Nutrition deficiency promotes apoptosis of cartilage endplate stem cells in a caspase-independent manner partially through upregulating BNIP3.

Nutrition deficiency is reported to induce apoptosis of chondrocytes and degeneration of cartilage endplate (CEP) in rabbit. Cartilage endplate stem cells (CESCs) are important for the integrity of structure and function of CEP. Bcl-2/adenovirus E1B 19-kDa-interacting protein 3 (BNIP3) has been reported to regulate apoptosis, autophagy, and cytoprotection. In this study, we aimed to determine whether nutrition deficiency induces apoptosis of CESCs, and whether or not the BNIP3-related pathway is activated in CESCs during nutrition deficiency. CESCs isolated from degenerated human CEP were cultured under normal or nutrition-deficient condition. Then, apoptosis was analyzed by flow cytometry. The expression and intracellular localization of BNIP3 were detected by quantitative real-time polymerase chain reaction, western blot analysis, and immunofluorescence assay, respectively. Mitochondrial membrane potential (MMP) and caspase-3 activity were measured by JC-1 staining and caspase-3 activity assay. Our results showed that nutrition deficiency promotes apoptosis and BNIP3 expression in CESCs. Notably, knockdown of BNIP3 could partially decrease nutrition deficiency-induced apoptosis of CESCs. In addition, nutrition deficiency could also induce upregulation of BNIP3, resulting in mitochondrial translocation of BNIP3 and loss of MMP in CESCs in a time-dependent manner. However, nutrition deficiency showed no effects on caspase-3 activity in CESCs. In summary, nutrition deficiency may promote CESC apoptosis partially through upregulating BNIP3, which might lead to activation of the BNIP3-related pathway and apoptosis of CESCs in a caspase-independent manner.