Transverse aortic constriction (TAC) in the mouse is a commonly used experimental model to study mechanisms underlying cardiac hypertrophy and heart failure development. Here, we describe procedures to constrict the aorta to create a reproducible degree of cardiac hypertrophy in mice.
Part 1: Preparation of Operating Field
Part 2: Preparation and Intubation of Mice
Part 3: Ligation of the Transverse Aorta
Part 4: Post-operative Recovery
Part 5: Confirmation of Successful Ligation of the Transverse Aorta
6: Representative Results
The typical surgical survival following TAC in wild-type mice is about 80-90%. Successful surgical ligation of the transverse aorta will lead to a Doppler flow velocity ratio between right and left carotid artery (RC/LC) of 5-10 (Figure 1). Compared to sham-operated mice (Figure 2A), mice with pressure overload are expected to develop cardiac hypertrophy within 1-2 weeks, and cardiac dilatation after 6-8 week, depending on the tightness of the constriction (Figure 2B). Mortality during the first month after TAC is typically low (<20%) in wild-type mice, although genetically-modified mice may exhibit different survival rates.6,7
Figure 1. Confirmation of Transverse Aorta Ligation using Doppler Velocity Measurement. Representative Doppler velocity signals of the right (RC) and left carotid (LC) arteries 6 days post-TAC. These recordings demonstrate a successful ligation with a RC/LC flow ratio of ~6.8. Please click here to see a larger version of figure 1.
Figure 2. Representative Whole Heart Images Following TAC. A. Sham-operated wild type mouse heart. B. Wild type mouse heart 16 weeks post-TAC. Each line = 1mm.
TAC, which mimics human aortic stenosis, is a common method to induce cardiac hypertrophy and heart failure in mice. Alternative sites for aortic constriction include the ascending and abdominal aorta. Ascending aortic constriction provides an extreme and more rapid overload on the left ventricle (LV). In contrast, abdominal aortic constriction leaves intact a larger portion of the circulation as a means of possible compensation.8 Therefore, TAC is often the preferred model as it provides for adequate LV overload in a time-dependant manner more amenable to investigation. Although this procedure can be technically challenging, with practice, we have achieved a survival rate of 80-90% in wild type mice.
The tightness of transverse aortic constriction determines the degree of hypertrophy development and the time frame in which cardiac failure and dilatation develops. Moreover, the age of the mice affects the recovery rate and kinetics of heart failure development. Older mice (>12 months of age) take longer to develop an adaptive response of the carotid arteries to TAC, and are likely to develop dilated cardiomyopathy faster than younger mice (3-4 months of age).5
Non-invasive intubation of mice takes some practice. An alternative method is as follows:
The endotracheal tube is then connected to a Harvard volume-cycled rodent ventilator cycling at 125-150 breaths/minute and a tidal volume of 0.1-0.3ml.
X.H.T.W. is a W.M. Keck Foundation Distinguished Young Scholar in Medical Research, and is also supported by NIH/NHLBI grants R01-HL089598 and R01- R01HL091947, and Muscular Dystrophy Association grant #69238. R.J.v.O. is the recipient of the 2008-2010 American Physiological Society Postdoctoral Fellowship in Physiological Genomics. This work is also supported in part by the Fondation Leducq Alliance for CaMKII Signaling in Heart.
Material Name | Type | Company | Catalogue Number | Comment |
---|---|---|---|---|
Gaymar T/pump | Harvard Apparatus | Model TP-500 | Circulating water pump | |
Temp. therapy pads | Harvard Apparatus | 60-3414 | ||
Hot bead sterilizer | Fine Science Tools | 18000-45 | ||
Blunt scissors | Roboz | RS-5980 | ||
Angled spring scissors | Roboz | RS-5668 | ||
Chest retractor | Fine Science Tools | 17002-02 | ||
Course curved forceps | Roboz | RS-5138 | ||
Dumont fine 45° angled forceps | Fine Science Tools | 11253-25 | ||
Needle holder | Fine Science Tools | 12565-14 | ||
Electric shaver | General Electric | For shaving mouse fur | ||
PE 90 tubing | BD | 427420 | For intubation | |
MiniVent (ventilator) | Harvard Apparatus | Type 845 | ||
Betadine | Fisher | 19-027132 | May be purchased at medical supply store | |
Sterile gloves | Mckesson | 20-1565 | ||
Stereo microscope | Unico | ZM186 | ||
6-0 silk suture | Fine Science Tools | 18020-60 | ||
27 ½ gauge needle | BD | 305109 | ||
6-0 prolene suture | Mckesson | 3286 | ||
Buprenorphine | Institutional Animal Facility |