Ultrasound-Microbubble-Mediated Gene Transfer of Inducible Smad7 Blocks Transforming Growth Factor-β Signaling and Fibrosis in Rat Remnant Kidney

Abstract

Transforming growth factor (TGF)-beta1 has been shown to play a critical role in hypertensive nephropathy. We hypothesized that blocking TGF-beta1 signaling could attenuate renal fibrosis in a rat model of remnant kidney disease. Groups of six rats were subjected to 5/6 nephrectomy and received renal arterial injection of a doxycycline-regulated Smad7 gene or control empty vector using an ultrasound-microbubble-mediated system. Smad7 transgene expression within the kidney was tightly controlled by the addition of doxycycline in the daily drinking water. All animals were euthanized at week 4 for renal functional and histological examination. Hypertension of equivalent magnitude (190 to 200 mmHg) developed in both Smad7- and empty vector-treated rats. However, treatment with Smad7 substantially inhibited Smad2/3 activation and prevented progressive renal injury by inhibiting the rise of 24-hour proteinuria (P < 0.001) and serum creatinine (P < 0.001), preserving creatinine clearance (P < 0.05), and attenuating renal fibrosis and vascular sclerosis such as collagen I and III expression (P < 0.01) and myofibroblast accumulation (P < 0.001). In conclusion, TGF-beta/Smad signaling plays a critical role in renal fibrosis in a rat remnant kidney model. The ability of Smad7 to block Smad2/3 activation and attenuate renal and vascular sclerosis demonstrates that ultrasound-mediated Smad7 gene therapy may be a useful therapeutic strategy for the prevention of renal fibrosis in association with hypertension.

TGFβ pathobiology in the eye

“…Adenoviral gene transfer of mouse Smad7 cDNA has been used in the treatment of tissue fibrosis in several disease models, that is, bleomycin-induced pulmonary fibrosis, drug-induced liver fibrosis, or kidney fibrosis by unilateral ureteral obstruction. [105][106][107] Our results show that in mice Smad7 gene introduction by topical application suppresses scarring and neovascularization of the burned cornea, restoring its transparency. 104 Smad7 also suppressed generation of myofibroblasts, macrophage invasion, and the expression of wound healing-related cytokines.…”

Gene therapy progress and prospects: Ultrasound for gene transfer

“…Most in vivo studies have concentrated on organs and tissues that are readily imaged by diagnostic ultrasound machines, including skeletal muscle, heart and kidneys. 35,36,[48][49][50][51][52][53][54][55][56][57][58][59][60][61][62] Table 1 summarizes the results of some recent studies in these tissues using reporter genes, 35,36,[48][49][50][51][52][53][54]58,60,61 and broadly similar data have begun to emerge from studies in the vascular, 4,63,64 neurology 65-67 and oncology 18,37,68 fields, the pancreas 69 and in hematology. 70 On first inspection the relatively modest enhancements in plasmid-mediated transfection after USE in vivo may appear disappointing compared with the results obtained in vitro.…”

Ultrasound-contrast agent mediated naked gene delivery in the peritoneal cavity of adult rat

“…17 Isolated reports have documented successful application of the ultrasound-microbubble-mediated system in transfecting naked-DNA in vivo in various types of murine tissues as well as in chicken embryos and murine fetuses. 16,[18][19][20][21][22][23] Although the ultrasound-microbubblemediated gene delivery has been applied in carotid or kidney in murine models, 18,19 isolation and temporary ligation of blood vessels or related organs during the transfection process are invasive and technically difficult to achieve for practical use in real life. Furthermore, intravenous injection leads not only to a dilution of genetic material in circulation but also to a retention of these substances in lung and liver.…”