The role of Serpina3n in the reversal effect of ATRA on dexamethasone-inhibited osteogenic differentiation in mesenchymal stem cells

SERPINA3 is expressed in human adipocytes and modulated by TNF-α and vitamin B6

SERPINA3G participates in the antiadipogenesis and insulin resistance induced by TNF-α in 3T3-F442A murine cells. Here, we show that the human orthologue SERPINA3 is expressed in human subcutaneous and visceral adipose depots of normal-weight individuals and that TNF-α and RA induced the overexpression of SERPINA3 mRNA in cultured human subcutaneous and visceral adipocytes, although only TNF-α induced the expression of serpin A3 protein. We also demonstrate that vitamin B6 abrogated the expression of the SERPINA3 gene and diminished the anti-adipogenic effects of TNF-α on mature adipocytes. Our results indicate that SERPINA3 is expressed in human adipose tissues and modulates the antiadipogenic effects of TNF-α, and suggest serpin A3 could be a promissory target in the inflammatory processes linked to obesity and other adipose dysfunctions.

Luteolin Inhibits Dexamethasone-Induced Osteoporosis by Autophagy Activation Through miR-125b-5p/SIRT3/AMPK/mTOR Axis, an In Vitro and In Vivo Study

Luteolin (LUT) has been suggested as an inhibitor of osteoporosis (OP). This investigation examines the pivotal role of the miR-125b-5p/SIRT3/AMPK/mTOR pathway in mediating luteolin-induced effects on OP. Mesenchymal stem cells derived from bone marrow (BMSCs) were exposed to dexamethasone (DEX) to create an in vitro model of OP. Following treatment with luteolin, the levels of miR-125b-5p and SIRT3 were quantified using reverse transcription polymerase chain reaction. Moreover, SIRT3, AMPK, mTOR protein levels, and osteogenesis (OPN, Runx2, OSX, and OCN), and autophagy (p62, ATG5, LC3, and BECN1) were evaluated using ELISA. Additionally, specific mimics and siRNA were constructed to overexpress miR-125b-5p or downregulate SIRT3. Furthermore, animal models of DEX-induced OP were constructed to assess the effects of LUT at doses of 50 and 100 mg/kg/day on bone histology, stereology, biochemistry, and the expression of the miR-125b-5p, SIRT3/AMPK/mTOR axis, and markers of osteogenesis and autophagy. The findings revealed that LUT suppressed miR-125b-5p expression, overexpressed SIRT3 and AMPK, and downregulated mTOR in BMSCs compared to DEX (p-value < 0.01). Interestingly, LUT restored the levels of markers for osteogenesis and autophagy (p-value < 0.001). The overexpression of SIRT3 or miR-125b-5p downregulation inhibited LUT therapeutic properties. In animals, LUT improved bone histology (p-value < 0.05) and inhibited miR-125b-5p and mTOR expression while overexpressing SIRT3 and AMPK (p-value < 0.001). RUNX2, OSX, OPN, and OCN levels were improved, and autophagy was enhanced in LUT-treated rats. The current findings revealed that LUT could promote osteogenesis and improve OP via autophagy activation through the miR-125b-5p/SIRT3/AMPK/mTOR pathway.

Initial therapeutic evidence of a borosilicate bioactive glass (BSG) and Fe3O4 magnetic nanoparticle scaffold on implant-associated Staphylococcal aureus bone infection

Implant-associated Staphylococcus aureus (S. aureus) osteomyelitis is a severe challenge in orthopedics. While antibiotic-loaded bone cement is a standardized therapeutic approach for S. aureus osteomyelitis, it falls short in eradicating Staphylococcus abscess communities (SACs) and bacteria within osteocyte-lacuna canalicular network (OLCN) and repairing bone defects. To address limitations, we developed a borosilicate bioactive glass (BSG) combined with ferroferric oxide (Fe3O4) magnetic scaffold to enhance antibacterial efficacy and bone repair capabilities. We conducted comprehensive assessments of the osteoinductive, immunomodulatory, antibacterial properties, and thermal response of this scaffold, with or without an alternating magnetic field (AMF). Utilizing a well-established implant-related S. aureus tibial infection rabbit model, we evaluated its antibacterial performance in vivo. RNA transcriptome sequencing demonstrated that BSG + 5%Fe3O4 enhanced the immune response to bacteria and promoted osteogenic differentiation and mineralization of MSCs. Notably, BSG + 5%Fe3O4 upregulated gene expression of NOD-like receptor and TNF pathway in MSCs, alongside increased the expression of osteogenic factors (RUNX2, ALP and OCN) in vitro. Flow cytometry on macrophage exhibited a polarization effect towards M2, accompanied by upregulation of anti-inflammatory genes (TGF-β1 and IL-1Ra) and downregulation of pro-inflammatory genes (IL-6 and IL-1β) among macrophages. In vivo CT imaging revealed the absence of osteolysis and periosteal response in rabbits treated with BSG + 5%Fe3O4 + AMF at 42 days. Histological analysis indicated complete controls of SACs and bacteria within OLCN by day 42, along with new bone formation, signifying effective control of S. aureus osteomyelitis. Further investigations will focus on the in vivo biosafety and biological mechanism of this scaffold within infectious microenvironment.

