Proliferating Infantile Hemangioma Tissues and Primary Cell Lines Express Markers Associated with Endothelial-to-Mesenchymal Transition.

backgroundWe have previously shown that the endothelium of the microvessels of infantile hemangioma (IH) exhibits a hemogenic endothelium phenotype and proposed its potential to give rise to mesenchymal stem cells, similar to the development of hematopoietic cells. This endothelial-to-mesenchymal transition (Endo-MT) process involves the acquisition of a migratory phenotype by the endothelial cells, similar to epithelial-to-mesenchymal transition that occurs during neural crest development. We hypothesized that proliferating IH expresses Endo-MT-associated proteins and investigated their expression at the mRNA, protein, and functional levels.

methodsImmunohistochemical staining of paraffin-embedded sections of proliferating IH samples from 10 patients was undertaken to investigate the expression of the Endo-MT proteins Twist1, Twist2, Snail1, and Slug. Transcriptional analysis was performed for the same markers on proliferating IH tissues and CD34

resultsThe endothelium of the microvessels and the cells within the interstitium of proliferating IH tissues expressed Twist1, Twist2, and Slug proteins. Twist1 was also expressed on the pericyte layer of the microvessels, whereas Snail1 was not expressed. Both CD34

conclusionsThe expression of Endo-MT-associated proteins Twist1, Twist2, and Slug by both the endothelium of the microvessels and cells within the interstitium, and Twist1 on the pericyte layer of the microvessels of proliferating IH, suggest the presence of a process similar to Endo-MT. This may enable a tightly controlled primitive endothelium of proliferating IH to acquire a migratory mesenchymal phenotype with the ability to migrate away, providing a plausible explanation for the development of a fibrofatty residuum observed during involution of IH.