The effect of osteogenic growth factors on bone growth into a ceramic filled defect around an implant

LncRNA TUG1 promoted osteogenic differentiation through promoting bFGF ubiquitination

LncRNA TUG1 has the potential to promote the osteogenic differentiation of several cells, but the role of lncRNA TUG1 in osteogenic differentiation of tendon stem/progenitor cells (TSPCs) is still unknown. This study aims to determine the role of lncRNA TUG1 in osteogenic differentiation of TSPCs. bFGF, RUNX2, and Osterix protein expressions were detected by western blot. LncRNA TUG1 and bFGF expression was detected by qRT-PCR. RNA immunoprecipitation (RIP) assay was used to confirm the interaction between TUG1 and bFGF2. Ubiquitination assay was used to determine the ubiquitination of bFGF protein. During osteogenic differentiation, the protein expression of bFGF was significantly downregulated in TSPCs, and the expression of TUG1 was significantly elevated in TSPCs. Interfering TUG1 or overexpressing bFGF suppressed osteogenic differentiation of TSPCs. In addition, lncRNA TUG1 interacted with bFGF, and lncRNA TUG1 promoted the ubiquitination of bFGF protein. We also determined that lncRNA TUG1 downregulated bFGF protein expression through promoting the ubiquitination of bFGF. LncRNA TUG1 promoted the osteogenic differentiation of TSPCs through promoting bFGF ubiquitination.

The effect of cationically-modified phosphorylcholine polymers on human osteoblasts in vitro and their effect on bone formation in vivo

The effect of introducing cationic charge into phosphorylcholine (PC)-based polymers has been investigated in this study with a view to using these materials as coatings to improve bone formation and osseointegration at the bone-implant interface. PC-based polymers, which have been used in a variety of medical devices to improve biocompatibility, are associated with low protein adsorption resulting in reduced complement activation, inflammatory response and cell adhesion. However, in some applications, such as orthopaedics, good integration between the implant and bone is needed to allow the distribution of loading stresses and a bioactive response is required. It has previously been shown that the incorporation of cationic charge into PC-based polymers may increase protein adsorption that stimulates subsequent cell adhesion. In this paper, the effect of cationic charge in PC-based polymers on human osteoblasts (HObs) in vitro and the effect of these polymers on bone formation in the rat tibia was assessed. Increasing PC positive surface charge increased HOb cell adhesion and stimulated increased cell differentiation and the production of calcium phosphate deposits. However, when implanted in bone these materials were at best biotolerant, stimulating the production of fibrous tissue and areas of loosely associated matrix (LAM) around the implant. Their development, as formulated in this study, as bone interfacing implant coatings is therefore not warranted.

Changes in bone regeneration by trehalose coating and basic fibroblast growth factor after implantation of tailor-made bone implants in dogs

In this study, we aimed to determine the effect of trehalose coating and the optimal dose of basic fibroblast growth factor (bFGF), an osteoinductive protein, loaded onto tailor-made bone implants for implant-induced bone formation in vivo. We fabricated tailor-made α-tricalcium phosphate bone implants (11 mm diameter with 2 parallel cylindrical holes). bFGF 0, 1, 10, 100 or 200 μg/implant was incorporated into implants with and without a trehalose coating, and these were subsequently implanted into dogs to correct temporal bone defects of the same size and shape. Four weeks after implantation, we analyzed the bone implants and surrounding tissues by using micro-computed tomography imaging and histological analyses, as well as gross evaluation. No significant difference in new bone formation was observed between implants with and without a trehalose coating at any of the bFGF doses. Bone implants with 100 and 200 μg bFGF showed significantly more new bone formation at the implant site and within the cylindrical holes of the implants than those without bFGF (P<0.05). However, heterotopic bone formation on the skull near the implant was observed in the group that received 200 μg bFGF. These results suggest that 100 μg bFGF is the optimal dose for this implant in dogs, and that the trehalose coating may not be necessary in vivo, probably due to the presence of blood proteins and electrolytes at the implant site.

