Leurcharusmee P, Sawaddiruk P, Punjasawadwong Y, et al. Ischemic preconditioning upregulates Mitofusin2 and preserves muscle strength in tourniquet-induced ischemia/reperfusion. J Orthop Transl. 2022;35:113-121. doi:10.1016/j.jot.2022.09.012
Abstracted by:
Lindsy Moore, PT, DPT, OCS, COMT Soldotna, Alaska – Fellowship Candidate, IAOM-US Fellowship Program & Jean-Michel Brismée, PT, ScD, Fellowship Director, IAOM-US Fellowship program.
Research: Tourniquet-induced ischemia and reperfusion (I/R) has been related to postoperative muscle atrophy through mechanisms involving protein synthesis/breakdown, cellular metabolism, mitochondrial dysfunction, and apoptosis. Ischemic preconditioning (IPC) could protect skeletal muscle against I/R injury. This study aims to determine the underlying mechanisms of IPC and its effect on muscle strength after total knee arthroplasty (TKA).
Methods: Twenty-four TKA patients were randomized to receive either sham IPC or IPC (3 cycles of 5-min ischemia followed by 5-min reperfusion). Vastus medialis muscle biopsies were collected at 30 min after tourniquet (TQ) inflation and the onset of reperfusion. Western blot analysis was performed in selected muscle proteins. Clinical outcomes including isokinetic muscle strength and quality of life were evaluated pre- and postoperatively.
Outcome measure: Mitofusion2 (Mfn2) Expression: The primary biochemical outcome was the level of Mitofusion2 protein expression, measured using Western blot analysis. Muscle strength: muscle strength was assessed postoperatively using isokinetic muscle strength testing. Other protein markers: The study also measured the expression of other proteins related to oxidative stress, inflammation, and mitochondrial function, including 4-HNE, SOD2, TNF-a, IL-6, and PGC-1a. Clinical outcomes: Postoperative peak torque for knee extension.
Results: IPC Significantly increased the expression of Mitofusion2 (Mfn2) during the reperfusion phase compared to the ischemic phase. Postoperative muscle strength, measured as peak torque for knee extension, was better preserved in the IPC group. There were no significant differences in the other protein markers such as 4-HNE, SOD2, TNF-a, IL-6, and PGC-1a. The results suggest that IPC can effectively upregulate beneficial proteins like Mfn2 and help preserve muscle strength during ischemia reperfusion injury.
IAOM-US Comments:
Total knee arthroplasty is successful in eliminating knee pain from osteoarthritis, however, postoperative recovery is often compromised by persistent muscle atrophy and reduced functional mobility.1 Quadriceps atrophy is responsible for the majority of functional deficits one to three years post total knee arthroplasty.2 Often impairing balance, reducing mobility and increasing fall risk.2 Tourniquets are used in TKA to control blood loss, maintain a clear surgical field, and facilitate proper bone implant cementing.2 Tourniquet ischemia followed by reperfusion can lead to greater postoperative pain, reduced range of motion, and greater postoperative edema.2 During ischemia, oxygen deprivation inhibits mitochondrial oxidative phosphorylation and electron transport chain leading to adenosine triphosphate depletion and reactive oxygen species overproduction.1 Tourniquet induced oxygen deficiency that occurs during total knee arthroplasty may disrupt cell and tissue metabolism and potentially contribute to the rapid loss of muscle (1% per day) measured within the first two weeks after surgery.2 Muscle atrophy following surgeries in older adults is likely permanent and has the added complication of accelerating sarcopenia.2 Identifying factors that may limit loss, such as attenuating ischemia reperfusion injury associated with tourniquet use is warranted to ensure the best clinical outcome for patients.2
