Kinetics of CD34+ Cells in the Peripheral Blood of Patients with Primary Myelofibrosis Undergoing Splenectomy

• Published in: Blood 2008-11, Vol.112 (11), p.3725-3725
• Main Authors: Campanelli, Rita, Massa, Margherita, Bonetti, Elisa, Viarengo, Gianluca, Rosti, Vittorio, Gattoni, Elisabetta, Moretti, Enza, Bergamaschi, Gaetano, Villani, Laura, Lucioni, Marco, Bandiera, Laura, Riboni, Roberta, Barosi, Gianni
• Format: Article
• Language: English
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood.V112.11.3725.3725

We have previously shown that primary myelofibrosis (PMF) is characterized by an increased number of circulating CD34+ cells and that the membrane expression of CXCR4 on these cells is significantly lower than in healthy subjects in terms both of percentage and of mean fluorescence intensity (MFI). The advanced phase of PMF is characterized by the accumulation in various organs of myeloid progenitor and precursor cells in a process known as extramedullary hematopoiesis. The accumulation and growth of these cells in the spleen lead to the pathologic enlargement of the organ and, in a limited number of cases, splenectomy is required. We have investigated the kinetic of circulating CD34+ and CD34+CXCR4+ cells in patients with PMF before and after splenectomy. We have also compared the percentages of CD34+ and CD34+CXCR4+ cells found in the peripheral blood (PB) with those found in cells derived from spleen tissue samples, obtained soon after splenectomy. Five milliliter of PB in EDTA was obtained from 8 patients with PMF and from 2 healthy subjects (CTRLs), who underwent splenectomy because of traumatic injury of the organ, before (T0) and at different time points (24 hours, 72 hours, and 14 days) after splenectomy. In 6/8 patients and in the 2 CTRLs, spleen samples were obtained immediately after the removal of the organ. After extensive rinsing, each spleen sample was minced to obtain a single cell suspension. For cytofluorimetric analysis, PB and spleen cells were stained with FITC-conjugated anti-CD34 and PE-conjugated anti-CXCR4 monoclonal antibodies. The membrane expression of CXCR4 was evaluated as percentage of CD34+ cells expressing the antigen and as CXCR4 MFI of CD34+ cells. Results are expressed as median (range) or mean where appropriate. The median percentage of circulating CD34+ cells in patients with PMF gradually decreased after splenectomy [24h: 5.5 (0.6–20.1); 72h: 3.1 (0.9–8.5); 14d: 1.6 (0.5–6.7)] with respect to T0 [3.7 (0.2–17.1)]. Vice versa, the percentage of circulating CD34+ cells expressing the CXCR4 antigen increased after the intervention [(24h: 27.3 (12.0–59.6); 72h: 51.4 (24.7–87.7); 14d: 49.0 (34.0–59.7)] with respect to T0 [23.3 (6.2–27.3)]. CXCR4 MFI similarly increased (not shown). In 3/13 patients, assessed 4 months after splenectomy a further decrease of the percentage of circulating CD34+ cells [0.65 (023–1.95)] and a stable percentage of CD34+ cells expressing CXCR4 [44.0 (29.4– 56.0)] were observed. The mean percentage