Myogenic stem cells

Avian Satellite Cell Plasticity

Simple Summary

Adult muscle regeneration and reconstruction is dependent on a population of adult stem cells, known as satellite cells. These cells were suggested to exhibit a certain degree of plasticity, being able to differentiate into lineages unassociated with muscle cells. In this study, we have used a range of visualization methods, as well as PCR, to identify a population of satellite cells obtained from samples of chicken muscles. Then, the cells, expressing a previously introduced detectable transgene, were introduced into chicken embryos and detected after three and eighteen days of their development. The traces of cell populations derived from the introduced satellite cells were detected in a range of embryonic tissues in both of the studied timeframes. The results of this study give further proof of the plasticity of muscle satellite cells, showing the potential locations of their migration during embryonic development.

Abstract

Adult myogenesis is dependent on a population of precursor cells, located between the sarcolemma and the basal lamina of the muscle fiber. These satellite cells, usually present in a quiescent state, become activated in response to mechanical muscle strain, differentiating and fusing to add new nuclei to enlarging muscles. As their myogenic lineage commitment is induced on demand, muscle satellite cells exhibit a certain amount of plasticity, possibly being able to be directed to differentiate into non-myogenic fates. In this study, myosatellite cells were isolated from chicken muscle samples, characterized in vitro and introduced into developing blastoderms. They were further investigated using fluorescence microscopy, immunohistochemistry and PCR, to determine their location in embryos after three and eighteen days. The results of the in vitro analysis confirmed that the cells obtained from the Pectoralis thoracicus are highly myogenic, based on the expression of Pax7, Myogenin, MyoD, Desmin and the myotube assay. Furthermore, the investigation of satellite cells within the embryo showed their migration to the regions of Pectoralis thoracicus, heart, liver, gizzard, proventriculus, intestine and brain. Overall, the results of the study proved the high myogenicity of chicken Pectoralis thoracicus cell isolates, as well as provided new information about their migration pathways following introduction into the blastocyst. The presence of the introduced LacZ or eGFP transgenes across the embryo, even 20 days after myosatellite cell injection, further supports the notion that satellite cells exhibit significant plasticity, potentially transdifferentiating into non-muscle lineages.

The Mutual Interactions between Mesenchymal Stem Cells and Myoblasts in an Autologous Co-Culture Model

Both myoblasts and mesenchymal stem cells (MSC) take part in the muscle tissue regeneration and have been used as experimental cellular therapy in muscular disorders treatment. It is possible that co-transplantation approach could improve the efficacy of this treatment. However, the relations between those two cell types are not clearly defined. The aim of this study was to determine the reciprocal interactions between myoblasts and MSC in vitro in terms of the features important for the muscle regeneration process. Primary caprine muscle-derived cells (MDC) and bone marrow-derived MSC were analysed in autologous settings. We found that MSC contribute to myotubes formation by fusion with MDC when co-cultured directly, but do not acquire myogenic phenotype if exposed to MDC-derived soluble factors only. Experiments with exposure to hydrogen peroxide showed that MSC are significantly more resistant to oxidative stress than MDC, but a direct co-culture with MSC does not diminish the cytotoxic effect of H2O2 on MDC. Cell migration assay demonstrated that MSC possess significantly greater migration ability than MDC which is further enhanced by MDC-derived soluble factors, whereas the opposite effect was not found. MSC-derived soluble factors significantly enhanced the proliferation of MDC, whereas MDC inhibited the division rate of MSC. To conclude, presented results suggest that myogenic precursors and MSC support each other during muscle regeneration and therefore myoblasts-MSC co-transplantation could be an attractive approach in the treatment of muscular disorders.

Regulating aging in adult stem cells with microRNA

Aging can be defined as the result of accumulated cellular damage and deregulation of the epigenome. These changes cause impaired cell maintenance systems, reduced tissue regeneration, weakening of the immune system and increased risk of malignancy. The higher mortality rate in older individuals is a result of these pathologies. The study of age-related changes in adult stem cells and their regenerative potential is crucial to our understanding of the physical deterioration of organs and tissues. The growing interest and knowledge in the field of microRNAs adds a further dimension to this field of research. MicroRNAs are important posttranscriptional regulators of gene expression. They co-regulate stem cell properties such as potency, differentiation, self-renewal and senescence. Various cell systems, e.g. defense mechanisms against reactive oxygen radicals (ROS), DNA repair and apoptosis are regulated by microRNAs. These properties and the assumption that microRNAs act as some kind of general switch make them highly relevant in aging research.

Stem cell homing in musculoskeletal injury

The regenerative potential of injured adult tissue suggests the physiological existence of cells capable of participating in the reparative process. Recent studies indicate that stem-like cells residing in tissues contribute to tissue repair and are replenished by precursor bone marrow-derived cells. Mesenchymal stromal cells (MSC) are among the candidates for reparative cells. These cells can potentially be mobilized into the circulation in response to injury signals and exert their reparative effects at the site of injury. Current therapies for musculoskeletal injuries pose unavoidable risks which can impede full recovery. Trafficking of MSC to the injury site and their subsequent participation in the regenerative process is thought to be a natural healing response that can be imitated or augmented by enhancing the endogenous MSC pool with exogenously administered MSC. Therefore, a promising alternative to the existing strategies employed in the treatment of musculoskeletal injuries is to reinforce the inherent reparative capacity of the body by delivering MSC harvested from the patient's own tissues to the site of injury. The aim of this review is to inform the reader of studies that have evaluated the intrinsic homing and regenerative abilities of MSC, with particular emphasis on the repair of musculoskeletal injuries. Research that supports the direct use of MSC (without in vitro differentiation into tissue-specific cells) will also be reported. Based on accruing evidence that the natural healing mechanism involves the recruitment of MSC and their subsequent reparative actions at the site of injury, as well as documented therapeutic response after the exogenous administration of MSC, the feasibility of the emerging strategy of instant stem-cell therapy will be proposed.