GIP reduces osteoclast activity and improves osteoblast survival in primary human bone cells.

OBJECTIVE: Drugs targeting the glucose-dependent insulinotropic polypeptide (GIP) receptor (GIPR) are emerging as treatments for type-2 diabetes and obesity. GIP acutely decreases serum markers of bone resorption and transiently increases bone formation markers in short-term clinical investigations. However, it is unknown whether GIP acts directly on bone cells to mediate these effects. Using a GIPR-specific antagonist, we aimed to assess whether GIP acts directly on primary human osteoclasts and osteoblasts. METHODS: Osteoclasts were differentiated from human CD14+ monocytes and osteoblasts from human bone. GIPR expression was determined using RNA-seq in primary human osteoclasts and in situ hybridization in human femoral bone. Osteoclastic resorptive activity was assessed using microscopy. GIPR signaling pathways in osteoclasts and osteoblasts were assessed using LANCE cAMP and AlphaLISA phosphorylation assays, intracellular calcium imaging and confocal microscopy. The bioenergetic profile of osteoclasts was evaluated using Seahorse XF-96. RESULTS: GIPR is robustly expressed in mature human osteoclasts. GIP inhibits osteoclastogenesis, delays bone resorption, and increases osteoclast apoptosis by acting upon multiple signaling pathways (Src, cAMP, Akt, p38, Akt, NFκB) to impair nuclear translocation of nuclear factor of activated T cells-1 (NFATc1) and nuclear factor-κB (NFκB). Osteoblasts also expressed GIPR, and GIP improved osteoblast survival. Decreased bone resorption and improved osteoblast survival were also observed after GIP treatment of osteoclast-osteoblast co-cultures. Antagonizing GIPR with GIP(3-30)NH2 abolished the effects of GIP on osteoclasts and osteoblasts. CONCLUSIONS: GIP inhibits bone resorption and improves survival of human osteoblasts, indicating that drugs targeting GIPR may impair bone resorption, whilst preserving bone formation.

Post-translational activation of Mmp2 correlates with patterns of active collagen degradation during the development of the zebrafish tail.

Matrix metalloproteinase-2 (a.k.a. Gelatinase A, or Mmp2 in zebrafish) is known to have roles in pathologies such as arthritis, in which its function is protective, as well as in cancer metastasis, in which it is activated as part of the migration and invasion of metastatic cells. It is also required during development and the regeneration of tissue architecture after wound healing, but its roles in tissue remodelling are not well understood. Gelatinase A is activated post-translationally by proteolytic cleavage, making information about its transcription and even patterns of protein accumulation difficult to relate to biologically relevant activity. Using a transgenic reporter of endogenous Mmp2 activation in zebrafish, we describe its accumulation and post-translational proteolytic activation during the embryonic development of the tail. Though Mmp2 is expressed relatively ubiquitously, it seems to be active only at specific locations and times. Mmp2 is activated robustly in the neural tube and in maturing myotome boundaries. It is also activated in the notochord during body axis straightening, in patches scattered throughout the epidermal epithelium, in the gut, and on cellular protrusions extending from mesenchymal cells in the fin folds. The activation of Mmp2 in the notochord, somite boundaries and fin folds associates with collagen remodelling in the notochord sheath, myotome boundary ECM and actinotrichia respectively. Mmp2 is likely an important effector of ECM remodelling during the morphogenesis of the notochord, a driving structure in vertebrate development. It also appears to function in remodelling the ECM associated with growing epithelia and the maturation of actinotrichia in the fin folds, mediated by mesenchymal cell podosomes.

Intracellular Localization in Zebrafish Muscle and Conserved Sequence Features Suggest Roles for Gelatinase A Moonlighting in Sarcomere Maintenance.

Gelatinase A (Mmp2 in zebrafish) is a well-characterized effector of extracellular matrix remodeling, extracellular signaling, and along with other matrix metalloproteinases (MMPs) and extracellular proteases, it plays important roles in the establishment and maintenance of tissue architecture. Gelatinase A is also found moonlighting inside mammalian striated muscle cells, where it has been implicated in the pathology of ischemia-reperfusion injury. Gelatinase A has no known physiological function in muscle cells, and its localization within mammalian cells appears to be due to inefficient recognition of its N-terminal secretory signal. Here we show that Mmp2 is abundant within the skeletal muscle cells of zebrafish, where it localizes to the M-line of sarcomeres and degrades muscle myosin. The N-terminal secretory signal of zebrafish Mmp2 is also challenging to identify, and this is a conserved characteristic of gelatinase A orthologues, suggesting a selective pressure acting to prevent the efficient secretion of this protease. Furthermore, there are several strongly conserved phosphorylation sites within the catalytic domain of gelatinase A orthologues, some of which are phosphorylated in vivo, and which are known to regulate the activity of this protease. We conclude that gelatinase A likely participates in uncharacterized physiological functions within the striated muscle, possibly in the maintenance of sarcomere proteostasis, that are likely regulated by kinases and phosphatases present in the sarcomere.

Zebrafish Xenograft: An Evolutionary Experiment in Tumour Biology.

