Fibroblasts inhibit osteogenesis by regulating nuclear-cytoplasmic shuttling of YAP in mesenchymal stem cells and secreting DKK1

BACKGROUND: Fibrous scars frequently form at the sites of bone nonunion when attempts to repair bone fractures have failed. However, the detailed mechanism by which fibroblasts, which are the main components of fibrous scars, impede osteogenesis remains largely unknown. RESULTS: In this study, we found that fibroblasts compete with osteogenesis in both human bone nonunion tissues and BMP2-induced ectopic osteogenesis in a mouse model. Fibroblasts could inhibit the osteoblastic differentiation of mesenchymal stem cells (MSCs) via direct and indirect cell competition. During this process, fibroblasts modulated the nuclear-cytoplasmic shuttling of YAP in MSCs. Knocking down YAP could inhibit osteoblast differentiation of MSCs, while overexpression of nuclear-localized YAP-5SA could reverse the inhibition of osteoblast differentiation of MSCs caused by fibroblasts. Furthermore, fibroblasts secreted DKK1, which further inhibited the formation of calcium nodules during the late stage of osteogenesis but did not affect the early stage of osteogenesis. Thus, fibroblasts could inhibit osteogenesis by regulating YAP localization in MSCs and secreting DKK1. CONCLUSIONS: Our research revealed that fibroblasts could modulate the nuclear-cytoplasmic shuttling of YAP in MSCs, thereby inhibiting their osteoblast differentiation. Fibroblasts could also secrete DKK1, which inhibited calcium nodule formation at the late stage of osteogenesis.

Evaluation of the Combination of Methylprednisolone and Tranilast after Spinal Cord Injury in Rat Models

OBJECTIVE: The aim of our study was to evaluate the neuroprotective functions of the combination therapy using methylprednisolone (MP) and tranilast (TR) after spinal cord injury (SCI) in adult rats. METHODS: Spinal cord compression injury model was achieved using Yasargil aneurysm clip. Rats were divided into control group, MP group, TR group, and combination therapy group using TR and MP. Rat models were assessed for locomotor functional recovery using Basso, Beattie, and Bresnahan (BBB) score, spinal cord water content and myeloperoxidase (MPO) activity 24 hours post SCI, haematoxylin and eosin staining and glial fibrillary acid protein (GFAP) staining at 7 and 14 days post SCI. RESULTS: The spinal cord water content and MPO activity in the combination therapy group was significantly lower than the control group and the individual therapy groups p0.05). At 2 weeks after SCI there was a slight decrease in GFAP expression compared to the first week but the difference was not statistically significant (p>0.05), GFAP expression between the groups was not statistically significant p>0.05. CONCLUSION: Combining MP and TR is therapeutically more effective in improving functional recovery, inhibiting inflammation and glial scar formation after acute SCI.

Effect of the 18kDa translocator protein on U251 cells of human glioma / 中华神经医学杂志

Objective To study the effect of the 18kDa translocator protein (TSPO) on U251cells of human glioma. Methods U251 cell line was cultured in vitro conventionally.The specific ligand ofTSPO,pk11195,was used in 5 experimental groups respectively with concentrations of 100,50,25,12.5 and 6.25 μmol/L,in comparison with a control group.MTr colorimetry and trypan blue staining were used to detect cell proliferation.Hoechst33342 staining and flow cytometry were applied to detect cell apoptosis. Western blotting and immumofluorescence method were used to detect the expression level of TSPO. DCFH-DA probe and GSH kit were used to respectively detect the level of reactive oxygen species (ROS) and GSH level in cells.Jc-1 staining was applied to detect the mitochondrial membrane potential.Luciferase enzyme was used to detect the quantity of ATP in cells. Results MTT showed the survival of U251 cells was significantly higher in the groups of 50 and 25 μmol/L pk11195than in the control group (P＜0.05). Trypan blue staining showed the cell death rate was significantlylower in the group of 50 μmol/L pk11195 than in the control group (P＜0.05).The apoptosis rate,TSPO expression,ROS and GSH levels decreased significantly in the groups of 6.25 and 50 μmol/L pk11195,compared with the control group; the apoptosis rate was significantly lower in the group of 50 μmol/Lpk11195 than in the group of 6.25 μmol/L pk11195 (P＜0.05).The cell membrane potential and ATP quantity were significantly higher in the groups of 6.25 and 50 μmol/L pk11195 than in the control group,and those in the group of 50 μmol/L pk11195 were significantly higher than in the group of 6.25 μmol/Lpk11195 (P＜0.05). Conclusion TSPO may promote apoptosis of U251 cells in human glioma and inhibit proliferation of glioma cells,functioning similarly as a cancer suppressor gene.