Adenoviral delivery of adiponectin ameliorates osteogenesis around implants in ovariectomized rats.

BACKGROUND: Adiponectin (APN) has been reported to promote bone formation. However, it is difficult to utilize a conventional method that administers sufficient APN to the implant site. The present study investigated the efficacy of an APN transgene to accelerate the implant osseointegration in ovariectomized (OVX) rats. METHODS: In vitro, bone marrow stromal cells were transduced with reconstructed adenovirus (Ad-APN-EGFP) and osteoclast precursor RAW264.7 cells were co-cultured with the conditioned medium secreted by transduced bone marrow stromal cells. Tartrate-resistant acid phosphatase staining and bone slice resorption assay were performed to evaluate the activity of osteoclastogenesis. In vivo, Ad-APN-EGFP was administered into the bone defect prior to implant placement in OVX rats. At 7 and 28 days post implantation, the femurs were harvested and prepared for a real-time reverse transcriptase-polymerase chain reaction, hemotoxylin and eosin staining, immunohistochemical staining, micro-computed tomography analysis and biomechanical testing. RESULTS: The results showed the formation and function of osteoclasts were significantly suppressed in vitro. Successful transgene expression was confirmed, and a significant increase of OCN, Runx2 and ALP expression was detected in the Ad-APN-EGFP group in vivo. Interestingly, we also found that the overexpression of APN decreased the expression level of potent adipogenic transcription factors such as PPARγ2 and C/EBP-α. At 28 days after implantation, the Ad-APN-EGFP group revealed a significantly increased osseointegration and implant stability in OVX rats compared to the control groups (Ad-EGFP and PBS groups). CONCLUSIONS: APN via direct adenovirus-mediated gene transfer could ameliorate osseointegration surrounding titanium implants in OVX-related osteoporosis rats. Furthermore, it may be an effective strategy for promoting bone regeneration under osteoporotic conditions.

Effects of strontium ranelate on osseointegration of titanium implant in osteoporotic rats.

OBJECTIVES: Previous studies have demonstrated the dual effects of strontium ranelate (SR) on osteoporotic and undisturbed bone. However, reports of its effect on titanium implant osseointegration in osteoporotic bodies were limited. This study was designed to investigate the effects of SR on osseointegration of titanium implant in ovariectomized rats. MATERIAL AND METHODS: Twelve weeks after bilateral ovariectomy in female Sprague-Dawley rats, each animal received two titanium implants in the distal metaphysis of femur. All rats were then randomly divided into two groups: Control and SR (625 mg/kg/day). Twelve weeks after implantation, serum levels of osteocalcin (OCN) and tartrate-resistant acid phosphatase (TRAP) 5b, implant osseointegration and peri-implant trabecular microarchitecture were analyzed by histomorphometry, micro-computerized tomography (micro-CT), and biomechanical test. RESULTS: Compared with control, SR treatment increased serum levels of OCN by 29.2%, and decreased the levels of TRAP 5b by 25.5% in serum analysis; SR treatment increased percent bone volume by 63.1% and percent osseointegration by 48.3% in micro-CT assessment, and increased bone area density by 55.6% and bone-to-implant contact by 49.0% in histomorphometry; SR treatment also increased the maximal push-out force by 117.7% and the ultimate shear strength by 103.5% in push-out test. CONCLUSIONS: Strontium ranelate treatment could improve titanium implant osseointegration in osteoporotic rats.

Effect of Human Wnt10b Transgene Overexpression on Peri-Implant Osteogenesis in Ovariectomized Rats.

This study aimed to investigate the efficacy of human Wnt10b (hWnt10b) transgene expression in ovariectomized (OVX) rats to accelerate osseointegration around titanium implants, and to provide a new strategy for treating osteoporosis with implants. An in vivo osteoporosis model was generated via bilateral ovariectomy in rats, and changes in expression of Wnt pathway-related genes were investigated. In OVX rats with a femur defect, hWnt10b expressed from an adenovirus vector was locally delivered to the defect site prior to implant placement. Surrounding femur tissues were collected 1 and 3 weeks after implantation for imaging, biomechanical testing, and molecular and histological analyses. In an in vitro model, bone-marrow stromal cells (BMSCs) transfected with adenovirus containing hWnt10b (Ad-hWnt10b) were cultured for 2 weeks in adipogenic medium followed by 2 weeks in osteogenic induction medium. Alizarin Red staining and Oil Red O staining, as well as reverse transcription polymerase chain reaction and Western blot analyses, were performed to assess the effect of hWnt10b expression on BMSC differentiation. Expression of Wnt pathway genes was significantly downregulated in OVX rats. OVX rats treated with Ad-hWnt10b prior to induction of a femur defect showed markedly increased ALP, Runx-2, and osteocalcin expression and decreased cathepsin K expression. Histological and imaging analysis showed increases in the number of osteocalcin-positive cells and the density of newly formed bone surrounding the implant in the Ad-hWnt10b group relative to the untreated control. Meanwhile, Ad-hWnt10b-BMSCs showed significantly increased osteogenesis and decreased adipogenesis. hWnt10b may accelerate osseointegration around implants and subsequently enhance bone regeneration and implant stabilization under OVX conditions.

Angiogenic suppression of osteoclasts may play a role in developing bisphosphonate-related osteonecrosis of the jaw.

