Background and objectives: Infantile haemangioma (IH) is the most common tumour of infancy with characteristic of rapid growth followed by a variable period of involution. The aim of this study is to investigate the role of macrophage in IH, and whether it contributes to the distinctive progression of IH.
Methods: Haemangioma stem cells (HemSCs) were isolated from proliferative IHs using CD133 + magnetic beads. Transwell chambers were used for establishing co-culture system of HemSCs and macrophages. EDU incorporation and colony formation assays were used to measure the proliferation and self-renewal abilities of HemSCs. Adipogenesis of HemSCs was measured by Oil Red staining and adipogenic transcription factor PPAR-γ expression. Immunohistochemical staining was performed to evaluate the expression and distribution of macrophage in proliferative and involuting phase of IH tissues.
Results: Macrophages suppressed HemSCs adipogenic differentiation using Oil Red staining in direct co-culture system. Also, adipogenetic transcription factors PPAR-γ was inhibited in both mRNA and protein levels. Nevertheless, conditioned medium of macrophages enhanced the proliferation and colony formation ability of HemSCs in vitro . Most importantly, propranolol, which was reported effective in the treatment of IHs, could reverse the effects of macrophages on suppression of adipogenesis of HemSCs, as well as on enhancing proliferation and colony formation. The distribution of macrophages (CD68 + ) in different phases of haemangioma was detected by immunohistochemistry and immunofluorescence, showing that macrophages were decreased significantly in involuting phase.
Conclusions: Macrophage in IH may play important role in maintaining the proliferative status of lesion by promoting HemSCs proliferation as well as suppressing their adipogenic differentiation. Targeting macrophage could promote IH involution.
Key words: infantile haemangioma; macrophage; adipogenesis; stem cells; propranolol