Transverse Aortic Constriction in Mice

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Summary

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.

Cite this Article

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deAlmeida, A. C., van Oort, R. J., Wehrens, X. H. Transverse Aortic Constriction in Mice. J. Vis. Exp. (38), e1729, doi:10.3791/1729 (2010).

Abstract

Transverse aortic constriction (TAC) in the mouse is a commonly used experimental model for pressure overload-induced cardiac hypertrophy and heart failure.1 TAC initially leads to compensated hypertrophy of the heart, which often is associated with a temporary enhancement of cardiac contractility. Over time, however, the response to the chronic hemodynamic overload becomes maladaptive, resulting in cardiac dilatation and heart failure.2 The murine TAC model was first validated by Rockman et al.1, and has since been extensively used as a valuable tool to mimic human cardiovascular diseases and elucidate fundamental signaling processes involved in the cardiac hypertrophic response and heart failure development. When compared to other experimental models of heart failure, such as complete occlusion of the left anterior descending (LAD) coronary artery, TAC provides a more reproducible model of cardiac hypertrophy and a more gradual time course in the development of heart failure. Here, we describe a step-by-step procedure to perform surgical TAC in mice. To determine the level of pressure overload produced by the aortic ligation, a high frequency Doppler probe is used to measure the ratio between blood flow velocities in the right and left carotid arteries.3, 4 With surgical survival rates of 80-90%, transverse aortic banding is an effective technique of inducing left ventricular hypertrophy and heart failure in mice.

Protocol

Part 1: Preparation of Operating Field

  1. The operating field is disinfected with 75% isopropyl alcohol.
  2. Make sure the heating pad is on and at the right temperature. A recommended system is a Gaymar circulating water pump connected to a therapy pad that is maintained at 37 °C ± 1 °C. It is important to maintain normal body temperature during surgery as to avoid a rapid decrease in heart rate.
  3. Surgical tools are sterilized in a hot bead sterilizer before surgery. For this procedure, you will need the following surgical instruments: blunt scissors, course curved forceps X 2, fine 45° angled forceps X 2, angled spring scissors, chest retractor, and needle holder.
  4. Cotton applicators should be on hand in case of bleeding.

Part 2: Preparation and Intubation of Mice

  1. Mice are anesthetized in an induction chamber with 2% isoflurane mixed with 0.5 -1.0 L/min 100% O2.
  2. Hair clippers are used to shave the fur from the neckline to mid chest level.
  3. The mouse is placed in a supine position atop a heating pad in order to maintain body temperature.
  4. A rubber band is placed over the animal s front teeth to extend the neck. Using curved forceps in one hand, the tongue is gently manipulated to the side. With the other hand, endotracheal intubation is performed using PE 90 tubing. 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. During the surgical procedure, anesthesia is maintained at 1.5-2% isoflurane with 0.5 - 1.0 L/min 100% O2. Correct level of anesthesia is verified by applying pressure on the mouse nail bed (toe-pinch reflex).
  5. The surgical field is disinfected with betadine solution followed by 70% alcohol. This procedure is repeated three times.
  6. To prevent contamination of the surgical field during the operation, a sterile drape is placed over the mouse leaving only the operation field exposed.
  7. A set of sterile gloves is used for each individual mouse.

Part 3: Ligation of the Transverse Aorta

  1. Partial thoracotomy to the second rib is performed under a surgical microscope and the sternum retracted using a chest retractor.
  2. Fine tip 45° angled forceps are used to gently separate the thymus and fat tissue from the aortic arch.
  3. Following identification of the transverse aorta, a small piece of a 6.0 silk suture is placed between the innominate and left carotid arteries (Figure 1).
  4. Two loose knots are tied around the transverse aorta and a small piece of a 27½ gauge blunt needle is placed parallel to the transverse aorta. The first knot is quickly tied against the needle, followed by the second and the needle promptly removed in order to yield a constriction of 0.4mm in diameter. In sham control mice, the entire procedure is identical except for the ligation of the aorta.
  5. The chest retractor is removed and the outflow of the ventilator pinched off for 2 seconds to re-inflate the lungs.
  6. The rib cage is closed using a 6.0 prolene suture with an interrupted suture pattern.
  7. The skin is closed using a 6.0 prolene suture with a continuous suture pattern.

Part 4: Post-operative Recovery

  1. For post-operative analgesia, the mouse is injected with buprenorphine (0.1 mg/kg) intraperitoneally. If there are signs of dehydration after surgery, sterile saline is given intraperitoneally.
  2. Anesthesia is gradually lowered to the off position and the endotracheal tube removed when signs of spontaneous breathing occur.
  3. The mouse is moved to the prone position and allowed to recover on a heating pad.

