SummarySkeletal muscle contains two distinct stem/progenitor populations. One is the satellite cell, which acts as a muscle stem cell, and the other is the mesenchymal progenitor, which contributes to muscle pathogeneses such as fat infiltration and fibrosis. Detailed and accurate characterization of these progenitors in humans remains elusive. Here, we performed comprehensive cell-surface protein profiling of the two progenitor populations residing in human skeletal muscle and identified three previously unrecognized markers: CD82 and CD318 for satellite cells and CD201 for mesenchymal progenitors. These markers distinguish myogenic and mesenchymal progenitors, and enable efficient isolation of the two types of progenitors. Functional study revealed that CD82 ensures expansion and preservation of myogenic progenitors by suppressing excessive differentiation, and CD201 signaling favors adipogenesis of mesenchymal progenitors. Thus, cell-surface proteins identified here are not only useful markers but also functionally important molecules, and provide valuable insight into human muscle biology and diseases.

We found higher prevalence of sarcopenia and lower leg muscle mass among patients with acute OVF compared with patients who did not have an OVF. These results suggest that sarcopenia may be a risk factor for OVF.

Thigh cross-sectional area decreased with age mainly because of a decrease in muscle cross-sectional area in men and fat cross-sectional area in women. The rate of decrease in muscle cross-sectional area was 1.5-fold higher in men than in women. Muscle cross-sectional area decreased with age mainly because of a decrease in quadriceps cross-sectional area, especially in women. Decrease in muscle quality with age was similar in both sexes.

Mesenchymal progenitors residing in the muscle interstitial space contribute to pathogeneses such as fat infiltration and fibrosis. Because fat infiltration and fibrosis are hallmarks of diseased muscle, it is important to establish an accurate and reproducible method for isolating mesenchymal progenitors for research on muscle diseases. In this chapter, we describe methods based on fluorescence-activated cell sorting (FACS) to purify mesenchymal progenitors from mouse and human skeletal muscle using the most reliable marker for mesenchymal progenitors, PDGFRα. These methods allow concurrent isolation of the muscle stem cells called satellite cells. The quality of isolated mesenchymal progenitors is confirmed by their remarkable adipogenic potential without myogenic capacity, while purified satellite cells possess robust myogenic activity with no adipogenic potential. Simultaneous isolation of both mesenchymal progenitors and satellite cells from mouse and human tissues provides a powerful platform for studying skeletal muscle regeneration and diseases.

Level IV, prognostic study.

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Collapse of the femoral head and the contralateral condition of ONFH strongly affect patients' activities of daily life.

Aim: Sarcopenia causes a decline in physical performance and decreased quality of life. However, there is little evidence for effective treatments. Because of the similarities between osteoporosis and sarcopenia, alfacalcidol used for osteoporosis might be beneficial for low muscle mass. Therefore, we investigated the effect of alfacalcidol on muscle mass in patients with low muscle mass. Methods:In this retrospective cohort analysis, patients from an osteoporosis database were divided into two groups: alfacalcidol-treated patients (vitamin D group; n = 156) and a control group without drug treatment (n = 233). Muscle mass was evaluated in terms of the skeletal muscle index (SMI; kg/m 2 ) obtained from dual-energy X-ray absorptiometry measurements that were taken at the start and end of a 1-year period. Low muscle mass was determined using specific SMI cut-offs for Japanese individuals.Results: Both the vitamin D group (mean age 73.7 ± 9.8 years) and the control group (mean age 72.3 ± 11.9 years) were primarily women (n = 141, 90.4%; n = 189, 81.1%, respectively). Low muscle mass was identified in 32.7% ). The change in the patients with low muscle mass was not significant. Conclusions:The vitamin D group maintained muscle mass, and the SMI increased in patients with low muscle mass. Thus, the use of alfacalcidol might be effective in osteoporotic patients with low muscle mass. Geriatr Gerontol Int 2014; 14 (Suppl. 1): 122-128.