Establishment of a Segmental Femoral Critical-size Defect Model in Mice Stabilized by Plate Osteosynthesis

The use of tissue-engineered bone constructs is an appealing strategy to overcome drawbacks of autografts for the treatment of massive bone defects. As a ...

Université Paris Diderot

Université Paris-Est

To describe stapled 1-stage functional end-to-end intestinal anastomosis for treatment of small intestinal obstruction in dogs and evaluate outcome when the technique is performed by nonexpert surgeons after limited training in the technique.

One stage functional end-to-end stapled intestinal anastomosis and resection performed by nonexpert surgeons for the treatment of small intestinal obstruction in 30 dogs.

Mouse models are invaluable tools for mechanistic and efficacy studies of the healing process of large bone defects resulting in atrophic nonunions, a severe medical problem and a financial health-care-related burden. Models of atrophic nonunions are usually achieved by providing a highly stable biomechanical environment. For this purpose, external fixators have been investigated, but plate osteosynthesis, despite its high clinical relevance, has not yet been considered in mice. We hereby proposed and investigated the use of an internal osteosynthesis for stabilizing large bone defects. To this aim, a 3.5-mm-long segmental bone defect was induced in the mid-shaft of the femur using a Gigli saw and a jig. Bone fixation was performed using a titanium microlocking plate with four locking screws. The bone defect was either left empty or filled with a syngenic bone graft or filled with a coralline scaffold. Healing was monitored using radiographs. The healing process was further assessed using microcomputed tomography and histology 10 weeks after surgery. With the exception of one mouse that died during the surgical procedure, no complications were observed. A stable and reproducible bone fixation as well as a reproducible fixation of the implanted materials with full weight bearing was obtained in all animals tested. Nonunion was consistently observed in the group in which the defects were left empty. Bone union was obtained with the syngenic bone grafts, providing evidence that, although such defects were of critical size, bone healing was possible when the gold-standard material was used to fill the defect. Although new bone formation was greater in the coralline scaffold group than in the left-empty animal group, it remained limited and localized close to the bony edges, a consequence of the critical size of such bone defect. Our study established a reproducible, clinically relevant, femoral, atrophic nonunion, critical-sized defect, low morbidity mouse model. The present study was successful in designing and testing in a small animal model, a novel surgical method for the assessment of bone repair; this model has the potential to facilitate investigations of the molecular and cellular events involved in bone regeneration in load-bearing, segmental-bone defects.

A novel murine femoral segmental critical-sized defect model stabilized by plate osteosynthesis for bone tissue engineering purposes.

A major limitation in the development of cellular therapies using human mesenchymal stem cells (hMSCs) is cell survival post-transplantation. In this study, we challenged the current paradigm of hMSC survival, which assigned a pivotal role to oxygen, by testing the hypothesis that exogenous glucose may be key to hMSC survival. We demonstrated that hMSCs could endure sustained near-anoxia conditions only in the presence of glucose. In this in vitro cell model, the protein expressions of Hif-1α and angiogenic factors were upregulated by the presence of glucose. Ectopically implanted tissue constructs supplemented with glucose exhibited four- to fivefold higher viability and were more vascularized compared to those without glucose at day 14. These findings provided the first direct in vitro and in vivo demonstration of the proangiogenic and prosurvival functions of glucose in hMSC upon transplantation and identified glucose as an essential component of the ideal scaffold for transplanting stem cells.

Proangiogenic and prosurvival functions of glucose in human mesenchymal stem cells upon transplantation.

