Cloning efficiency of CPSCs. A–C, morphology of colonies formed by CPSCs from P3, P15, and P25 after 7 days of culture (100×). D, bar chart showing the cloning rates for CPSCs from P3, P15, P25; the colony-forming levels were 28.67 ± 2.87%, 23.33 ± 1.7%, and 18.67 ± 1.7%, respectively.