Porcine urinary bladder extracellular matrix activates skeletal myogenesis in mouse muscle cryoinjury

Background: Accelerated muscle regeneration is highly desirable after direct injury in trauma patients. Though the advantage of extracellular matrix extracted from porcine urine bladder (UBM) on tissue regeneration is feasible, the mechanisms by which skeletal myogenesis is improved are not clear. The current study aim was to determine whether UBM affects skeletal satellite cells during muscle repair after cryoinjury. Methods: RAG2-/-, γc-/mice underwent bilateral gluteus muscle cryoinjury under general anesthesia. 200μg UBM suspended in 20 μl of Matrigel solution was implanted on one side of the wound intramuscularly, and 20μl of vehicle was applied on the contralateral side as a sham treatment. Five animals without any operation served as baseline. Mice were sacrificed from days 1 to 28 after injury for muscle tissue collection. Tissue morphology was estimated via H&E staining. Satellite cell proliferation was examined by immunofluorescence staining and western blot. Myogenesis markers were assessed by qPCR. Results: H&E staining results showed that muscle regeneration area increased in both sham and UBM treated muscles following injury. The number of regenerating myotubes was significantly higher in UBM treated tissue at 28 days (p<0.05, vs. sham group). Both Pax7+ and Ki-67+ satellite cell number significantly increased in muscle with UBM treatment compared to sham treated muscles (p<0.05). Protein levels of proliferating cell nuclear antigen (PCNA) were greater in muscle with UBM treatment at day 14 and 28 (p<0.05). MyoD1 and myogenin mRNA levels were also significantly higher in UBM treated animal muscle at day 28 (p<0.05). Conclusion: UBM treatment increased skeletal satellite cell proliferation and myogenic differentiation at 28 days after local muscle injury.