Blood Flow Restriction Therapy Stimulates Intercellular Mitochondria Transfer and Improves Muscle Regeneration and Shoulder Function in a Murine Rotator Cuff Injury Model - PubMed (original) (raw)

. 2026 Apr;54(5):1114-1125.

doi: 10.1177/03635465261424875. Epub 2026 Mar 8.

Aboubacar Wague 1 2 3, Luke Sang 1 2 3, Alex Youn 1 2 3, Ryan Sadjadi 1 2 3, Yusef Samimi 1 2, Cristhian Montenegro 1 2, Miguel Lizarraga 1 2 3, Justin Lau 1 2 4, Allan I Basbaum 5, Michael R Davies 1 2, Hubert T Kim 1 2, Brian T Feeley 1 2, Jarret A P Weinrich 6, Xuhui Liu 1 2

Affiliations

Blood Flow Restriction Therapy Stimulates Intercellular Mitochondria Transfer and Improves Muscle Regeneration and Shoulder Function in a Murine Rotator Cuff Injury Model

Nesa Milan et al. Am J Sports Med. 2026 Apr.

Abstract

Background: Rotator cuff (RC) tears are among the most common causes of shoulder dysfunction in sports medicine. Muscle atrophy and degeneration are important risk factors for RC tendon retearing and suboptimal recovery of shoulder function after tendon repair. Although blood flow restriction (BFR) can stimulate muscle regeneration after lower extremity trauma and anterior cruciate ligament reconstruction, the mechanisms that underlie BFR remain unknown, and its application to RC tears has not yet been explored.

Hypothesis: The authors hypothesized that BFR induces transfer of mitochondria from intramuscular fibro-adipogenic progenitors (FAPs) to myocytes, enhances muscle regeneration, and improves shoulder function after RC injury.

Study design: Controlled laboratory study.

Methods: To assess mitochondrial transfer after BFR, the authors used Prrx1-Cre/MitoTag reporter mice, in which FAP mitochondria are labeled. Mice underwent unilateral forelimb BFR, and supraspinatus (SS) muscles were collected at baseline and days 1, 2, 3, 5, and 7 for histology. To model massive RC tears, mice received unilateral SS and infraspinatus tendon transection with denervation (TT+DN) and then were randomized to a BFR (every 3 days) or control group. At 2 or 6 weeks after surgery, SS muscles were analyzed for mitochondrial transfer, fiber size, and fiber-type distribution. Additionally, forelimb gait and weightbearing were captured using the Blackbox system.

Results: BFR was associated with increased FAP-mediated mitochondrial transfer in healthy SS muscle as early as 1 day after BFR treatment and lasted for up to 3 days after BFR. The authors observed an enhanced effect of BFR-induced FAP mitochondrial transfer in SS muscle after RC injury, compared with the control, at both 2 and 6 weeks after TT+DN. BFR-treated mice had significantly reduced muscle atrophy, fatty infiltration, and fibrosis after RC injury. They also observed a significant improvement in forepaw weightbearing ratio and ipsilateral forepaw stride length at 6 weeks after injury in BFR-treated mice compared with controls.

Conclusion: BFR significantly improves muscle quality and shoulder function after RC injury. These effects occur alongside increased mitochondrial transfer from FAPs to myocytes.

Clinical relevance: Understanding the mechanism of BFR by which BFR enhances muscle regeneration could pave the way for its use as a novel rehabilitation strategy to improve recovery in patients with RC injuries and other muscle-related conditions.

Keywords: blood flow restriction; fibro-adipogenic progenitors; mitochondrial transfer; rotator cuff tears.

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Conflict of interest statement

One or more of the authors has declared the following potential conflict of interest or source of funding: This work was supported by the US Department of Veterans Affairs, Office of Research and Development: Rehabilitation Research and Development Service (VA ORD RR&D; Award No. 1I01RX005293) and Biomedical Laboratory Research and Development Service (VA ORD BLR&D; Award No. 1I01BX006098). AOSSM checks author disclosures against the Open Payments Database (OPD). AOSSM has not conducted an independent investigation on the OPD and disclaims any liability or responsibility relating thereto.

