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.

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.

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 hybridisation 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.

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.

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.