In vivo Measurement of Knee Extensor Muscle Function in Mice

Brightwell, Camille R.; Graber, Ted G.; Brightwell, Benjamin D.; Borkowski, Matthew; Noehren, Brian; Fry, Christopher S.

doi:10.3791/62211

Cited by 5 publications

(4 citation statements)

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“…Assessment of quadriceps strength or gait alteration would add functional depth, linking protein metabolic perturbations to weakness. Previous work has shown ACLT results in robust deficits in quadriceps torque in mice, 4 and future studies should seek to determine whether early reductions in muscle protein anabolism predict functional deficits. Additionally, our murine injury model involves surgical transection of the ACL.…”

Section: Discussionmentioning

confidence: 99%

Depressed Protein Synthesis and Anabolic Signaling Potentiate ACL Tear–Resultant Quadriceps Atrophy

et al. 2022

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Background: Anterior cruciate ligament (ACL) tear (ACLT) leads to protracted quadriceps muscle atrophy. Protein turnover largely dictates muscle size and is highly responsive to injury and loading. Regulation of quadriceps molecular protein synthetic machinery after ACLT has largely been unexplored, limiting development of targeted therapies. Purpose: To define the effect of ACLT on (1) the activation of protein synthetic and catabolic signaling within quadriceps biopsy specimens from human participants and (2) the time course of alterations to protein synthesis and its molecular regulation in a mouse ACL injury model. Study Design: Descriptive laboratory study. Methods: Muscle biopsy specimens were obtained from the ACL-injured and noninjured vastus lateralis of young adult humans after an overnight fast (N = 21; mean ± SD, 19 ± 5 years). Mice had their limbs assigned to ACLT or control, and whole quadriceps were collected 6 hours or 1, 3, or 7 days after injury with puromycin injected before tissue collection for assessment of relative protein synthesis. Muscle fiber size and expression and phosphorylation of protein anabolic and catabolic signaling proteins were assessed at the protein and transcript levels (RNA sequencing). Results: Human quadriceps showed reduced phosphorylation of ribosomal protein S6 (–41%) in the ACL-injured limb ( P = .008), in addition to elevated phosphorylation of eukaryotic initiation factor 2α (+98%; P = .006), indicative of depressed protein anabolic signaling in the injured limb. No differences in E3 ubiquitin ligase expression were noted. Protein synthesis was lower at 1 day ( P = .01 vs control limb) and 3 days ( P = .002 vs control limb) after ACLT in mice. Pathway analyses revealed shared molecular alterations between human and mouse quadriceps after ACLT. Conclusion: (1) Global protein synthesis and anabolic signaling deficits occur in the quadriceps in response to ACL injury, without notable changes in measured markers of muscle protein catabolism. (2) Importantly, these deficits occur before the onset of significant atrophy, underscoring the need for early intervention. Clinical Relevance: These findings suggest that blunted protein anabolism as opposed to increased catabolism likely mediates quadriceps atrophy after ACL injury. Thus, future interventions should aim to restore muscle protein anabolism rapidly after ACLT.

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Section: Discussionmentioning

confidence: 99%

Depressed Protein Synthesis and Anabolic Signaling Potentiate ACL Tear–Resultant Quadriceps Atrophy

et al. 2022

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“…This protocol was adapted and modified from our previously published methods [ 68 , 69 ]. Briefly, mice were anesthetized with isoflurane (∼2.5% for maintenance of anesthesia via nose cone; oxygen maintained at ∼1 l/min with a VetEquip vaporizer) and placed on a platform (Aurora Scientific 809c in situ testing apparatus; Aurora, ON, Canada) heated to 37 °C (with an Anova Industries Model 10 water circulator; Stafford, TX, USA) with an attached nose cone for anesthesia maintenance.…”

Section: Methodsmentioning

confidence: 99%

Inhibition of p53-MDM2 binding reduces senescent cell abundance and improves the adaptive responses of skeletal muscle from aged mice

