Novel approaches to fracture healing

LncRNA KCNQ1OT1 accelerates fracture healing via modulating miR-701-3p/FGFR3 axis

Emerging evidence highlights the role of the long noncoding RNA (lncRNA) KCNQ1OT1 in fracture healing. Osteoblast proliferation, migration, and survival are pivotal during this process. In this study, we aimed to improve our understanding of the regulatory role of lncRNA KCNQ1OT1 during osteoblast proliferation, migration, and survival. We searched the gene expression omnibus databases and LncBase Experimental V.2 to identify key microRNAs (miRNAs) targets of KCNQ1OT1. MiR-701-3p was selected as a differentially expressed miRNA and RNA immunoprecipitation assays were performed to verify its interaction with KCNQ1OT1. Fibroblast growth factor receptor 3 (FGFR3) was also identified as a target of miR-701-3p. We further identified KCNQ1OT1 as a competing endogenous RNA of miR-701-3p that could influence osteoblast proliferation, migration, and apoptosis in vitro and in vivo. Taken together, our results indicate that the KCNQ1OT1/miR-701-3p/FGFR3 axis is an important regulator of osteoblast proliferation, migration, and apoptosis, and provide a new therapeutic avenue for fracture healing.

Nanomedicine for safe healing of bone trauma: Opportunities and challenges

Historically, high-energy extremity injuries resulting in significant soft-tissue trauma and bone loss were often deemed unsalvageable and treated with primary amputation. With improved soft-tissue coverage and nerve repair techniques, these injuries now present new challenges in limb-salvage surgery. High-energy extremity trauma is pre-disposed to delayed or unpredictable bony healing and high rates of infection, depending on the integrity of the soft-tissue envelope. Furthermore, orthopedic trauma surgeons are often faced with the challenge of stabilizing and repairing large bony defects while promoting an optimal environment to prevent infection and aid bony healing. During the last decade, nanomedicine has demonstrated substantial potential in addressing the two major issues intrinsic to orthopedic traumas (i.e., high infection risk and low bony reconstruction) through combatting bacterial infection and accelerating/increasing the effectiveness of the bone-healing process. This review presents an overview and discusses recent challenges and opportunities to address major orthopedic trauma through nanomedical approaches.

Can bone healing in distraction osteogenesis be accelerated by local application of IGF-1 and TGF-beta1?

Because complications of distraction osteogenesis are largely related to the long duration of therapy, increasing efforts were reached to shorten treatment by using osteoconductive replacement materials incorporating bioactive molecules such as IGF-1 and TGF-beta1. The controlled release of IGF-1 and TGF-beta1 from coated biodegradable poly(D,L-lactide) implants could stimulate fracture healing locally. We investigated the effect of locally applied IGF-1 and TGF-beta1 from IGF-1/TGF-beta1-enriched polylactide membranes on fracture healing in a sheep model of delayed callus formation. Twenty-eight sheep were used for this study. Callus distraction of 1 mm/day by means of a unilateral fixator was continued for 30 days. At the beginning of the subsequent consolidation phase, either growth factors were applied locally or the defect was packed with cancellous bone, or both. The groups treated with growth factors were compared to a control group. The consolidation phase lasted for 60 days and both tibiae were dissected for histological and histomorphometric analyses. This investigation found a reduced absolute callus area in the lengthening zone in all treatment groups. The two treatment groups that received a membrane coated with growth factors showed distinctly higher relative bone areas than the groups treated with an uncoated membrane or packing of the osteotomy defect with cancellous bone. The differences in bone areas were not statistically significant. Application of the growth factors accelerated bone healing and achieved results comparable with those of established treatment methods (packing with autologous cancellous bone). The best results were achieved with a combination of both methods.

Prediction of biomechanical stability after callus distraction by high resolution scanning acoustic microscopy

Accurate clinical prediction of the resistance to fracture after callus distraction requires a detailed understanding of structural and elastic properties of the newly formed bone. We investigated 26 sheep that underwent middiaphyseal callus distraction at a rate of 0.5 mm every 12 h for 30 d using a standard unilateral fixator system. The sample population included four groups undergoing different treatments to improve bone healing, including bone grafting and the local application of growth factors. All animals were sacrificed eight weeks after the end of distraction. The fracture forces of the lengthened tibia and the contralateral control tibia from each animal were evaluated by biomechanical (four-point bending) testing. The microstructure and anisotropic acoustic impedance distributions were assessed by quantitative 50-MHz scanning acoustic microscopy. The relationships between resistance to fracture, structural properties and acoustic impedance of the newly formed callus tissue and adjacent cortical tissue were investigated. A significant linear multivariate regression model was developed that predicts the fracture force with a high accuracy (RMSE = 248 N, R(2) = 0.86, p < 0.0001).

