Gene therapy for renal diseases: its potential and limitation

Enhancing the expression of a key mitochondrial enzyme at the inception of ischemia-reperfusion injury can boost recovery and halt the progression of acute kidney injury

Hydrodynamic fluid delivery has shown promise in influencing renal function in disease models. This technique provided pre-conditioned protection in acute injury models by upregulating the mitochondrial adaptation, while hydrodynamic injections of saline alone have improved microvascular perfusion. Accordingly, hydrodynamic mitochondrial gene delivery was applied to investigate the ability to halt progressive or persistent renal function impairment following episodes of ischemia-reperfusion injuries known to induce acute kidney injury (AKI). The rate of transgene expression was approximately 33% and 30% in rats with prerenal AKI that received treatments 1 (T_1hr) and 24 (T_24hr) hours after the injury was established, respectively. The resulting mitochondrial adaptation via exogenous IDH2 (isocitrate dehydrogenase 2 (NADP+) and mitochondrial) significantly blunted the effects of injury within 24 h of administration: decreased serum creatinine (≈60%, p < 0.05 at T_1hr; ≈50%, p < 0.05 at T_24hr) and blood urea nitrogen (≈50%, p < 0.05 at T_1hr; ≈35%, p < 0.05 at T_24hr) levels, and increased urine output (≈40%, p < 0.05 at T_1hr; ≈26%, p < 0.05 at T_24hr) and mitochondrial membrane potential, Δψ_m, (≈ by a factor of 13, p < 0.001 at T_1hr; ≈ by a factor of 11, p < 0.001 at T_24hr), despite elevated histology injury score (26%, p < 0.05 at T1_hr; 47%, p < 0.05 at T_24hr). Therefore, this study identifies an approach that can boost recovery and halt the progression of AKI at its inception.

A carbohydrate mimetic peptide modified size-shrinkable micelle nanocluster for anti-tumor targeting and penetrating drug delivery

Purpose

To deliver the chemotherapeutics through the nanoparticles, the delivery system should accumulate at the tumor site first and then penetrate through the interstitium into the interior. The specific tumor-targeting pathway mediated via the receptor-ligand binding could achieve the desirable accumulation of nanoparticles, and the nanoparticles with smaller sizes were required for penetration.

Methods and materials

We constructed a size-shrinkable nanocluster modified with a tumor-targeting motif IF-7 (IF-7-MNC) based on a pH-sensitive framework which could be disintegrated in an acid environment to release the micelles aggregated inside. The micelles were constructed by amphiphilic block copolymers PEG−PLA to encapsulate paclitaxel (PTX), while the cross-linked framework consisting of TPGS-PEI was used as a net to gather and release micelles. This nanoplatform could specifically bind with the tumor receptor Annexin A1 through the ligand IF-7 and then shrunk into small micelles with a desirable size for penetration.

Conclusion

IF-7-MNC of 112.27±6.81 nm could shrink into micelles in PBS (0.01 M, pH 5.0) with sizes of 14.89±0.32 nm. The cellular-uptake results showed that IF-7-MNC could be significantly internalized by A549 cells and HUVEC cells, while the penetration of IF-7-MNC could be more prominent into the 3D-tumor spheroids compared with that of MNC. The biodistribution results displayed that the fluorescence of IF-7-MNC in the tumor site at 24 hrs was 4.5-fold stronger than that of MNC. The results of anti-tumor growth demonstrated that IF-7-MNC was more favorable for the tumor therapy than MNC, where the inhibitory rate of tumor growth was 88.29% in the PTX-loaded IF-7-MNC (IF-7-PMNC) treated group, significantly greater than PMNC treatment group (p<0.05).

Direct Delivery of Recombinant Pin1 Protein Rescued Osteoblast Differentiation of Pin1-Deficient Cells

Pin1 is a peptidyl prolyl cis-trans isomerase that specifically binds to the phosphoserine-proline or phosphothreonine-proline motifs of several proteins. We reported that Pin1 plays a critical role in the fate determination of Smad1/5, Runx2, and β-catenin that are indispensable nuclear proteins for osteoblast differentiation. Though several chemical inhibitors has been discovered for Pin1, no activator has been reported as of yet. In this study, we directly introduced recombinant Pin1 protein successfully into the cytoplasm via fibroin nanoparticle encapsulated in cationic lipid. This nanoparticle-lipid complex delivered its cargo with a high efficiency and a low cytotoxicity. Direct delivery of Pin1 leads to increased Runx2 and Smad signaling and resulted in recovery of the osteogenic marker genes expression and the deposition of mineral in Pin1-deficient cells. These result indicated that a direct Pin1 protein delivery method could be a potential therapeutics for the osteopenic diseases. J. Cell. Physiol. 232: 2798-2805, 2017. © 2016 Wiley Periodicals, Inc.

