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Contribution of minced muscle graft progenitor cells to muscle fiber formation after volumetric muscle loss injury in wild ‐ type and immune deficient mice

View Article: PubMed Central - PubMed

ABSTRACT

Volumetric muscle injury (VML) causes an irrecoverable loss of muscle fibers, persistent strength deficits, and chronic disability. A crucial challenge to VML injury and possible regeneration is the removal of all of the in situ native elements necessary for skeletal muscle regeneration. Our first goal was to establish a reliable VML model in the mouse tibialis anterior (TA) muscle. In adult male wild‐type and nude mice, a non‐repaired ≈20% VML injury to the TA muscle resulted in an ≈59% loss in nerve evoked muscle strength, ≈33% loss in muscle mass, and ≈29% loss of muscle fibers at 28 day post‐injury. Our second goal was to investigate if minced muscle grafts (≈1 mm3 tissue fragments) promote recovery of muscle fibers after VML injury and to understand if the graft‐derived progenitor cells directly contribute to fiber regeneration. To assess donor cell contribution, donor muscle tissue was derived from UBC‐GFP mice in a subset of experiments. Minced grafts restored ≈34% of the lost fibers 28 days post‐injury. The number of GFP+ fibers and the estimated number of regenerated fibers were similar, regardless of host mouse strain. The muscle tissue regeneration promoted by minced grafts did not improve TA muscle strength at this time post‐injury. These findings demonstrate the direct contribution of minced muscle graft‐derived myogenic stem/progenitor cells to recovery of muscle fibers after VML injury and signify the utility of autologous myogenic stem cell therapies for this indication.

No MeSH data available.


Minced muscle graft‐derived muscle progenitor cells directly contribute to muscle fiber regeneration after repair of VML injury. TA muscles were harvested at 28 days post‐injury. (A) Biological replicates of whole TA muscle cross‐sections stained with Hematoxylin and Eosin are presented from wild‐type mice with UBC‐GFP minced graft repair. Scale bar = 400 μm. (B) Corresponding images of GFP expression in each replicate shown above. White lines define the boundaries of the cross‐section. Scale bar = 200 μm. (C) Whole TA muscle fiber number plotted per experimental group with wild type and nude observations collapsed based on a separate statistical analysis (Sample Sizes [Wild Type, Nude, Group Total]: Contralateral (3, 3, 6), No Repair (4, 4, 8), and Minced Graft (3, 3, 6). The No Repair group data is represented in this and Fiure 1 for comparison. One‐way ANOVA demonstrated an experimental group effect (P < 0.001). *, <Contralateral; †, <Minced Graft; P < 0.05. (D) Total estimated (see methods) number of regenerated muscle fibers and GFP+ muscle fibers. No statistical difference was observed (P = 0.232).
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phy213249-fig-0002: Minced muscle graft‐derived muscle progenitor cells directly contribute to muscle fiber regeneration after repair of VML injury. TA muscles were harvested at 28 days post‐injury. (A) Biological replicates of whole TA muscle cross‐sections stained with Hematoxylin and Eosin are presented from wild‐type mice with UBC‐GFP minced graft repair. Scale bar = 400 μm. (B) Corresponding images of GFP expression in each replicate shown above. White lines define the boundaries of the cross‐section. Scale bar = 200 μm. (C) Whole TA muscle fiber number plotted per experimental group with wild type and nude observations collapsed based on a separate statistical analysis (Sample Sizes [Wild Type, Nude, Group Total]: Contralateral (3, 3, 6), No Repair (4, 4, 8), and Minced Graft (3, 3, 6). The No Repair group data is represented in this and Fiure 1 for comparison. One‐way ANOVA demonstrated an experimental group effect (P < 0.001). *, <Contralateral; †, <Minced Graft; P < 0.05. (D) Total estimated (see methods) number of regenerated muscle fibers and GFP+ muscle fibers. No statistical difference was observed (P = 0.232).

Mentions: To assess the contribution of minced graft donor cell contribution to muscle fiber regeneration after VML injury, a second experiment was performed in which minced grafts were derived from UBC‐GFP mice. When assessing the total number of muscle fibers in contralateral, injured non‐repaired, and injured minced graft‐repaired groups from wild‐type and nude mice, the results were similar to those observed with autologous repair. There were no differences between strains. Non‐repaired muscles presented a ≈26% decrease in fiber number and UBC‐GFP minced graft repair promoted a ≈11% increase compared to non‐repaired muscles, leaving a ≈18% residual loss of fibers compared to contralateral controls (Fig. 2). In these samples, the estimated number of fibers regenerated by minced graft repair was 243 ± 55 fibers. The number of GFP+ fibers counted in each UBC‐GFP repaired TA muscle was 284 ± 46 fibers, indicating that the muscle progenitor cells in donor minced muscle grafts were the primary contributor to muscle fiber regeneration in VML injured muscle (Fig. 2).


