Innervation of dystrophic muscle after muscle stem cell therapy

Introduction: Duchenne muscular dystrophy (DMD) is caused by loss of the structural protein, dystrophin, resulting in muscle fragility. Muscle stem cell (MuSC) transplantation is a potential therapy for DMD. It is unknown whether donor‐derived muscle fibers are structurally innervated. Methods: Green fluorescent protein (GFP)–expressing MuSCs were transplanted into the tibials anterior of adult dystrophic mdx/mTR mice. Three weeks later the neuromuscular junction was labeled by immunohistochemistry. Results: The percent overlap between pre‐ and postsynaptic immunolabeling was greater in donor‐derived GFP⁺ myofibers, and fewer GFP⁺ myofibers were identified as denervated compared with control GFP^– fibers (P = 0.001 and 0.03). GFP⁺ fibers also demonstrated acetylcholine receptor fragmentation and expanded endplate area, indicators of muscle reinnervation (P = 0.008 and 0.033). Conclusion: It is unclear whether GFP⁺ fibers are a result of de novo synthesis or fusion with damaged endogenous fibers. Either way, donor‐derived fibers demonstrate clear histological innervation. Muscle Nerve 54 : 763–768, 2016     

Moderate exercise improves gait stability in disabled elders

Background: Decreased muscle strength impedes elders' functional performance in daily activities such as gait. The mechanisms whereby increased strength improves gait are unknown.Methods: A prospective, blinded, randomized trial of moderate intensity strength exercise was conducted and its impact was measured on functional mobility during gait in 132 functionally limited elders. Lower extremity strength was measured, including hip abductor, hip extensor, and knee extensor strength. Of the 132 subjects, 120 subjects (mean age, 75.lyrs) completed 6 months of elastic band resistance training at least 3 times a week or served as no-exercise controls.Results: Subjects increased their lower extremity strength in the exercise and control groups, by 17.6% and 7.3% (p < .01), respectively. Gait stability improved significantly more in the exercise group than in the control group (p < .05). Increases in forward gait velocity were not significantly different between groups. Peak mediolateral velocity and base of support improved in the exercise group, but not in the control group. Change in lower extremity strength correlated significantly but weakly with many of the gait variables.Conclusions: Gait stability, especially mediolateral steadiness, improved in the exercise group but not in the control group. These results show that even moderate strength gains benefit gait performance in elders and thus provide a sound basis for encouraging low-intensity strength training for elders with functional limitations.     

The temporal and spatial dynamics of microscale collagen scaffold remodeling by smooth muscle cells

Smooth muscle cells (SMCs) and collagen scaffolds are widely used in vascular tissue engineering but their interactions in remodeling at the microscale level remained unclear. We characterized microscale morphologic alterations of collagen remodeled by SMCs in six dimensions: three spatial, time, multichannel and multi-position dimensions. In live imaging assays, computer-assisted cell tracking showed locomotion characteristics of SMCs; reflection and fluorescent confocal microscopy and spatial reconstruction images of each time point showed detailed morphologic changes of collagen fibers and spatial collagen–SMC interactions. The density of the collagen around the SMCs was changed dynamically by the leading edges of the cells. The density of the collagen following 24 h of cell-induced remodeling increased 51.61 ± 9.73% compared to unremodeled collagen containing cells for 1 h (P < 0.0001, n = 40) (NS vs. collagen without cells). Fast Fourier transform analysis showed that the collagen fibers' orientation changed from random (alignment index = 0.047 ± 0.029, n = 40) after 1 h into concordant with that of the SMCs (alignment index = 0.379 ± 0.098, P < 0.0001, n = 40) after 24 h. Mosaic imaging extended the visual field from a single cell to a group of cells in one image without loss of optical resolution. Direct visualization of alignment of actin fibers and collagen fibers showed the molecular machinery of the process of scaffold remodeling. This is a new approach to better understanding the mechanism of scaffold remodeling and our techniques represent effective tools to investigate the interactions between cells and scaffold in detail at the microscale level.