Examination of Mineralized Nodule Formation in Living Osteoblastic Cultures Using Fluorescent Dyes

Background Heterotopic ossification (HO) may occur after musculoskeletal trauma, traumatic brain injury, and total joint arthroplasty. As such, HO is a compelling clinical concern in both military and civilian medicine. A possible etiology of HO involves dysregulated signals in the bone morphogenetic protein osteogenic cascade. Contemporary treatment options for HO (ie, nonsteroidal antiinflammatory drugs and radiation therapy) have adverse effects associated with their use and are not biologically engineered to abrogate the molecular mechanisms that govern osteogenic differentiation. Questions/purposes We hypothesized that (1) nanogelmediated short interfering RNA (siRNA) delivery against Runt-related transcription factor 2 (Runx2) and osterix (Osx) genes will decrease messenger RNA expression; (2) inhibit activity of the osteogenic marker alkaline phosphatase (ALP); and (3) inhibit hydroxyapatite (HA) deposition in osteoblast cell cultures. Methods Nanogel nanostructured polymers delivered siRNA in 48-hour treatment cycles against master osteogenic regulators, Runx2 and Osx, in murine calvarial preosteoblasts (MC3T3-E1.4) stimulated for osteogenic differentiation by recombinant human bone morphogenetic protein (rhBMP-2). The efficacy of RNA interference (RNAi) therapeutics was determined by quantitation of messenger RNA knockdown (by quantitative reverse transcription-polymerase chain reaction), downstream protein knockdown (determined ALP enzymatic activity assay), and HA deposition (determined by OsteoImage TM assay). Results Gene expression assays demonstrated that nanogelbased RNAi treatments at 1:1 and 5:1 nanogel:short interfering RNA weight ratios reduced Runx2 expression by 48.59% ± 19.53% (p \ 0.001) and 43.22% ± 18.01% (both p \ 0.001). The same 1:1 and 5:1 treatments against both Runx2 and Osx reduced expression of Osx by 51.65% ± 10.85% and 47.65% ± 9.80% (both p \ 0.001). Moreover, repeated 48-hour RNAi treatment cycles against Runx2 and Osx rhBMP-2 administration reduced ALP activity after 4 and 7 days. ALP reductions after 4 days in culture by nanogel 5:1 and 10:1 RNAi treatments were 32.4% ± 12.0% and 33.6% ± 13.8% (both p \ 0.001). After 7 days in culture, nanogel 1:1 and 5:1 RNAi treatments produced 35.9% ± 14.0% and 47.7% ± 3.2% reductions in ALP activity. Osteoblast mineralization data after 21 days suggested that Two of the authors (ARS, EH) contributed equally.

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“…5). Day 7 analyses reflected minimal HA deposition, because mineralization processes typically peak after 2 weeks in culture [28,60,68,70]. …”

Section: Resultsmentioning

confidence: 99%

Cationic Nanogel-mediated Runx2 and Osterix siRNA Delivery Decreases Mineralization in MC3T3 Cells

Shrivats

Hsu

Averick

et al. 2015

Clinical Orthopaedics &Amp; Related Research

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“…Fixed samples were processed into cryoblocks, and nondecalcified sections (5 lm) were obtained to qualitatively observe repair, the mineral deposition pattern visualized by bone labels, and alkaline phosphatase (AP) staining for osteoblastic activity [21,22,41,44]. Slides were imaged at 9 5 magnification and high-resolution image mosaics were acquired.…”

Section: Vital Bone Labelsmentioning

confidence: 99%

Hydrogel-based Delivery of rhBMP-2 Improves Healing of Large Bone Defects Compared With Autograft

