Photo-crosslinked alginate hydrogels support enhanced matrix accumulation by nucleus pulposus cells in vivo

SummaryObjectiveIntervertebral disc (IVD) degeneration is a major health concern in the United States. Replacement of the nucleus pulposus (NP) with injectable biomaterials represents a potential treatment strategy for IVD degeneration. The objective of this study was to characterize the extracellular matrix (ECM) assembly and functional properties of NP cell-encapsulated, photo-crosslinked alginate hydrogels in comparison to ionically crosslinked alginate constructs.MethodsMethacrylated alginate was synthesized by esterification of hydroxyl groups with methacrylic anhydride. Bovine NP cells were encapsulated in alginate hydrogels by ionic crosslinking using CaCl2 or through photo-crosslinking upon exposure to long-wave UV light in the presence of a photoinitiator. The hydrogels were evaluated in vitro by gross and histological analysis and in vivo using a murine subcutaneous pouch model. In vivo samples were analyzed for gene expression, ECM localization and accumulation, and equilibrium mechanical properties.ResultsIonically crosslinked hydrogels exhibited inferior proteoglycan accumulation in vitro and were unable to maintain structural integrity in vivo. In further studies, photo-crosslinked alginate hydrogels were implanted for up to 8 weeks to examine NP tissue formation. Photo-crosslinked hydrogels displayed temporal increases in gene expression and assembly of type II collagen and proteoglycans. Additionally, hydrogels remained intact over the duration of the study and the equilibrium Young's modulus increased from 1.24±0.09kPa to 4.31±1.39kPa, indicating the formation of functional matrix with properties comparable to those of the native NP.ConclusionsThese findings support the use of photo-crosslinked alginate hydrogels as biomaterial scaffolds for NP replacement

Modelling and prediction of water current using artificial neural networks: A case study of the commodore channel

Water current modelling and prediction techniques along coastal inlets have attracted growing concern in recent years. This is largely so because water current component continues to be a major contributor to movement of sediments, tracers and pollutants, and to a whole range of offshore applications in engineering, environmental observations, exploration and oceanography. However, most research works are lacking adequate methods for developing precise prediction models along the commodore channel in Lagos State. This research work presents water current prediction using Artificial Neural Networks (ANNs). The Back Propagation (BP) technique with feed forward architecture and optimized training algorithm known as Levenbergq-Marquardt was used to develop a Neural Network Water Current Prediction model-(NNWLM) in a MATLAB programming environment. It was passed through model sensitivity analysis and afterwards tested with data from the Commodore channel (Lagos Lagoon). The result revealed prediction accuracy ranging from 0.012 to 0.045 in terms of Mean Square Error (MSE) and 0.80 to 0.83 in terms of correlation coefficient (R-value). With this high performance, the Neural network developed in this work can be used as a veritable tool for water current prediction along the Commodore channel and in extension a wide variety of coastal engineering and development, covering sediment management program: dredging, sand bypassing, beach-contingency plans, and protection of beaches vulnerable to storm erosion and monitoring and prediction of long-term water current variations in coastal inlets. Keywords: Artificial Neural Network, Commodore Channel, Coastal Inlet, Water Current, Back Propagation

β-catenin Initiates Tooth Neogenesis in Adult Rodent Incisors

β-catenin signaling is required for embryonic tooth morphogenesis and promotes continuous tooth development when activated in embryos. To determine whether activation of this pathway in the adult oral cavity could promote tooth development, we induced mutation of epithelial β-catenin to a stabilized form in adult mice. This caused increased proliferation of the incisor tooth cervical loop, outpouching of incisor epithelium, abnormal morphology of the epithelial-mesenchymal junction, and enhanced expression of genes associated with embryonic tooth development. Ectopic dental-like structures were formed from the incisor region following implantation into immunodeficient mice. Thus, forced activation of β-catenin signaling can initiate an embryonic-like program of tooth development in adult rodent incisor teeth

Alpha-TCP improves the apatite-forming ability of calcium-silicate hydraulic cements soaked in phosphate solutions.

Alpha-TCP is a biocompatible reactive ion-releasing calcium-phosphate able to provide calcium and phosphate ions due to its biodegradation by hydrolysis and progressive dissolution. Alpha-TCP could enhance/improve the apatite-forming ability of calciumsilicate portland-derived hydraulic cements currently used in endodontics and oral surgery. Aim: An innovative calcium-silicate hydraulic self-setting cement containing alphatricalcium phosphate (alpha-TCP) has been conceived and designed for dentistry. The kinetic of the in vitro apatite formation was studied in simulated body fluids. Materials & methods: An experimental calcium-silicate portland-derived cement containing di- and tricalcium-silicate and alpha-TCP (wTC-TCP) was designed and prepared. The same cement free from alpha-TCP was used as control (wTC). The cements were soaked in different phosphate-containing solutions, namely Dulbecco\u2019s Phosphate Buffered Saline (DPBS) or Hank\u2019s Balanced Salt Solution (HBSS), at 37\ub0C and the surface chemistry was investigated over time (from 24hrs to 6months) by SEM/EDX, micro-Raman and ATR-FTIR. Results: The early formation (24hrs) of an aragonite/calcite layer onto both cements in both media was observed. Calcium phosphate deposits precipitated within 1-3days in DPBS; spherical calcium-phosphate particles (apatite spherulites) appeared after 3-7days. wTC-TCP cement showed earlier, thicker and more homogeneous calcium phosphate deposits than wTC. In HBSS calcite deposits were mainly noticed, while phosphate bands appeared only after 7days; the presence of globular deposits after 14-28days was mostly detected on wTC-TCP. After 6months, an approx 900microns carbonated apatite layer formed in DPBS whilst a 150-350microns thick calcite/apatite layer generated in HBSS. Even in HBSS the carbonated apatite coating was earlier and thicker on wTC-TCP than wTC. Conclusions: Calcium-silicate cements showed the formation of a bone-like apatite layer, depending on the medium composition and ageing time. The addition of alpha-TCP increases the apatite-forming ability of calcium-silicate cements. Calcium-silicate hydraulic cements doped with alpha-TCP represent attractive materials to improve apical bone healing in oral surgery

