Figure 4.

Clonal analysis from skin biopsies and primary cultures. Clonal analysis was performed as described in Figure 3B. Human skin samples were obtained as anonymized surgical waste, typically from abdominoplasty or mammoplasty. Skin samples were cut in three parts for (1) direct cloning from intact skin, (2) direct cloning from wounded skin, (3) preparation of primary cultures. (1) Clonal analysis performed directly from the skin biopsy unveiled that the majority of clonogenic cells of intact skin generate holoclones (stem cells). (2) The epidermis was mechanically removed from the center of the biopsy to mimic a wound and the biopsy was kept in the incubator in keratinocyte growth medium (Hirsch et al. 2017). Clonal analysis, performed 24 hours later from a skin section taken in between the two edges of the wound, showed that the majority of clonogenic cells during the wound-healing process generates meroclones and paraclones (transient amplyfing progenitors). A similar distribution of clonogenic cells was detected in primary cultures (3), confirming that such cultures recapitulate a wound-healing process.