Though the cancer research community has used mouse xenografts for decades more than zebrafish xenografts, zebrafish have much to offer: they are cheap, easy to work with, and the embryonic model is relatively easy to use in high-throughput assays. Zebrafish can be imaged live, allowing us to observe cellular and molecular processes in vivo in real time. Opponents dismiss the zebrafish model due to the evolutionary distance between zebrafish and humans, as compared to mice, but proponents argue for the zebrafish xenograft's superiority to cell culture systems and its advantages in imaging. This review places the zebrafish xenograft in the context of current views on cancer and gives an overview of how several aspects of this evolutionary disease can be addressed in the zebrafish model. Zebrafish are missing homologs of some human proteins and (of particular interest) several members of the matrix metalloproteinase (MMP) family of proteases, which are known for their importance in tumour biology. This review draws attention to the implicit evolutionary experiment taking place when the molecular ecology of the xenograft host is significantly different than that of the donor.

Mammalian fibroblast cells avoid residual stress zone caused by nanosecond laser pulses.

This study investigates the effects of laser irradiation on crystalline silicon and its application in biomaterials. We used an analytical model to predict the ablation depth and pit size resulting from laser exposure of silicon samples. The temperatures generated are predicted correlate with laser power, and to result in the formation of a residual stress zone bordering the ablated groove. Different crystal orientations found in the substrate confirm that there was crystal distortion, which consequently induces these residual stress zones. Mouse embryonic fibroblasts avoid the stress areas and accumulate outside of these zones. Higher laser power results in broader residual stress zone and a larger zone of cellular exclusion. We argue that residual stress resulting from high-energy laser ablation of silicon may be a promising avenue to explore as a method for patterning cell growth on these materials.

Mammalian fibroblast cells show strong preference for laser-generated hybrid amorphous silicon-SiO2 textures.

BACKGROUND: In this study, we investigated a method to produce bioactive hybrid amorphous silicon and silicon oxide patterns using nanosecond laser pulses. METHODS: Microscale line patterns were made by laser pulses on silicon wafers at different frequencies (25, 70 and 100 kHz), resulting in ablation patterns with frequency-dependent physical and chemical properties. RESULTS: Incubating the laser-treated silicon substrates with simulated body fluid demonstrated that the physicochemical properties of the laser-treated samples were stable under these conditions, and favored the deposition of bone-like apatite. More importantly, while NIH 3T3 fibroblasts did colonize the untreated regions of the silicon wafers, they showed a strong preference for the laser-treated regions, and further discriminated between substrates treated with different frequencies. CONCLUSIONS: Taken together, these data suggest that laser materials processing of silicon-based devices is a promising avenue to pursue in the production of biosensors and other bionic devices.

Mouse embryonic fibroblasts accumulate differentially on titanium surfaces treated with nanosecond laser pulses.

Biomaterial engineering, specifically in bone implant and osseointegration, is currently facing a critical challenge regarding the response of cells to foreign objects and general biocompatibility of the materials used in the production of these implants. Using the developing technology of the laser surface treatment, this study investigates the effects of the laser repetition rate (frequency) on cell distribution across the surface of the titanium substrates. The main objective of this research is building a fundamental understanding of how cells interact with treated titanium and how different treatments affect cell accumulation. Cells respond differently to surfaces treated with different frequency lasers. The results of this research identify the influence of frequency on surface topography properties and oxidation of titanium, and their subsequent effects on the pattern of cell accumulation on its surface. Despite increased oxidation in laser-treated regions, the authors observe that fibroblast cells prefer untreated titanium to laser-treated regions, except the regions treated with 25 kHz pulses, which become preferentially colonized after 72 h.

The zebrafish embryo: a powerful model system for investigating matrix remodeling.

Extracellular matrix (ECM) remodeling is a process that is crucial to the development of embryos, the growth and metastasis of tumors, and wound healing and homeostasis of tissues in adults. As such, it involves dozens of gene products that are regulated by mechanisms operating at transcriptional and multiple posttranslational levels. This complexity of regulation has made the development of a comprehensive understanding of the biology of ECM remodeling in vivo an unusually challenging task, yet such an understanding would be of profound value to our knowledge of and clinical approaches to the treatment of many cancers. The primary effectors of ECM remodeling are the matrix metalloproteinases (MMPs). Homologs of this gene family have been identified in every metazoan examined. We propose that the zebrafish embryo is an ideal system for the study of the regulation of MMP activity, and we present some progress we have made in the development of this organism as a platform for MMP research. We have identified 25 genes encoding MMPs in the zebrafish genome, and 5 genes encoding their endogenous inhibitors, the tissue inhibitors of MMPs. Based on a phylogenetic analysis, we have identified the most probable homologies of these sequences and found that there are two that are of equivocal identity. We have developed 17 antibodies specific to zebrafish MMPs and have begun characterizing the ontogeny of these molecules. Finally, we have developed two novel assays that allow the detection and characterization of active MMPs in vivo (differential in vivo zymography and activity-based protease profiling). In combination with the array of powerful biochemical, genomic, cell, and molecular biological techniques available to zebrafish researchers already, we feel that these new reagents and techniques make the zebrafish the best model system for the study of MMP regulation currently available.