Infantile Hemangiomas Lose Vascular Endothelial Cadherin During Involution: Potential Role in Cell Death?

BACKGROUND

Infantile hemangiomas (IHs) are benign endothelial cell (EC) tumors that undergo a predictable natural history, with rapid proliferation, stabilization, and involution. However, mechanisms regulating these transitions are not well understood. We have observed loss of vascular endothelial cadherin (VECAD) in involuting/involuted IHs. VECAD plays a critical role in angiogenesis, cell cycle progression, and EC survival. We hypothesize that loss of VECAD is associated with apoptosis occurring during IH involution.

METHODS

Resected IH samples were clinically categorized as proliferating (n = 4), stable (n = 4), or involuting/involuted (n = 5). Neonatal dermal tissues were used as controls (n = 5). Immunohistochemistry was conducted on sectioned specimens using antibodies against EC markers VECAD and CD31. Apoptosis was assessed with terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling assay.

RESULTS

CD31 signal intensity in proliferating, stable, and involuting/involuted IH ECs was unchanged relative to each other and to control ECs. VECAD signal significantly and progressively diminished as IHs progressed from proliferation to involution. Involuting/involuted IHs had significantly reduced VECAD expression compared with control ECs ( < 0.0001), proliferating IHs ( < 0.0001), and stable IHs ( < 0.001). As expected, the number of terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling-positive ECs was significantly higher in involuting/involuted IHs ( < 0.05) relative to control ECs and proliferating IHs.

CONCLUSIONS

Loss of VECAD expression in IH endothelium corresponded to IH involution and increased apoptosis. It is unclear whether loss of VECAD is causative of IH involution; further studies are needed to elucidate the role of VECAD function in EC survival.