Mouse Cre Models for the Study of Bone Diseases

Dallas, Sarah L.; Xie, Yixia; Shiflett, Lora A.; Ueki, Yasuyoshi

doi:10.1007/s11914-018-0455-7

Cited by 60 publications

(57 citation statements)

References 84 publications

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“…This promoter was originally thought to be expressed in preosteocytes, osteocytes, odontoblasts and some pulp cells (Toyosawa et al, 2001; Feng et al, 2003; Kalajzic et al, 2004; Lu et al, 2007). However, subsequent studies have shown that it is expressed in some late osteoblasts as well (Kalajzic et al, 2013; Dallas et al, 2018), which may be due to the sensitivity of the tdTomato reporter in the Ai9 mouse line, even to extremely low levels of Cre recombinase (reviewed in Dallas et al, 2018). In our hands, in bone tissue, the tdTomato transgene was strongly expressed in the majority of embedded osteocytes, preosteocytes, and some late osteoblasts on the bone surface when used with the 10 kb Dmp1 Cre driver (Figure 1A) (a Cre negative littermate control is shown at right).…”

Section: Resultsmentioning

confidence: 99%

Collagen Dynamics During the Process of Osteocyte Embedding and Mineralization

Shiflett

Tiede-Lewis

Xie

et al. 2019

Front. Cell Dev. Biol.

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Bone formation, remodeling and repair are dynamic processes, involving cell migration, ECM assembly, osteocyte embedding, and bone resorption. Using live-cell imaging, we previously showed that osteoblast assembly of the ECM proteins fibronectin and collagen is highly dynamic and is integrated with cell motility. Additionally, osteoblast-to-osteocyte transition involved arrest of cell motility, followed by dendrite extension and retraction that may regulate positioning of embedding osteocytes. To further understand how osteocytes differentiate and embed in collagen, mice were generated that co-expressed GFPtopaz-tagged collagen with a Dmp1-Cre-inducible tdTomato reporter targeted to preosteocytes/osteocytes. Dual live-cell imaging of collagen and osteocyte dynamics in mineralizing primary calvarial cell cultures showed that Dmp1-Cre/tdTomato turned on in early bone nodule forming regions, demarcated by foci of concentrated GFP-collagen bundles that appeared structurally distinct from the surrounding collagen. Dmp1-Cre/tdTomato-positive cells were post-mitotic and were continuously induced throughout the 2 week timecourse, whereas the majority of collagen was assembled by day 7. GFP-collagen fibrils showed global (tissue-level) motions, suggesting coordinated cell layer movement, and local fibril motions mediated by cell-generated forces. Condensation of collagen fibril networks occurred within bone nodules prior to mineralization. Intravital imaging confirmed a similar structural appearance of GFP-collagen in calvarial bone, with analogous global motions of mineralizing areas adjacent to sutures. In early (unmineralized) calvarial cell cultures, Dmp1-Cre/tdTomato-positive cells were motile (mean velocity 4.8 μm/h), moving freely in and around the forming bone nodule, with a small number of these cells embedded in collagen, constraining their motion. In mineralizing cultures, the average velocity of Dmp1-Cre/tdTomato-positive cells was significantly reduced (0.7 μm/h), with many immobilized in the mineralizing nodule. Three apparent mechanisms for embedding of Dmp1-Cre/tdTomato-positive cells were observed. In some cases, a previously motile Dmp1-Cre/tdTomato-positive cell became immobilized in collagen fibril networks that were newly assembled around the cell, thereby entrapping it. In other cases, a motile Dmp1-Cre/tdTomato-positive cell moved into an already formed “collagen lacuna,” arrested its motility and became embedded. Alternatively, some cells switched on tdTomato expression in situ within a lacuna. These data provide new insight into the dynamic process of bone collagen assembly and suggest multiple mechanisms for osteocyte entrapment in collagen matrix.

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Section: Resultsmentioning

confidence: 99%

Collagen Dynamics During the Process of Osteocyte Embedding and Mineralization

Shiflett

Tiede-Lewis

Xie

et al. 2019

Front. Cell Dev. Biol.

