| BackgroundInfantile hemangioma (IH) is a benign vascular tumor that exhibits a unique yet predictable lifecycle of rapid proliferation followed by spontaneous regression. Recent studies have identified that hamangioma is composed of stem cells (HemSCs), endothelial cells (HemECs) and pericytes, but the pathogenesis and origin is still unclear. It is believed to origin from hemangioma stem cells, which differentiate toward hemangioma endothelial cell phenotype. The therapeutic effect of beta-blockers on IH was discovered serendipitously and propranolol was quickly propelled first-line treatment of complicated IH, but the exact mechanism remains enigmatic, the effect of propranolol on HemSCs is still unknown. We investigate the effect of propranolol on HemSCs to explain the mechanism of propranolol treating IH.Objective1. To detect the expression of β1-AR,β2-AR on HemSCs.2. To observe the role of propranolol in proliferation and differentiation of HemSCs.3. Explain the origin of IH and mechanism of propranolol treating IH by stem cell hypothesis.Methods1. Specimens of proliferative infantile hemangioma (≤8month; untreated) were obtained from Department of Stomotology in Qilu hospital Shandong University. The expression of GLUT1was tested by immunohistochemistry (IHC).2. HemECs was isolated from adherent proliferating infantile hemangioma specimens, HemSCs were isolated from by CD133-tagged immunomagnetic beads and was observed by flow cytometry. 3. β1-AR, β2-AR, CD31, CD34were selected as the markers to observe stem cells by immunocytochemistry (ICC).4. The proliferation of both the endothelial cells and stem cells treated with1μM,10μM>50μM and100μM of propranolol and Isoprineline for24h,48h and96h, were assessed respectively by MTT assay and cell counting.5. The stem cells were treated with10μM propranolol for48hours, and the differentiation was observed by flow cytometry.Results1. GLUT1is strongly expressed in obtained tissue, which proves that the tissue is from proliferative IH.2. The CD133+cells we isolated comprising about5%of the cells in proliferating-phase IH, was much higher than the0.1%-1%that previously reported.3. CD31and CD34are positive in The mature HemECs (about11th generation) and HUVECs, in contrast, CD31expression in CD133+or CD133-cells isolated from proliferating hemangiomas was very weak, whereas after cultured in vitro, the expression become much more strong.4. Proliferation of endothelial cells was inhibited by propranolol in a dose-dependent manner, whereas negative in stem cells.5. Proportion of CD133+cells reduced in propranolol-treated stem cells when compared with untreated controls.Conclusion1.The results supported the hypothesis that HemSCs may be the origin of the immature HemECs in proliferating hemangioma.2.propranolol accelerates IH involution by inhibiting proliferation of hemangioma endothelial cells and accelerating differentiation of hemangioma stem cells. |
