Zhang, X, Xie, C, Lin, AS, Ito, H, Awad, H, Lieberman, JR et al.. Periosteal progenitor cell fate in segmental cortical bone graft transplantations: implications for functional tissue engineering. J Bone Miner Res 20: 2124-2137

Department of Orthopaedics, University of Rochester Medical Center, New York, USA.
Journal of Bone and Mineral Research (Impact Factor: 6.83). 01/2006; 20(12):2124-37. DOI: 10.1359/JBMR.050806
Source: PubMed


A murine segmental femoral bone graft model was used to show the essential role of donor periosteal progenitor cells in bone graft healing. Transplantation of live bone graft harvested from Rosa 26A mice showed that approximately 70% of osteogenesis on the graft was attributed to the expansion and differentiation of donor periosteal progenitor cells. Furthermore, engraftment of BMP-2-producing bone marrow stromal cells on nonvital allografts showed marked increases in cortical graft incorporation and neovascularization, suggesting that gene-enhanced, tissue engineered functional periosteum may improve allograft incorporation and repair.
The loss of cellular activity in a structural bone allograft markedly reduces its healing potential compared with a live autograft. To further understand the cellular mechanisms for structural bone graft healing and repair and to devise a therapeutic strategy aimed at enhancing the performance of allograft, we established a segmental femoral structural bone graft model in mice that permits qualitative and quantitative analyses of graft healing and neovascularization.
Using this segmental femoral bone graft model, we transplanted live isografts harvested from Rosa 26A mice that constitutively express beta-galactosidase into their wildtype control mice. In an attempt to emulate the osteogenic and angiogenic properties of periosteum, we applied a cell-based, adenovirus-mediated gene therapy approach to engraft BMP-2-producing bone marrow stromal cells onto devitalized allografts.
X-gal staining for donor cells allowed monitoring the progression of periosteal progenitor cell fate and showed that 70% of osteogenesis was attributed to cellular proliferation and differentiation of donor progenitor cells on the surface of the live bone graft. Quantitative muCT analyses showed a 3-fold increase in new bone callus formation and a 6.8-fold increase in neovascularization for BMP-2/stromal cell-treated allograft compared with control acellular allografts. Histologic analyses showed the key features of autograft healing in the BMP-2/stromal cell-treated allografts, including the formation of a mineralized bone callus completely bridging the segmental defects, abundant neovascularization, and extensive resorption of bone graft.
The marked improvement of healing in these cellularized allografts suggests a clinical strategy for engineering a functional periosteum to improve the osteogenic and angiogenic properties of processed allografts.

