PARK7 enhances antioxidative-stress processes of BMSCs via the ERK1/2 pathway.

Oxidative stresss in the microenvironment surrounding lesions induces apoptosis of transplanted bone-marrow-derived mesenchymal stem cells (BMSCs). Hence, there is an urgent need for improving antioxidative-stress processes of transplanted BMSCs to further promote their survival. The present study reports the role and mechanism of Parkinson's disease protein 7 (PARK7) in enhancing antioxidative activity in BMSCs. We used a PARK7 lentivirus to transfect BMSCs to up- or downregulate PARK7, and then used H2 O2 to simulate oxidative stress in BMSCs in vitro. Overexpression of PARK7 effectively reduced reactive oxygen species and malondialdehyde, protected mitochondrial membrane potential, and resisted oxidative-stress-induced apoptosis of BMSCs, but the expression of PARK7 was downregulated, these results were reversed. At the same time, we also found that overexpression of PARK7 increased extracellular-regulated protein kinase 1/2 (ERK1/2) phosphorylation and nuclear translocation, as well as upregulated Elk1 phosphorylation and superoxide dismutase (SOD) expression. In contrast, when U0126 was used to block the ERK1/2 pathway, ERK1/2 and Elk1 phosphorylation levels were downregulated, ERK1/2 nuclear translocation and SOD content were significantly reduced, and PARK7-overexperssion-induced antioxidative activity was completely blocked. Collectively, our results suggest that PARK7 overexpression increased antioxidative-stress processes and survival of BMSCs subjected to H2 O2 via activating the ERK1/2 signaling pathway. Our findings may guide the development of a PARK7-specific strategy for improving the transplantation efficacy of BMSCs.

[Effect of LOC103693069 on hypoxic apoptosis of bone marrow mesenchymal stem cells].

Objective: To investigate the effect of LOC103693069 on hypoxic apoptosis of bone marrow mesenchymal stem cells (BMSCs). Methods: BMSCs from 1-week-old Sprague Dawley rat bone marrow were isolated, cultured, and passaged by the whole bone marrow adherent culture method. After identification of adipogenic, chondrogenic, and osteogenic differentiation, the 3rd generation cells were treated with hypoxia under 5%O 2, 1%O 2, and anaerobic conditions. After 48 hours, the cell viability, apoptosis, and apoptosis-related proteins [hypoxia inducible factor 1α (HIF-1α), Caspase-3, B cell lymphoma/leukemia 2 (Bcl-2)] expressions were detected, and normal BMSCs were used as controls. Based on the research results, the concentration group with the most obvious apoptosis was selected and used for subsequent experiments. After 48 hours of hypoxia treatment, BMSCs were taken and analyzed by gene chip and real-time fluorescence quantitative PCR (qRT-PCR) to screen the most significantly down-regulated gene and construct their high-expression, low-expression, and negative control lentiviruses; BMSCs were transfected with the different lentiviruses, respectively. After qRT-PCR detection confirmed that the transfection was successful, the BMSCs were treated with hypoxia for 48 hours to observe the cell viability and the expressions of apoptosis-related proteins. Results: After cell viability, apoptosis, and apoptosis-related proteins were detected, cell apoptosis was the most significant under anaerobic conditions after 48 hours. The above indicators were significantly different from other groups ( P<0.05), and this group was used for treatment conditions for subsequent experiments. Gene chip analysis showed that after 48 hours of hypoxia treatment, AC125847.1, LOC102547753, AABR07017208.2, and LOC103693069 were significantly down-regulated in BMSCs, and the expressions of LOC103693069 was the most significant down-regulation detected by qRT-PCR ( P<0.05). It was selected to construct lentivirus and transfect BMSCs. Afterwards, qRT-PCR detection showed the successful transfection into the cells. After hypoxia treatment, the apoptosis rate and the expressions of apoptosis-related proteins of BMSCs overexpressed by the gene were significantly reduced ( P<0.05). Conclusion: LOC103693069 can relieve the hypoxic apoptosis of BMSCs.

PARK7 promotes repair in early steroid-induced osteonecrosis of the femoral head by enhancing resistance to stress-induced apoptosis in bone marrow mesenchymal stem cells via regulation of the Nrf2 signaling pathway.

Novel therapies for the treatment of early steroid-induced osteonecrosis of the femoral head (SONFH) are urgently needed in orthopedics. Transplantation of bone marrow mesenchymal stem cells (BMSCs) provides new strategies for treating this condition at the early stage. However, stress-induced apoptosis of BMSCs transplanted into the femoral head necrotic area limits the efficacy of BMSC transplantation. Inhibiting BMSC apoptosis is key to improving the efficacy of this procedure. In our previous studies, we confirmed that Parkinson disease protein 7 (PARK7) is active in antioxidant defense and can clear reactive oxygen species (ROS), protect the mitochondria, and impart resistance to stress-induced apoptosis in BMSCs. In this study, we investigated the mechanism driving this PARK7-mediated resistance to apoptosis in BMSCs. Our results indicate that PARK7 promoted the disintegration of nuclear factor (erythroid-derived 2)-like 2 (Nrf2)/Kelch-like echinacoside-associated protein 1 (Keap1) complex. The free Nrf2 then entered the nucleus and activated the genetic expression of manganese superoxide dismutase (MnSOD), catalase (CAT), glutathione peroxidase (GPx), and other antioxidant enzymes that clear excessive ROS, thereby protecting BMSCs from stress-induced apoptosis. To further explore whether PARK7-mediated resistance to stress-induced apoptosis could improve the efficacy of BMSC transplantation in early-stage SONFH, we transplanted BMSCs-overexpressing PARK7 into rats with early-stage SONFH. We then evaluated the survival of transplanted BMSCs and bone regeneration in the femoral head necrotic area of these rats. The results indicated that PARK7 promoted the survival of BMSCs in the osteonecrotic area and improved the transplantation efficacy of BMSCs on early-stage SONFH. This study provides new ideas and methods for resisting the stress-induced apoptosis of BMSCs and improving the transplantation effect of BMSCs on early-stage SONFH.