Krishnan

Priddy

Esancy

et al. 2015

Clinical Orthopaedics &Amp; Related Research

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Background Autologous bone grafting remains the gold standard in the treatment of large bone defects but is limited by tissue availability and donor site morbidity. Recombinant human bone morphogenetic protein-2 (rhBMP-2), delivered with a collagen sponge, is clinically used to treat large bone defects and complications such as delayed healing or nonunion. For the same dose of rhBMP-2, we have shown that a hybrid nanofiber mesh-alginate (NMA-rhBMP-2) delivery system provides longer-term release and increases functional bone regeneration in critically sized rat femoral bone defects compared with a collagen sponge. However, no comparisons of healing efficiencies have been made thus far between this hybrid delivery system and the gold standard of using autograft. Questions/purposes We compared the efficacy of the NMA-rhBMP-2 hybrid delivery system to morselized autograft and hypothesized that the functional regeneration of large bone defects observed with sustained BMP delivery would be at least comparable to autograft treatment as measured by total bone volume and ex vivo mechanical properties. Methods Bilateral critically sized femoral bone defects in rats were treated with either live autograft or with the NMA-rhBMP-2 hybrid delivery system such that each animal received one treatment per leg. Healing was monitored by radiography and histology at 2, 4, 8, and 12 weeks. Defects were evaluated for bone formation by longitudinal micro-CT scans over 12 weeks (n = 14 per group). The bone volume, bone density, and the total new bone formed beyond 2 weeks within the defect were calculated from micro-CT reconstructions and values compared for the 2-, 4-, 8-, and 12-week scans within and across the two treatment groups. Two animals were used for bone labeling with subcutaneously injected dyes at 4, 8, and 12 weeks followed by histology at 12 weeks to

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“…These time periods were selected because previous studies showed that a great increase in the calcium content was observed during in vitro cell cultures between 12 to 21 days. 46 CPC disks with hESCd-MSCs cultured in the osteogenic medium were fixed with 10% formaldehyde and stained with Alizarin Red S (ARS; Millipore, Billerica, MA), which stained calcium-rich deposits by cells into a red color. An osteogenesis assay (Millipore) was used to extract the stained minerals and measure the ARS concentration, following the manufacturer's instructions.…”

Section: Mineral Synthesis By Hescd-mscsmentioning

confidence: 99%

Human Embryonic Stem Cell-Derived Mesenchymal Stem Cell Seeding on Calcium Phosphate Cement-Chitosan-RGD Scaffold for Bone Repair

Chen

Zhou

Weir

et al. 2013

Tissue Engineering Part A

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Calcium phosphate cement (CPC) has in situ-setting ability and excellent osteoconductivity. Human embryonic stem cells (hESCs) are exciting for regenerative medicine due to their strong proliferative ability and multilineage differentiation capability. However, there has been no report on hESC seeding with CPC. The objectives of this study were to obtain hESC-derived mesenchymal stem cells (hESCd-MSCs), and to investigate hESCd-MSC proliferation and osteogenic differentiation on novel CPC with chitosan immobilized with RGD (CPC-chitosan-RGD). RGD was covalently bonded with chitosan, which was then incorporated into CPC. The CPC-chitosan-RGD scaffold had higher strength and toughness than CPC-chitosan control without RGD ( p < 0.05). hESCs were cultured to form embryoid bodies (EBs), and the MSCs were then migrated out of the EBs. Flow cytometry indicated that the hESCd-MSCs expressed typical surface antigen profile of MSCs. hESCd-MSCs had good viability when seeded on CPC scaffolds. The percentage of live cells and the cell density were significantly higher on CPC-chitosan-RGD than CPC-chitosan control. Scanning electron microscope examination showed hESCd-MSCs with a healthy spreading morphology adherent to CPC. hESCd-MSCs expressed high levels of osteogenic markers, including alkaline phosphatase, osteocalcin, collagen I, and Runx2. The mineral synthesis by the hESCd-MSCs on the CPC-chitosan-RGD scaffold was twice that for CPC-chitosan control. In conclusion, hESCs were successfully seeded on CPC scaffolds for bone tissue engineering. The hESCd-MSCs had good viability and osteogenic differentiation on the novel CPC-chitosan-RGD scaffold. RGD incorporation improved the strength and toughness of CPC, and greatly enhanced the hESCd-MSC attachment, proliferation, and bone mineral synthesis. Therefore, the hESCd-MSC-seeded CPC-chitosan-RGD construct is promising to improve bone regeneration in orthopedic and craniofacial applications.

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Examination of Mineralized Nodule Formation in Living Osteoblastic Cultures Using Fluorescent Dyes

Cited by 125 publications

References 15 publications

Cationic Nanogel-mediated Runx2 and Osterix siRNA Delivery Decreases Mineralization in MC3T3 Cells

Cationic Nanogel-mediated Runx2 and Osterix siRNA Delivery Decreases Mineralization in MC3T3 Cells

Hydrogel-based Delivery of rhBMP-2 Improves Healing of Large Bone Defects Compared With Autograft

Human Embryonic Stem Cell-Derived Mesenchymal Stem Cell Seeding on Calcium Phosphate Cement-Chitosan-RGD Scaffold for Bone Repair

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