New transgenic evidence for a system of sympathetic axons able to express tissue plasminogen activator (t-PA) within arterial/arteriolar walls.

Sympathetic axons embedded in a few arterioles and vasa vasora were recently shown to store tissue plasminogen activator (t-PA) in vesicles. But the extension of such t-PA axons to arteries and arterioles throughout the organism has not been verified. Confirmation of this anatomy would identify a second significant source of vessel wall t-PA. To visualize fine embedded axons independent of endothelium, we created a transgenic mouse whose expressions of the t-PA promoter and enhanced green fluorescent protein are confined to sympathetic neurons and other neural crest derivatives. Confocal images reveal the extension of t-PA axons to arterioles serving heart, brain, kidney, lung, mesentery, and skin; plus aortic, carotid, and mesenteric artery walls. Ganglion neurons and adrenal chromaffin cells also show strong expressions. These new sightings confirm the existence of a system of t-PA axons that is prominent in arterioles, and compatible with the release of neural t-PA into their walls.