OBJECTIVETo construct a co- culture system of mesenchymal stem cells (MSC) and multiple myeloma (MM) cells and investigate the alterations of connexin 43 (CX43) expression and stromal derived growth factor (SDF)- 1α secretion of MSC.

METHODSCX43 expression and SDF- 1α secretion of MM cell lines (RPMI8226) and human primary MM cells were analyzed by western blot and immunofluorescence. Western blot, RT- PCR and immunofluorescence were employed to detect the alterations of CX43 expression and distribution in MSC directly and indirectly co-cultured with myeloma cells. Lucifer yellow dye spread was utilized to evaluate gap junctional intercellular communication (GJIC) between co- cultured MSC. Transwell was applied to study the transmigration of RPMI8266 induced by MSC under the condition of 18α- glycyrrhetinic acid (18α-GA). The level of SDF- 1α was detected by EILSA.

RESULTSRPMI8266, U266 and one-third primary MM cells expressed CX43 at low or moderate levels. CX43 wasn't expressed in XG- 4 and XG- 7 cells but highly expressed in MSC. The expressions of CX43 mRNA of MSC were up- regulated after directly and indirectly co- cultured with RPMI8226, 1.36 and 2.10 times that of MSC cultured alone respectively. Western blot analysis showed that CX43 protein expression of MSC was also up-regulated, mainly distributed in cytoplasm. Lucifer yellow dye spread showed that GJIC was up-regulated in MSC. SDF-1α concentration in supernatant of MSC directly and indirectly co-cultured with RPMI8226 were (373.02±10.11)pg/ml and (309.71±10.71)pg/ml respectively, which were higher than that of MSC cultured alone (237.84±9.23)pg/ml (P<0.01), and could be inhibited by 18α-GA [(237.84±9.23)pg/ml and (94.31±6.44)pg/ml] respectively (P<0.01). 18α-GA could inhibit the transmigration of RPMI8226 induced by MSC, decrease from (8.00±0.67)% to (4.82±0.19)%.

CONCLUSIONCX43 expression of MSC was up-regulated after directly and indirectly co-cultured with MM cells, which could improve the level of SDF-1α secretion of MSC. GJ inhibitor could downregulate SDF-1α secretion of MSC and inhibit the transmigration of MM cells induced by MSC.