Effect of recombinant human transforming growth factor-beta2 dose on bone formation in rat femur titanium implant model

Previously, we reported that application of 10 microg recombinant human TGF-beta2 (rhTGF-beta2) enhanced peri-implant bone formation and bone-implant contact in a rat model. To further investigate the dose effect, the present experiment evaluated doses of rhTGF-beta2 bracketed around 10 microg (5, 10, 20 microg) using the same model. Four groups (including buffer-only control) received femoral implantation of hydroxyapatite/tricalcium phosphate-coated titanium implants. Four weeks post-surgery, all femurs were collected and analyzed by micro computed tomography followed by a mechanical test or histology. Compared with control, all rhTGF-beta2-treated groups had significantly higher bone volume. Bone-implant contact was not different between the control, 5, and 10 microg groups; however, the 20 microg group had less contact than the control. There were significant decreases in the strength of fixation in all rhTGF-beta2 treated groups compared with the control. In particular, while rhTGF-beta2 was able to enhance bone formation in the vicinity of the implant, the relative lack of bone-implant contact in the 20 microg group depressed the strength of fixation, suggesting that the location as well as the amount of new bone formed is important for implant fixation.

Regulation of the protein-loading capacity of hydroxyapatite by mercaptosuccinic acid modification

Loading and releasing protein in a controllable way is extremely important for the protein vehicles used in bone tissue engineering. To obtain a suitable carrier material for basic proteins, such as BMP or bFGF, hydroxyapatite particles containing mercaptosuccinic acid (mercaptosuccinic acid (Mer), (Mer-HAp)) were synthesized. Physicochemical evaluation of Mer-HAp suggested that Mer was contained in HAp particles: it either simply adsorbed onto HAp crystals or was trapped among the HAp crystals. A protein adsorption study using basic and acidic model proteins indicated that the synthesized Mer-HAp had selective loading properties of the basic protein. The loaded protein was gradually released from Mer-HAp in phosphate buffered saline. The protein release rate was different in each Mer-HAp synthesized with a different concentration of Mer. In addition, the protein release from Mer-HAp showed a similar profile with the Ca dissolution in different pH solutions, indicating that the Mer-HAp dissolution was concerned with the protein release from Mer-HAp. Thus, Mer-HAp is a useful candidate for the basic protein carrier because it has properties which enable the loading and releasing of protein in a controllable way.

Basic fibroblast growth factor suspended in Matrigel improves titanium implant fixation in ovariectomized rats

Basic fibroblast growth factor (bFGF) has high potential for tissue regeneration; however, its in vivo effects are unpredictable due to the short-term survival. This study sought to evaluate the effects of bFGF suspended in Matrigel on the implant fixation in ovariectomized (OVX) rats. In vitro, the release kinetics of bFGF was tested using an immuno-ligand-assay. In vivo, eighty titanium implants were randomly divided into 4 groups and inserted in the tibiae of forty OVX rats: no treatment group, bFGF alone group, Matrigel alone group and bFGF+Matrigel group. At 3 months after implantation, tibiae were examined by histology, micro-CT and push-out test. We found that Matrigel could prolong the life span of bFGF in vitro with a sustained release during the 21 days. In vivo, bFGF or Matrigel alone had little effect on the fixation of implant in OVX rats, but bFGF suspended in Matrigel induced nearly 2-fold of peri-implant new bone formation and 4-fold of implant mechanical stability when compared to other 3 groups. The results of this study suggest that Matrigel could be used as a carrier of bFGF and prolonged its release around implant, which may improve implant fixation, especially in site of post-menopausal osteoporosis.

The effect of simvastatin on bone formation and ceramic resorption in a peri-implant defect model

Experimental use of statins as stimulators of bone formation suggests they may have widespread applicability in the field of orthopaedics. With their combined effects on osteoblasts and osteoclasts, statins have the potential to enhance resorption of synthetic materials and improve bone ingrowth. In this study, the effect of oral and local administration of simvastatin to a beta tricalcium phosphate (betaTCP)-filled defect around an implant was compared with recombinant human bone morphogenetic protein 2 (rhBMP2). On hundred and sixty-two Sprague-Dawley rats were assigned to treatment groups: local application of 0.1, 0.9 or 1.7 mg of simvastatin, oral simvastatin at 5, 10 or 50 mg kg(-1) day(-1) for 20 days, local delivery of 1 or 10 microg of rhBMP2, or control. At 6 weeks rhBMP2 increased serum tartrate-resistant acid phosphatase 5b levels and reduced betaTCP area fraction, particle size and number compared with control, suggesting increased osteoclast activity. There was reduced stiffness and increased mechanical strength with this treatment. Local simvastatin resulted in a decreased mineral apposition rate at 6 weeks and increased fibrous area fraction, betaTCP area fraction, particle size and number at 26 weeks. Oral simvastatin had no effect compared with control. Local application of rhBMP2 increased resorption and improved mechanical strength whereas simvastatin was detrimental to healing. Oral simvastatin was ineffective at promoting either ceramic resorption or bone formation. The effect of statins on the repair of bone defects with graft substitute materials is influenced by its bioavailability. Thus, further studies on the optimal delivery system are needed.

