Accelerated Endothelial to Mesenchymal Transition Increased Fibrosis via Deleting Notch Signaling in Wound Vasculature

Abstract

Skin wound healing in adults is characterized by a peak of angiogenesis followed by regression of the excessive vasculature in parallel with collagen deposition and fibrosis in the wound. We hypothesized that regressing vessels in healing wounds were in fact entering an endothelial to mesenchymal transition contributing to scarring. Using vascular-specific fate tracking (Cdh5-cre/ROSA-YFP mice), full-thickness excisional wounds were analyzed to reveal a time-dependent transition from endothelial phenotype characterized by vascular endothelial-cadherin, CD31, and CD34 toward a mesenchymal phenotype characterized by alpha-smooth muscle actin and fibroblast-specific protein 1 expression. We next conditionally ablated RBPJ in the vasculature (Rbpj/Cdh5-creROSA-YFP) to evaluate the role of canonical Notch signaling in this process. Endothelial to mesenchymal transition was clearly accelerated after the loss of Notch signaling within the vasculature. The acceleration of endothelial to mesenchymal transition resulted in delayed wound healing, increased fibrosis, and extensive scar tissue formation, with the rapid loss of key endothelial genes and proteins and upregulation of mesenchymal protein expression (alpha-smooth muscle actin and fibroblast-specific protein 1) in vessels. Our findings here uncover a cellular contributor to skin wound scarring through the process of endothelial to mesenchymal transition in skin wounds and demonstrate the importance of Notch signaling in regulating this critical process during healing.

Triggering of a Dll4–Notch1 loop impairs wound healing in diabetes

“…Interestingly, this effect is specific for diabetes, where Notch1 is overactivated, and inhibition of Notch signaling using GSIs or skin-specific Notch1 gene ablation did not affect wound healing in nondiabetic control animals. The latter observation receives support from other studies, reporting that in nondiabetic animals, there was either no effect (43) or even delaying (22,44) of the wound-healing rate when Notch signaling was blocked.…”

The Small Molecule NLRP3 Inflammasome Inhibitor MCC950 Does Not Alter Wound Healing in Obese Mice

“…What we observed was a trend toward reduced angiogenesis in our mice at D14 wounds; however, this difference was not statistically significant. Further studies investigating long-term effects on endothelial-to-mesenchymal transition (EndMT) could also be useful in studying long-term scar formation due to the reduction in NLRP3-associated inflammation [ 27 ].…”

TGF-β-Induced Endothelial to Mesenchymal Transition in Disease and Tissue Engineering

“…TGF-β and Notch signaling cooperate to induce the expression of Snail, thereby downregulating the expression of VE-cadherin and promoting EndMT (Fu et al, 2009). In contrast, Patel et al (2018) demonstrated that EC specific deletion of Notch signaling resulted in enhancement of EndMT since more CD31 − FSP + cells were detectable in skin wounds of endothelial specific transcription factor Rbpj-deficient mice. Interestingly, TGF-β1 expression was found to be increased in these CD34 − /FSP-1 + wound ECs, which suggests that TGF-β is the main driver of EndMT in mice deficient for endothelial specific Notch signaling (Patel et al, 2018).…”