Biomimetic calcium-silicate cements support differentiation of human orofacial mesenchymal stem cell.

Human orofacial bone mesenchymal stem cells (OFMSCs) from maxilla and mandible have robust osteogenic regenerative properties on the basis of our previous reports that demonstrate phenotypic and functional differences between jaw and axial bone mesenchymal stem cells in same individuals. Furthermore, a combination of OFMSCs with bioactive calcium-releasing cements can potentially improve OFMSC multilineage differentiation capacity, but biocompatibility of calcium-silicate cements with OFMSCs is still unclear. We tested the hypothesis that material extracts of calcium-releasing calcium-silicate cements support biomimetic microenvironment for survival and differentiation of human OFMSCs. METHODS: Two experimental calcium-silicate cements, (1) calcium-silicate mineral powder (wTC) containing dicalcium and tricalcium-silicate, calcium sulfate, and calcium chloride and (2) wTC doped with alpha-tricalcium phosphate (wTC-αTCP), were designed and prepared. Cement setting times were assessed by Gilmore needles, ability to release calcium and hydroxyl ions was assessed by potentiometric methods, and OFMSC attachment to calcium-silicate discs was assessed. Calcium-silicate material extracts were tested for ability to support OFMSC survival and in vitro/in vivo differentiation. RESULTS: Fewer OFMSCs attached to calcium-silicate discs relative to tissue culture plastic (P = .001). Extracts of calcium-silicate cements sustained OFMSC survival, maintained steady state levels of vascular cell adhesion molecule-1, alkaline phosphatase, and bone sialoprotein while up-regulating their respective gene transcripts. Adipogenic and in vivo bone regenerative capacities of OFMSCs were also unaffected by calcium-silicate extracts. CONCLUSIONS: Ion-releasing calcium-silicate cements support a biomimetic microenvironment conducive to survival and differentiation of OFMSCs. Combination of OFMSCs and calcium-silicate cement can potentially promote tissue regeneration in periapical bone defects

Targeted Inhibition of CD133+ Cells in Oral Cancer Cell Lines

Resistance to treatment and the appearance of secondary tumors in head and neck squamous cell carcinomas (HNSCC) have been attributed to the presence of cells with stem-cell-like properties in the basal layer of the epithelium at the site of the lesion. In this study, we tested the hypothesis that these putative cancer stem cells (CSC) in HNSCC could be specifically targeted and inhibited. We found that 9 of 10 head and neck tumor biopsies contained a subpopulation of cells that expressed CD133, an unusual surface-exposed membrane-spanning glycoprotein associated with CSC. A genetically modified cytolethal distending toxin (Cdt), from the periodontal pathogen Aggregatibacter actinomycetemcomitans, was conjugated to an anti-human CD133 monoclonal antibody (MAb). The Cdt-MAb complex preferentially inhibited the proliferation of CD133+ cells in cultures of established cell lines derived from HNSCC. Inhibition of the CD133+ cells was rate- and dose-dependent. Saturation kinetics indicated that the response to the Cdt-MAb complex was specific. Healthy primary gingival epithelial cells that are native targets of the wild-type Cdt were not affected. Analysis of these data provides a foundation for the future development of new therapies to target CSC in the early treatment of HNSCC. Abbreviations: Cdt, cytolethal distending toxin; CSC, cancer stem cells; HNSCC, head and neck squamous cell carcinoma; MAb, monoclonal antibody

Rare Bone Diseases and Their Dental, Oral, and Craniofacial Manifestations

Hereditary diseases affecting the skeleton are heterogeneous in etiology and severity. Though many of these conditions are individually rare, the total number of people affected is great. These disorders often include dental-oral-craniofacial (DOC) manifestations, but the combination of the rarity and lack of in-depth reporting often limit our understanding and ability to diagnose and treat affected individuals. In this review, we focus on dental, oral, and craniofacial manifestations of rare bone diseases. Discussed are defects in 4 key physiologic processes in bone/tooth formation that serve as models for the understanding of other diseases in the skeleton and DOC complex: progenitor cell differentiation (fibrous dysplasia), extracellular matrix production (osteogenesis imperfecta), mineralization (familial tumoral calcinosis/hyperostosis hyperphosphatemia syndrome, hypophosphatemic rickets, and hypophosphatasia), and bone resorption (Gorham-Stout disease). For each condition, we highlight causative mutations (when known), etiopathology in the skeleton and DOC complex, and treatments. By understanding how these 4 foci are subverted to cause disease, we aim to improve the identification of genetic, molecular, and/or biologic causes, diagnoses, and treatment of these and other rare bone conditions that may share underlying mechanisms of disease