Estimating hemodynamic shear stress in murine peripheral collateral arteries by two-photon line scanning

Abstract

Changes in wall shear stress of blood vessels are assumed to be an important component of many physiological and pathophysiological processes. However, due to technical limitations experimental in vivo data are rarely available. Here, we investigated two-photon excitation fluorescence microscopy as an option to measure vessel diameter as well as blood flow velocities in a murine hindlimb model of arteriogenesis (collateral artery growth). Using line scanning at high frequencies, we measured the movement of blood cells along the vessel axis. We found that peak systolic blood flow velocity averaged 9 mm/s and vessel diameter 42 µm in resting collaterals. Induction of arteriogenesis by femoral artery ligation resulted in a significant increase in centerline peak systolic velocity after 1 day with an average of 51 mm/s, whereas the averaged luminal diameter of collaterals (52 µm) changed much less. Thereof calculations revealed a significant fourfold increase in hemodynamic wall shear rate. Our results indicate that two-photon line scanning is a suitable tool to estimate wall shear stress e.g., in experimental animal models, such as of arteriogenesis, which may not only help to understand the relevance of mechanical forces in vivo, but also to adjust wall shear stress in ex vivo investigations on isolated vessels as well as cell culture experiments.

Contribution of the Potassium Channels KV1.3 and KCa3.1 to Smooth Muscle Cell Proliferation in Growing Collateral Arteries

“…Elevated shear stress is the driving force for arteriogenesis [2,3]. This mechanical stress can be sensed by ECs but not by SMCs.…”

“…The laser Doppler perfusion measurements, however, evidenced a reduced perfusion recovery after femoral artery ligation (Figure 4). Interestingly, K Ca 3.1 has been shown to be upregulated by fluid shear stress [39], the driving force for arteriogenesis [2,3]. Moreover, it has been demonstrated by blocking studies employing TRAM-34 in vivo, that K Ca 3.1 plays a role in EC proliferation during angiogenesis (Grigic, Eichler 2005) and in SMC proliferation, e.g., during atherogenesis [27].…”

“…Prior to tissue sampling for (immuno-) histology, mice were perfused with an adenosine buffer (1% adenosine, 5% bovine serum albumin (BSA), both from Sigma-Aldrich dissolved in PBS, PAN Biotech, pH 7.4) for maximal vasodilation followed by perfusion with 3% paraformaldehyde (PFA, Merck) dissolved in PBS, pH 7.4, for cryoconservation, or 4% PFA for paraffin embedding [2]. For qRT-PCR analyses, mice were perfused with latex flexible compound (Chicago Latex) to visualize superficial collateral arteries (see also Figure 1) for dissection.…”

“…Arteriogenesis, which is defined as the growth of pre-existing arteriolar connections into functional arteries compensating for the loss of an artery due to occlusion [1], particularly involves the proliferation of vascular endothelial cells (ECs) and smooth muscle cells (SMCs). The driving force for arteriogenesis is increased fluid shear stress [2,3]. This mechanical force, which can be sensed directly by ECs, has recently been shown to be linked to local activation of collateral ECs.…”

Is there a Chance to Promote Arteriogenesis by DPP4 Inhibitors Even in Type 2 Diabetes? A Critical Review

“…Due to the increased blood flow, the endothelial cells of detouring arterioles experience elevated mechanical load, i.e. fluid shear stress [ 6 ], leading to their activation [ 7 ]. In contrast to angiogenesis, which is defined as the sprouting of capillaries, collateral artery growth not only involves the proliferation of endothelial cells, but also of smooth muscle cells.…”