**5.8 Endothelium**

There are many papers which indicate that endothelial cells *in vitro* can express transgenes delivered by UTMD methods (see {Su *et al.* 2010} and internal references for recent examples). Su and colleagues found that treatment with 1 MHz US of 1 MPa Pr together with pGL3 pDNA and MBs yielded a 100-fold increase in luciferase expression relative to pDNA treatment alone. It remains to be determined if endothelial cells *in vivo* can be 'recruited' as effective synthesizers and secretors of therapeutic gene expression products.
