Compensatory hypertrophy of the teres minor muscle after large rotator cuff tear model in adult male rat

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• 作者：Tsuyoshi Ichinose ; PhD^a ; ^{t-ichinose@gunma-u.ac.jp" class="auth_mail" title="E-mail the corresponding author} ; Atsushi Yamamoto ; PhD^a ; Tsutomu Kobayashi ; PhD^b ; Hitoshi Shitara ; PhD^a ; Daisuke Shimoyama ; MD^a ; Haku Iizuka ; PhD^a ; Noriyuki Koibuchi ; PhD^c ; Kenji Takagishi ; PhD^a
• 关键词：Basic Science Study ; Physiology ; Animal Model
• 刊名：Journal of Shoulder and Elbow Surgery
• 出版年：2016
• 出版时间：February 2016
• 年：2016
• 卷：25
• 期：2
• 页码：316-321
• 全文大小：450 K

文摘

Rotator cuff tear (RCT) is a common musculoskeletal disorder in the elderly. The large RCT is often irreparable due to the retraction and degeneration of the rotator cuff muscle. The integrity of the teres minor (TM) muscle is thought to affect postoperative functional recovery in some surgical treatments. Hypertrophy of the TM is found in some patients with large RCTs; however, the process underlying this hypertrophy is still unclear. The objective of this study was to determine if compensatory hypertrophy of the TM muscle occurs in a large RCT rat model.

Methods

Twelve Wistar rats underwent transection of the suprascapular nerve and the supraspinatus and infraspinatus tendons in the left shoulder. The rats were euthanized 4 weeks after the surgery, and the cuff muscles were collected and weighed. The cross-sectional area and the involvement of Akt/mammalian target of rapamycin (mTOR) signaling were examined in the remaining TM muscle.

Results

The weight and cross-sectional area of the TM muscle was higher in the operated-on side than in the control side. The phosphorylated Akt/Akt protein ratio was not significantly different between these sides. The phosphorylated-mTOR/mTOR protein ratio was significantly higher on the operated-on side.

Conclusion

Transection of the suprascapular nerve and the supraspinatus and infraspinatus tendons activates mTOR signaling in the TM muscle, which results in muscle hypertrophy. The Akt-signaling pathway may not be involved in this process. Nevertheless, activation of mTOR signaling in the TM muscle after RCT may be an effective therapeutic target of a large RCT.