In vitro testing of Advanced JAX Bone Void Filler System: species differences in the response of bone marrow stromal cells to beta tri-calcium phosphate and carboxymethylcellulose gel

The Advanced JAX Bone Void Filler System (AJBVFS) is a novel bone graft material manufactured by Smith and Nephew Orthopaedics Ltd. and comprises beta tri-calcium phosphate granules with carboxymethylcellulose (CMC) gel as a handling agent. This study investigated the potential, in vitro, of the AJBVFS to function as a delivery system for cell therapy to enhance healing of bone defects. The attachment of rabbit bone marrow stromal cells (rbBMSCs), human BMSCs (hBMSCs) and human bone-derived cells (hBDCs) to JAX granules and the effect of CMC gel on cell proliferation and differentiation were investigated. There were slight species differences in the number and morphology of cells attached on the JAX granules with less rbBMSC attachment than human. All cells tolerated the presence of CMC gel and a reduction in cell number was only seen after longer exposure to higher gel concentrations. Low concentrations of CMC gel enhanced proliferation, alkaline phosphatase (ALP) expression and ALP activity in human cells but had no effect on rbBMSC. This study suggests that AJBVFS is an appropriate scaffold for the delivery of osteogenic cells and the addition of CMC gel as a handling agent promotes osteogenic proliferation and differentiation and is therefore likely to encourage bone healing.

Development of New Drug Delivery System for Implant Bone Augmentation Using a basic Fibroblast Growth Factor-gelatin Hydrogel Complex

This study sought to clarify the effectiveness of bFGF-gelatin hydrogel complex on bone regeneration around implants for the development of a new drug delivery system for bone augmentation. Twenty-four titanium implants (03.3 mmX 10 mm) were placed into edentulous areas of the mandibles of four beagle dogs with the upper four screw threads exposed at buccal side. bFGF-gelatin hydrogel complex with 0, 0.1, 1, 10, 100 microg bFGF or autogenous bone (as control) then filled the bone defect site to cover the exposed screw threads. After eight weeks, tissue specimens including implants were evaluated histologically and histomorphometrically. Histological observation showed new bone formation around exposed screw threads in the groups with 1, 10, 100 microg bFGF and autogenous bone-a striking contrast to the groups with contents of 0 and 0.1 microg bFGF. These results thus suggested that bFGF-gelatin hydrogel complex using an optimum amount of bFGF was useful for bone augmentation around implants.

Repair of segmental bone defects in rabbit tibiae using a complex of beta-tricalcium phosphate, type I collagen, and fibroblast growth factor-2

The objective of this study was to evaluate the effects of a complex of beta-tricalcium phosphate (beta-TCP) granules, collagen, and fibroblast growth factor-2 (FGF-2) on cortical bone repair in rabbits. Segmental bone defects of 5 mm in length were created in the middle of the tibial shaft. The defect was stabilized with a plate and screws, and was filled with 0.3 ml of a complex of beta-TCP granules and 5% collagen, with or without 200 microg of recombinant human fibroblast growth factor-2 (rhFGF-2). Bone regeneration and beta-TCP resorption were assessed by X-ray and micro-CT scanner. A three-point bending test was also performed. The results showed that the segmental bone defect was not only radiologically, but also mechanically healed with cortical bone 12 weeks after implantation of the complex with rhFGF-2. In contrast, after implantation of the complex without rhFGF-2, most of the defect was filled with beta-TCP and only a small amount of bone formation was found. These results suggest that resorption of beta-TCP is important for bone formation and may be promoted by FGF-2 in the beta-TCP implantation site. In addition, the complex of beta-TCP granules and collagen combined with rhFGF-2 provides a paste-like material that is easy to handle. This material may be of considerable use in the treatment of cortical bone defects.