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Background/purpose Dental pulp stem cells (DPSCs) are candidate seed cells for bone tissue engineering, but the molecular regulation of osteogenic differentiation in DPSCs is not fully understood. Long non-coding RNAs (lncRNAs) are important regulators of gene expression, and whether they play roles in osteogenic differentiation of DPSCs requires more study. Materials and methods DPSCs were isolated and cultured. The mRNA and lncRNA expression profiles were compared through microarray assay between osteo-differentiated DPSCs and non-differentiated DPSCs. Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses, Gene ontology (GO) analyses, and the mRNA-lncRNA co-expression analyses were performed for functional annotation of differentially expressed RNAs. Small interfering RNA (siRNA) was used to interfere the expression of lncRNA ENST00000533992 (also named smooth muscle-induced lncRNA or SMILR), a candidate regulator, then the osteogenic differentiation potential of DPSCs was analyzed. Results DPSCs were isolated and cultured successfully. The expression of 273 mRNAs and 184 lncRNAs changed significantly in DPSCs after osteogenic induction. KEGG analyses and GO analyses showed that the differentially expressed RNAs were enriched in several pathways and biological processes. The mRNA-lncRNA co-expression network was constructed to reveal the potential relationships between mRNAs and lncRNAs. The osteogenic differentiation potential of DPSCs decreased when SMILR was interfered. Conclusion The present study provides clues for seeking for lncRNAs that participate in the regulation of osteogenic differentiation in DPSCs. LncRNA SMILR could play a role in regulating osteogenic differentiation of DPSCs.

The influence of hyperlipidemia on titanium implant osseointegration and the underlying mechanisms remain elusive. Here, we studied the effects of hyperlipidemia on osseointegration and the related mechanisms. In vivo, specialized titanium implants were implanted in the femurs of diet-induced or genetic hyperlipidemia mice. In vitro, primary murine osteoblasts were cultured on titanium surface. Results showed that hyperlipidemia led to poor bone formation on bone-implant interface in two types of mice in vivo. In vitro, high-fat medium caused significant overproduction of reactive oxygen species (ROS) and inhibiting of Wnt/β-catenin pathway in osteoblasts on titanium surface, inducing obvious cell dysfunction. Both N-acetyl-L-cysteine(NAC, a ROS antagonist) and Wnt3a(an activator of Wnt/β-catenin pathway) could effectively attenuated the poor osteogenic ability of osteoblasts. Besides, NAC reactivated the Wnt/β-catenin pathway in osteoblasts under high-fat stimulation. Our results suggested that the cellular oxidative stress leads to osteoblasts dysfunction via the Wnt/β-catenin pathway, which plays a critical role in the compromised implant osseointegration under hyperlipidemia conditions. These results demonstrated new insights into the negative effect of hyperlipidemia on osseointegration and also provided ROS or Wnt/β-catenin pathway as promising therapeutic targets for developing novel implant materials to accelerate the osseointegration of implants in hyperlipidemia patients.

The osseointegration process of implant is seriously impaired in type 2 diabetes mellitus (T2DM) that causes high failure rate, and insufficiency exists in current insulin therapy, creating a demand for new bone-synergistic agent. Cinaciguat, a novel type of soluble guanylate cyclase (sGC) activator, plays a vital role in glucose metabolism, inflammation control and bone regeneration. We hypothesized that the combined application of cinaciguat and insulin could reverse poor implant osseointegration in diabetes. To test this hypothesis, streptozotocin-induced diabetic rats were placed implants in the femur, and divided into five groups: control, T2DM, cinaciguat-treated T2DM (7 μg/kg), insulin-treated T2DM (12 IU/kg), cinaciguat plus insulin combination-treated T2DM (7 μg/kg and 12 IU/kg respectively), according to different treatment received. The weight and glucose levels of rats were evaluated at fixed times, and plasma level of cyclic guanosine monophosphate (cGMP) was determined before euthanasia. Three months after therapy, the femurs were isolated for pull-out test, environmental scanning electron microscope observation, microscopic computerized tomography evaluation and various histology analysis. Results revealed that diabetic rats showed the highest blood glucose level and lowest cGMP content, which led to the worst structural damage and least osseointegration. Combined treatment could attenuate the diabetes induced hyperglycemia to be normal, restore the cGMP content, protein kinase G II (PKG II) expression, phosphodiesterase-5 (PDE5) activity and ameliorate the mechanical strength, the impaired bone microarchitecture and osseointegration to the highest level. Meanwhile, monotreatment (insulin or cinaciguat) also showed restorative effect, but less. Our findings demonstrated that the cGMP/PKG II signaling pathway activated by cinaciguat mediated the favorable effects of the combined application on improving implant fixation under T2DM condition.