Potential Effect of CD271 on Human Mesenchymal Stromal Cell Proliferation and Differentiation.

The Low-Affinity Nerve Growth Factor Receptor (LNGFR), also known as CD271, is a member of the tumor necrosis factor receptor superfamily. The CD271 cell surface marker defines a subset of multipotential mesenchymal stromal cells and may be used to isolate and enrich cells derived from bone marrow aspirate. In this study, we compare the proliferative and differentiation potentials of CD271+ and CD271- mesenchymal stromal cells. Mesenchymal stromal cells were isolated from bone marrow aspirate and adipose tissue by plastic adherence and positive selection. The proliferation and differentiation potentials of CD271+ and CD271- mesenchymal stromal cells were assessed by inducing osteogenic, adipogenic and chondrogenic in vitro differentiation. Compared to CD271+, CD271- mesenchymal stromal cells showed a lower proliferation rate and a decreased ability to give rise to osteocytes, adipocytes and chondrocytes. Furthermore, we observed that CD271+ mesenchymal stromal cells isolated from adipose tissue displayed a higher efficiency of proliferation and trilineage differentiation compared to CD271+ mesenchymal stromal cells isolated from bone marrow samples, although the CD271 expression levels were comparable. In conclusion, these data show that both the presence of CD271 antigen and the source of mesenchymal stromal cells represent important factors in determining the ability of the cells to proliferate and differentiate.

Correlation between leukocytosis and thrombosis in Philadelphia-negative chronic myeloproliferative neoplasms.

The evidence that leukocytes may contribute to the pathogenesis of thrombosis in Chronic Myeloproliferative Neoplasms is increasing but not definitive. To further enforces whether an increased leukocyte count is associated with thrombosis and whether this effect can be modulated by cytoreductive therapy, we analyzed the clinical course of 187 patients with Polycythemia Vera (PV) and Essential Thrombocythemia (ET) followed at two Italian Institutions over a period of 7 years. The association was measured at diagnosis or before thrombotic events: a multivariable analysis was carried out using data at baseline and time-dependent covariates. We found that white blood cells (WBC) count above 9.5 x 10(9)/L at diagnosis (baseline analysis) was associated with thrombosis during the follow-up (Hazard Ratio [HR] of 1.8, p 0.03). At the time-dependent analysis, therapy with hydroxyurea (HU), lowering by 35% the baseline WBC level, reduced such strength of association giving a HR of 1.3 (p value non significant). We found a trend between WBC level and thrombosis in untreated low-risk patients (RR of 1.9, 95% CI 0.9 to 3.1); in high-risk patients treated with HU this correlation was clearly lost (RR 1.1, 95% CI 0.2 to 2.7). Finally, we could not identify the presence of JAK2 (V617F) as a risk factor for thrombosis. Properly designed prospective studies should corroborate such results.