Gene delivery to renal tubular epithelial cells using adeno-associated virus vector in domestic cats

Recombinant adeno-associated virus (rAAV) vectors provide excellent gene delivery into the kidney in several mammals. This study evaluated gene delivery into the cat kidney using an rAAV vector. First, infection and reporter gene expression using rAAV vector encoding the enhanced green fluorescent protein gene (rAAV-EGFP) was examined in vitro in epithelial crandell reese feline kidney (CRFK) cells. At 12h after transduction, green fluorescence was detected in cells. Next, the rAAV-EGFP construct was injected into the kidneys of two anesthetized cats via the skin, similar to a renal biopsy. On 3 and 12days after injection, green fluorescence was detected in renal tubules localized near the injected site, but not in glomeruli, blood vessels, or interstitial cells. Finally, the rAAV-EGFP construct was transduced into kidney sections cultured ex vivo. EGFP was expressed in renal tubules between the outer cortex and inner medulla regions. These results demonstrate that rAAV vectors effectively mediate gene delivery into cat renal tubules, and may prove usefulness in gene therapy for cats with renal diseases.

Specific molecular targeting of renal injury in obstructive nephropathy

Progression of most renal disease involves tubulointerstitial injury, characterized by tubular atrophy, inflammatory cell infiltration, and interstitial fibrosis. Transforming growth factor-beta1 is central in this process. As reported by Moon et al., molecular targeting of the transforming growth factor-beta1 signaling pathway can markedly suppress renal injury resulting from unilateral ureteral obstruction, an established model of obstructive nephropathy. Specific kinase inhibitors are promising therapeutic agents to slow or attenuate progressive renal fibrosis.

Obstructive nephropathy: towards biomarker discovery and gene therapy

Obstructive nephropathy is a major cause of renal failure, particularly in infants and children. Cellular and molecular mechanisms responsible for the progression of the tubular atrophy and interstitial fibrosis-processes that lead to nephron loss-have been elucidated in the past 5 years. Following urinary tract obstruction and tubular dilatation, a cascade of events results in upregulation of the intrarenal renin-angiotensin system, tubular apoptosis and macrophage infiltration of the interstitium. This is followed by accumulation of interstitial fibroblasts through proliferation of resident fibroblasts and epithelial-mesenchymal transformation of renal tubular cells. Under the influence of cytokines, chemokines and other signaling molecules produced by tubular and interstitial cells, fibroblasts undergo transformation to myofibroblasts that induce expansion of the extracellular matrix. The cellular interactions that regulate development of interstitial inflammation, tubular apoptosis and interstitial fibrosis are complex. Changes in renal gene expression and protein production afford many potential biomarkers of disease progression and targets for therapeutic manipulation. These include signaling molecules and receptors involved in macrophage recruitment and proliferation, tubular death signals and survival factors, and modulators of epithelial-mesenchymal transformation. Targeted gene deletion and various forms of gene therapy have been used in experimental obstructive nephropathy, mostly rodent models of unilateral ureteral obstruction or cell culture techniques. Further refinement of these models is needed to develop a matrix of biomarkers with clinical predictive value, as well as molecular therapies that will prevent or reverse the renal structural and functional consequences of obstructive nephropathy.

Perioperative acute renal failure

PURPOSE OF REVIEW

Recent biochemical evidence increasingly implicates inflammatory mechanisms as precipitants of acute renal failure. In this review, we detail some of these pathways together with potential new therapeutic targets.

RECENT FINDINGS

Neutrophil gelatinase-associated lipocalin appears to be a sensitive, specific and reliable biomarker of renal injury, which may be predictive of renal outcome in the perioperative setting. For estimation of glomerular filtration rate, cystatin C is superior to creatinine. No drug is definitively effective at preventing postoperative renal failure. Clinical trials of fenoldopam and atrial natriuretic peptide are, at best, equivocal. As with pharmacological preconditioning of the heart, volatile anaesthetic agents appear to offer a protective effect to the subsequently ischaemic kidney.

SUMMARY

Although a greatly improved understanding of the pathophysiology of acute renal failure has offered even more therapeutic targets, the maintenance of intravascular euvolaemia and perfusion pressure is most effective at preventing new postoperative acute renal failure. In the future, strategies targeting renal regeneration after injury will use bone marrow-derived stem cells and growth factors such as insulin-like growth factor-1.

Macrophages and progressive tubulointerstitial disease

Macrophages and progressive tubulointerstitial disease. In chronic renal disease, tubulointerstitial inflammation and injury is associated with infiltrating macrophages. As a consequence of primary injury, proteinuria, chronic hypoxia, and glomerular-derived cytokines may all differentially modulate the expression of factors that promote macrophage recruitment. In addition to adhesion molecules and chemokines, products of complement system and renin-angiotensin system activation may direct this process. Once present at interstitial sites, macrophages interact with resident cells and extracellular matrix to generate a proinflammatory microenvironment that amplifies tissues injury and promotes scarring. There is now increasing evidence for the efficacy of interventions directed against factors that recruit, activate, or are produced by macrophages. A detailed understanding of the biology of this area may lead to the further development of therapies that will improve the outcome of renal disease.