The secretome of aged fibroblasts promotes EMT-like phenotype in primary keratinocytes from elderly donors through BDNF-TrkB axis.

Abstract Age-related changes in the dermis can play a primary role in tumor initiation promoting the unrestrained proliferation of precancerous keratinocytes through cytokines and growth factor secretion. We found that a high percentage of epithelial-mesenchymal transition (EMT)-like colonies raised in primary human keratinocyte cultures from old subjects after treatment with aged fibroblast supernatants (SPN). Continuous extracellular signals were required for maintaining these changes. Conversely, the secretome did not induce EMT-like colonies in keratinocytes from youngs. SPN-treated aged keratinocytes displayed the activation of pathways involved in the disjunction of cell-cell adhesion, ECM remodeling, manifestation of mesenchymal phenotype and dedifferentiation programs. Moreover, they recovered proliferation and clonogenic ability, and showed enhanced migration. We identified an age-related increase of the BDNF secretion from fibroblasts as well as of the expression of its receptor TrkB in keratinocytes. BDNF-treatment of aged keratinocytes induces TrkB phosphorylation and recapitulated modifications promoted by aged fibroblast SPN. Furthermore, the treatment with a specific antibody against BDNF or a TrkB antagonist inhibited the paracrine signaling preventing SPN-mediated morphological and molecular changes. Finally, BDNF induced signs of matrix invasion in a 3D organotypic model. Therefore, we demonstrate that aged fibroblast SPN promotes phenotypic plasticity in keratinocytes from the elderly through BDNF-TrkB axis.