Figures

Figure 1.

Figure 1.

(A) Schematic illustrating the unilateral forelimb blood flow restriction (BFR) protocol. (B-G) Representative histological images of supraspinatus muscle from FAP mitochondria reporter mice at baseline and at various days after ipsilateral arm BFR (scale bar, 50 µm). Mitochondria transferred from FAPs to myofibers are visualized by the MitoTag–green fluorescent protein (GFP) reporter. (H) Quantification of FAP-derived mitochondrial transfer at each time point after BFR, expressed as the percentage of GFP+ mitochondria-containing myofibers out of the total myofibers.

Figure 2.

Figure 2.

(A-C) Blood flow restriction (BFR) improves forelimb function after rotator cuff (RC) injury. Blackbox setup schematic: 4-chamber arena, near-infrared camera, transillumination (TL), and frustrated total internal reflectance (FTIR) LED strips. (D) Representative plantar pressure heatmap of the ipsilateral (right) mouse forepaw, with red/orange colors denoting higher applied pressure, demonstrating decreased weightbearing after RC injury and improved weightbearing after BFR treatment. (E) Sum of the FTIR intensity in the right forepaw. (F) Quantification of forepaw weightbearing as a right-to-left ratio, where 1.0 indicates equal weight distribution between limbs. Percentage of total weightbearing borne by the (G) pad and (H) toes of the right forepaw. (I) Quantification of right forepaw stride length. *P < .05.

Figure 3.

Figure 3.

Fibro-adipogenic progenitor (FAP)–mediated mitochondrial transfer and myofiber size in supraspinatus (SS) muscle after blood flow restriction (BFR) and rotator cuff injury. (A-D) Representative histological images of SS muscle from FAP mitochondria reporter mice at baseline and at various days after ipsilateral arm BFR in the Prrx1-Cre/MitoTag reporter mice at 2 and 6 weeks after unilateral SS and infraspinatus tendon transection and denervation (TT+DN), with or without ipsilateral arm BFR (scale bar, 100 µm). (E) Quantification of myofiber cross-sectional area (CSA) in each group. (F) Quantification of mitochondrial transfer postinjury, defined as the percentage of green fluorescent protein–positive (GFP+) myofibers per total myofibers. *P < .05.

Figure 4.

Figure 4.

Comparison of muscle fiber type and MitoTag fiber distribution after rotator cuff injury between blood flow restriction (BFR) and control groups. (A-T) Representative muscle fiber histological images of supraspinatus (SS) muscle after unilateral SS and infraspinatus tendon transection and denervation (TT+DN) in Prrx1-Cre/MitoTag mice receiving BFR and control. Muscle fiber types were determined via major histocompatibility complex (MHC) expression staining. (U-Z) Quantification of green fluorescent protein–positive (GFP+) fibers per fiber type, calculated as follows: % GFP+ per fiber type = (number of GFP+ fibers of a given fiber type)/(total fibers of that fiber type) × 100. Graphs show significantly increased mitochondrial transfer in BFR groups across MHC-IIA, IIB, and IIX fibers at both (U-W) 2 weeks and (X-Z) 6 weeks after injury. Data are shown as mean ± SEM. *P < .05 by unpaired Student t test.

Figure 5.

Figure 5.

Effects of blood flow restriction (BFR) on fatty infiltration (FI) and fibrosis after rotator cuff injury. (A-D) Representative histological images of supraspinatus (SS) muscle Oil Red O staining to determine the amount of degenerative FI (scale bars, 100 μm) in control and BFR-treated mice at 2 and 6 weeks after unilateral SS and infraspinatus tendon transection and denervation (TT+DN). (E) Quantification of the percent area of FI (positive stain signal per total section area). (F-I) Representative histological images of SS muscle Masson Trichrome staining to determine the amount of fibrosis development (scale bars, 100 μm) in control and ipsilateral arm BFR-treated mice at 2 and 6 weeks after TT+DN. (J) Quantification of percent area of fibrosis (positive stain signal per total section area) *P < .05.

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