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Gene therapy for ocular diseases meditated by ultrasound and microbubbles (Review).

Wan C, Li F, Li H - Mol Med Rep (2015)

Bottom Line: Ultrasound‑targeted microbubble destruction (UTMD), with the advantages of high safety, repetitive applicability and tissue targeting, has become a potential strategy for gene‑ and drug delivery.High‑amplitude oscillations of microbubbles act as cavitation nuclei which can effectively focus ultrasound energy, produce oscillations and disruptions that increase the permeability of the cell membrane and create transient pores in the cell membrane.In addition, appropriately powered, focused ultrasound combined with microbubbles can induce a reversible disruption of the blood‑retinal barrier with no significant side effects.

View Article: PubMed Central - PubMed

Affiliation: Department of Ultrasound, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai 200127, P.R. China.

ABSTRACT
The eye is an ideal target organ for gene therapy as it is easily accessible and immune‑privileged. With the increasing insight into the underlying molecular mechanisms of ocular diseases, gene therapy has been proposed as an effective approach. Successful gene therapy depends on efficient gene transfer to targeted cells to prove stable and prolonged gene expression with minimal toxicity. At present, the main hindrance regarding the clinical application of gene therapy is not the lack of an ideal gene, but rather the lack of a safe and efficient method to selectively deliver genes to target cells and tissues. Ultrasound‑targeted microbubble destruction (UTMD), with the advantages of high safety, repetitive applicability and tissue targeting, has become a potential strategy for gene‑ and drug delivery. When gene‑loaded microbubbles are injected, UTMD is able to enhance the transport of the gene to the targeted cells. High‑amplitude oscillations of microbubbles act as cavitation nuclei which can effectively focus ultrasound energy, produce oscillations and disruptions that increase the permeability of the cell membrane and create transient pores in the cell membrane. Thereby, the efficiency of gene therapy can be significantly improved. The UTMD‑mediated gene delivery system has been widely used in pre‑clinical studies to enhance gene expression in a site‑specific manner in a variety of organs. With reasonable application, the effects of sonoporation can be spatially and temporally controlled to improve localized tissue deposition of gene complexes for ocular gene therapy applications. In addition, appropriately powered, focused ultrasound combined with microbubbles can induce a reversible disruption of the blood‑retinal barrier with no significant side effects. The present review discusses the current status of gene therapy of ocular diseases as well as studies on gene therapy of ocular diseases meditated by UTMD.

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Distribution of EGFP-positive cells in tissue-stretched preparation. The number of transfected cells in (A) the AAV and microbubble with ultrasound group was higher than that in (B) the AAV and normal saline group (magnification, x100). EGFP expression was mainly shown in (C) retinal pigment epithelial cells and (D) neural retina cells, respectively (magnification, x 400). Image taken from Li et al (4). EGFP, enhanced green fluorescence protein; AAV, adeno-associated virus.
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f4-mmr-12-04-4803: Distribution of EGFP-positive cells in tissue-stretched preparation. The number of transfected cells in (A) the AAV and microbubble with ultrasound group was higher than that in (B) the AAV and normal saline group (magnification, x100). EGFP expression was mainly shown in (C) retinal pigment epithelial cells and (D) neural retina cells, respectively (magnification, x 400). Image taken from Li et al (4). EGFP, enhanced green fluorescence protein; AAV, adeno-associated virus.

Mentions: Compared to other viral vectors that have recently been investigated, rAAV has the advantages of low immunogenicity and stable long-term transgene expression (63), which has been widely studied in retinal diseases. Ultrasound-meditated microbubble destruction was able to enhance rAAV-mediated gene delivery into retina cells (11,12). Li et al (11) reported that UTMD enhanced rAAV2 transfection efficiency in human RPE cells in vitro and in Wistar rat retina in vivo. In this study, UTMD induced rAAV2-mediated EGFP expression earlier after injection and substantially increased gene expression prior to the peak (35 days) with no evident tissue damage. Fluorescence microscopic analysis of a tissue-stretched preparation showed that the number of EGFP-positive cells in the group treated with AAV, microbubbles and ultrasound was higher than that in the AAV and normal saline groups, and that EGFP expression mainly appeared in the layer of RPE cells and neural retina (Fig. 4). Recently, a study using mouse models of proliferative vitreoretinopathy demonstrated that UTMD produced a therapeutic effect by facilitating the insertion of rAAV2-conjugated genes into tumors (64). Xie et al (12) investigated the efficiency and safety of UTMD-mediated delivery of rAAV2-EGFP into RGCs of rats and demonstrated that EGFP expression in the group treated with rAAV2-EGFP, ultrasound and microbubbles was the highest, and that the number of transfected RGCs was the largest compared to that in the other groups. No obvious damage was observed by histopathological analysis. Zheng et al (65) investigated the feasibility of UTMD-enhanced rAAV or plasmid-mediated transfection into the human RPE cell line ARPE-19. The result showed that the transfection efficiency of rAAV and plasmid in ARPE-19 cells was enhanced by UTMD without any adverse effects on cell viability (Fig. 5). The transfection efficiency of rAAV was higher than that of plasmid. UTMD-enhanced rAAV-mediated transfection was therefore thought to be an appropriate method for retinal gene therapy.


