Origins, potency, and heterogeneity of skeletal muscle fibro-adipogenic progenitors—time for new definitions

Skeletal Muscle

Table 2 Summary of endogenous human skeletal muscle fibro-adipogenic progenitors

Human cell	Canonical Markers	Alternative markers	Negative markers	Localization	Differentiation potential	Additional comments	References
Embryonic-fetal FAPs	PDGFRA	DCN FN1 LUM OSR1 POSTN FAP THY1/CD90 VIM NT5E/CD73 COL1A1 COL1A2 COL3A1 PTN OGN FBLN5	PAX3 PAX7	Similar to what is found in mouse development, although not evaluated in detail	Not evaluated but probably similar to what is found in mouse development	No information about their origin, gene regulation, function, and potency	[70]^a
Adult FAPs	PDGFRA, CD34 (when negative for CD56, CD31 and CD45)	CD201 CD166 CD105 CD90 CD73 CD34 CD15 COL1A1 TCF7L2/TCF4	CD31 CD45 CD56 α7-Integrin NG2/CSPG4 RSG5	Fascia, epimysium, perimysium, and endomysium; abundant as perivascular cells	Adipocytes, myofibroblasts, osteocytes, and chondrocytes in diseased states and in vitro. Lack of myogenic potential	Increased numbers in diverse pathologies	[16]; [51]; [71]; [72]; [52]; [53, 54, 64]

^aThese other alternative markers suggested by Pyle and colleagues are based on scRNAseq data (Xi et al., [70])

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