Since it was firstly reported in 2003, a large number of cases have been published concerning bisphosphonate-related osteonecrosis of the jaw (BRONJ). It has generated great interest in the medical and research communities yet remains an enigma, given its unknown pathogenesis. Many hypotheses concerning the underlying pathophysiology are discussed, including two most popular hypotheses: bone remodeling suppression and angiogenesis suppression, but none of them could explain all the unique characters of BRONJ. Bisphosphonates are potent osteoclast inhibitors, and recent studies revealed that osteoclasts were important for bone angiogenesis. Therefore, we hypothesize that bisphosphonates could inhibit osteoclast stimulation of angiogenesis, which plays an important role in developing BRONJ. Our hypothesis could help to explain some unintelligible characters of BRONJ, and deserves further studies.

Adiponectin may improve osseointegration of dental implants in T2DM patients.

Type 2 diabetes mellitus (T2DM) is the most common form of diabetes. Compared with the general population, a higher failure rate is seen in T2DM patients. There is also evidence that chronically high levels of plasma glycemia leads to inflammatory effect and a negative influence on bone formation and remodeling, and reduce osseointegration of implants. Recently studies reveal that adiponectin is an insulin-sensitizing adipokine, and closely associated with T2DM. Adiponectin has potent anti-inflammatory properties and has been shown to increase bone density by inhibiting osteoclast formation and promoting the formation of osteoblasts. We therefore hypothesize systemically infused or locally used adiponectin could accelerate osseointegration of dental implants in T2DM. Our hypothesis could help to create an option to improve success ratio of dental implants in T2DM by the replenishment of adiponectin in T2DM patients.

Computer-assisted condylar reconstruction in bilateral ankylosis of the temporomandibular joint using autogenous coronoid process.

During the past 10 years, more than 20 patients a year have been treated at our centre for bilateral ankylosis of the temporomandibular joint (TMJ). Here we describe the use of computer-assisted three-dimensional surgical planning and its clinical effects in condylar reconstruction for such patients using autogenous coronoid process. Sixteen patients with bilateral bony ankylosis of the TMJ from March 2006 to March 2009 were randomly divided into 2 groups and treated by bilateral osteoarthrectomy and condylar reconstruction by free grafting of autogenous coronoid process with and without three-dimensional simulation using Surgicase CMF™ (Materialise, Belgium) software. Clinical examination, radiographs, photographs, and details of the operation and its outcome were used postoperatively to evaluate the clinical effects of the technique. Satisfactory mouth opening was achieved in all cases. There were fewer postoperative malocclusions among patients who had three-dimensional simulation. The combination of computer-assisted three-dimensional surgical planning and simulation and free grafting of autogenous coronoid process is a sound and predictable method for the reconstruction of condyles in patients with bilateral ankylosis of the TMJ as it makes the operation easier and more accurate.

Effects of ibandronate-hydroxyapatite on resorptive activity of osteoclasts.

INTRODUCTION: Bisphosphonates (BPs) can be locally used to improve the osteogenesis around hydroxyapatite (HA) implants. However, there are almost no reports discussing the effects of BPs in the bound state with HA on osteoclasts. Ibandronate is a BP widely used in clinical practice. This study was designed to evaluate the effects of ibandronate combined with HA on the morphology and resorptive activity of osteoclasts. MATERIAL AND METHODS: The HA and ibandronate-HA were prepared. Osteoclasts were isolated from Sprague-Dawley rats and then the cells were cultured with both HA and ibandronate-HA. Then the cell morphology was inspected by inverted phase contrast microscope and transmission electron microscopy observation. The resorptive activity was tested using the dyeing agent seminaphthofluorescein and bone resorption assay. RESULTS: Compared with the control group, the osteoclasts demonstrated morphological alterations, and the hydrogen ion concentration was significantly lower in the ibandronate-HA group. Areas of the resorption pits formed by the osteoclasts were significantly smaller, the trabecula thickness appeared thicker, and concentration of CTx was also significantly lower in the experimental group. CONCLUSIONS: Resorptive activity of osteoclasts cultured with ibandronate-HA was weaker than that of the control group. Ibandronate on HA in the bound state could maintain its action as an inhibitor to osteoclasts.

Effects of clodronate combined with hydroxyapatite on multi-directional differentiation of mesenchymal stromal cells.

INTRODUCTION: Bisphosphonates (BPs) can be locally used to improve the osteogenesis around hydroxyapatite (HA) implants. However, there are almost no reports discussing the effects of BPs in the bonding state with HA on bone mesenchymal stromal cells (BMSCs). Clodronate is a BP widely used in clinical practice. This study was designed to evaluate the effects of clodronate combined with HA on BMSCs' multi-directional differentiation. MATERIAL AND METHODS: The HA and clodronate-HA complex were prepared. BMSCs were isolated from Sprague-Dawley rat bone marrow and then the cells were cultured with both HA and clodronate-HA. The method of transcriptional and translational assay (MTT) and multi-directional induction (including osteogenic, adipogenic, and myogenic differentiation) were used to evaluate the effect of clodronate-HA on BMSC differentiation. RESULTS: Scanning electron microscopy indicated active proliferation of the cells on clodronate-HA and HA. MTT of BMSCs cultured on clodronate-HA and HA demonstrated no significant differences between the two groups. BMSCs differentiated into osteocytes, adipocytes, and myocytes after being cultured with both clodronate-HA and HA. This indicated that BMSCs still retained multi-directional capability. The alkaline phosphatase activity of osteogenic induced BMSCs of both groups had no significant difference. However, there was a significant difference in total protein found between them. CONCLUSIONS: The results suggest that clodronate in the bonding state with HA has no obvious inhibition of the proliferation and activity of BMSCs on the complex, and there was no evidence of a negative effect on multi-directional capability of the BMSCs.