Osteoblast Precursors, but Not Mature Osteoblasts, Move into Developing and Fractured Bones along with Invading Blood Vessels

Massachusetts General Hospital and Harvard Medical School, Boston, 02114, USA.
Developmental Cell (Impact Factor: 9.71). 08/2010; 19(2):329-44. DOI: 10.1016/j.devcel.2010.07.010
Source: PubMed


During endochondral bone development, the first osteoblasts differentiate in the perichondrium surrounding avascular cartilaginous rudiments; the source of trabecular osteoblasts inside the later bone is, however, unknown. Here, we generated tamoxifen-inducible transgenic mice bred to Rosa26R-LacZ reporter mice to follow the fates of stage-selective subsets of osteoblast lineage cells. Pulse-chase studies showed that osterix-expressing osteoblast precursors, labeled in the perichondrium prior to vascular invasion of the cartilage, give rise to trabecular osteoblasts, osteocytes, and stromal cells inside the developing bone. Throughout the translocation, some precursors were found to intimately associate with invading blood vessels, in pericyte-like fashion. A similar coinvasion occurs during endochondral healing of bone fractures. In contrast, perichondrial mature osteoblasts did not exhibit perivascular localization and remained in the outer cortex of developing bones. These findings reveal the specific involvement of immature osteoblast precursors in the coupled vascular and osteogenic transformation essential to endochondral bone development and repair.

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Available from: Sanford Irwin Roth, Apr 30, 2015
    • "Vasculature plays a key role in regulating the development (Yin and Pacifici, 2001; Yin et al., 2002; Wang et al., 2007), growth (Maes et al., 2010; Liu et al., 2012), and repair (Rabie et al., 2002; Street et al., 2002; Pacicca et al., 2003; Jacobsen et al., 2008) of the endochondral limb skeleton. In order to examine the role of vasculature during development of intramembranous scleral ossicles, we injected highlighter ink into the vasculature of the embryonic chick enabling us to visualize, with high resolution, scleral blood vessels during the key stages of scleral ossicle development from induction (HH 35) through to mineralization (HH 38.5). "
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    ABSTRACT: Intramembranous ossification is a complex multi-step process which relies on extensive interactions among bone cells and surrounding tissues. The embryonic vasculature is essential in regulating endochondral ossification; however, its role during intramembranous ossification remains poorly understood, and in vivo studies are lacking. Previous research from our lab on the development of the intramembranous scleral ossicles has demonstrated an intriguing pattern of vascular development in which the areas of future osteogenesis remain avascular until after bone induction has occurred. Such avascular zones are located directly beneath each of the conjunctival papillae, epithelial structures which provide osteogenic signals to the underlying mesenchyme. Here we provide a high-resolution map of the developing vasculature from the time of ossicle induction to mineralization using a novel technique. We show that vegfa is expressed by the papillae and nearby mesenchymal tissue throughout HH 34-37, when vascular growth is taking place, and is down-regulated thereafter. Localized inhibition of Vegf results in expansion of the avascular zone surrounding the implanted papilla and mispatterning of the scleral ossicles. These results demonstrate that Vegf signaling could provide important insights into the complex relationship between bone and vasculature during intramembranous bone development. Copyright © 2015. Published by Elsevier Inc.
    No preview · Article · Jul 2015 · Developmental Biology
    • "Able to regenerate soft tissue (Liu et al., 2013) and cartilage (Veronesi et al., 2014), the SVF has also been reported as an enhancer of bone ingrowth (Yoon et al., 2007). It is known that bone formation is an angiogenesis-dependent process (Gerber et al., 1999), since studies have shown that osteoblast precursors may use the blood vessels along the abluminal surface of the endothelium as a conduit to support their entry into the new bone (Maes et al., 2010; Dirckx et al., 2013). In this context, the maintenance in culture of endothelial and mesenchymal progenitors from the SVF has been shown to enhance orthotopic bone regeneration (Güven et al., 2011). "
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    ABSTRACT: Osteoradionecrosis of the jaw is a major side-effect of radiotherapy used in the treatment of squamous cell carcinomas of the upper aerodigestive tract. The standard reconstruction procedure is a free flap transfer of autogenous bone. A new approach using a tissue engineering strategy has shown that total bone marrow (TBM) associated with biphasic calcium phosphate (BCP) is the best combination for bone regeneration in an irradiated area. Recently, the stromal vascular fraction from adipose tissue (SVF) was described as an alternative to TBM for promoting new bone formation. The aim of this study was to identify the capacity of a freshly isolated SVF to induce new bone formation in an irradiated area. Four weeks after irradiation of the hind limbs of 15 rats, bone defects were created and filled with either SVF or TBM with and without BCP. Three weeks after the implantations, analysis showed that the BCP-TBM mixture improved new bone formation after radiation (p < 0.05). The BCP-SVF association induced significant neoangiogenesis but failed to enhance new bone formation. The BCP-SVF mixture was insufficient to enhance new bone formation in the irradiated area, suggesting that the role of the environment might be crucial for ossification. Copyright © 2015 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.
    No preview · Article · Jun 2015 · Journal of Cranio-Maxillofacial Surgery
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    • "j o u r n a l h o m e p a g e : w w w. e l s e v i e r. c o m / l o c a t e / g e p MMPs have long been recognised to be essential for embryonic and post-natal bone development, and are required for angiogenesis and vascular endothelial growth factor (VEGF) expression (Eisenach et al., 2010; Karelina et al., 1995; Raza and Cornelius, 2000). Elegant studies in mice, combining osteoblast lineage tracing with monitoring of the vascular endothelium, have shown that osteoblast precursors at E12.5 within the perichondrium translocate to the nascent primary ossification centre giving rise to trabecular osteoblasts and cortical osteocytes by E16.5 (Maes et al., 2010). Throughout this translocation the osteoblast precursors are intimately associated with invading blood vessels; processes that require MMP activity for ECM remodelling. "
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    ABSTRACT: Osteocytes within bone differentiate from osteoblast precursors which reside in a mineralised extracellular matrix (ECM). Fully differentiated osteocytes are critical for bone development and function but the factors that regulate this differentiation process are unknown. The enzymes primarily responsible for ECM remodelling are matrix metalloproteinases (MMP) however, the expression and role of MMPs during osteocytogenesis is undefined. Here we used MLO-A5 cells to determine the temporal gene expressions of the MMP family and their endogenous inhibitors - tissue inhibitors of metalloproteinases (TIMPs) during osteocytogenesis. RT-qPCR revealed expression of 14 Mmps and 3 Timps in MLO-A5 cells. Mmp2, Mmp23 and Mmp28 were decreased concurrent with mineralisation onset (P<0.05*). Mmp14 and Mmp19 mRNAs were also significantly increased at day 3 (P<0.05*) before returning to baseline levels at day 6. Decreased expressions of Timp1, Timp2 and Timp3 mRNA was observed by day 6 compared to day 0 (P<0.05*). To examine whether these changes are linked to osteocytogenesis, we determined Mmp/Timp mRNA expressions in mineralisation-limited conditions. RT-qPCR revealed that the previously observed decreases in Mmp2, Mmp23 and Mmp28 were not observed in these mineralisation-limited cultures, therefore closely linking these MMPs with osteocyte differentiation. Similarly, we found differential expression of Timp1, Timp2 and Timp3 mRNA in mineralisation-restricted cultures (P<0.05*). In conclusion, we have identified several members of the MMP/TIMP families as regulators of ECM remodelling necessary for the acquisition of the osteocyte phenotype. Copyright © 2015. Published by Elsevier B.V.
    Full-text · Article · May 2015 · Gene Expression Patterns
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