Gene therapy for ocular diseases meditated by ultrasound and microbubbles (Review).

Wan C, Li F, Li H - Mol Med Rep (2015)

Distribution of EGFP-positive cells in tissue-stretched preparation. The number of transfected cells in (A) the AAV and microbubble with ultrasound group was higher than that in (B) the AAV and normal saline group (magnification, x100). EGFP expression was mainly shown in (C) retinal pigment epithelial cells and (D) neural retina cells, respectively (magnification, x 400). Image taken from Li et al (4). EGFP, enhanced green fluorescence protein; AAV, adeno-associated virus.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4581786&req=5

f4-mmr-12-04-4803: Distribution of EGFP-positive cells in tissue-stretched preparation. The number of transfected cells in (A) the AAV and microbubble with ultrasound group was higher than that in (B) the AAV and normal saline group (magnification, x100). EGFP expression was mainly shown in (C) retinal pigment epithelial cells and (D) neural retina cells, respectively (magnification, x 400). Image taken from Li et al (4). EGFP, enhanced green fluorescence protein; AAV, adeno-associated virus.
Mentions: Compared to other viral vectors that have recently been investigated, rAAV has the advantages of low immunogenicity and stable long-term transgene expression (63), which has been widely studied in retinal diseases. Ultrasound-meditated microbubble destruction was able to enhance rAAV-mediated gene delivery into retina cells (11,12). Li et al (11) reported that UTMD enhanced rAAV2 transfection efficiency in human RPE cells in vitro and in Wistar rat retina in vivo. In this study, UTMD induced rAAV2-mediated EGFP expression earlier after injection and substantially increased gene expression prior to the peak (35 days) with no evident tissue damage. Fluorescence microscopic analysis of a tissue-stretched preparation showed that the number of EGFP-positive cells in the group treated with AAV, microbubbles and ultrasound was higher than that in the AAV and normal saline groups, and that EGFP expression mainly appeared in the layer of RPE cells and neural retina (Fig. 4). Recently, a study using mouse models of proliferative vitreoretinopathy demonstrated that UTMD produced a therapeutic effect by facilitating the insertion of rAAV2-conjugated genes into tumors (64). Xie et al (12) investigated the efficiency and safety of UTMD-mediated delivery of rAAV2-EGFP into RGCs of rats and demonstrated that EGFP expression in the group treated with rAAV2-EGFP, ultrasound and microbubbles was the highest, and that the number of transfected RGCs was the largest compared to that in the other groups. No obvious damage was observed by histopathological analysis. Zheng et al (65) investigated the feasibility of UTMD-enhanced rAAV or plasmid-mediated transfection into the human RPE cell line ARPE-19. The result showed that the transfection efficiency of rAAV and plasmid in ARPE-19 cells was enhanced by UTMD without any adverse effects on cell viability (Fig. 5). The transfection efficiency of rAAV was higher than that of plasmid. UTMD-enhanced rAAV-mediated transfection was therefore thought to be an appropriate method for retinal gene therapy.

Bottom Line: Ultrasound‑targeted microbubble destruction (UTMD), with the advantages of high safety, repetitive applicability and tissue targeting, has become a potential strategy for gene‑ and drug delivery.High‑amplitude oscillations of microbubbles act as cavitation nuclei which can effectively focus ultrasound energy, produce oscillations and disruptions that increase the permeability of the cell membrane and create transient pores in the cell membrane.In addition, appropriately powered, focused ultrasound combined with microbubbles can induce a reversible disruption of the blood‑retinal barrier with no significant side effects.

View Article: PubMed Central - PubMed

Affiliation: Department of Ultrasound, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai 200127, P.R. China.

ABSTRACT
The eye is an ideal target organ for gene therapy as it is easily accessible and immune‑privileged. With the increasing insight into the underlying molecular mechanisms of ocular diseases, gene therapy has been proposed as an effective approach. Successful gene therapy depends on efficient gene transfer to targeted cells to prove stable and prolonged gene expression with minimal toxicity. At present, the main hindrance regarding the clinical application of gene therapy is not the lack of an ideal gene, but rather the lack of a safe and efficient method to selectively deliver genes to target cells and tissues. Ultrasound‑targeted microbubble destruction (UTMD), with the advantages of high safety, repetitive applicability and tissue targeting, has become a potential strategy for gene‑ and drug delivery. When gene‑loaded microbubbles are injected, UTMD is able to enhance the transport of the gene to the targeted cells. High‑amplitude oscillations of microbubbles act as cavitation nuclei which can effectively focus ultrasound energy, produce oscillations and disruptions that increase the permeability of the cell membrane and create transient pores in the cell membrane. Thereby, the efficiency of gene therapy can be significantly improved. The UTMD‑mediated gene delivery system has been widely used in pre‑clinical studies to enhance gene expression in a site‑specific manner in a variety of organs. With reasonable application, the effects of sonoporation can be spatially and temporally controlled to improve localized tissue deposition of gene complexes for ocular gene therapy applications. In addition, appropriately powered, focused ultrasound combined with microbubbles can induce a reversible disruption of the blood‑retinal barrier with no significant side effects. The present review discusses the current status of gene therapy of ocular diseases as well as studies on gene therapy of ocular diseases meditated by UTMD.

Show MeSH
Related in: MedlinePlus