TERT and systemic sclerosis: Therefore, in order to assess the therapeutic effect of TERT−/− BMMSCs, we infused either regular BMMSCs (WT; from TERT+/+ littermates) or TERT−/− BMMSCs into B6.Cg-Fbn1Tsk/J (Tsk/+) systemic sclerosis (SS) mice at 8 weeks of age and analyzed treatment response at 12 weeks of age (Fig 2A).