OBJECTIVETo study the influence of multiple myeloma (MM) cells on normal endothelial cells in co-culture system in vitro.

METHODSA co-culture system of human MM cell line RPMI8226 with human umbilical vein endothelial cells (HUVECs) was established in vitro. Mono-cultured normal endothelial cells were used as control. Light microscopy and transmission electron microscopy were used to observe the morphology of the endothelial cells. The effects of HUVECs co-cultured with RPMI8226 on HUVECs angiogenesis were studied by modified transwell migration assay and net-like formation assay. The protein expression of brain derived neurotrophic factor (BDNF), TrkB, Endoglin, Tie-2, beta 3 integrin and vascular cell adhesion molecule-1 (VCAM-1) in HUVECs were determined by FACS and Western blot analysis, respectively.

RESULTSThe morphology of HUVECs co-cultured with RPMI8226 cells became a narrower apart of extended shape as they began to align themselves. The sizes of nucleus and nucleolus were enlarged with an increased ratio of nuclear to nucleoplasm. The endoplasm was lose and distorted and the number of surface microvilli decreased. The RPMI8226 cell stimulated the migration and net-like formation of HUVEC, the number of net-like structure and migration cell being increased by 112% and 136%, respectively, compared with that of mono-cultured HUVECs. The expressions of BDNF, TrkB, Endoglin, Tie-2, beta 3 integrin and VCAM-1 in the ECs co-cultured with RPMI8226 were all up-regulated in comparison with those in the controls.

CONCLUSIONThe MM cells promote formation of new vessels in co-cultured endothelial cells and the endothelial cells in MM are different from the normal ECs in character, and behavior.