FIG. 6.

Muscle recovery with 28-day implantation of combined SMU. H&E images of explanted TA muscles indicated (A) minimal regeneration in animals subjected to a VML deficit alone, in comparison to (C) those receiving an engineered tdT SMU implant. IHC for myosin heavy chains (MF20, recolored in red), laminin (green), and DAPI (blue) (B) demonstrated substantial extracellular matrix deposition in the VML Only group and (D) indicated some formation of distinct muscle fibers in the VML+SMU group. It is important to note that the MF20 was labeled with a far red antibody to avoid potential overlap with the tdT signal. Arrows indicate the suture landmarks used to locate the VML defect or SMU implant and differ in color only to provide visible contrast. (I) There was no significant difference in the size of VML defect between VML Only (101 ± 10 mg) and VML+SMU (91 ± 8.0 mg) subjects. (E–H) Show higher magnification H&E and IHC images of the implanted tissue from two other animals. All images are serial sections to those in Figure 5. (J) Implantation of the combined SMU did lead to a significant decrease in the size of the VML deficit following 28 days of recovery, with the VML Only deficit remaining largely unchanged at 105 ± 14 mg and the VML+SMU deficit falling to 60 ± 14 mg. This decrease can partially be attributed to the added mass of the engineered tissue itself, but the formation of muscle fibers in the implant area suggests some degree of myogenesis due to the SMU. (K) Quantification of CSA indicated that regenerating fibers in the implant area (166 ± 16 μm²) were ∼9.5% of the average CSA of control native fibers, 1931 ± 216 μm². # indicates significant different from VML Only or Native control (p < 0.05). CSA, cross-sectional area; H&E, Hematoxylin and Eosin; IHC, immunohistochemical.