Knockdown Epithelial Membrane Protein 1 Suppresses Human Degenerative Intervertebral Disc–Derived Nucleus Pulposus Cell Proliferation

OBJECTIVE Our previous work showed that epithelial membrane protein 1 (EMP1) is highly expressed in nucleus pulposus of the human degenerative intervertebral disc. The present study was designed to investigate the role of EMP1 in nucleus pulposus cells in intervertebral disc degeneration (IDD). DESIGN Human nucleus pulposus cells derived from degenerative intervertebral discs were cultured. EMP1 expression was knocked down by lentivirus-mediated specific interfering RNA. Cell morphology was observed, and cell proliferation, apoptosis, and cycle were evaluated. RESULTS Knockdown of EMP1 inhibited cell proliferation, caused cells to shrink, and accelerated the apoptosis induced by serum deprivation or addition of cycloheximide but did not evoke apoptosis in normal culture conditions. CONCLUSIONS These findings suggest that EMP1 promoted chondrocyte proliferation, survival, and morphological change of cells during IDD, implying that EMP1 may be a target for biological therapy for IDD.