Targeted adenoviral gene transfer to the kidney

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The ability to introduce DNA into mammalian cells capsule, and the vascular endothelium and weakly expressed in the tubular epithelium. However, no delineain vitro has revolutionized the understanding of both nortion of which intrarenal vascular compartments (for exammal physiology and pathophysiologic mechanisms of disple, cortical vs. medullary) was described. Additionally, ease. Although gene transfer in vitro has met with great v integrins are aberrantly expressed in numerous neosuccess, this has not been the case for in vivo studies. plasms, including invasive glioblastomas, metastatic melThe general lack of clinical efficacy has led to a critical anomas, and renal carcinoma [9, 11, 12]. These characterevaluation of current generation vectors and has emphaistics make v integrins an attractive target for gene sized the need for improved gene transfer vectors. The transfer strategies. replication incompetent human adenovirus is a vector Filamentous bacteriophage peptide display libraries system for which much is already known regarding struchave been used both in vitro and in vivo to identify peptide ture and function. Specifically, adenoviral vectors have sequences, which preferentially bind specific cell surface been used to deliver genes to a number of tissues, includreceptors. Koivunen et al have used this system to isolate ing vascular, lung, neuronal, and muscle tissues in vivo a high-affinity peptide ligand to the v integrins [13]. [1–4]. Advantages of adenoviral vectors include (1) the This nine-amino acid cyclic peptide, ACDCRGDCFCG, ability to transfer genes into multiple cell types in differcontains the arginine glycine aspartate (RGD) integrinent species without the need for cell replication, (2) the binding motif known to bind to the v integrins with ability to produce high-titer stocks ( 1012 particles/mL), approximately 100-fold higher affinity than the GRGDSP thus enabling highly efficient in vivo gene transfer, (3) sequence from fibronectin. This bacteriophage intraveacceptance of DNA fragments of up to approximately nously injected preferentially homed to murine models 28 kb and regulated expression of cDNAs, (4) relative of malignant melanomas and breast carcinoma [14]. In stability in the systemic circulation, and (5) safety. an effort to target adenoviral transfer to the v integrins Many human tissues, including skeletal muscle, smooth of the vascular endothelium, we used a chimeric adenomuscle, endothelium, and kidney, have low-level adenoviral vector [AdZ.F(RGD)] with this same RGD integrin viral receptor expression, thus limiting adenoviral bindbinding motif incorporated into the C terminus of the ing [5, 6]. Adenoviral gene transfer could be enhanced adenovirus fiber protein [15]. by targeting binding to receptors on specific cells or tisWe demonstrate that this modified adenoviral vector sues of interest or targeting receptors, which are upresults in ligand-specific gene transfer to vascular endoregulated in specific diseases states. An example of this thelial cells in vitro. In vivo administration of the chimetype of receptor is the v integrin. Integrins are transric adenoviral vector into the renal artery of the rat membrane glycoproteins involved in cell–cell and cell– resulted in significantly enhanced -galactosidase exmatrix interaction. The v integrins have been shown to pression in the vascular endothelium of the kidney combe present in the vascular endothelium in general, includpared with an adenoviral vector containing the native ing the kidney specifically [7–9]. They are also up-reguadenoviral fiber protein (AdZ). Additionally, the incorlated in the presence of basic fibroblast growth factor/ poration of the high-affinity peptide ligand into the adevascular endothelial growth factor (bFGF/VEGF) [10]. noviral fiber knob resulted in a novel distribution of Rabb et al evaluated human tissue kidney samples obtransgene expression (renal cortex and the subcapsular tained from patients undergoing nephrectomy to remove region) compared with AdZ. a neoplastic lesion [9]. They found the v integrins to be expressed in glomerular epithelial cells, Bowman’s GENE DELIVERY BY AdZ AND AdZ.F(RGD) TO BOVINE ENDOTHELIAL CELLS