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Fig. 3 | Stem Cell Research & Therapy

Fig. 3

From: Secretome of adipose-derived mesenchymal stem cells promotes skeletal muscle regeneration through synergistic action of extracellular vesicle cargo and soluble proteins

Fig. 3

Total ADSC secretome and its EV fraction modulate different aspects of in vivo skeletal muscle regeneration. The regenerative effect of an intravenous injection of either total ADSC secretome or its isolated EV fraction was assessed in the acute skeletal muscle degeneration model induced by CTX injection into the right tibialis anterior muscle. a–c Staining for acid phosphatase revealed a significant decrease in the lysosomal activity in mice that had been treated with the whole ADSC secretome. d–g Quantification of the cross-sectional area (CSA) demonstrated that the skeletal muscle regeneration is significantly enhanced by whole secretome, with a greater effect with the EV fraction. Scale bar: 100 μm. h–k Immunohistochemical staining and quantification of satellite cell myogenic progression showed an increase in the number of quiescent (Pax7+/MyoD−) satellite cells following whole secretome treatment. Both the whole secretome and the EV fraction decrease the number of activated (Pax7+/MyoD+) satellite cells, with a decrease in the number of differentiating satellite cells (Pax7−/MyoD+) only observed following treatment with the EV fraction (red arrow: quiescent satellite cell, yellow arrow: differentiating satellite cell, white arrow: activated satellite cell. Scale bar: 20 μm. l–o Immunohistochemical stainings for CD68 revealed that both fractions of ADSC secretome decreased the number of infiltrating macrophages. Scale bar: 50 μm. p–s Immunohistochemical analysis of CD31 within the muscle tissue showed that only the total secretome had an angiogenic effect. Scale bar: 100 μm. p < 0.05 (*), p < 0.01 (**) or p < 0.001 (***). Three separate batches of ADSC secretome and isolated EV fraction were tested

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