Part 5: Confirmation of Successful Ligation of the Transverse Aorta

  1. One week after TAC, the mouse is re-anesthetized to determine the degree of pressure overload induced by ligation of the transverse aorta. As described above, anesthesia is maintained at 1.5-2% isoflurane with 0.5 - 1.0 L/min 100% O2 and body temperature maintained at 37 °C ± 1 °C.
  2. A 20 MHz Doppler probe is placed on the left and right sides of the neck at a 45° angle to detect flow velocities. A computer-based Doppler signal processor (Indus Instruments, Houston, TX) was used to display and store Doppler signals.5
  3. Depending on the degree of pressure overload required for the experimental protocol, only mice with a right carotid (RC)/left carotid (LC) flow ratio within a certain range are included for further analysis. For example, a moderate degree of pressure overload leads to a ratio of 5-8, whereas a tighter constriction resulting in severe pressure overload leads to a ratio of 8-10 (Figure 5.3A). A sham animal (operated but not ligated), however, is expected to have a ratio of ~1 (Figure 5.3B).

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
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
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.

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Discussion

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:

  1. A small midline cervical incision is made with blunt scissors and tissue separated around the trachea using curved forceps in order to expose the trachea.
  2. A piece of suture is placed around the front teeth and gently pulled away from the animal's body to extend the neck.
  3. Using curved forceps in one hand, the tongue is gently manipulated to the side.
  4. With the other hand, endotracheal intubation is performed using PE 90 tubing beveled on the edge for ease of entry.

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.

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Acknowledgments

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.

Materials

Name Company Catalog Number Comments
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 Surgical Instruments Co. RS-5980
Angled spring scissors Roboz Surgical Instruments Co. RS-5668
Chest retractor Fine Science Tools 17002-02
Course curved forceps Roboz Surgical Instruments Co. RS-5138
Dumont fine 45° angled forceps Fine Science Tools 11253-25
Needle holder Fine Science Tools 12565-14
Electric shaver GE Healthcare For shaving mouse fur
PE 90 tubing BD Biosciences 427420 For intubation
MiniVent (ventilator) Harvard Apparatus Type 845
Betadine Fisher Scientific 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 Biosciences 305109
6-0 prolene suture Mckesson 3286
Buprenorphine Institutional Animal Facility

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References

  1. Rockman, H. A., Ross, R. S., Harris, A. N., Knowlton, K. U., Steinhelper, M. E., Field, L. J., Ross, J. Jr, Chein, K. R. Segregation of atrial-specific and inducible expression of an atrial natriuretic factor transgene in an in vivo murine model of cardiac hypertrophy. Proc. Natl. Acad. Sci. USA. 88, 8277-8281 (1991).
  2. Heineke, J., Molkentin, J. D. Regulation of cardiac hypertrophy by intracellular signaling pathways. Nat. Rev. Mol. Cell. Biol. 7, 589-600 (2006).
  3. Hartley, C. J., Reddy, A. K., Madala, S., Michael, L. H., Entman, M. L., Taffett, G. E. Doppler estimation of reduced coronary flow reserve in mice with pressure overload cardiac hypertrophy. Ultrasound Med. Biol. 34, 892-901 (2008).
  4. Reddy, A. K., Taffett, G. E., Li, Y. -H., Lim, S. -W., Pham, T. T., Pocius, J. S., Entman, M. L., Michael, L. H., Hartley, C. J. Doppler signal processing for use in mice: applications. IEEE Trans. Biomed. Eng. 52, 1771-1783 (2005).
  5. Li, Y. -H., Reddy, A. K., Ochoa, L. N., Pham, T. T., Hartley, C. J., Micheal, L. H., Entman, M. L., Taffett, G. E. Effect of age on peripheral vascular response to transverse aortic banding in mice. J. Gerontol. 58A, 895-899 (2003).
  6. Bourajjaj, M., Armand, A. S., Martins, daC. osta, Weijts, P. A., Nagel, B. V. ander, Heeneman, R., Wehrens, S., Windt, X. H. D. e, J, L. NFATc2 is a necessary mediator of calcineurin-dependent cardiac hypertrophy and heart failure. J. Biol. Chem. 28, 22295-22303 (2008).
  7. Oort, R. J. van, Respress, J. L., Li, N., Reynolds, C., Almeida, A. C. D. e, Skapura, D. G., Windt, L. J. D. e, Wehrens, X. H. Accelerated development of pressure overload induced cardiac hypertrophy and dysfunction in an RyR2-R176Q knockin mouse model. Hypertension. 55, (2010).
  8. Tarnavski, O., McMullen, J. R., Schinke, M., Nie, Q., Kong, S., Izumo, S. Mouse cardiac surgery: comprehensive techniques for the generation of mouse models of human diseases and their application for genomic studies. Physiol Genomics. 16, 349-360 (2004).

