Role of brain-derived neurotrophic factor in bone marrow angiogenesis in multiple myeloma

This study examined the expression of brain-derived neurotrophic factor (BDNF) in multiple myeloma (MM) and its role in bone marrow angiogenesis. The peripheral blood plasma was harvested from 71 MM patients and 63 patients without hematological malignancy. The BDNF level in the blood plasma was determined by ELISA. Human bone marrow endothelial cells (HBMECs) were cultured. The mRNA and protein expression levels of the BDNF receptor TrkB in HBMECs were detected by using RT-PCR and flow cytometry, respectively. The viability of HBMECs treated with recombinant human (rh) BDNF or not was measured by using MTT assay. The migration of HBMECs in the presence of rhBDNF or not was determined by modified Boyden chamber assay. In vitro tube formation assay was used to assess the effect of rhBDNF on HBMECs differentiation. The results of ELISA revealed that the BDNF level was significantly higher in peripheral blood plasma of MM patients than in that of control patients (4.39±0.67 vs. 1.96±0.39 ng/mL, P<0.05). The BDNF receptor TrkB was expressed in HBMECs at mRNA and protein level. MTT assay manifested that rhBDNF could significantly concentration-dependently promote the HBMECs proliferation. The number of HBMECs treated with 160 ng/mL rhBDNF for 48 h was 1.57±0.10 folds higher than that in control group (P<0.05). Moreover, rhBDNF could enhance HBMECs migration in a concentration-dependent manner and the maximal migration was reached in the presence of 100 ng/mL rhBDNF. The migration indexes were 1.40±0.11, 1.64±0.16, 2.06±0.25 and 2.18±0.21 in 25, 50, 100 ng/mL rhBDNF groups and 25 ng/mL rhVEGF group, respectively. In vitro tube formation assay demonstrated that the area of the formed tubular structure was increased with the rhBDNF concentration. In control group, there was no formation of intact tubular structure and the HBMECs on the matrigel were irregularly dispersed. HBMECs treated with 100 ng/mL rhBDNF could form intact tubular structure and the area and the diameter of tubes were significantly greater than those in control group (P<0.05). There was no significant difference in the formed tubular area between 25 ng/mL VEGF group and 100 ng/mL rhBDNF group. It was concluded that BDNF plays an important role in myeloma cell-induced angiogenesis, and it may become a new target of anti-angiogenesis treatment for MM.