From blood vessels to lymphatics and back again

Abstract

Figures

Full text

From blood vessels to lymphatics and back again—the path for fluid transport from the circulation, through the interstitial space, into lymphatic capillaries, and eventually back into large veins, in many ways parallels the impacts made by researchers during our careers. Recognizing the overlaps between both systems, leading vascular physiologists leveraged opportunities to apply methods, approaches, and a fundamental understanding to elucidate how lymphatic vessels work (1, 2). In this journal, Davis and King (3) provide a nice example of in turn applying what they have learned about lymphatic function to advance our understanding of how blood vessels work (Fig. 1). Based on servo-nulling micropipette pressure measurements in isolated veins from mice, the results implicate a causal relationship between venous tone and venous valve closure.

The work refreshingly extends methods used to describe pressure differences across valves in isolated lymphangions (4, 5) to link the contractile state of venous smooth muscle cells to venous valve leak. Scientific rigor is highlighted by a simple story based on technically challenging physiology methods, which are less common these days, probably due to the length of required training time and the juxtaposition with pace-driven pressures of academic research. The application of the old methods provokes new questions and reconsideration of what we know about venous smooth muscle cell constriction and venous valve function. How many valves are needed along veins? Are venous valves heterogenous? Does heterogeneity matter? Can rescuing venous tone improve venous valve function? Can the relationship between venous tone and valve function explain dysfunction associated with disease states? As Dr. Davis passes his servonulling systems to the next generation of vascular physiologists, maybe the most pressing question is—who will be measuring pressures?