Comments

14 Comments

  1. Hi, it says to cut down to the level of the second rib, but it looks like in the movie they have cut the whole rib cage. is that right?

    Reply
    Posted by: Petey H.
    April 30, 2010 - 9:21 PM
  2. Hello and thanks for the comment, cutting to the second rib is sufficient for this procedure however we cut a bit further in order for the videographer to get a better view for the movie.

    Reply
    Posted by: Anonymous
    May 1, 2010 - 5:02 PM
  3. Good video. There is another less invasive technique that requires only a small incision, avoiding intubation. This would be another great video to post here.

    Reply
    Posted by: Derek T.
    May 27, 2010 - 1:10 PM
  4. I agree with you . Here is the link to a less invasive technique that doesn't require mechanical ventilation. Did you have any other technique in mind?

    http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3718611/

    Reply
    Posted by: hadi j.
    January 29, 2014 - 7:46 PM
  5. it is really a good video, i have a small question, how do you avoid damaging the internal thoracic artery? i saw your incision is close to the sternal border. Thanks!

    Reply
    Posted by: ali z.
    June 28, 2010 - 2:21 PM
  6. I use a pair of angular spring scissors from Roboz (cat #5668) when making the incision to avoid damaging the thoracic artery. Thanks for your comment!

    Reply
    Posted by: Anonymous
    June 28, 2010 - 6:53 PM
  7. why cann't i watch the video? anything wrong with my computor ?

    Reply
    Posted by: Anonymous
    July 1, 2011 - 12:10 PM
  8. Please email us at support@jove.com and we'll help you ASAP.

    Reply
    Posted by: Anonymous
    July 1, 2011 - 12:23 PM
  9. Hi, for the last step of closing chest cavity, Is there any particular way to close the chest cavity and withdrawal of remaining air? I found my mice tend to die within 1-7 days post-surgery? Could it because of pneumothorax? Thank you very much.

    Reply
    Posted by: Anonymous
    February 16, 2012 - 3:22 PM
  10. You should be able to inflate the lungs simply by closing off the outflow circulation (pinching the tube for a couple of seconds) on the ventilator...exactly how it is shown in the JOVE video. If this dŒsn²17;t work, maybe there is some fluid accumulation in the thoracic cavity which would put added pressure on the lungs when the chest is closed. You can remove this fluid by inserting a catheter into the cavity before it is closed. After the cavity is closed, connect a syringe to the catheter and suck out the fluid (while slowly pulling out the catheter). This technique is shown in the LAD ligation JOVE video ( http://www.jove.com/video/1438/lad-ligation-a-murine-model-of-myocardial-infarction).
    Hope this helps.

    Laboratory of Dr. Xander Wehrens

    Reply
    Posted by: William L.
    February 17, 2012 - 12:27 PM
  11. Thanks for this article..
    I have following queries

    1. What percentage diameter reduction of Transverse Aorta to get the
    sufficient pressure overload-induced cardiac hypertrophy without
    mortality of animals (for transverse aortic constriction (TAC)-induced
    hypertrophy and heart failure model).

    ². Whether this Ligation of the Transverse Aorta is maintained for any
    study e.g. Drug trial study to reduce the cardiac hypertrophy until
    study gets study over

    Reply
    Posted by: Santosh M.
    July 18, 2012 - 8:51 AM
  12. I have a small question. I found my mice tend to develop a subcutaneous edema 1 day post-surgery. How can this happen? I don't have any idea. Could it be because of banding the Vena Cava Sup.? Or do you have any explanations? Thank you very much.

    Reply
    Posted by: Anna H.
    September 12, 2012 - 6:03 AM
  13. Hello
    We observed such a phenomenon in our experiments as well, however our mice developed edema around the neck. It's possibly seroma due to invasive dissection or hematoma as a result of poor hemostasis during surgery. In our case, The problem was resolved by cauterizing the sternal edges more aggressively than before.

    Reply
    Posted by: hadi j.
    January 29, 2014 - 7:44 PM
  14. very nice video, very nice technology ,thank you for sharing to us

    Reply
    Posted by: rongjun c.
    November 28, 2018 - 5:05 AM

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