Nolt,

Keeble,

Wen

et al. 2023

GeroScience

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Skeletal muscle adaptation to external stimuli, such as regeneration following injury and hypertrophy in response to resistance exercise, are blunted with advanced age. The accumulation of senescent cells, along with defects in myogenic progenitor cell (MPC) proliferation, have been strongly linked as contributing factors to age-associated impairment in muscle adaptation. p53 plays an integral role in all these processes, as upregulation of p53 causes apoptosis in senescent cells and prevents mitotic catastrophe in MPCs from old mice. The goal of this study was to determine if a novel pharmaceutical agent (BI01), which functions by upregulating p53 through inhibition of binding to MDM2, the primary p53 regulatory protein, improves muscle regeneration and hypertrophy in old mice. BI01 effectively reduced the number of senescent cells in vitro but had no effect on MPC survival or proliferation at a comparable dose. Following repeated oral gavage with 2 mg/kg of BI01 (OS) or vehicle (OV), old mice (24 months) underwent unilateral BaCl2 injury in the tibialis anterior (TA) muscle, with PBS injections serving as controls. After 7 days, satellite cell number was higher in the TA of OS compared to OV mice, as was the expression of genes involved in ATP production. By 35 days, old mice treated with BI01 displayed reduced senescent cell burden, enhanced regeneration (higher muscle mass and fiber cross-sectional area) and restoration of muscle function relative to OV mice. To examine the impact of 2 mg/kg BI01 on muscle hypertrophy, the plantaris muscle was subjected to 28 days of mechanical overload (MOV) in OS and OV mice. In response to MOV, OS mice had larger plantaris muscles and muscle fibers than OV mice, particularly type 2b + x fibers, associated with reduced senescent cells. Together our data show that BI01 is an effective senolytic agent that may also augment muscle metabolism to enhance muscle regeneration and hypertrophy in old mice.

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“…Due to Covid19 restrictions and laboratory limitations we were unable to collect this data for the OA mice. Methods have been published elsewhere (Graber et al, 2019b;Neelakantan et al, 2019;Brightwell et al, 2021;Graber et al, 2021) and see further details in the online supplement. In brief, we anesthetized the mouse using isoflurane (~3% isoflurane and 1.5 L/m of O 2 , to effect) to remove conscious control of skeletal muscle.…”

Section: In Vivo Contractile Physiologymentioning

confidence: 99%

Endurance exercise preserves physical function in adult and older male C57BL/6 mice: high intensity interval training (HIIT) versus voluntary wheel running (VWR)

Pajski,

Byrd,

Nandigama

et al. 2024

Front. Aging

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Exercise has been shown to improve physical function, mitigate aspects of chronic disease and to potentially alter the trajectory of age-related onset of frailty and sarcopenia. Reliable and valid preclinical models are necessary to elucidate the underlying mechanisms at the intersection of age, exercise, and functional decline. The purpose of this study was to compare, head to head, the effects of two common pre-clinical models of endurance exercise: high intensity interval training (HIIT) and voluntary wheel running (VWR). The hypothesis was that a prescribed and regimented exercise program, HIIT, would prove to be a superior training method to unregulated voluntary exercise, VWR. To investigate this hypothesis, we evaluated adult (n = 24, designated 10 m, aged 6 months at the beginning of the study, 10 months at its completion) and older adult (n = 18, designated 26 m, aging from 22 months to 26 months over the course of the study) C57BL/6 male mice. These mice were randomly assigned (with selection criteria) to a 13-week program of voluntary wheel running (VWR), high intensity interval training (HIIT), or sedentary control (SED). The functional aptitude of each mouse was determined pre- and post-training using our composite CFAB (comprehensive functional assessment battery) scoring system consisting of voluntary wheel running (volitional exercise and activity rate), treadmill (endurance), rotarod (overall motor function), grip meter (forelimb strength), and inverted cling (whole body strength/endurance). To measure sarcopenia, we tracked body mass, body composition (with EchoMRI), plantar flexor torque (in 10 m), and measured muscle wet mass post-training. Overall, adult CFAB scores decreased while body mass and percent body fat increased as they matured; however, exercise significantly mitigated the changes (p < 0.05) compared to SED. Older adults demonstrated preservation of function (CFAB) and reduced body fat (p < 0.05) compared to SED. To conclude, both types of exercise maintained physical function equally in older mice.

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In vivo Measurement of Knee Extensor Muscle Function in Mice

Cited by 5 publications

References 0 publications

Depressed Protein Synthesis and Anabolic Signaling Potentiate ACL Tear–Resultant Quadriceps Atrophy

Depressed Protein Synthesis and Anabolic Signaling Potentiate ACL Tear–Resultant Quadriceps Atrophy

Inhibition of p53-MDM2 binding reduces senescent cell abundance and improves the adaptive responses of skeletal muscle from aged mice

Endurance exercise preserves physical function in adult and older male C57BL/6 mice: high intensity interval training (HIIT) versus voluntary wheel running (VWR)

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