Corrigendum to: 'Mesenchymal stromal cells-exosomes: a promising cell-free therapeutic tool for wound healing and cutaneous regeneration'. Issue 1 (23rd January 2020) - Hu, Peng; Yang, Qinxin; Wang, Qi; Shi, Chenshuo; Wang, Dali; Armato, Ubaldo; Prà, Ilaria Dal; Chiarini, Anna