If you start a program of vigorous exercise, your muscles will sprout new capillaries. Behind that performance-enhancing response lies an elaborate interplay of genes and proteins. Conceivably, the same molecular machinery could be switched on to make new blood vessels in a diseased heart. Then, doctors could induce heart muscle to grow arteries that bypass life-threatening blockages, sparing their patients the sliced flesh and cracked bones of open-heart surgery.
That’s one of the hopes for cardio-vascular gene therapy. If realized, it would work roughly as follows. Identify a protein whose presence causes blood vessels to form. Produce and package strands of DNA that contain the gene for making the protein. Deliver the DNA to heart muscle.
Of those steps, the last is the most challenging. The heart lies within the rib cage and behind the lungs. With each beat, it fluctuates in volume by about 25%. Directly injecting DNA...
