*4.7. Mitochondrial Superoxide Measurement*

hCPCs were plated on a confocal plate (50,000 cells per well) and incubated overnight. The following day, cells were pretreated with/without histochrome (in 2% Ham's F-12 medium) and incubated for 24 h. Cells were washed and incubated in low serum Ham's F-12 medium supplemented with 5 μM MitoSOX Red (#M36008, Thermo Fisher Scientific, Carlsbad, CA, USA ) and 100 nM Mitotracker green (#M7514, Thermo Fisher Scientific, Carlsbad, CA, USA) for 30 min. Further, the cells were washed twice with PBS prior to analysis using a Lionheart FX automated microscope (BioTek, Winooski, VT, USA).

#### *4.8. Cell Death Assay*

hCPCs were pretreated with histochrome for 24 h in low serum (2% FBS) Ham's F-12 medium. After incubation, cells were washed with PBS and exposed to 1 mM H2O2 for 4 h in low serum medium. Further, cells were harvested and suspended in 1 × annexin binding buffer supplemented with Annexin

V (AnV; BD Pharminogen, #550475, San Diego, CA, USA) and 7-AAD(BD Pharminogen, San Diego, CA, USA).
