Mechanical loading differentially regulates membrane-bound and soluble RANKL availability in MC3T3-E1 cells.

To understand the biochemical response of RANKL in response to mechanical loading, MC3T3-E1 cells were biequiaxially stretched. A murine RANKL cDNA with double epitopes, pEF6 HA-RANKL-V5His, was transfected into MC3T3-E1 cells, which were then stretched. Endogenous RANKL protein expression increased in response to mechanical loading. Membrane-bound RANKL (HA-RANKL-V5His) increased in cell lysates while soluble RANKL (RANKL-V5His) decreased in the conditioned media after mechanical loading. This may have resulted from the decreased activity of TACE after mechanical loading. Increased membrane-bound RANKL may be one of the mechanisms through which osteoblasts adapt to mechanical loading by regulating osteoclastogenic activity in a region-specific manner.