What is injected with the salt solution to trace the flow of blood?
Answers
An alternative approach to deliver gene vectors is to take advantage of muscle's rich vascular supply, as each myofiber is in close contact with capillaries (Lee and Schmid-Schonbein, 1995; Browning et al., 1996). However, muscle capillaries have a continuous, nonfenestrated endothelium with low permeability. Using pharmacologic agents and increased intravascular pressure, we first showed using an intraarterial route that naked pDNA could be efficiently expressed throughout the limb muscles of rodents and nonhuman primates (Zhang et al., 2001). Subsequently, we showed that an intravenous route also enabled high levels of foreign gene expression and small interfering RNA (siRNA) delivery (Hagstrom et al., 2004; Wells, 2004). The intravenous procedure, termed hydrodynamic limb vein (HLV) injection, is performed under conditions similar to those used for the Bier block procedure that is commonly used clinically for limb anesthesia during orthopedic surgery. The HLV procedure entails placing a tourniquet over the proximal part of the limb to block all blood flow and injecting the gene vector rapidly in a large volume so as to enable the gene vector to be extravasated and access the myofibers (Hagstrom et al., 2004). Presumably, the procedure enables egress of the pDNA by transiently disrupting the interendothelial cell junctions within the muscle vasculature (Vigen et al., 2007). Other groups have also reported the successful use of similar intraarterial and intravenous procedures to deliver plasmid DNA, adenoviral vectors, and adeno-associated viral vectors (Cho et al., 2000; Liang et al., 2004; Danialou et al., 2005; Su et al., 2005; Rodino-Klapac et al., 2007; Qiao et al., 2008; Suda et al., 2008; Toromanoff et al., 2008; Gregorevic et al., 2009). An advantage of the HLV procedure over the intraarterial procedure is that the HLV procedure is not as sensitive to the injection volume. With the intraarterial procedure in rats, lower volumes of injection solution resulted in much reduced expression from the injected pDNA. With HLV injection, however, volumes in the same range were similarly efficient (Budker et al., 1998; Hagstrom et al., 2004; Sebestyén et al., 2007). High levels of pDNA expression are obtained with the HLV procedure in nonhuman primates when the injection volume is sufficient to achieve the swelling necessary for efficient delivery to all limb muscles (Vigen et al., 2007).