Kidney-specific Sonoporation-mediated Gene Transfer

Abstract

Sonoporation can deliver agents to target local organs by systemic administration, while decreasing the associated risk of adverse effects. Sonoporation has been used for a variety of materials and in a variety of organs. Herein, we demonstrated that local sonoporation to the kidney can offer highly efficient transfer of oligonucleotides, which were systemically administrated to the tubular epithelium with high specificity. Ultrasonic wave irradiation to the kidney collapsed the microbubbles and transiently affected the glomerular filtration barrier and increased glomerular permeability. Oligonucleotides were passed through the barrier all at once and were absorbed throughout the tubular epithelium. Tumor necrosis factor alpha (TNFα), which plays a central role in renal ischemia-reperfusion injury, was targeted using small interfering RNA (siRNA) with renal sonoporation in a murine model. The reduction of TNFα expression after single gene transfer significantly inhibited the expression of kidney injury markers, suggesting that systemic administration of siRNA under temporary and local sonoporation could be applicable in the clinical setting of ischemic acute kidney injury.

Figure 1

Dylight547-labeled oligonucleotides (DLO) were delivered into the kidney using sonoporation. (a) Sonitron 2000 V (left) and its probe of 12 mm in diameter (middle). Bar = 10 mm. Ultrasound irradiation was performed on the left kidney (arrowhead) for 1 minute (right). (b) Experimental scheme. After median incisions, the mixtures of 1 nmol of DLO and microbubbles (MB) were injected via IVC using a syringe equipped with a 34-gauge needle. Immediately after injection, ultrasound irradiation was performed with an input frequency of 3 MHz, an output intensity of 2 W/cm², and a pulse duty ratio of 50%, using Sonitron 2000 V. The mice were sacrificed at day 1. (c) Distribution of DLO signals under different conditions of the intervention. DLO signal was detected more frequently in the animals injected with DLO and MB, with ultrasound irradiation, than in other animals. Co-staining with LTL showed DLO localization to nearby brush border in proximal tubular cells. Bar = 50 μm. (d,e) Relative expression of KIM1 and NGAL mRNAs. The result indicated that the kidney was not injured by DLO, MB, or ultrasound irradiation. Results are expressed as a ratio of the animals of DLO(-) MB(-) US(-) (n = 3). Data were expressed as mean ± SE. DLO, Dylight547-labeled oligonucleotides; IVC, inferior vena cava; LTL, Lotus tetragonolobus lectin; MB, microbubble; US, ultrasound irradiation.

Figure 2

DLO was delivered mainly into proximal tubular cells. Upper two rows: Immunofluorescence staining with LTL shows that DLO was detected immediately inside the brush border of tubular proximal epithelial cells. Immunofluorescence staining with DBA shows that DLO was weakly detected in the collecting duct. Middle three rows: In the glomerulus, DLO was detected slightly in endothelial cells, podocytes, and mesangial cells as indicated by the immunofluorescence staining with CD31, podocin, and PDGFRβ, respectively. Lower three rows: In the interstitium, immunofluorescence staining with CD31 shows that DLO was slightly detected in endothelial cells. Bar = 10 μm. DBA, Dolichos biflorus agglutinin; DLO, Dylight547-labeled oligonucleotides; LTL, Lotus tetragonolobus lectin.

Figure 3

DLO into the urine was transiently increased by sonoporation. (a) Experimental scheme. After median incisions, 1 nmol of DLO with/without microbubbles (MB) were injected via IVC using a syringe equipped with a 34-gauge needle. Immediately after injection, ultrasound irradiation was performed. The urine was collected at 0, 3, and 24 hours after injection. (b,c) Fluorescence intensity of the urine. Fluorescence intensity was assessed using fluorescent microscopy and a 96-well microplate reader. The urine showed significantly stronger fluorescence intensity in animals injected with a mixture of DLO and microbubble with ultrasound irradiation than that in other animals. Results are expressed as a ratio in comparison to the animals of DLO(+) MB(+) US(-) at 0 hour (*P < 0.05; **P < 0.01; n = 3). (d) Transient increase of the glomerular capillary permeability caused by sonoporation. We considered the urine albumin–creatinine ratio as a parameter for glomerular permeability. The urine albumin–creatinine ratio transiently increased and returned to the original state. Results are expressed as a ratio in comparison to the animals of DLO(+) MB(+) US(-) at 0 hour (*P < 0.05; n = 3). Data were expressed as mean ± SE. ACR, albumin–creatinine ratio; DLO, Dylight547-labeled oligonucleotides; IVC, inferior vena cava; MB, microbubble; US, ultrasound irradiation.

