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Kwon, Park, Jeong, Kim, Bae, Hwang, Kim, and Cho: A Slight Variation in the Age of Rats Commonly used as a Carotid Artery Injury Model Results in a Large Difference in Neointima Formation
Original Article
Korean Circulation Journal

Korean Circulation Journal 2007; 37(2): 78-83.

Published online: 28 February 2007

DOI: https://doi.org/10.4070/kcj.2007.37.2.78

A Slight Variation in the Age of Rats Commonly used as a Carotid Artery Injury Model Results in a Large Difference in Neointima Formation

Jin-Sook Kwon, DVM, No-Kwan Park, MS, Il Ha Jeong, MS, Yu-Kyung Kim, MS, Jang-Han Bae, MD, Kyung-Kuk Hwang, MD, Dong-Woon Kim, MD, Myeong-Chan Cho, MD

Department of Internal Medicine, College of Medicine, Chungbuk National University, Cheongju, Korea.

Corresponding author (kdwoon@chungbuk.ac.kr)

Received 22 December 2006       Revised 5 February 2007       Accepted 9 February 2007

© 2007, The Korean Society of Circulation

Abstract

Background and Objectives

The degree of neointima formation after infliction of a carotid artery balloon injury in rats varies greatly depending on the sex, age, species and operational method. Strong variation is common, even within only a single control. This study attempted to find if there was any significant difference in neointima formation following a carotid artery balloon injury in 6 to 12 week old rats; the age commonly used in these types of experiments.

Subjects and Methods

A balloon injury was inflicted on the carotid arteries of male Sprague-Dawley rats at 6 (n=9, 250-270 g), 8 (n=8, 280-300 g) and 11 weeks (n=10, 320-340 g) of age. Two weeks post-operation, a histomorphometric analysis was carried out. The vascular smooth muscle cell proliferation was measured in situ via BrdU incorporation 2 days after injury infliction.

Results

The neointima areas of the 6 week (0.22±0.04 mm2) and 8 week old groups (0.17±0.08 mm2) were 3.1 and 2.4 times larger than that of the 11 week old group (0.07±0.03 mm2). The mitotic index was significantly reduced in 11 week old group (n=4, 9.22±1.51%) compared to those of the 6 (n=4, 25.03±3.92%) and 8 week old (n=4, 21.66±3.66%) groups.

Conclusion

Special care should be taken when interpreting neointima formation, as even a slight variation in the age and weight in 6 to 12 week old (250-340 g) rats; the age commonly used in these types of experiments, results in an unexpectedly large difference.

Keywords: Neointimal formation, Carotid artery injuries, Aging

Figures and Tables

Fig. 1
Photomicrographs of cross-sections of the rat carotid artery taken 14 days after infliction of a balloon injury demonstrating a significant difference in the vessels of the 11 week old group compared to those of the 6 and 8 week old groups. A: 6 week old group. B: 8 week old group. C: 11 week old group.
kcj-37-78-g001
Fig. 2
The mitotic index (assessed by in situ BrdU labeling) 2 days after the infliction of a balloon injury was significantly reduced in the 11 week old group (n=4, 9.22±1.51%) compared to the 6 week (n=4, 25.03±3.92%) and 8 week old (n=4, 21.66±3.66%) groups. A: 6 week old group. B: 8 week old group. C: 11 week old group. BrdU: bromodeoxyuridine.
kcj-37-78-g002
Fig. 3
Representative carotid angiograms of 6, 8 and 11 week old rats. The mean luminal diameter (MLD) of the right carotid artery was measured by comparison with a 5F coronary catheter. The MLDs of 6, 8 and 11 week old rats were 1.20±0.03 (n=3), 1.18±0.06 (n=3) and 1.29±0.02 mm (n=3), respectively. A: 6 week old group. B: 8 week old group. C: 11 week old group.
kcj-37-78-g003
Table 1
Quantitative histomorphological analysis of the rat carotid artery obtained 14 days after the infliction of a carotid artery injury
kcj-37-78-i001

Results are reported as the mean±S.D. *: p<0.05 vs. 11 weeks

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