Barriers in contribution of human mesenchymal stem cells to murine muscle regeneration

Figure 1 Histological analysis of subcutaneous murine muscle implants. A: Representative images of HPS-stained (upper panel) and desmin-stained (lower panel) sections of a cryopreserved mouse mince muscle implant at 30 d after implantation. From top to bottom are visible the skin layers (epidermis, dermis and hypodermis), the panniculus carnosus muscle (PC, arrow), a thin layer of connective tissue surrounding the implant (light yellow, arrowhead) and tissues composing the implant (e.g., adipose, skeletal muscle, nerves and other tissues). The intense brown desmin stain (lower panel) identifies myofibers of the PC (host) and myoblasts as well as regenerating myofibers of the implant. Scale bar is 500 μm; B: Higher magnifications of the marked areas in A. (1 and 4), connective tissue encapsulating the implant (asterisk). Arrows indicate PC. (2 and 5), adipose tissue and myoblast/myofibers in the central part of the implant. (3 and 6), areas of regeneration with myofibers positioned at different angles. Scale bar is 100 μm; C: Exemplary areas showing specific cells and structures as observed both in fresh and cryopreserved implants. For each pair of images the upper panels correspond to HPS- and desmin-stained tissue sections, respectively. (1, 5, 2 and 6), myoblasts and newly formed myofibers of different sizes and positioned at different angles. (3, 7, 4 and 8), blood vessels (asterisks) and nerves (n) usually located at the edges of the implants. (9, 13, 10 and 14), areas of active regeneration with centronucleated myofibers of different sizes. (11 and 15), degenerated myofibers devoid of nuclei and desmin. (12 and 16), myoregeneration within an adipogenic area. Scale bar is 100 μm for 1-8 and 50 μm for 9-16 is 50 μm. Note the images of HPS- and desmin-stained tissue sections do not always show overlapping areas.