Figure 4

siRNA against GFP (siGFP) was delivered into the kidney using sonoporation. (a) Experimental scheme. After median incisions, the mixtures of 1 nmol of siGFP and microbubbles were injected via IVC using a syringe equipped with a 34-gauge needle. Immediately after injection, ultrasound irradiation was performed. The mice were sacrificed at day 1. (b) Relative expression of GFP mRNA in various organs. The expression level of GFP mRNA in the kidney in which sonoporation was performed significantly decreased in comparison to the expression in the contralateral kidney and other organs. Results are expressed as a ratio of the sham kidney (*P < 0.05; n = 3). Data were expressed as mean ± SE. IVC, inferior vena cava; siGFP & MB, mice injected with siRNA against GFP and microbubble; Untreated, untreated mice; US, ultrasound irradiation.

Figure 5

DLO was delivered into the injured epithelial cells. (a) Experimental scheme. After median incisions and 30-minute bilateral I/R, a mixture of 1 nmol of DLO and microbubbles were injected via IVC using a syringe equipped with a 34-gauge needle. Immediately after injection, sonoporation was performed on the left kidney. The mice were sacrificed at day 1. (b, c) Relative expression of KIM1 and NGAL mRNAs. KIM1 and NGAL mRNA levels increased in renal I/R animals. Neither injection of DLO nor sonoporation caused additional elevation of KIM1 and NGAL mRNAs. Results are expressed as a ratio of the sham (n = 3). Data were expressed as mean ± SE. Sham means DLO(-) US(-) I/R(-). (d) Co-immunofluorescence staining with KIM1 and DLO. DLO signal was detected in the KIM1-positive injured epithelial cells (upper row). Bar = 50 μm. DLO, Dylight547-labeled oligonucleotides; I/R, ischemia-reperfusion. IVC, inferior vena cava; US, ultrasound irradiation.

Figure 6

Kidney injury significantly improved in animals injected with siTNFα with sonoporation in renal IRI model. (a) Experimental scheme. After median incisions, 30-min unilateral I/R, and right nephrectomy, the mixture of 1 nmol of siTNFα and microbubbles were injected via IVC using a syringe equipped with a 34-gauge needle. Immediately after injection, ultrasound irradiation was performed. The mice were sacrificed at day 1. (b–d) Relative expression of TNFα, KIM1, and NGAL mRNAs. The mRNA expression level of TNFα and KIM1 significantly decreased in animals injected with siTNFα with sonoporation compared to the expression in untreated I/R animals. The mRNA levels of NGAL tended to decrease with injection of siTNFα with sonoporation compared to the levels in other animals. Results of relative expression of mRNAs are expressed as a ratio of the sham (*P < 0.05; n = 10). Data were expressed as mean ± SE. (e) Periodic acid–Schiff (PAS) staining (upper row) and immunofluorescence staining with KIM1 (lower row). KIM1 was detected in proximal tubular epithelial cells in the IRI groups, and the strength of the fluorescence decreased in animals injected with siTNFα with sonoporation. (f) Western blot analysis of KIM1 and GAPDH was used as an internal control. KIM1 protein decreased in animals injected with siTNFα with sonoporation. Bar = 50 μm. I/R, ischemia–reperfusion; IVC, inferior vena cava; N, negative control siRNA; NGAL, neutrophil gelatinase-associated lipocalin; siTNFα, kidney injected with siRNA against TNFα and microbubble; US, ultrasound irradiation.

Figure 7

The analysis of the inflammatory cytokines. The mRNA level of TGFβ and IL1β significantly decreased in animals injected with siTNFα, with sonoporation. The mRNA levels of IL1α, MIP2, and MCP1 also decreased in animals injected with siTNFα with sonoporation. Results of relative expression of mRNAs are expressed as a ratio of the sham (*P < 0.05; n = 10). Data were expressed as mean ± SE. I/R, ischemia-reperfusion; N, negative control siRNA; siTNFα, kidney injected with siRNA against TNFα and microbubble; US, ultrasound irradiation.