Trans-illuminated laser speckle imaging of collateral artery blood flow in ischemic mouse hindlimb

Abstract

Abstract. The mouse ischemic hindlimb model is used widely for studying collateral artery growth (i.e., arteriogenesis) in response to increased shear stress. Nonetheless, precise measurements of regional shear stress changes along individual collateral arteries are lacking. Our goal is to develop and verify trans-illumination laser speckle flowmetry (LSF) for this purpose. Studies of defibrinated bovine blood flow through tubes embedded in tissue-mimicking phantoms indicate that trans-illumination LSF better maintains sensitivity with an increasing tissue depth when compared to epi-illumination, with an ∼50% reduction in the exponential decay of the speckle velocity signal. Applying trans-illuminated LSF to the gracilis muscle collateral artery network in vivo yields both improved sensitivity and reduced noise when compared to epi-illumination. Trans-illuminated LSF images reveal regional differences in collateral artery blood velocity after femoral artery ligation and are used to measure an ∼2-fold increase in the shear stress at the entrance regions to the muscle. We believe these represent the first direct measurements of regional shear stress changes in individual mouse collateral arteries. The ability to capture deeper vascular signals using a trans-illumination configuration for LSF may expand the current applications for LSF, which could have bearing on determining how shear stress magnitude and direction regulate arteriogenesis. © The Authors.Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

Mechanisms of Amplified Arteriogenesis in Collateral Artery Segments Exposed to Reversed Flow Direction

“…Using transillumination laser speckle flowmetry (LSF), we recently determined that shear stress magnitude increases 2-fold in both the muscular and saphenous collateral entrance regions 30 minutes post-FAL. Additionally, we confirmed the predicted flow directions in this ligation scheme through observation of circulating fluorescent microspheres during intravital imaging 18 .…”

“…Femoral arterial ligation (FAL), performed as previously described 18 , was used to induce arteriogenesis in the gracilis adductor muscle collateral arteries. In agreement with previous studies 19,20 , perfusion measurements of the plantar surface of the foot indicated moderate ischemia immediately post-FAL, followed by a return to full perfusion by day 7 post-FAL (Supplemental Figure I).…”

“…Recently, we applied transillumination based laser speckle flowmetry (LSF) to quantify, for the first time, the in-vivo “segment-to-segment” spatial distribution of collateral artery hemodynamics before and after femoral artery ligation in the mouse ischemic hindlimb, the most widely used model of peripheral arteriogenesis. While shear stress magnitude increased ~2-fold along the length of the collateral vessels in the gracilis adductor muscle, some pre-existing collateral artery segments also experienced a reversal of flow direction after femoral artery ligation 18 . In the present study, we tested the hypothesis that a change in flow direction has a profound influence on both arteriogenesis and mechanotransductive endothelial cell signaling.…”

Exposure of Endothelium to Biomimetic Flow Waveforms Yields Identification of miR-199a-5p as a Potent Regulator of Arteriogenesis

“…A cone and plate flow apparatus, 82 which maintains cells at 5% CO 2 and 37°C, was used to induce a shear stress protocol. The applied shear stress protocol consisted of a 24-hr preconditioning period at a steady 15 dyne/cm 2 , which was then either increased to 30 dynes/cm 2 (non-reversed flow) or increased to 30 dynes/cm 2 and reversed in direction (reversed flow) to simulate relative hemodynamics previously quantified in our in vivo FAL model 11 . Fresh culture medium, consisting of M199 with 4% dextran from Leuconostoc spp (Sigma-Aldrich, M r ∼500,000), 2% fetal bovine serum, 100 U/mL penicillin-G + 100 μg/mL streptomycin, 2 mmol/L L-glutamine, 5 μg/mL EC growth supplement, and 10 μg/mL heparin, was added to cells before exposure to shear stress, and it was continuously exchanged throughout the duration in the cone and plate apparatus.…”

Noninvasive assessment of hemodynamic and brain metabolism parameters following closed head injury in a mouse model by comparative diffuse optical reflectance approaches

“…Assuming Lorentzian velocity distribution, ðK s Þ 2 is inversely proportional to the blood flow velocity (motion of scattering particles), such that lower speed results in higher K S and vice versa. [86][87][88] For instance, K s is close to unity if there is no movement within the medium. Concomitant to flow measurements, temporal changes in concentrations of the brain metabolism biomarkers oxyhemoglobin (ΔHbO 2 ) and deoxyhemoglobin (ΔHbr) can be extracted from the diffuse reflectance data by the Beer-Lambert method.…”