ACTA1 and chronic kidney disease: However, after 7 days of kidney ligation the fraction of αSMA+ REP cells that responded to FG‐4592 was similar to the overall fraction of αSMA positive REP cells (Figure S8C,D), suggesting that also the αSMA+ subset of recently active REP cells contributes to FG‐4592‐induced Epo production in CKD.