RESUMO
Human skeletal muscle stem cells from healthy donors aged 2-82 years (n = 13) and from three children suffering from Duchenne Muscular Dystrophy (DMD) were implanted into soleus muscles of immunoincompetent mice and were also expanded in vitro until senescence. Growth of implanted cells was quantified by structural features and by the amount of human DNA present in a muscle. Proliferative capacity in vitro and in vivo was inversely related to age of the donor. In vitro, a decline of about two mean population doublings (MPDs) per 10 years of donor's age was observed. Muscle stem cells from DMD children were prematurely aged. In general, cell preparations with low or decreasing content in desmin-positive cells produced more MPDs than age-matched high-desmin preparations and upon implantation more human DNA and more nonmyogenic than myogenic tissue. Thus, a "Desmin Factor" was derived which predicts "quality" of the human muscle tissue growing in vivo. This factor may serve as a prognostic tool.
Assuntos
Fatores Etários , Proliferação de Células , Mioblastos Esqueléticos/transplante , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Animais , Biópsia , Células Cultivadas , Criança , Pré-Escolar , DNA/isolamento & purificação , Desmina/análise , Feminino , Humanos , Hospedeiro Imunocomprometido , Masculino , Camundongos , Pessoa de Meia-Idade , Músculo Esquelético/patologia , Distrofia Muscular de Duchenne/patologia , Transplante de Células-TroncoRESUMO
The ageing process causes a reduction in the regenerative potential of skeletal muscles eventually leading to diminished muscle strength. In this work we investigated if ageing affects the excitation-contraction coupling mechanism in human myotubes derived from human satellite cells, thereby contributing to the loss in muscle strength in the aged. To test this hypothesis, satellite cells from differently aged donors were differentiated in vitro and the maturation of the excitation-contraction mechanism was followed by the videoimaging technique monitoring the efficiency of such a mechanism in generating intracellular calcium transients. Our experiments showed a delay in the establishment of the excitation-contraction coupling mechanism depending on the age of the donor. Remarkably, the effect was reproducible in human satellite cells from a young donor aged in vitro, suggesting that the delayed functional maturation was strictly dependent on the number of satellite cell divisions and independent from the host environment.