Ischemic preconditioning (IPC) can be considered as a pre-habilitation strategy to protect muscle strength during procedures that involve ischemia reperfusion, such as surgeries using tourniquets.1 This could help with faster recovery and better postoperative outcomes for patients.1 IPC can be particularly useful for patients who are at higher risk of muscle damage due to prolonged ischemia, such as those undergoing orthopedic surgeries.1 IPC is a noninvasive and cost-effective intervention that can be easily integrated into clinical practice.1 It involves cycles of blood flow restriction and reperfusion (3 cycles of 5-min ischemia followed by 5-min reperfusion), making it accessible for various settings.1
The protective mechanism of IPC is the up regulation of Mitofusion2 (Mfn2).1 Mitofusion2 (Mfn2) is integral in mitochondrial activity.3 Mitochondria are organelles whose functions are essential for cell sustainability.3 Mitochondria are remodeled through fusion and fission events.3 Mitochondrial fusion proteins are essential for the maintenance of mitochondrial and skeletal muscle health.4 Elevated mitochondrial fission and reduced mitochondrial fusion are linked to increased cellular apoptosis and muscle fiber atrophy in disuse muscle and sarcopenia.4 Mitochondria has close contact with the endoplasmic reticulum which allows modulation of cellular pathways.3 Age-related Mfn2-depletion in muscles has been associated with inhibited mitophagy and accumulation of dysfunctional mitochondria which has been linked to sarcopenia.4 Enhancing mitochondrial fusion proteins such as Mfn2 has been shown to prevent skeletal muscle ischemia reperfusion injury.1 The study found that skeletal muscle pretreated with IPC preserved quadriceps strength and had elevated Mfn2 following surgery with tourniquet.1 This highlights the importance of mitochondrial health and muscle recovery.1 IPC enhances mitochondrial function through mitochondrial fusion and could be beneficial in the rehabilitation program.1
Limitations: small sample size, need for higher sensitivity analyses to further show protective effects underlying IPC, and age of participants which affects mitochondrial quality.1
In this study the IPC group pressure was 100 mm Hg above systolic blood pressure.1 The inflation time was 5 min and deflation time 5 min for 3 cycles.1 The sham group had the unpressurized cuff on for 30 minutes.1 IPC was applied before surgery the same day.1 Ischemic preconditioning can be applied before or after exercise.5 When used before surgery and exercise it has been shown to protect cardiac and skeletal muscles against ischemia-reperfusion injury, and exercise induced muscle damage as well as delayed onset muscle soreness, respectively.5 IPC used after surgery or exercise helps to attenuate ischemia-reperfusion injury and accelerate recovery.5 IPC is used in the passive supine position.6 According to smarttools cuff system when completing an IPC session occlusion pressure should be 80-100% with 5 minutes occlusion and 5 minutes deflation for 3-5 rounds.6 This should be followed by high intensity exercise, which would help attenuate the muscle damage.6
Figure 1: IPC set up for the lower extremity, performed in supine.
References:
- Leurcharusmee P, Sawaddiruk P, Punjasawadwong Y, et al. Ischemic preconditioning upregulates Mitofusin2 and preserves muscle strength in tourniquet-induced ischemia/reperfusion. J Orthop Transl. 2022;35:113-121. doi:10.1016/j.jot.2022.09.012
- Muyskens JB, Hocker AD, Turnbull DW, et al. Transcriptional profiling and muscle cross-section analysis reveal signs of ischemia reperfusion injury following total knee arthroplasty with tourniquet. Physiol Rep. 2016;4(1):e12671. doi:10.14814/phy2.12671
- Filadi R, Pendin D, Pizzo P. Mitofusin 2: from functions to disease. Cell Death Dis. 2018;9(3):1-13. doi:10.1038/s41419-017-0023-6
- Leduc-Gaudet JP, Hussain SNA, Barreiro E, Gouspillou G. Mitochondrial Dynamics and Mitophagy in Skeletal Muscle Health and Aging. Int J Mol Sci. 2021;22(15):8179. doi:10.3390/ijms22158179
- de França IM, Cerqueira MS, Barros de Sousa Oliveira YM, Patterson SD, de Brito Vieira WH. Effects of Ischemic Pre and Postconditioning on Indirect Markers of muscle damage: A Systematic Review and Meta-Analysis. Muscles Ligaments Tendons J MLTJ. 2024;14(1):87-101. doi:10.32098/mltj.01.2024.09
- smartcuffs pro user manual high res3.pdf (smarttoolsplus.com)