Tissue constructs containing mesenchymal stem cells (MSC) are an appealing strategy for repairing massive segmental bone defects. However, their therapeutic effectiveness does not match that of autologous bone grafts; among the complicating reasons, the scaffold resorbability has been identified as a critical feature for achieving bone regeneration. In the present study, the osteogenic potential of constructs obtained by expanding autologous MSC onto granules of Acropora coral, a natural fully-resorbable scaffold, was investigated. MSC adhered and proliferated well in vitro after 1 week. When implanted in vivo into long-bone, critical-size defects in sheep (n=5), these constructs exhibited a two-fold increase in bone formation 6 months postimplantation compared to Acropora scaffolds alone (n=5). Interestingly, osteogenesis, mediated by MSC, within these constructs was found continuous not only with the bony stumps, but also at the core of the implants. Scaffold resorption was almost complete at 6 months, leading to full bone regeneration in one animal. Acropora coral appear to be an appealing scaffold for bone tissue engineering because it supported in vitro MSC adhesion and proliferation. Moreover, these results provided evidence that MSC could promote bone regeneration in sheep when loaded one a natural fully resorbable scaffold.

Bone regeneration in sheep using acropora coral, a natural resorbable scaffold, and autologous mesenchymal stem cells.

The purposes of this study were to assess tissue ingrowth within the Ligament Advanced Reinforcement System (LARS) artificial ligament (LARS AC; LARS, Arc sur Tille, France) and to study the biomechanical characteristics of the reconstructed knees in a sheep model of anterior cruciate ligament (ACL) replacement.

Biological and biomechanical evaluation of the ligament advanced reinforcement system (LARS AC) in a sheep model of anterior cruciate ligament replacement: a 3-month and 12-month study.

Tissue-engineered constructs combining bone marrow mesenchymal stem cells with biodegradable osteoconductive scaffolds are very promising for repairing large segmental bone defects. Synchronizing and controlling the balance between scaffold-material resorption and new bone tissue formation are crucial aspects for the success of bone tissue engineering. The purpose of the present study was to determine, and compare, the osteogenic potential of ceramic scaffolds with different resorbability. Four clinically relevant granular biomaterial scaffolds (specifically, Porites coral, Acropora coral, beta-tricalcium phosphate and banked bone) with or without autologous bone marrow stromal cells were implanted in the ectopic, subcutaneous-pouch sheep model. Scaffold material resorption and new bone formation were assessed eight weeks after implantation. New bone formation was only detected when the biomaterial constructs tested contained MSCs. New bone formation was higher in the Porites coral and Acropora coral than in either the beta-tricalcium phosphate or the banked bone constructs; furthermore, there was a direct correlation between scaffold resorption and bone formation. The results of the present study provide evidence that, among the biomaterials tested, coral scaffolds containing MSCs promoted the best new bone formation in the present study.

Comparative study of the osteogenic ability of four different ceramic constructs in an ectopic large animal model.

This study investigates the impact of polystyrene sodium sulfonate (PolyNaSS) grafting onto the osseo-integration of a polyethylene terephthalate artificial ligament (Ligament Advanced Reinforcement System, LARS™) used for Anterior Cruciate Ligament (ACL). The performance of grafted and non-grafted ligaments was assessed in vitro by culturing human osteoblasts under osteogenic induction and this demonstrated that the surface modification was capable of up-regulating the secretion of ALP and induced higher level of mineralisation as measured 6 weeks post-seeding by Micro-Computed Tomography. Grafted and non-grafted LARS™ were subsequently implanted in an ovine model for ACL reconstruction and the ligament-to-bone interface was evaluated by histology and biomechanical testings 3 and 12 months post-implantation. The grafted ligaments exhibited more frequent direct ligament-to-bone contact and bone formation in the core of the ligament at the later time point than the non-grafted specimens, the grafting also significantly reduced the fibrous encapsulation of the ligament 12 months post-implantation. However, this improved osseo-integration was not translated into a significant increase in the biomechanical pull-out loads. These results provide evidences that PolyNaSS grafting improved the osseo-integration of the artificial ligament within the bone tunnels. This might positively influence the outcome of the surgical reconstructions, as higher ligament stability is believed to limit micro-movement and therefore permits earlier and enhanced healing.

The effect of polystyrene sodium sulfonate grafting on polyethylene terephthalate artificial ligaments on in vitro mineralisation and in vivo bone tissue integration.

