Figure 4. Functionality of PAX7::GFP MPCs in muscle regeneration of NSG and NSG-mdx mice.

(A) Schematic of reinjury experiment of NSG mice. (B) huDystrophin and huLaminA/C expression in TAs engrafted with PAX7::GFP+ cells and repetitively injured. Scale bar=500μm (C-D) Quantification of huDystrophin+ fiber number and the percentage of area in TA in reinjury experiment (n(PAX7::GFP MPC)=7, n(Control)=3; Student’s t-test, *p<0.05). (E) Schematic of serial transplantation using NSG mice. (F) PAX7::GFP+ cells were isolated from the first recipient mouse and transplanted into the second recipient mouse. TAs of the second recipient mice were sectioned and Pax7 and huLaminA/C were used to trace transplanted cells. The co-labeled cells were found to reside within the basal lamina (yellow arrow). Scale bar=100μm (G) Quantification of huDystrophin+ fibers from the entire TA (n(Control)=3, n(1^st transplantation)=6, n(2^nd transplantation)=4; One-way ANOVA, *p<0.05). (H) Quantification of ratio of huDystrophin+ fibers to cell number being injected (n(Control)=3, n(1^st transplantation)=6, n(2^nd transplantation)=4; One-way ANOVA, **p<0.01). (I) Quantification of cells located between muscle fiber and basal lamina (huLaminin labeled) that originated from PAX7::GFP MPCs (Pax7+, huLaminA/C+) after 1^st or 2^nd transplantation, as a proportion of the total number of PAX7::GFP MPCs transplanted. (n=3; Student’s t-test, **p<0.001). (J) Schematic of PAX7::GFP MPCs transplantation into NSG-mdx mice. (K) Images of PAX7::GFP MPCs formed huDystrophin+ muscle fibers in TAs, gastrocnemius (Gas), and quadriceps (Quad). Scale bar=50μm (L) Quantification of huDystrophin+ fibers in TA, Gas, and Quad in NSG-mdx mice. (n(Control)=4, n(PAX7::GFP MPC)=5; Student’s t-test, *p<0.05). (M) Treadmill running exhaustion test showing PAX7::GFP MPC transplanted NSG-mdx mice ran longer distance than medium-injected control mice (n(PAX7::GFP MPC)=9, n(Control)=8; Student’s t-test, *p<0.05). Result=Mean±SEM. See also Figure S4.