Prospective isolation of skeletal muscle stem cells with a Pax7 reporter

D Bosnakovski, Z Xu, W Li, S Thet, O Cleaver… - Stem …, 2008 - academic.oup.com
Stem cells, 2008academic.oup.com
Muscle regeneration occurs through activation of quiescent satellite cells whose progeny
proliferate, differentiate, and fuse to make new myofibers. We used a transgenic Pax7-
ZsGreen reporter mouse to prospectively isolate stem cells of skeletal muscle by flow
cytometry. We show that Pax7-expressing cells (satellite cells) in the limb, head, and
diaphragm muscles are homogeneous in size and granularity and uniformly labeled by
certain cell surface markers, including CD34 and CD29. The frequency of the satellite cells …
Abstract
Muscle regeneration occurs through activation of quiescent satellite cells whose progeny proliferate, differentiate, and fuse to make new myofibers. We used a transgenic Pax7-ZsGreen reporter mouse to prospectively isolate stem cells of skeletal muscle by flow cytometry. We show that Pax7-expressing cells (satellite cells) in the limb, head, and diaphragm muscles are homogeneous in size and granularity and uniformly labeled by certain cell surface markers, including CD34 and CD29. The frequency of the satellite cells varies between muscle types and with age. Clonal analysis demonstrated that all colonies arising from single cells within the Pax7-sorted fraction have myogenic potential. In response to injury, Pax7+ cells reduce CD34, CD29, and CXCR4 expression, increase in size, and acquire Sca-1. When directly isolated and cultured in vitro, Pax7+ cells display the hallmarks of activation and proliferate, initially as suspension aggregates and later distributed between suspension and adherence. During in vitro expansion, Pax7 (ZsGreen) and CD34 expression decline, whereas expression of PSA-NCAM is acquired. The nonmyogenic, Pax7neg cells expand as Sca1+ PDGRα+ PSA-NCAMneg cells. Satellite cells expanded exclusively in suspension can engraft and produce dystrophin+ fibers in mdx−/− mice. These results establish a novel animal model for the study of muscle stem cell physiology and a culture system for expansion of engraftable muscle progenitors.
Disclosure of potential conflicts of interest is found at the end of this article.
Oxford University Press