Increased ex vivo expansion of late-endothelial progenitor cells in patients with Kaposi’s sarcoma

Background Kaposi’s Sarcoma (KS) is an angioproliferative disorder associated with human herpesvirus-8 (HHV-8) infection. Spindle cells are the predominant cell type in the KS lesions and are endothelial in origin. We previously demonstrated that late-Endothelial Progenitor Cells (late-EPCs) cultured ex vivo from KS patients are HHV-8-infected and support viral productive replication. Aim of this study was to investigate whether HHV-8 infection induced a different in vitro behaviour of KS late-EPCs. Methods Late-EPCs were cultured from peripheral blood mononuclear cells (PBMCs) of 15 classic KS patients and 15 healthy controls. Cultures from all subjects were observed for initial late-EPCs colony appearance, number of colonies, cell proliferation, cytokine production and in vitro angiogenesis. Results The average time of initial late-EPCs colony appearance was 19.42 ± 1.05 days in healthy controls and 12.84 ± 0.47 days in KS patients (P<0.001). The number of late-EPCs colonies/20x106 seeded PBMCs was 0.58 ± 0.08 in healthy controls and 5.64 ± 2.48 in KS patients (P<0.05). In this preliminary set of data no difference was observed in time of late-EPCs appearance and colony count related to clinical stage and evolution of KS disease. Conclusions We conclude that ex vivo expansion of late-EPCs is strikingly higher in KS patients than controls. These findings may be particularly relevant to KS pathogenesis, as late-EPCs are possibly considered putative precursors of spindle cells of KS lesions