Mast Cell Infiltration is Associated with Myelofibrosis and Angiogenesis in Myelodysplastic Syndromes

Abstract

Myelodysplastic syndromes are a heterogeneous group of clonal hematopoietic stem cell disorders characterized by persistent peripheral cytopenia with morphological and functional abnormalities of hematopoietic cells. Mast cells infiltrate into or around tumor tissues and play a role in remodeling of the stromal microenvironment, contributing to tumor progression. Increased mast cell numbers are associated with fibrosis, angiogenesis and a poor prognosis in human carcinomas. The aim of this study was to determine whether mast cell infiltration contributes to myelofibrosis or angiogenesis in myelodysplastic syndromes. We evaluated the correlation between mast cell density and the extent of myelofibrosis and angiogenesis in myelodysplastic syndromes. Fifty bone marrow biopsies taken from patients with a diagnosis of myelodysplastic syndromes were examined. Grading of myelofibrosis was evaluated by silver impregnation staining. Mast cell density and microvessel density were evaluated by immunohistochemistry. Human mast cells have been divided into two phenotypes. We designated a tryptase-positive mast cell as MC_T and a chymase-positive mast cell as MC_TC. Microvessels were identified by CD34-positive endothelial cells. Microvessel density and the extent of myelofibrosis were significantly greater in patients with high MC_T and MC_TC density compared to those with low MC density. Based on this, we suggest that the presence of high mast cell numbers is associated with myelofibrosis and angiogenesis in myelodysplastic syndromes.