Figure 6. TnC declines with aging and is required for muscle maintenance and regeneration of aged skeletal muscles.

(A) Western blot for TnC on young (3–5 months old) and old (18–26 months old) WT mice and quantification of TnC protein relative expression (n=4).

(B) Representative immunofluorescence (IF) images of 5 DPI TA muscles of young and old mice (TnC red; laminin gray; DAPI blue). Scale bar= 50 µm..

(C) Quantification of the number of FACS isolated MuSC per mg of muscle tissue in young and old mice (n≥4 mice)..

(D) Representative IF images of cross-sections of uninjured TA muscles from young (4–6 months old) and old WT (23–29 months old) and TnC-KO mice (laminin, green; DAPI, blue) (scale bar= 50 µm) and quantification of the cross-sectional area (CSA) in µm² (n=3)..

(E) Representative IF images of cross-sections of uninjured TA muscles from old WT and TnC-KO mice (Pax7, green; laminin, red; DAPI blue) (scale bar= 50 µm) for Pax7⁺ cell quantification (n=3)..

(F) Representative IF images of cross-sections of injured (5 DPI) TA muscles from young and old WT and TnC-KO mice (laminin, green; eMyHC, red; DAPI, blue) (scale bar= 50 µm) and quantification of the percentage of regenerating area (eMyHC⁺) (n=3)..

(G) Quantification of migrated aged WT MuSC through transwell matrix (48 hours culture) normalized on WT young mice (n≥4)..

(H) Representative IF images of migrated cells with or without recombinant TnC treatment (timepoint= 48 hours) (DAPI, gray) (scale bar= 50 µm) and quantification of migrated aged WT MuSC through transwell matrix after TnC treatment normalized on control non-treated cells (n=4 mice)..

Data are represented as mean ± SEM; *p<0.05, **p<0.01, t test (A, C, E, G, H), *p<0.05, **p<0.005, ***p<0.0001, one-way ANOVA (D, F).