Contribution of minced muscle graft progenitor cells to muscle fiber formation after volumetric muscle loss injury in wild ‐ type and immune deficient mice
Minced muscle graft‐derived muscle progenitor cells directly contribute to muscle fiber regeneration after repair of VML injury. TA muscles were harvested at 28 days post‐injury. (A) Biological replicates of whole TA muscle cross‐sections stained with Hematoxylin and Eosin are presented from wild‐type mice with UBC‐GFP minced graft repair. Scale bar = 400 μm. (B) Corresponding images of GFP expression in each replicate shown above. White lines define the boundaries of the cross‐section. Scale bar = 200 μm. (C) Whole TA muscle fiber number plotted per experimental group with wild type and nude observations collapsed based on a separate statistical analysis (Sample Sizes [Wild Type, Nude, Group Total]: Contralateral (3, 3, 6), No Repair (4, 4, 8), and Minced Graft (3, 3, 6). The No Repair group data is represented in this and Fiure 1 for comparison. One‐way ANOVA demonstrated an experimental group effect (P < 0.001). *, <Contralateral; †, <Minced Graft; P < 0.05. (D) Total estimated (see methods) number of regenerated muscle fibers and GFP+ muscle fibers. No statistical difference was observed (P = 0.232).
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phy213249-fig-0002: Minced muscle graft‐derived muscle progenitor cells directly contribute to muscle fiber regeneration after repair of VML injury. TA muscles were harvested at 28 days post‐injury. (A) Biological replicates of whole TA muscle cross‐sections stained with Hematoxylin and Eosin are presented from wild‐type mice with UBC‐GFP minced graft repair. Scale bar = 400 μm. (B) Corresponding images of GFP expression in each replicate shown above. White lines define the boundaries of the cross‐section. Scale bar = 200 μm. (C) Whole TA muscle fiber number plotted per experimental group with wild type and nude observations collapsed based on a separate statistical analysis (Sample Sizes [Wild Type, Nude, Group Total]: Contralateral (3, 3, 6), No Repair (4, 4, 8), and Minced Graft (3, 3, 6). The No Repair group data is represented in this and Fiure 1 for comparison. One‐way ANOVA demonstrated an experimental group effect (P < 0.001). *, <Contralateral; †, <Minced Graft; P < 0.05. (D) Total estimated (see methods) number of regenerated muscle fibers and GFP+ muscle fibers. No statistical difference was observed (P = 0.232).
Mentions: To assess the contribution of minced graft donor cell contribution to muscle fiber regeneration after VML injury, a second experiment was performed in which minced grafts were derived from UBC‐GFP mice. When assessing the total number of muscle fibers in contralateral, injured non‐repaired, and injured minced graft‐repaired groups from wild‐type and nude mice, the results were similar to those observed with autologous repair. There were no differences between strains. Non‐repaired muscles presented a ≈26% decrease in fiber number and UBC‐GFP minced graft repair promoted a ≈11% increase compared to non‐repaired muscles, leaving a ≈18% residual loss of fibers compared to contralateral controls (Fig. 2). In these samples, the estimated number of fibers regenerated by minced graft repair was 243 ± 55 fibers. The number of GFP+ fibers counted in each UBC‐GFP repaired TA muscle was 284 ± 46 fibers, indicating that the muscle progenitor cells in donor minced muscle grafts were the primary contributor to muscle fiber regeneration in VML injured muscle (Fig. 2).

View Article: PubMed Central - PubMed

ABSTRACT

Volumetric muscle injury (VML) causes an irrecoverable loss of muscle fibers, persistent strength deficits, and chronic disability. A crucial challenge to VML injury and possible regeneration is the removal of all of the in&nbsp;situ native elements necessary for skeletal muscle regeneration. Our first goal was to establish a reliable VML model in the mouse tibialis anterior (TA) muscle. In adult male wild&#8208;type and nude mice, a non&#8208;repaired &asymp;20% VML injury to the TA muscle resulted in an &asymp;59% loss in nerve evoked muscle strength, &asymp;33% loss in muscle mass, and &asymp;29% loss of muscle fibers at 28&nbsp;day post&#8208;injury. Our second goal was to investigate if minced muscle grafts (&asymp;1&nbsp;mm3 tissue fragments) promote recovery of muscle fibers after VML injury and to understand if the graft&#8208;derived progenitor cells directly contribute to fiber regeneration. To assess donor cell contribution, donor muscle tissue was derived from UBC&#8208;GFP mice in a subset of experiments. Minced grafts restored &asymp;34% of the lost fibers 28&nbsp;days post&#8208;injury. The number of GFP+ fibers and the estimated number of regenerated fibers were similar, regardless of host mouse strain. The muscle tissue regeneration promoted by minced grafts did not improve TA muscle strength at this time post&#8208;injury. These findings demonstrate the direct contribution of minced muscle graft&#8208;derived myogenic stem/progenitor cells to recovery of muscle fibers after VML injury and signify the utility of autologous myogenic stem cell therapies for this indication.

No MeSH data available.