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Figure 3. Schematic representation of T-oligo-mediated photoprotective effects in human skin. I) Before UV irradiation, T-oligo induces epidermal pigmentation (an effect without prior DNA damage). II) Immediately after UV irradiation in control explants, all keratinocytes, including those in the basal layer with its presumptive stem cells (shown in green), are substantially UV damaged (shown in yellow), whereas in T-oligo-treated explants, basal and suprabasal ketatinocytes are largely protected from the same initial UV damage by T-oligo-induced pigmentation. III) 24–48 h after UV irradiation in control-treated explants, after the UV-induced transient growth arrest, epidermal keratinocytes, including those in the basal layer, begin to proliferate (shown in red) before the removal of DNA damage is completed, whereas UV-induced growth arrest is prolonged in T-oligo-treated skin and there is more rapid removal of UV-induced photoproducts (CPDs). IV) 72 h after UV irradiation in control-treated explants, many epidermal keratinocytes, including those in the basal layer, proliferate (shown in red), a phenomenon known as UV-induced "hyperprolifertive rebound" while the UV-induced DNA damage persists, whereas UV-induced growth arrest is prolonged in T-oligo-treated explants and removal of UV-induced photoproducts (CPDs) is substantially complete.