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“…Other considerations may relate to when in development insulin signaling disruption in osteoblasts occurs (prenatally vs. postnatally); at what stage of osteoblastogenesis the disruption manifests (progenitor vs mature osteoblast, etc. ); as well as possible issues with certain Cre-recombinase mouse models and the lack-of specificity for targeting only bone cells 27,28 .…”

Section: Discussionmentioning

confidence: 99%

Postnatal loss of the insulin receptor in osteoprogenitor cells does not impart a metabolic phenotype

Fowlkes

Bunn

Kalaitzoglou

et al. 2020

Sci Rep

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The relationship between osteoblast-specific insulin signaling, osteocalcin activation and glucometabolic homeostasis has proven to be complex and potentially inconsistent across animal-model systems and in humans. Moreover, the impact of postnatally acquired, osteoblast-specific insulin deficiency on the pancreas-to-skeleton-to-pancreas circuit has not been studied. To explore this relationship, we created a model of postnatal elimination of insulin signaling in osteoprogenitors. Osteoprogenitor-selective ablation of the insulin receptor was induced after ~10 weeks of age in IR l°x/ lox /Osx-Cre +/− genotypic male and female mice (designated postnatal-OIRKO). At ~21 weeks of age, mice were then phenotypically and metabolically characterized. postnatal-oiRKo mice demonstrated a significant reduction in circulating concentrations of undercarboxylated osteocalcin (ucOC), in both males and females compared with control littermates. However, no differences were observed between postnatal-oiRKo and control mice in: body composition (lean or fat mass); fasting serum insulin; HbA1c; glucose dynamics during glucose tolerance testing; or in pancreatic islet area or islet morphology, demonstrating that while ucOC is impacted by insulin signaling in osteoprogenitors, there appears to be little to no relationship between osteocalcin, or its derivative (ucOC), and glucose homeostasis in this model.

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“…For example, a recent study in which PDGFRb was deleted from Osterix-expressing cells found no notable defects in skeletal development, but severe impairment of fracture healing (8) , demonstrating contextual distinctions between development and fracture repair. Further, skeletal cell-and bone-specific gene deletion during development may alter the number, location, or niche of progenitor cells that, during injury, are activated for skeletal regeneration (9) . In this study, we assessed the effects of conditional gene deletion from osteochondroprogenitors on endochondral bone fracture repair, with deletion performed either constitutively during development or inducibly after normal development to skeletal maturity prior to fracture.…”

Section: Introductionmentioning

confidence: 99%

YAP and TAZ promote periosteal osteoblast precursor expansion and differentiation for fracture repair

Kegelman

Nijsure

Moharrer

et al. 2020

Preprint

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In response to bone fracture, periosteal progenitor cells proliferate, expand, and differentiate to form cartilage and bone in the fracture callus. These cellular functions require the coordinated activation of multiple transcriptional programs, and the transcriptional regulators Yes-associated protein (YAP) and transcriptional co-activator with PDZ-binding motif (TAZ) regulate osteochondroprogenitor activation during endochondral bone development.However, recent observations raise important distinctions between the signaling mechanisms used to control bone morphogenesis and repair. Here, we tested the hypothesis that YAP and TAZ regulate osteochondroprogenitor activation during endochondral bone fracture healing. Constitutive YAP and/or TAZ deletion from Osterixexpressing cells impaired both cartilage callus formation and subsequent mineralization. However, this could be explained either by direct defects in osteochondroprogenitor differentiation after fracture, or by developmental deficiencies in the progenitor cell pool prior to fracture. Consistent with the second possibility, we found that developmental YAP/TAZ deletion produced long bones with impaired periosteal thickness and cellularity. Therefore, to remove the contributions of developmental history, we next generated adult onset-inducible knockout mice (using Osx1-Cre tetOff ) in which YAP and TAZ were deleted prior to fracture, but after normal development. Adult onset-induced YAP/TAZ deletion had no effect on cartilaginous callus formation, but impaired bone formation at 14 days post-fracture (dpf). Earlier, at 4 dpf, adult onset-induced YAP/TAZ deletion impaired the proliferation and expansion of osteoblast precursor cells located in the shoulder of the callus. Further, activated periosteal cells isolated from this region at 4 dpf exhibited impaired osteogenic differentiation in vitro upon YAP/TAZ deletion. Finally, confirming the effects on osteoblast function in vivo, adult onset-induced YAP/TAZ deletion impaired bone formation in the callus shoulder at 7 dpf, prior to the initiation of endochondral ossification. Together, these data show that YAP and TAZ promote the expansion and differentiation of periosteal osteoblast precursors to accelerate bone fracture healing.

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Mouse Cre Models for the Study of Bone Diseases

Cited by 60 publications

References 84 publications

Collagen Dynamics During the Process of Osteocyte Embedding and Mineralization

Collagen Dynamics During the Process of Osteocyte Embedding and Mineralization

Postnatal loss of the insulin receptor in osteoprogenitor cells does not impart a metabolic phenotype

YAP and TAZ promote periosteal osteoblast precursor expansion and differentiation for fracture repair

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