urine in cyst-like structures. Newly developed metanephroi were able to initiate a regenerative-like process in host renal tissues adjacent to the graft in MWF male rats as indicated by an increase in cell proliferation and vascular density, accompanied by mRNA and protein upregulation of VEGF, FGF2, HGF, IGF-1 and Pax-2. The expression of SMP30 and NCAM was induced in tubular cells. Oxidative stress and apoptosis markedly decreased. Our study shows that embryonic kidneys generate functional nephrons when transplanted into animals with severe renal disease and at the same time activate events at least partly mimicking those observed in kidney tissues during renal regeneration.

Darkness at the end of the tunnel: poststenotic kidney injury

Renal artery stenosis remains an important contributor to renal failure in the elderly population, but uncertainty continues to surround the mechanisms underlying progressive renal dysfunction. Here, we present the current understanding of the pathogenic mechanisms responsible for renal injury in these patients, with emphasis on those involved in disease progression.