We provide a detailed protocol for side-by-side wire myography to assess vascular reactivity in conduit versus resistance arteries isolated from mice and rats.
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Method Article
* These authors contributed equally
We provide a detailed protocol for side-by-side wire myography to assess vascular reactivity in conduit versus resistance arteries isolated from mice and rats.
Wire myography is a widely used ex vivo technique for the quantitative assessment of vascular function in isolated arteries. Because large conduit and small resistance arteries differ fundamentally in structure and physiological role, analyzing both vessel classes in parallel using arteries harvested from the same mouse or rat enables paired comparisons that reduce inter-animal variability and reveal vessel-specific functional changes. This article presents a step-by-step protocol for assessing vascular reactivity in isolated murine conduit and resistance arteries using isometric wire myography. We describe the preparation of fresh, oxygenated physiological buffer; careful dissection, cleaning, and mounting of arterial segments; and normalization to set vessels near their optimal length for active force generation. A troubleshooting guide and an example experimental sequence for generating cumulative concentration-response curves to standard vasoconstrictors and vasodilators are provided. This protocol allows quantitative measurement of both endothelial and smooth muscle function and facilitates detection of vessel-specific alterations in vascular reactivity associated with vascular disease, such as hypertension.
Hypertension is characterized by altered vascular reactivity, such as endothelial dysfunction and vascular smooth muscle hyperreactivity to vasoconstrictors1. These functional changes, together with microvascular remodeling and rarefaction, contribute to impaired tissue perfusion and dysregulated blood pressure2,3,4. Ex vivo assays of isolated vessels are powerful tools for dissecting the cellular and molecular mechanisms that control vascular tone in health and disease, as they allow precise control of the vascular microenvironment and selective pharmacological manipulation of smooth muscle and endothelial signaling pathways.
Vascular reactivity in isolated arteries is commonly assessed using two complementary ex vivo techniques: wire myography and pressure myography5,6. In wire myography, vessel rings or segments are mounted on pins or wires, and isometric force is recorded7,8. In pressure myography, intact vessel segments are cannulated and pressurized to a defined intraluminal pressure, and vessel diameter is tracked by video microscopy9. Unlike wire myography, pressure myography permits control of transmural pressure and intraluminal flow. Thus, it more closely recapitulates the in vivo hemodynamic environment of resistance arteries and is commonly used to study myogenic tone, flow-mediated responses, and vascular structural or mechanical properties9,10. Conversely, wire myography is technically easier to implement (no cannulation or video microscopy), supports higher throughput using commercial multi-chamber systems, and is well-suited for generating reproducible pharmacological concentration-response curves in small-to-medium arteries with diameters on the order of tens to several hundred micrometers5,6. Accordingly, wire myography is often preferred for side-by-side pharmacological profiling of vascular reactivity in conduit and resistance arteries isolated from mice or rats.
Conduit (large elastic) and resistance (small muscular) arteries differ fundamentally in structure and function, and these differences dictate distinct experimental considerations and endpoints. Conduit arteries (e.g., descending thoracic aorta) contain large amounts of elastic tissue and substantial smooth muscle mass; resistance arteries (e.g., mesenteric arteries) have relatively greater smooth-muscle-to-lumen ratios and are major determinants of peripheral resistance and local autoregulation11,12. Because the same agonist can activate different molecular responses in these vascular beds, side-by-side comparison of conduit and resistance vessels from the same animal provides useful complementary information. For instance, in conduit arteries, endothelium-derived nitric oxide release is the predominant relaxant pathway by which acetylcholine (ACh) induces vasorelaxation13,14. In contrast, in small resistance arteries, ACh induces relaxation via nitric oxide, prostacyclin, and, importantly, endothelium-derived hyperpolarizing factors (EDHF)15,16. Accordingly, side-by-side wire myography of conduit and resistance arteries harvested from the same mouse or rat enables paired comparisons that facilitate detection of vessel-specific functional changes while reducing inter-animal variability.