lncRNA MEG3 Promotes PDK4/GSK-3β/β-Catenin Axis in MEFs by Targeting miR-532-5p

Studies reported the positive and negative osteogenic effects of MEG3 in mesenchymal stem cells (MSCs). This study aims at clarifying the osteogenic potential of MEG3 and the underlying mechanism. Bone morphogenetic protein 9- (BMP9-) transfected MSCs were recruited as an osteogenic model in vitro, and ectopic bone formation were used in vivo to explore the effect of MEG3 on osteogenesis. We found that overexpression of MEG3 facilitated BMP9-induced osteogenic markers, ALP activities, and matrix mineralization. However, knockdown of MEG3 attenuated BMP9-induced osteogenic markers. MEG3 increased the phosphorylation of GSK-3β and the protein level of β-catenin. Pyruvate dehydrogenase kinase 4 (PDK4) can also combine with GSK-3β and increase the latter phosphorylation. Moreover, MEG3 increased the mRNA level of PDK4. The ceRNA analysis showed that MEG3 may regulate the expression of PDK4 via microRNA 532-5p (miR-532-5p). The MEG3-enhanced GSK-3β/β-catenin axis can be attenuated by miR-532-5p, and miR-532-5p inhibitor partly rescued endogenous PDK4 and MEG3-mediated expression of PDK4. MEG3 may potentiate PDK4 and GSK-3β/β-catenin by inhibiting miR-532-5p.

Pyruvate dehydrogenase kinase 4 promotes osteoblastic potential of BMP9 by boosting Wnt/β-catenin signaling in mesenchymal stem cells

Bone morphogenetic protein 9 (BMP9) is an effective osteogenic factor and a promising candidate for bone tissue engineering. The osteoblastic potential of BMP9 needs to be further increased to overcome its shortcomings. However, the details of how BMP9 triggers osteogenic differentiation in mesenchymal stem cells (MSCs) are unclear. In this study, we used real-time PCR, western blot, histochemical staining, mouse ectopic bone formation model, immunofluorescence, immunoprecipitation, and chromatin immunoprecipitation to investigate the role of pyruvate dehydrogenase kinase 4 (PDK4) in BMP9-induced osteogenic differentiation of C3H10T1/2 cells, as well as the underlying mechanism. We found that PDK4 was upregulated by BMP9 in C3H10T1/2 cells. BMP9-induced osteogenic markers and bone mass were increased by PDK4 overexpression, but decreased by PDK4 silencing. β-catenin protein level was increased by BMP9, which was enhanced by PDK overexpression and decreased by PDK4 silencing. BMP9-induced osteogenic markers were reduced by PDK4 silencing, which was almost reversed by β-catenin overexpression. PDK4 increased the BMP9-induced osteogenic markers, which was almost eliminated by β-catenin silencing. Sclerostin was mildly decreased by BMP9 or PDK4, and significantly decreased by combined BMP9 and PDK4. In contrast, sclerostin increased significantly when BMP9 was combined with PDK4 silencing. BMP9-induced p-SMAD1/5/9 was increased by PDK4 overexpression, but was reduced by PDK4 silencing. PDK4 interacts with p-SMAD1/5/9 and regulates the sclerostin promoter. These findings suggest that PDK4 can increase the osteogenic potential of BMP9 by enhancing Wnt/β-catenin signaling via the downregulation of sclerostin. PDK4 may be an effective target to strengthen BMP9-induced osteogenesis.

The SIRT1 activator SRT2104 promotes BMP9-induced osteogenic and angiogenic differentiation in mesenchymal stem cells

Bone defects resulting from trauma, bone tumors, infections and skeletal abnormalities are a common osteoporotic condition with respect to clinical treatment. Of the known bone morphogenetic proteins (BMPs), BMP9 has the strongest osteogenic differentiation potential, which could be beneficial in the construction of tissue-engineered bone. Silent mating type information regulator 2 homolog-1 (SIRT1) is a highly conserved nicotinamide adenine dinucleotide-dependent deacetylase that deacetylates and modulates histone or non-histone substrates. However, the role of SIRT1 in BMP9-induced osteogenic differentiation of stem cells has not been studied. Furthermore, it is unclear whether SIRT1 interacts with the BMP/Smad and BMP/MAPK pathways in stem cells. We found that SIRT1 expression decreased gradually in a time-dependent manner during BMP9-induced osteogenic differentiation of MSCs. Interactions between SIRT1 and Smad7 promoted degradation of Smad7 and increased Smad1/5/8 phosphorylation. SRT2104, an activator of SIRT, enhanced the expression of osteogenic- and angiogenic-related proteins in BMP9-induced MSCs. In addition, we found that activation of the BMP/MAPK pathway led to osteogenic and angiogenic differentiation of MSCs. Our study demonstrated that SIRT1 expression decreased during BMP9-induced differentiation. The SIRT1 activator SRT2104 promoted BMP9-induced osteogenic and angiogenic differentiation of MSCs through the BMP/Smad and BMP/MAPK signaling pathways.

Screening and preliminary identification of long non-coding RNAs critical for osteogenic differentiation of human umbilical cord mesenchymal stem cells

Human umbilical cord mesenchymal stem cells (hUCMSCs) are attractive therapeutic cells for tissue engineering to treat bone defects. However, how the cells can differentiate into bone remains unclear. Long non-coding RNAs (lncRNAs) are non-coding RNAs that participate in many biological processes, including stem cell differentiation. In this study, we investigated the profiles and functions of lncRNAs in the osteogenic differentiation of hUCMSCs. We identified 343 lncRNAs differentially expressed during osteogenic differentiation, of which 115 were upregulated and 228 were downregulated. We further analyzed these lncRNAs using bioinformatic analyses, including Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis. GO and KEGG pathway analysis showed that ‘intracellular part’ and ‘Phosphatidylinositol signaling system’ were the most correlated molecular function and pathway, respectively. We selected the top 10 upregulated lncRNAs to construct six competing endogenous RNA networks. We validated the impact of the lncRNA H19 on osteogenic differentiation by overexpressing it in hUCMSCs. Overall, our results pave the way to detailed studies of the molecular mechanisms of hUCMSC osteogenic differentiation, and they provide a new theoretical basis to guide the therapeutic application of hUCMSCs.