Recombinant human osteopontin expressed in Nicotiana benthamiana stimulates osteogenesis related genes in human periodontal ligament cells.

Tissue engineering aims to utilise biologic mediators to facilitate tissue regeneration. Several recombinant proteins have potential to mediate induction of bone production, however, the high production cost of mammalian cell expression impedes patient access to such treatments. The aim of this study is to produce recombinant human osteopontin (hOPN) in plants for inducing dental bone regeneration. The expression host was Nicotiana benthamiana using a geminiviral vector for transient expression. OPN expression was confirmed by Western blot and ELISA, and OPN was purified using Ni affinity chromatography. Structural analysis indicated that plant-produced hOPN had a structure similar to commercial HEK cell-produced hOPN. Biological function of the plant-produced hOPN was also examined. Human periodontal ligament stem cells were seeded on an OPN-coated surface. The results indicated that cells could grow normally on plant-produced hOPN as compared to commercial HEK cell-produced hOPN determined by MTT assay. Interestingly, increased expression of osteogenic differentiation-related genes, including OSX, DMP1, and Wnt3a, was observed by realtime PCR. These results show the potential of plant-produced OPN to induce osteogenic differentiation of stem cells from periodontal ligament in vitro, and suggest a therapeutic strategy for bone regeneration in the future

Bone morphogenetic protein-2 gene controls tooth root development in coordination with formation of the periodontium

Formation of the periodontium begins following onset of tooth-root formation in a coordinated manner after birth. Dental follicle progenitor cells are thought to form the cementum, alveolar bone and Sharpey's fibers of the periodontal ligament (PDL). However, little is known about the regulatory morphogens that control differentiation and function of these progenitor cells, as well as the progenitor cells involved in crown and root formation. We investigated the role of bone morphogenetic protein-2 (Bmp2) in these processes by the conditional removal of the Bmp2 gene using the Sp7-Cre-EGFP mouse model. Sp7-Cre-EGFP first becomes active at E18 in the first molar, with robust Cre activity at postnatal day 0 (P0), followed by Cre activity in the second molar, which occurs after P0. There is robust Cre activity in the periodontium and third molars by 2 weeks of age. When the Bmp2 gene is removed from Sp7(+) (Osterix(+)) cells, major defects are noted in root, cellular cementum and periodontium formation. First, there are major cell autonomous defects in root-odontoblast terminal differentiation. Second, there are major alterations in formation of the PDLs and cellular cementum, correlated with decreased nuclear factor IC (Nfic), periostin and α-SMA(+) cells. Third, there is a failure to produce vascular endothelial growth factor A (VEGF-A) in the periodontium and the pulp leading to decreased formation of the microvascular and associated candidate stem cells in the Bmp2-cKO(Sp7-Cre-EGFP). Fourth, ameloblast function and enamel formation are indirectly altered in the Bmp2-cKO(Sp7-Cre-EGFP). These data demonstrate that the Bmp2 gene has complex roles in postnatal tooth development and periodontium formation

Osteoclasts control reactivation of dormant myeloma cells by remodelling the endosteal niche

Multiple myeloma is largely incurable, despite development of therapies that target myeloma cell-intrinsic pathways. Disease relapse is thought to originate from dormant myeloma cells, localized in specialized niches, which resist therapy and repopulate the tumour. However, little is known about the niche, and how it exerts cell-extrinsic control over myeloma cell dormancy and reactivation. In this study, we track individual myeloma cells by intravital imaging as they colonize the endosteal niche, enter a dormant state and subsequently become activated to form colonies. We demonstrate that dormancy is a reversible state that is switched ‘on’ by engagement with bone-lining cells or osteoblasts, and switched ‘off’ by osteoclasts remodelling the endosteal niche. Dormant myeloma cells are resistant to chemotherapy that targets dividing cells. The demonstration that the endosteal niche is pivotal in controlling myeloma cell dormancy highlights the potential for targeting cell-extrinsic mechanisms to overcome cell-intrinsic drug resistance and prevent disease relapse

Murine TMJ Loading Causes Increased Proliferation and Chondrocyte Maturation

The purpose of this study was to examine the effects of forced mouth opening on murine mandibular condylar head remodeling. We hypothesized that forced mouth opening would cause an anabolic response in the mandibular condylar cartilage. Six-week-old female C57BL/6 mice were divided into 3 groups: (1) control, (2) 0.25 N, and (3) 0.50 N of forced mouth opening. Gene expression, micro-CT, and proliferation were analyzed. 0.5 N of forced mouth opening caused a significant increase in mRNA expression of Pthrp, Sox9, and Collagen2a1, a significant increase in proliferation, and a significant increase in trabecular spacing in the subchondral bone, whereas 0.25 N of forced mouth opening did not cause any significant changes in any of the parameters examined. Forced mouth opening causes an increase in the expression of chondrocyte maturation markers and an increase in subchondral trabecular spacing

Specific Hippocampal Interneurons Shape Consolidation of Recognition Memory

Oliveira da Cruz et al. show that a specific subpopulation of hippocampal CB1 and D1 receptor-positive neurons controls late consolidation of recognition memory and associated synaptic plasticity by moderating local inhibitory GABAergic activity in the hippocampus