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    • "Femurs were harvested at indicated time points and scanned using a Viva micro-CT system (Scanco Medical, Switzerland) at a voxel size of 10.5 µm to image bone. New bone formation was measured as previously described [21]. The threshold was chosen using 2D evaluation of several slices in the transverse anatomical plane. "
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    ABSTRACT: Periosteum provides a major source of mesenchymal progenitor cells for bone fracture repair. Combining cell-specific targeted Cox-2 gene deletion approaches with in vitro analyses of the differentiation of periosteum-derived mesenchymal progenitor cells (PDMPCs), here we demonstrate a spatial and temporal role for Cox-2 function in the modulation of osteogenic and chondrogenic differentiation of periosteal progenitors in fracture repair. Prx1Cre-targeted Cox-2 gene deletion in mesenchyme resulted in marked reduction of intramembraneous and endochondral bone repair, leading to accumulation of poorly differentiated mesenchyme and immature cartilage in periosteal callus. In contrast, Col2Cre-targeted Cox-2 gene deletion in cartilage resulted in a deficiency primarily in cartilage conversion into bone. Further cell culture analyses using Cox-2 deficient PDMPCs demonstrated reduced osteogenic differentiation in monolayer cultures, blocked chondrocyte differentiation and hypertrophy in high density micromass cultures. Gene expression microarray analyses demonstrated downregulation of a key set of genes associated with bone/cartilage formation and remodeling, namely Sox9, Runx2, Osx, MMP9, VDR and RANKL. Pathway analyses demonstrated dysregulation of the HIF-1, PI3K-AKT and Wnt pathways in Cox-2 deficient cells. Collectively, our data highlight a crucial role for Cox-2 from cells of mesenchymal lineages in modulating key pathways that control periosteal progenitor cell growth, differentiation, and angiogenesis in fracture repair.
    PLoS ONE 07/2014; 9(7):e100079. DOI:10.1371/journal.pone.0100079 · 3.23 Impact Factor
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    • "Analysis of vascular volume within the external fracture callus was also performed for selected samples harvested at 10 and 14 days postoperatively. As previously described, lead chromate paint was perfused to visualize all vascular structures [32]. Briefly, mice were anesthetized and a thoracotomy was performed to permit catheterization of the left ventricle and an incision to the right atrium. "
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    ABSTRACT: Introduction Impaired healing and non-union of skeletal fractures is a major public health problem, with morbidity exacerbated in patients with diabetes mellitus (DM). DM is prevalent worldwide and affects approximately 25.8 million US adults, with >90% having obesity-related type 2 DM (T2DM). While fracture healing in type 1 DM (T1DM) has been studied using animal models, an investigation into delayed healing in an animal model of T2DM has not yet been performed. Methods Male C57BL/6J mice at 5 weeks of age were placed on either a control lean diet or an experimental high-fat diet (HFD) for 12 weeks. A mid-diaphyseal open tibia fracture was induced at 17 weeks of age and a spinal needle was used for intra-medullary fixation. Mice were sacrificed at days 7, 10, 14, 21, 28, and 35 for micro-computed tomography (μCT), histology-based histomorphometry and molecular analyses, and biomechanical testing. Results HFD-fed mice displayed increased body weight and impaired glucose tolerance, both characteristic of T2DM. Compared to control mice, HFD-fed mice with tibia fractures showed significantly (p<0.001) decreased woven bone at day 28 by histomorphometry and significantly (p<0.01) decreased callus bone volume at day 21 by μCT. Interestingly, fracture calluses contained markedly increased adiposity in HFD-fed mice at days 21, 28, and 35. HFD-fed mice also showed increased PPARγ immunohistochemical staining at day 14. Finally, calluses from HFD-fed mice at day 35 showed significantly (p<0.01) reduced torsional rigidity compared to controls. Discussion Our murine model of T2DM demonstrated delayed fracture healing and weakened biomechanical properties, and was distinctly characterized by increased callus adiposity. This suggests altered mesenchymal stem cell fate determination with a shift to the adipocyte lineage at the expense of the osteoblast lineage. The up-regulation of PPARγ in fracture calluses of HFD-fed mice is likely involved in the proposed fate switching.
    PLoS ONE 06/2014; 9(6):e99656. DOI:10.1371/journal.pone.0099656 · 3.23 Impact Factor
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    • "Histomorphometric analyses of bone graft healing. Paraffin-embedded tissue sections were prepared by H&E/Alcian Blue staining as previously described.5 Histomorphometric analyses were performed using at least three nonconsecutive sections of each sample, 50 µm apart in the center region of the callus. "
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    ABSTRACT: While activation of hedgehog (Hh) signaling has been shown to induce osteogenic differentiation in vitro and bone formation in vivo, the underlying mechanisms and the potential utility of Hh-activated mesenchymal progenitors in bone defect repair remain elusive. Here we demonstrated that implantation of periosteal-derived mesenchymal progenitor cells (PDMPCs) that overexpressed an N-terminal sonic hedgehog peptide (ShhN) via an adenoviral vector (Ad-ShhN) restored periosteal bone collar formation in a 4mm segmental bone allograft model in immunodeficient mice. Ad-ShhN enhanced donor cell survival and microvessel formation in collagen scaffold at two weeks post-surgery and induced donor cell-dependent bone formation at 6 weeks post-surgery. Fluorescence-activated cell sorting analysis further showed that Ad-ShhN-PDMPC-seeded scaffold contained a 2-fold more CD45(-)Sca-1(+)CD34(+)VEGFR2(+) endothelial progenitors than Ad-LacZ-PDMPC-seeded scaffold at day 7 post-surgery. Ad-ShhN-transduced PDMPCs induced a 1.8-fold more CD31(+) microvessel formation than Ad-LacZ-transduced PDMPCs in a coculture of endothelial progenitors and PDMPCs. Taken together, our data show that overexpression of ShhN in mesenchymal progenitors improves bone defect reconstruction via enhancing donor progenitor cell survival, differentiation, and scaffold revascularization at the site of compromised periosteum. Hh agonist-based therapy therefore merits further investigation in tissue engineering-based applications aimed at enhancing bone defect repair and reconstruction.Molecular Therapy (2013); doi:10.1038/mt.2013.222.
    Molecular Therapy 10/2013; 22(2). DOI:10.1038/mt.2013.222 · 6.23 Impact Factor
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