Objective　　　 To investigate whether the dermal derived stem cells be activated and then participate in cutaneous wound healing in mice.　　　 Methods　　　 After full-thickness skin defect in a dimeter of 1.6 cm in the back was made

the mice were sacrificed in 1

3

5

7

9

15

and 20 d post injury after they were given an intraperitoneal injection of 125 mg/kg BrdU in 2 h before death. The labeled rapidly dividing cells (RDCs) were observed for the cell proliferation of the skin wound at different time points. Another group of mice received a single intraperitoneal injection of BrdU in 60 h after skin tissue resection

and then the normal skin or wound bed were collected in 3

5

7

9

and 15 d after injury. Label-retaining cells (LRCs) were identified at the 15th day after twice daily intraperitoneally injection of BrdU on days 1 to 3 after injury. Colony forming unit-fibroblast (CFU-F) assay and BrdU immunofluorescent staining was processed between isolated granulation tissue and normal dermal tissue cells after BrdU labeling to test the activation and participation of dermal stem cells after wounding.　　　 Results　　　 In 2 h after a single intraperitoneally injection of BrdU

few BrdU labeled cells were found only in the epidermis and outer root sheath of the hair follicle in normal skin. After wounding

epidermis

hair follicle

dermis of wound edge and granulation tissue exhibited active cell proliferation. After 3 days’ BrdU labeling

LRCs were found in granulation tissue rather than normal dermis. Further more

granulation tissue cells formed more colonies in the CFU-F assay than normal dermal cells

and BrdU labeled LRCs were observed in formed colonies of granulation tissue cells rather than normal dermal cells.　　　 Conclusion　　　 There are LRCs with stem cells characteristics existing in granulation tissue

suggesting that the dermal stem cells are activated and participate in cutaneous wound healing.