Myeloma Cell-induced Bone Marrow Microenvirnment Remodelling And Its Implication On Pathogenesis Of Multiple Myeloma

【Objective】The study aimed to explore the effects of MM cells on the proliferation,osteogenic differentiation potential, gene and chemokines expression of bone marrowderived mesenchymal stem cells (BMMSCs) in different co-culture systems in vitro. Thechange of MM cell cycle and the expression of gap junction protein (connexin, Cx) Cx43and Cx45gene after co-cultured in vitro were also investigated. Through which we canelucidate whether the biological behavior of BMMSCs can be affected by myeloma cellswhen co-cultured in vitro and the effects of BMMSCs on the function of gap junctionalintercellular communication (GJIC) of MM cell.【Methods】 The experiment was divided into control group, indirect co-culturegroup and U266conditioned media (U266-CM) direct co-culture group. After MM cellsand BMMSCs were incubated in different culture system in vitro, the proliferation ofBMMSCs was determined by cell counting; osteogenic differentiation potential ofBMMSCs was assayed with Von Kossa staining; the expression of RANKL/OPG, IL-1β,DKK1, SDF-1α, IGF-1of BMMSCs were detected by RT-PCR.The effect of BMMSCs onMM cell cycle was measured by FCM with PI staining; the expression of Cx43and Cx45gene after the BMMSCs and MM cell co-cultured in vitro was detected by RT-PCR.【Results】 There was no significant change of the proliferation of BMMSCs whenthe cells were co-cultured with U266cells in different conditions; the osteogenicdifferentiation potential of BMMSCs was inhibited by U266cells in co-culture groups. theexpression of RANKL, IL-1β, DKK1and IGF-1were upregulated while the expression ofOPG and SDF-1α were downregulated in BMMSCs after24hours co-cultured with U266cells. The proportion of U266cells in S phase was increased after direct or indirect co-cultured with BMMSCs; the expression of Cx43of U266cells have no significantchange in indirect co-culture group, but decreased significantly in direct co-culture group;the expression of Cx45of U266cells between co-culture groups and the control group hasno significant difference.【Conclusion】 The biological behavior of BMMSCs can be affected by myelomacells when co-cultured in vitro. MM cells can inhibit the osteogenic differentiationpotential of BMMSCs, and upregulate the expression of osteoclast activating gene andosteoblast inhibition factors, which is similar to MM-BMMSCs, suggesting that MM cellscan induce changes in BMMSCs. The BMMSCs may stimulate MM cell proliferationthrough inhibiting the expression of Cx43.