Assessment of Bone Repair Associated with the Use of Organic Bovine Bone and Membrane Irradiated at 830 nm

OBJECTIVE

The aim of the present investigation was to assess histologically the effect of LLLT (GaAIAs, 830 nm, 40 mW, CW, (Phi) approximately 0.6 mm, 16 J/cm(2) per session) on the repair of surgical defects created in the femur of the Wistar Albinus rat. The defects were filled to lyophilized bovine bone (Gen-ox), organic matrix) associated or not to GTR (Gen-derm).

BACKGROUND DATA

A major problem on modern Dentistry is the recovery of bone defects caused by trauma, surgical procedures or pathologies. Several types of biomaterials have been used in order to improve the repair of these defects. These materials are often associated to procedures of GTR. Previous studies have shown positive effects of LLLT on the repair of soft tissue wounds, but there are a few on its effects on bone healing.

METHODS

Surgical bone defects were created in 42 animals divided into five groups: Group I (control, 6 animals); Group II (Gen-ox, 9 animals); Group III (Gen-ox + Laser, 9 animals); Group IV (Gen-ox + Gen-derm, 9 animals); Group V (Gen-ox + Gen-derm + Laser, 9 animals). The animals on the irradiated group received 16 J/cm(2) per session divided into four points around the defect (4 J/cm(2)) being the first irradiation immediately after surgery and repeated seven times at every 48 h. The animals were humanly killed after 15, 21, and 30 days.

RESULTS

The results of the present investigation showed histological evidence of improved amount of collagen fibers at early stages of the bone healing (15 days) and increased amount of well organized bone trabeculae at the end of the experimental period (30 days) on irradiated animals compared to non irradiated ones.

CONCLUSIONS

It is concluded that a positive biomodulative effect on the healing process of one defect associated or not to the use of organic lyophilized bone and biological bovine lyophilized membrane on the femur of the rat.

Efficient bone formation by gene transfer of human LIM mineralization protein-3

LIM mineralization protein (LMP) is a novel positive regulator of the osteoblast differentiation program. In humans, three different LMP splice variants have been identified: LMP-1, LMP-2, and LMP-3. Gene transfer of human LMP-1 (hLMP-1) induces expression of genes involved in bone formation, including certain bone morphogenetic proteins (BMPs), promotes bone nodule formation in vitro, ectopic bone formation in vivo, and is therapeutic in animal models of posterior thoracic and lumbar spine fusion. To examine the osteoinductive properties of the LMP-3 in vitro and in vivo, we have generated plasmid and adenoviral vectors expressing codon-optimized hLMP-3. Here we demonstrate that gene transfer of hLMP-3 induces expression of the bone-specific genes osteocalcin, osteopontin, and bone sialoprotein and induced bone mineralization in preosteoblastic and fibroblastic cells. We also demonstrate that hLMP-3 is able to induce bone mineralization and the expression of the bone-specific genes, BMP-2, OSX, RunX2, and alkaline phosphatase in human mesenchymal stem cells in a dose-dependent manner. Finally, we demonstrate that direct gene transfer of hLMP-3 into murine skeletal muscle results in ectopic bone formation more efficiently than BMP-2. These results demonstrate that hLMP-3 gene transfer can be used to promote bone formation in cell culture and in vivo as or more efficiently than BMP-2, thus establishing feasibility and efficacy of direct gene delivery of hLMP-3 to produce bone in vivo. These results suggest that gene transfer of hLMP-3 could be developed as a bone-inductive therapeutic agent for clinical applications.

Enhancement of bone repair with a helper-dependent adenoviral transfer of bone morphogenetic protein-2

Regional gene therapy, which involves the delivery of growth factors to a specific anatomic site, has the potential to enhance bone formation in clinical application. Helper-dependent adenoviral vectors, which have deleted all of the viral coding regions, have been shown to be safe and highly efficient with long-lasting transgene expression. In this study, we constructed a helper-dependent adenoviral vector producing bone morphogenetic protein-2 (AdHDBMP-2). The AdHDBMP-2 increased the alkaline phosphatase activity of W-20-17 cells in vitro. In addition, when AdHDBMP-2 infected rat bone marrow cells were implanted into the hindlimbs of SCID mice, orthotopic bone formation was shown at 2 weeks. To our knowledge, this is the first study to demonstrate bone formation with the helper-dependent adenoviral vector with the BMP-2 expression cassette. This type of gene therapy vector could prove to be highly useful for bone augmentation in patients with bone loss associated with trauma, revision total joint arthroplasty, or cancer.