Objectives: Hemangioma is a primary tumor of the microvasculature in which angiogenesis is initially excessive, followed by regression of the newly formed vessels. Intervention is necessary in up to 20% of cases, high-dose systemic or intralesional steroids being the first-line treatment. As the mechanism of action of steroids is unknown, we undertook an investigation of the cellular and molecular effects of their action.
Study design: A unique opportunity to study the effect of steroid treatment was presented when biopsy material was obtained from an infant with an ulcerated proliferating hemangioma before and after intralesional triamcinolone injection, which resulted in an accelerated regression of the lesion. Histochemical quantitation of mast cells, molecular analysis by reverse transcriptase-polymerase chain reaction (RT-PCR) for 7 growth factor transcripts and differential display RT-PCR (DD RT-PCR) were conducted.
Results: After steroid therapy, the mast cell number increased (untreated = 2.22 +/-.27 [standard error of the mean ¿SEM¿]; treated = 8.7 +/-.71 [SEM] mast cells per field, respectively; P <.0001; n = 40 fields for each group), and the transcriptional expression of cytokines: platelet-derived growth factor-A and -B; interleukin-6; transforming growth factor-beta1 and -beta3 decreased, while that of basic fibroblast growth factor (bFGF) and vascular endothelial cell growth factor remained unaltered. Elevated urinary bFGF levels noted in cases of proliferating hemangioma, persisted even after steroid treatment. Using DD RT-PCR an amplicon that shared 100% sequence homology with the human mitochondrial cytochrome b gene was detected in the hemangioma biopsy after steroid treatment.
Conclusions: The regression of this hemangioma subsequent to steroid therapy was accompanied by a significant increase in mast cell density, reduced transcription of several cytokines, and an enhanced expression of the mitochondrial cytochrome b gene.