Exposure of endothelial cells to doxorubicin inhibits extracellular matrix production by dermal fibroblasts in a paracrine manner.

Doxorubicin (Dox) is a potent chemotherapeutic with known vascular toxicity and connective-tissue damage. Endothelial cells (EC) and fibroblasts crosstalk is essential for vascular homeostasis and extracellular matrix (ECM) remodeling. This study aimed to explore whether Dox induces endothelial-to-mesenchymal transition (EndMT) and the paracrine effects of Dox-exposed EC on fibroblasts activation, senescence, and ECM synthesis. Human umbilical vein endothelial cells (HUVECs) were treated with Dox, and conditioned medium (CM) from EC was applied to human dermal fibroblasts for short- and long-term culture. Dox induced EndMT in ECs. Fibroblasts exposed to CM from Dox-treated EC exhibited early activation with increased fibroblast activation protein (FAP) and α-smooth muscle actin (α-SMA) at day 3, followed by a progressive senescent phenotype marked by elevated p21 and reduced Lamin B1 at day 21. ECM formation was impaired, with reduced collagen and increased transcriptional expression of matrix-degrading enzymes (MMP1 and MMP9). Cytokines profiling of the CM revealed decreased interleukin-1β (IL-1β), C-C motif ligand 2 (CCL2), and C-X-C motif ligand 10 (CXCL10), and elevated interleukin-6 (IL-6) levels. These findings demonstrate that exposure of EC to Dox induced endothelial dysfunction and elicited pathological paracrine signaling, driving fibroblast activation, myofibroblast transition, senescence, and ECM disruption. This mechanism may underlie Dox-related skin aging and delayed wound healing, and emphasizes the importance of endothelial dysfunction in chemotherapy-associated connective tissue damage and impaired repair.