Ureteral obstruction secondary to ureterolithiasis in cats is a challenging situation. Ureteral stenting has recently been introduced to prevent complications that often occurred after ureterotomy or other invasive surgeries. The purpose of this study is to describe the stenting technique and perioperative difficulties, as well as long-term outcome and complications with ureteral stenting in 12 cats with ureteroliths. Fifteen 2.5 Fr soft double pigtail multi-fenestrated ureteral stents were placed in an anterograde fashion under open surgical approaches and with fluoroscopic guidance in 12 cats. Nine cats received a unilateral stent and three received bilateral stents. Ureterotomy or ureteral resection and end-to-end anastomosis were performed in three and four cases, respectively. In six cats, papillotomy was performed to facilitate dilatator and stent placement. All cats recovered well from the surgical procedure, except one cat, which died during the anaesthesia recovery period. Postoperative complications included dysuria (three cases, diagnosed at 15 days, 1 month and 3 months, respectively), urinary tract infection (one case, 1 month after surgery), stent migration requiring stent replacement (one case, 19 months after surgery) and stent obstruction requiring stent removal (three cases with previously end-to-end anastomosis between 2 and 8 months after surgery). Nine cats (75%) were alive at a mean follow-up of 453 ± 194 (123-720) days. The median survival time was >415 days. Stent placement appeared to be a valuable and safe option for treating ureteral obstruction in cats. However, periodic and long-term monitoring of stents is warranted.

Indwelling double pigtail ureteral stent combined or not with surgery for feline ureterolithiasis: complications and outcome in 15 cases.

Our objectives were: 1) to review the complications associated with stabilization of appendicular fractures in cats and small dogs using locking compression plates (LCP), and 2) to identify factors that could influence fixation construct stability.

Complications of appendicular fracture repair in cats and small dogs using locking compression plates.

Tissue constructs containing mesenchymal stem cells (MSCs) are appealing strategies for repairing large segmental bone defects, but they do not allow consistent bone healing and early cell death was identified as a cause of failure. However, little is known about cell survival in the clinical microenvironment encountered during bone healing process. Osteoconductive coral scaffold with or without luciferase-labeled human MSCs were implanted either in a critical segmental femoral bone defect stabilized by plate or subcutaneously in 44 mice. Cell survival was evaluated by serial bioluminescence imaging (BLI) and osteogenic capabilities by histology and microcomputed tomography. Comparisons between groups were performed with two-way analysis of variance test. Twenty mice were sacrificed 2 weeks after surgery for short-term evaluation and 24 mice at 10 weeks for long-term evaluation. BLI provided evidence of fast and continuous cell death: 85% decrease of the BLI signal over the first 2 weeks in both locations; in fact, less than 2% of the initial cell number was present in all constructs analyzed 4 weeks postimplantation and less than 1% of the initial cell number by 8 weeks postimplantation. By 2 weeks postimplantation, the amount of newly formed bone was self-limited and was similar to ectopic and orthotopic groups. By 10 weeks postimplantation, bone formation was significantly enhanced in the presence of MSCs in orthotopic site and the amount of newly formed bone in cell-containing constructs implanted in orthotopic locations was significantly higher than that observed in the ectopic group. Our results indicated that hMSCs promote bone formation despite early and massive cell death when loaded on coral scaffolds. Interestingly, bone formation was higher in orthotopic than ectopic site despite the same survival pattern. Ectopic implantation of cell-containing constructs is suitable to evaluate cell survival, but assessment of bone formation ability requires orthotopic implantation.

Mathieu Manassero

Laboratoire de Bioingénierie et Biomécanique Ostéo-Articulaires (B2OA - UMR CNRS 7052)

Université Paris Diderot

Establishment of a Segmental Femoral Critical-size Defect Model in Mice Stabilized by Plate Osteosynthesis

Mathieu Manassero

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Laboratoire de Bioingénierie et Biomécanique Ostéo-Articulaires (B2OA - UMR CNRS 7052)

Université Paris Diderot

Establishment of a Segmental Femoral Critical-size Defect Model in Mice Stabilized by Plate Osteosynthesis

Laboratoire de Bioingénierie et Biomécanique Ostéo-Articulaires (B2OA - UMR CNRS 7052)