Regenerating human skeletal muscle forms an emerging niche in vivo to support PAX7 cells

Michael R Hicks; Kholoud K Saleh; Ben Clock; Devin E Gibbs; Mandee Yang; Shahab Younesi; Lily Gane; Victor Gutierrez-Garcia; Haibin Xi; April D Pyle

doi:10.1038/s41556-023-01271-0

Regenerating human skeletal muscle forms an emerging niche in vivo to support PAX7 cells

Nat Cell Biol. 2023 Dec;25(12):1758-1773. doi: 10.1038/s41556-023-01271-0. Epub 2023 Nov 2.

Authors

Michael R Hicks^{1

2

3}, Kholoud K Saleh^{4

5}, Ben Clock⁶, Devin E Gibbs^{4

7}, Mandee Yang⁸, Shahab Younesi^{4

8}, Lily Gane⁸, Victor Gutierrez-Garcia⁹, Haibin Xi^{4

8}, April D Pyle^{10

11

12

13}

Affiliations

¹ Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research, University of California, Los Angeles, CA, USA. mrhicks1@uci.edu.
² Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, CA, USA. mrhicks1@uci.edu.
³ Physiology and Biophysics, University of California, Irvine, CA, USA. mrhicks1@uci.edu.
⁴ Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research, University of California, Los Angeles, CA, USA.
⁵ Molecular, Cellular & Integrative Physiology Program, University of California, Los Angeles, CA, USA.
⁶ Physiology and Biophysics, University of California, Irvine, CA, USA.
⁷ Molecular Biology Institute, University of California, Los Angeles, CA, USA.
⁸ Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, CA, USA.
⁹ CIRM Bridges Program, California State University, Northridge, CA, USA.
¹⁰ Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research, University of California, Los Angeles, CA, USA. apyle@mednet.ucla.edu.
¹¹ Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, CA, USA. apyle@mednet.ucla.edu.
¹² Molecular Biology Institute, University of California, Los Angeles, CA, USA. apyle@mednet.ucla.edu.
¹³ Jonnson Comprehensive Cancer Center, University of California, Los Angeles, CA, USA. apyle@mednet.ucla.edu.

Abstract

Skeletal muscle stem and progenitor cells including those derived from human pluripotent stem cells (hPSCs) offer an avenue towards personalized therapies and readily fuse to form human-mouse myofibres in vivo. However, skeletal muscle progenitor cells (SMPCs) inefficiently colonize chimeric stem cell niches and instead associate with human myofibres resembling foetal niches. We hypothesized competition with mouse satellite cells (SCs) prevented SMPC engraftment into the SC niche and thus generated an SC ablation mouse compatible with human engraftment. Single-nucleus RNA sequencing of SC-ablated mice identified the absence of a transient myofibre subtype during regeneration expressing Actc1. Similarly, ACTC1⁺ human myofibres supporting PAX7⁺ SMPCs increased in SC-ablated mice, and after re-injury we found SMPCs could now repopulate into chimeric niches. To demonstrate ACTC1⁺ myofibres are essential to supporting PAX7 SMPCs, we generated caspase-inducible ACTC1 depletion human pluripotent stem cells, and upon SMPC engraftment we found a 90% reduction in ACTC1⁺ myofibres and a 100-fold decrease in PAX7 cell numbers compared with non-induced controls. We used spatial RNA sequencing to identify key factors driving emerging human niche formation between ACTC1⁺ myofibres and PAX7⁺ SMPCs in vivo. This revealed that transient regenerating human myofibres are essential for emerging niche formation in vivo to support PAX7 SMPCs.

MeSH terms

Animals
Humans
Mice
Muscle, Skeletal* / physiology
PAX7 Transcription Factor* / genetics
PAX7 Transcription Factor* / metabolism
Pluripotent Stem Cells
Regeneration*
Satellite Cells, Skeletal Muscle* / physiology

Substances

PAX7 protein, human
PAX7 Transcription Factor

Abstract

MeSH terms

Substances

Grants and funding