Background: Amyotrophic Lateral Sclerosis (ALS) is a fatal neurodegenerative disease characterized by progressive muscle weakness. Blood flow restriction (BFR), involving temporary blood flow restriction followed by reperfusion, promotes beneficial skeletal muscle adaptations, including the beige differentiation of fibroadipogenic progenitors (FAPs). We hypothesize that BFR could be a therapeutic approach to potentially delay the onset of motor dysfunction in ALS.
Objectives: SOD1 mice were randomly divided into BFR and no-treatment groups, with each group containing 6 males and 6 females (5 females in the BFR group). Under 1-2% isoflurane anesthesia, the BFR group underwent weekly unilateral hindlimb BFR using a rubber band on the left thigh for three 10-minute cycles, each separated by a 10-minute break. Survival was monitored over 28 weeks, and functional data were collected biweekly using Blackbox, a device that combines imaging and machine learning to track body posture and paw contact forces. Beige-differentiated FAPs were analyzed via single-cell mRNA sequencing to investigate genes potentially explaining the observed improvement in ALS outcomes.
Results: The median survival of ALS mice treated with BFR therapy was 24 weeks, compared to 20 weeks in controls (p=0.021). Multivariate Cox regression confirmed improved survival associated with BFR (HR 0.38; 95% CI 0.15-0.98, p=0.030), independent of sex. Functional analysis showed that BFR-treated mice maintained stride length until death (p>0.05) and exhibited significantly faster walking speeds at 18 weeks (p=0.018), 20 weeks (p=0.009), and 24 weeks (p=0.046). BFR-treated ALS mice showed improved biomechanics, with paw weight-bearing during walking resembling WT mice more than untreated controls (p=0.03). Single-cell analysis revealed significant downregulation of FUS and upregulation of SOD1 and C9orf72 in beige-differentiated FAPs.
Discussion: Our encouraging results indicate the potential of BFR to manage functional decline and improve survival in ALS. Although BFR was applied only to the left hindlimb, it demonstrated systemwide effects, delaying the onset of paralysis in all limbs. Further research is needed to evaluate the combined effects of BFR and low-intensity exercise, which traditionally yields better outcomes than BFR at rest. Additional studies should investigate the factors released into the bloodstream due to BFR, as they may serve as direct therapeutic targets for ALS.