Accurate interpretation of wire myography data depends on careful attention to a set of technical variables: composition and oxygenation of the physiological salt solution (PSS), tissue handling and dissection, mounting technique, optimal resting pretension (normalization), bath temperature, and selection of appropriate pharmacological controls6. Normalization refers to the technical procedure of setting the mechanical operating point of the vessel so that active force development is optimized and approximates physiological operating conditions5. Practically, for aortic rings, it is common practice to use a fixed pretension, often determined empirically to avoid overdistension while giving stable responses. For small resistance arteries, normalization is performed by first determining the internal circumference corresponding to an equivalent transmural pressure of 100 mmHg (IC100). The vessel is then set to a defined fraction of this value to establish the normalized internal circumference (IC1). In practice, many protocols set IC1 near 0.9 × IC100 for rat MRA and around 1.0 × IC100 for mouse MRA, although these values may be adjusted based on vessel type, species, and experimental goals5,17.
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The following protocol adheres to the guidelines set and has been approved by The University of Toledo Health Science Campus Animal Care and Use Committee.
CAUTION Before you begin, please follow Institutional Animal Care and Use Committee (IACUC) and Institutional Biosafety Committee (IBC) guidelines at all times; use appropriate personal protective equipment (PPE); exercise care when using surgical or other sharp instruments; consult and comply with relevant Safety Data Sheets (SDS) when handling chemicals and biological tissues; handle carbogen as a pressurized gas cylinder using approved regulators and secure storage; and dispose of biological and chemical waste according to institutional procedures.
1. Preparation of PSS/modified Krebs bicarbonate (Krebs) buffer
NOTE: Krebs buffer composition (final concentrations, pH 7.4): 130 mM NaCl, 4.7 mM KCl, 1.17 mM MgSO4, 1.18 mM KH2PO4, 1.6 mM CaCl2, 25 mM NaHCO3, 5.5 mM glucose, and 0.03 mM EDTA.
2. Dissection of the descending thoracic aorta and mesenteric arcade
3. Isolation and mounting of aortic rings on pin myographs
4. Isolation and mounting of MRA on wire myographs
5. Normalization procedure for the MRA
NOTE: Aortic rings are mounted at a fixed, predefined pretension. Therefore, a separate normalization step is not performed.
| Parameter | Mouse | Rat |
| Pretension Value for Aortic Rings | 5 mN | 10 mN |
| Target IC1 Ratio for MRA | 1 | 0.9 |
| Typical MRA Branch Order for 200-250 μm Internal Diameter | 2nd | 3rd-4th |
Table 1: Key parameter differences between mice and rats.
6. Experimental protocol (example sequence)
7. Data analysis and reporting
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A schematic depicting the overall workflow of wire myography in conduit and resistance arteries isolated from mice or rats is shown in Figure 1. Representative images of isolation and mounting of a mouse thoracic aortic ring and a 2nd-order MRA are shown in Figure 2 and Figure 3, respectively. Software screenshots depicting pretensioning and normalization procedures using a rat aortic ring and an MRA are shown in
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Wire myography remains a powerful, high-resolution approach for interrogating vascular function ex vivo. When executed carefully, this method provides reliable quantitative endpoints that address distinct biological questions while allowing rigorous comparison of macro- and microvascular beds within the same animal. Conduit artery studies reveal changes in global arterial mechanics and large-vessel reactivity relevant to pulse pressure and aortic stiffness, whereas resistance artery experiments probe microvascul...
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The authors have no conflicts of interest to disclose.
The work was supported by an NHLBI award (R00 HL153896 to I.O.) and startup funds from the University of Toledo.
