In the interfollicular epidermis, self-renewing stem cells (KSC) generate a short-lived population of transit amplifying (TA) cells that undergo terminal differentiation after a number of cell divisions. Here, we isolated KSC and highly proliferative early TA cells, based on their capacity to adhere to type IV collagen. Because in infancy epidermis appears to be immature and the barrier not fully protective, this work aims to characterize KSC and early TA cells during transition from infant to child in term of differentiation, stemness, proliferation and regenerative capacity. We report that reconstructed human epidermis (RHE) generated from infant skin is more damaged by UV irradiation, as compared to RHE from older children. Moreover, genes of differentiation and barrier increase with age, while the interfollicular stem cell genes appear to be reduced from infancy to childhood. The proliferation rate of KSC and the early TA cells is higher in infants than in children, while the capacity of forming colonies was more pronounced in KSC from infants than from children. Finally, KSC derived from 1-2 years aged infant showed more regenerative capacity in 3D skin equivalent, while child-early ETA cells express high level of involucrin and keratin 1 than infant-early TA cells. In conclusion, KSC and early ETA cells undergo substantial changes during transition from infant to child in term of differentiation, stemness and proliferation. This study reports a clear correlation between age and structural maturation of the skin barrier that becomes increasingly organized and competent during the first years of life.

ESDR331 - Characterisation of interfollicular stem cells and early TA cells during the transition from infant to child skin

50th Annual Meeting of the European Society for Dermatological Research. VIRTUAL MEETING