Further examination revealed evidence that enhanced FGF2 signaling due to increased 6-O-sulfation (6-O-sufated HS is required for fibroblast growth factor receptor, FGFR, binding and FGF2 signaling) in the aging mice exhausted the quiescent SCs leading to fibrosis and sarcopenia (123). The gene discussed is FGF2; the disease is sarcopenia.