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| Name | Company | Catalog Number | Comments |
|---|---|---|---|
| 15 mL Conical Centrifuge Tubes | Thermo Fisher Scientific | 14-959-70C | |
| 50 mL Conical Centrifuge Tubes | Thermo Fisher Scientific | 14-959-49A | |
| Acetic acid | Thermo Fisher Scientific | A490-212 | |
| Acetylcholine | Millipore Sigma | A6625-100G | |
| Analytical Balance | Mettler Toledo | MX304 | |
| CaCl2 | Thermo Fisher Scientific | C79-500 | |
| Carbogen (95% O2/5% CO2) | Airgas | CD USP50 | |
| Dissection Microscope | ZEISS | ZEISS Stemi 305 | |
| Dissection petri dish | Living Systems Instrumentation | DD-90-S-BLK | |
| Dissection pins | Danish Myo Technology | 400626 | |
| Dissection tool kit | Danish Myo Technology | 101017 | Kit consists of dissection scissor (1), multi-purpose scissor (1), Petri dishes (5), forceps (3) and dissection pins. |
| Dumont #5 - Fine Forceps | Fine Science Tools | 11254-20 | |
| EDTA | Thermo Fisher Scientific | BP2482-500 | |
| Freezer (-20 °C) | Thermo Fisher Scientific | TSG2325FA | |
| Freezer Hinged Boxes | USA Scientific | 2310-5848 | |
| Gloves (Large) | Thermo Fisher Scientific | 19-041-171D | |
| Gloves (Medium) | Thermo Fisher Scientific | 19-041-171C | |
| Gloves (Small) | Thermo Fisher Scientific | 19-041-171B | |
| Glucose | Thermo Fisher Scientific | D16-500 | |
| Graduated Cylinder | Thermo Fisher Scientific | 08-572G | |
| GraphPad Prism | GraphPad Software | N/A | Data analysis and graphical presentation |
| Hydrochloric Acid Solution | Thermo Fisher Scientific | SA48-1 | |
| Ice Bucket | Thermo Fisher Scientific | 03-395-156 | |
| KCl | Thermo Fisher Scientific | P217-500 | |
| KH2PO4 | Thermo Fisher Scientific | P380-500 | |
| LabChart 8 Software | AD Instruments | N/A | Data capture software |
| Laboratory Refrigerator | Thermo Fisher Scientific | FBG49RPGA | |
| LED Light Source | Thermo Fisher Scientific | AMPSILED21 | |
| Magnetic Stirrer | Thermo Fisher Scientific | FB30786159 | |
| Magnetic Stirring Bars (Large) | Thermo Fisher Scientific | 14-513-68 | |
| Magnetic Stirring Bars (Medium) | Thermo Fisher Scientific | 14-513-61 | |
| MgSO4 | Thermo Fisher Scientific | M63-500 | |
| Micro Spoon and Spatula Sampling Set | Thermo Fisher Scientific | S43322 | |
| Microcentrifuge Tubes | USA Scientific | 1615-5510 | |
| Mini Microcentrifuge | Thermo Fisher Scientific | 07-203-954 | |
| Mini-screwdriver | Thermo Fisher Scientific | NC1349489 | |
| Multi wire myograph system | Danish Myo Technology | DMT 620M | |
| NaCl | Thermo Fisher Scientific | S271-3 | |
| NaHCO3 | Thermo Fisher Scientific | S233-500 | |
| pH Meter | Thermo Fisher Scientific | 01-912-351 | Includes pH meter, LE420 sensor, installation QuickGuide, and pH buffer starter pack |
| Phenylephrine | Millipore Sigma | P6126-5G | |
| Pipet Controller | Thermo Fisher Scientific | 01-001-023 | |
| Pipette Tips in Racks (10 µL) | USA Scientific | 1111-3810 | |
| Pipette Tips in Racks (1000 µL) | USA Scientific | 1111-2830 | |
| Pipette Tips in Racks (200 µL) | USA Scientific | 1111-1810 | |
| PYREX Reusable Media Storage Bottles | Thermo Fisher Scientific | 06-414-1D | |
| Serological Pipettes (10 mL) | Thermo Fisher Scientific | 02-923-204 | |
| Serological Pipettes (25 mL) | Thermo Fisher Scientific | 02-923-205 | |
| Single-Channel micropipette Multi-Pack | Thermo Fisher Scientific | 13-684-250 | 3x pipettes (0.5-10 μL, 10-100 μL, 100-1000 μL) |
| Stainless steel wire (40 μm) | Danish Myo Technology | 400447 | |
| Timer | Thermo Fisher Scientific | 02-261-840 | |
| Ultra Pure Water System | Sartorius | H2O-MM-UV-SET-US | |
| Vannas Spring Scissors | Fine Science Tools | 15000-00 | |
| Volumetric Flask | Thermo Fisher Scientific | 13-756-400 | |
| Vortex Mixer | Thermo Fisher Scientific | 10-320-807 | |
| Water bath | Thermo Fisher Scientific | 07-202-155 | |
| Weighing Dishes | Thermo Fisher Scientific | 02-202-101 |
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