A new murine osteoblastic cell line immortalized with the SV40 large T antigen

Leveraging selective knockdown of Sost gene by polyethyleneimine-siRNA-chitosan reduced gold nanoparticles to promote osteogenesis in MC3T3-E1 & MEF cells

Aim: Osteoporosis is a systemic skeletal disorder characterized by reduced osteoblast differentiation, predominantly by overexpression of the Sost gene. A layer-by-layer approach enabled encapsulation of Sost siRNA to enhance the short half-life and poor transfection capacity of siRNA. Materials & methods: Polyethyleneimine and siRNA on chitosan-coated gold nanoparticles (PEI/siRNA/Cs-AuNPs) were engineered using chitosan-reduced gold nanoparticles. They were characterized by dynamic light scattering, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared and gel-mobility assays. Detailed in vitro experiments, gene silencing and western blots were performed. Results: A total of 80% knockdown of the target sclerostin protein was observed by PEI/siRNA/Cs-AuNPs, q-PCR showed threefold downregulation of the Sost gene. Osteogenic markers RunX2 and Alp were significantly upregulated. Conclusion: We report a safe, biocompatible nanotherapeutic strategy to enhance siRNA protection and subsequent silencing to augment bone formation.

Live Simultaneous Monitoring of Mineral Deposition and Lipid Accumulation in Differentiating Stem Cells

Mesenchymal stem cells (MSCs) are progenitors for bone-forming osteoblasts and lipid-storing adipocytes, two major lineages co-existing in bone marrow. When isolated in vitro, these stem cells recapitulate osteoblast or adipocyte formation if treated with specialised media, modelling how these lineages interact in vivo. Osteogenic differentiation is characterised by mineral deposits accumulating in the extracellular matrix, typically assessed using histological techniques. Adipogenesis occurs with accumulation of intracellular lipids that can be routinely visualised by Oil Red O staining. In both cases, staining requires cell fixation and is thus limited to end-point assessments. Here, a vital staining approach was developed to simultaneously detect mineral deposits and lipid droplets in differentiating cultures. Stem cells induced to differentiate produced mixed cultures containing adipocytes and bone-like nodules, and after two weeks live cultures were incubated with tetracycline hydrochloride and Bodipy to label mineral- and lipid-containing structures, respectively. Fluorescence microscopy showed the simultaneous visualisation of mineralised areas and lipid-filled adipocytes in live cultures. Combined with the nuclear stain Hoechst 33258, this approach further enabled live confocal imaging of adipogenic cells interspersed within the mineralised matrix. This multiplex labelling was repeated at subsequent time-points, demonstrating the potential of this new approach for the real-time high-precision imaging of live stem cells.

Particulate and ion forms of cobalt-chromium challenged preosteoblasts promote osteoclastogenesis and osteolysis in a murine model of prosthesis failure

This study investigated the interactive behavior of the particulate and ion forms of cobalt-chromium (Co-Cr) alloy challenged preosteoblasts during the process of prosthetic implant loosening. Preosteoblasts were challenged with Co-Cr particles or Co(II) ions for 72 h, followed by the proliferation and PCR assays. For in vivo test, a titanium pin was implanted into proximal tibia of SCID mice to mimic knee replacement. Co-Cr particles or Co(II) ion challenged preosteoblasts (5 × 10⁵ ) were intra-articularly injected into the implanted knee. The animals were sacrificed 5 weeks post-op, and the prosthetic knees were harvested for biomechanical pin-pullout testing, histological evaluations, and microCT assessment. In vitro study suggested that Co-Cr particles and Co(II) ions significantly suppressed the proliferation of preosteoblasts in a dose-dependent manner. RT-PCR data on the challenged cells indicated overexpression of receptor activator of nuclear factor kappa-B ligand (RANKL) and inhibited osteoprotegerin (OPG) gene expression. Introduction of the differently challenged preosteoblasts to the pin-implant mouse model resulted in reduced implant interfacial shear strength, thicker peri-implant soft-tissue formation, more TRAP+ cells, lower bone mineral density, and bone volume fraction. In conclusion, both Co-Cr particles and Co(II) ions interfered with the growth, maturation, and functions of preosteoblasts, and provides evidence that the metal ions as well play an important role in effecting preosteoblasts in the pathogenesis of aseptic loosening. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 187-194, 2019.

Proliferation and osteogenic response of MC3T3-E1 pre-osteoblastic cells on porous zirconia ceramics stabilized with magnesia or yttria

Dense zirconia ceramics are used in bone applications due to their mechanical strength and biocompatibility, but lack osseointegration. A porous interface in contact with bone tissue may lead to better bone bonding but the biological properties of porous zirconia are not widely explored. The present study focuses on the manufacturing of an yttria- (YSZ) and a magnesia-stabilized (MgSZ) porous zirconia, and on their in vitro biological investigation. The sintered ceramics had similar characteristics of porosity, pore size and interconnectivity. Their elastic moduli and compressive strength values were within the range of the values of human cortical bone. MC3T3-E1 pre-osteoblasts were used to investigate the proliferation, alkaline phosphatase (ALP) activity, collagen deposition and expression profile of four genes involved in bone metabolism of cells on porous ceramics. Scanning electron and fluorescence microscopy were employed to visualize cell morphology and growth. Pre-osteoblasts adhered well on both ceramics but cell numbers on YSZ were higher. Cells exhibited an increase in ALP activity and collagen deposition after 14 days on both MgSZ and YSZ, with higher levels on YSZ. Real-time quantitative polymerase chain reaction (qPCR) showed that the expression of bone sialoprotein (Bsp) and collagen type I (col1aI) were significantly higher on YSZ. No significant differences were found in their ability to regulate the early gene expression of Runx2 and Alp. Nevertheless, the biomineralized calcium content was similar on both ceramics after 21 days, indicating that despite chemical differences, both scaffolds direct the pre-osteoblasts toward a mature state capable of mineralizing the extracellular matrix.

Biological responses of preosteoblasts to particulate and ion forms of Co-Cr alloy

This study compared the particulate and ion forms of a cobalt-chrome (Co-Cr) alloy on the differentiation/activation of preosteoblasts. Mouse preosteoblasts (MC3T3-E1) were cultured in an osteoblast-induction medium in the presence of particulate and ion forms of a Co-Cr alloy, followed by cell proliferation and cytotoxicity evaluations. The maturation and function of osteoblasts were assessed by alkaline phosphatase (ALP) assay and related gene expressions. Both particulate and ion forms of the metals significantly reduced the proliferation of MC3T3-E1 cells in a dose-dependent manner. Similarly, cells challenged with high concentrations of particles and ions exhibited a marked cytotoxic effect and diminished expression of ALP. Real-time (RT) polymerase chain reaction (PCR) data have suggested that cells with Co-Cr particles dramatically promoted over-expression of monocyte chemo-attractant protein-1 (MCP-1), tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6), whereas Co(2+) ions treatment predominately up-regulated expressions of receptor activator of nuclear factor kappa-B ligand (RANKL), nuclear factor of activated T-cells cytoplasmic 1 (NFATc1), and down-regulated expression of osteoprotegerin (OPG) and Osterix (Osx). Overall, this study provides evidence that both Co-Cr alloy particles and metal ions interfered with the MC3T3-E1 cells for their growth, maturation, and functions. Further, Co-Cr particles exhibited stronger effects on inflammatory mediators, while metal ions showed more influence on inhibition of osteoblast differentiation and promotion of osteoclastogenesis.