Engineering skeletal muscle tissue--new perspectives in vitro and in vivo.
Bottom Line: However, the field of skeletal muscle TE has been developing tremendously and new approaches and techniques have emerged.This review will highlight recent developments in the field of nanotechnology, especially electrospun nanofibre matrices, as well as potential cell sources for muscle TE.Important developments in cardiac muscle TE and clinical studies on Duchenne muscular dystrophy (DMD) will be included to show their implications on skeletal muscle TE.
Affiliation: Department of Plastic and Hand Surgery, University Hospital of Erlangen, Friedrich-Alexander-University of Erlangen-Nürnberg, Erlangen, Germany.Show MeSH
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Mentions: In opposite to the impressive developments in nanotechnology there are still great shortcomings on the cell side. Regarding the cell source, the satellite cell is the most prominent one (Fig. 5) [76–77]. The term ‘satellite cell’ is a histological description of undifferentiated cells residing between the sarcolemma and the basement membrane of muscle fibres but their exact biological characterization, their origin and differentiation potential and the question whether satellite cells are actually stem cells have been a point of discussion for a long time . Today, it is common knowledge that satellite cells are characterized through the expression of the muscle-specific paired box (Pax) transcription factor Pax7 . But it is also known that Pax7+ cells are a heterogeneous cell population consisting of a majority of Myf5+ cells and a minority (10%) of Myf5− cells . The expression of Myf5 as an initiator of myogenic differentiation  marks the commitment of this cell population to the myogenic lineage . Therefore, the majority of the satellite cell population actually consists of muscle precursor cells with a strong myogenic imprinting, whereas the Pax7+/Myf5− subpopulation of the satellite cells (only 10%) show stem cell properties continuously renewing the Pax7+/Myf5+ cell population. High hopes have been built on this stem cell like subpopulation regarding their proliferative capacity in vitro because these cells are capable of allowing for regeneration of large parts of the musculature in vivo[82–83]. Yet, Yaffe and coworkers have demonstrated that isolated satellite cells undergo rapid dedifferentiation in vitro after few cell cycles . Boonen et al. have explained this phenomenon by the loss of the highly specific stem cell niche which preserves normal function of satellite cells in vivo[85–86]. Therefore, in vitro expansion of satellite cells does not lead to an efficient amount of cells for muscle TE. Yet, the commitment to the myogenic line of the majority of satellite cells represents an unmatched myogenic potential and implies safety concerning clinical applications without the risk of tumour genesis.
Affiliation: Department of Plastic and Hand Surgery, University Hospital of Erlangen, Friedrich-Alexander-University of Erlangen-Nürnberg, Erlangen, Germany.