Fig. 2: Stem and progenitor cells generate different niches, and the ability to enter the niche changes as development proceeds.
From: Regenerating human skeletal muscle forms an emerging niche in vivo to support PAX7 cells
a. Human skeletal muscle tissues show foetal and adult PAX7 + SMPC/SCs in niches compared with hPSC SMPC engraftment. Immunofluorescent images show PAX7 (green), spectrin (red), laminin (grey) and 4′,6-diamidino-2-phenylindole (DAPI) (blue). Engrafted hPSC SMPCs are also stained with lamin AC (red) to identify human cells. N = 3 human tissue samples. Scale bar, 20 μm. b, Over time, PAX7 SMPCs associate within the basal lamina niches through association with human-only myofibres, which generate myofibre bundles integrated with spectrin cross bridges (arrows). Scale bar, 10 μm (left). Phenotypically, hPSC SMPC niches resemble foetal SMPC niches in vivo with formation of spectrin cross bridges within the myofibre bundles. Scale bar, 5 μm (right). c, Dynamics of SC niche occupancy by PAX7+ SCs and SMPCs 30 days post engraftment. Immunofluorescent images show representative location of PAX7 cells in chimeric SC niches, outside of chimeric SC niches, near human myofibres, or no niche interstitial space. Shown are PAX7 (green), lamin AC and spectrin (red), laminin (grey) and DAPI (blue). Scale bar, 5 μm. Graph of percentage mean ± standard error of the mean shows that adult SCs are better able to reside in niches of chimeric myofibres, while hPSC and foetal SMPCs are less efficient. N = 6 adult, N = 9 foetal, N = 14 hPSC SMPC engrafted tissues.
