Stem Cell Reports Article Combined Notch and PDGF Signaling Enhances Migration and Expression of Stem Cell Markers while Inducing Perivascular Cell Features in Muscle Satellite Cells Mattia Francesco Maria Gerli, 1,2,15 Louise Anne Moyle, 1,9,15 Sara Benedetti, 1,3,4 Giulia Ferrari, 1 Ekin Ucuncu, 1,10 Martina Ragazzi, 1,11 Chrystalla Constantinou, 1,12 Irene Louca, 1,13 Hiroshi Sakai, 5,6,14 Pierpaolo Ala, 7 Paolo De Coppi, 2 Shahragim Tajbakhsh, 5,6 Giulio Cossu, 8 and Francesco Saverio Tedesco 1,7, * 1 Department of Cell and Developmental Biology, University College London, WC1E 6DE London, UK 2 Stem Cell and Regenerative Medicine Section, Great Ormond Street Institute of Child Health, University College London, WC1N 1EH London, UK 3 Molecular and Cellular Immunology Section, Great Ormond Street Institute of Child Health, University College London, WC1N 1EH London, UK 4 NIHR Great Ormond Street Hospital Biomedical Research Centre, WC1N 1EH London, UK 5 Department of Developmental & Stem Cell Biology, Institut Pasteur, 75015 Paris, France 6 CNRS UMR 3738, Institut Pasteur, 75015 Paris, France 7 The Dubowitz Neuromuscular Centre, Great Ormond Street Institute of Child Health, University College London, WC1N 1EH London, UK 8 Division of Cell Matrix Biology and Regenerative Medicine, University of Manchester, M13 9PL Manchester, UK 9 Present address: Institute of Biomaterials and Biomedical Engineering, University of Toronto, M5S 3E1 Toronto, Canada 10 Present address: Institut Imagine, INSERM UMR 1163, Paris Descartes-Sorbonne Paris Cite ´ Universite ´, Paris 75015, France 11 Present address: MolMed S.p.A., 20132 Milan, Italy 12 Present address: National Heart and Lung Institute, Imperial College London, SW3 6LY London, UK 13 Present address: Division of Neuroscience and Experimental Psychology, University of Manchester, M13 9PL Manchester, UK 14 Present address: Division of Integrative Pathophysiology, Proteo-Science Center, Ehime University, Toon, Ehime 791-0295, Japan 15 Co-first author *Correspondence: f.s.tedesco@ucl.ac.uk https://doi.org/10.1016/j.stemcr.2019.01.007 SUMMARY Satellite cells are responsible for skeletal muscle regeneration. Upon activation, they proliferate as transient amplifying myoblasts, most of which fuse into regenerating myofibers. Despite their remarkable differentiation potential, these cells have limited migration capacity, which curtails clinical use for widespread forms of muscular dystrophy. Conversely, skeletal muscle perivascular cells have less myogenic potential but better migration capacity than satellite cells. Here we show that modulation of Notch and PDGF pathways, involved in developmental specification of pericytes, induces perivascular cell features in adult mouse and human satellite cell-derived myoblasts. DLL4 and PDGF-BB-treated cells express markers of perivascular cells and associate with endothelial networks while also upregulating markers of satellite cell self-renewal. Moreover, treated cells acquire trans-endothelial migration ability while remaining capable of engrafting skeletal muscle upon intramuscular transplantation. These results extend our understanding of muscle stem cell fate plasticity and provide a druggable pathway with clinical relevance for muscle cell therapy. INTRODUCTION Skeletal muscle homeostasis and regeneration rely on resi- dent stem cells named satellite cells (SCs), which reside un- derneath the basal lamina of the myofibers and express the transcription factor Pax7. Upon injury, activated SCs generate transient amplifying precursors called myoblasts, which fuse to form multinucleated myofibers (Sambasivan and Tajbakhsh, 2015). The regenerative capacity of SCs has led to the development of cellular therapies to replace lost or damaged muscle (Tedesco et al., 2010). Despite some promising pre-clinical results and a good safety profile, clinical trials based upon intramuscular myoblast trans- plantation in patients with Duchenne muscular dystrophy (DMD) have reported limited efficacy (Briggs and Morgan, 2013). This outcome has been ascribed to the poor survival of myoblasts, their limited ability to migrate, and the host immune reaction (Partridge, 2002), although this is still a matter of active debate (Skuk and Tremblay, 2014). More recently, local delivery of myoblasts to affected muscles in oculopharyngeal muscular dystrophy patients has shown encouraging results (Perie et al., 2014). Neverthe- less, myoblasts are considered unsuitable for systemic delivery, preventing their use for the treatment of patients affected by severe myopathies with widespread muscle involvement such as DMD. Perivascular cells (pericytes in particular) support skeletal muscle perfusion, development, and regeneration (Birbrair and Delbono, 2015; Cappellari and Cossu, 2013; Murray et al., 2017). Despite evidence in transgenic mice showing that SCs (Relaix and Zammit, 2012) and not pericytes (Gui- maraes-Camboa et al., 2017) are required for muscle regener- ation, there are reports indicating that pericyte-derived cells can also contribute to skeletal myogenesis, including SC generation and maintenance (Dellavalle et al., 2011, 2007; Kostallari et al., 2015; Sacchetti et al., 2016; Tedesco et al., 2011). Discrepancies among reports may be due to the use of different markers to identify interstitial/perivascular cells Stem Cell Reports j Vol. 12 j 461–473 j March 5, 2019 j ª 2019 The Authors. 461 This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).