Earlier effect of alendronate in mouse metaphyseal versus diaphyseal bone healing

Alendronate enhances osseointegration in a murine implant model

Administration of bisphosphonates following total joint arthroplasty might be beneficial to reduce aseptic loosening. However, their effects on peri-implant bone formation and bone-implant interface strength have not been investigated yet. We used a physiologically loaded mouse implant model to investigate the short-term effects of postoperative systemic alendronate on osseointegration. A titanium implant with a rough surface was inserted in the proximal tibiae of 17-week-old female C57BL/6 mice (n = 44). Postimplantation mice were given alendronate (73 μg/kg/days, n = 22) or vehicle (n = 22) 5 days/week. At 7- and 14-day postimplantation, histology and histomorphometry were conducted. At 28 days, microcomputed tomography and biomechanical testing were performed (n = 10/group). Postoperative alendronate treatment enhanced osseointegration, increasing maximum pullout load by 45% (p < .001) from 19.1 ± 4.5 N in the control mice to 27.6 ± 4.9 N in the treated mice, at day 28 postimplantation. Alendronate treatment increased the bone volume fraction by 139% (p < .001) in the region distal to the implant and 60% (p < .05) in the peri-implant region. At 14-day postimplantation, alendronate treatment decreased the number of osteoclasts per bone perimeter (p < .05) and increased bone volume fraction (p < .01) when compared with the control group. Postimplantation, short-term alendronate treatment enhanced osseointegration as demonstrated by increased bone mass, trabecular bone thickness, and maximum pullout load. Alendronate decreased peri-implant osteoclasts while preserving peri-implant osteoblasts and endothelial cells, in turn, increasing bone volume fraction. This data supports the postoperative clinical use of bisphosphonates, especially in patients with high risks of aseptic loosening.

The Effect of Bisphosphonates on Fracture Healing Time and Changes in Bone Mass Density: A Meta-Analysis

BACKGROUND

Osteoporosis is a common complication of acute fracture, which can lead to fracture delayed union or other complications and resulting in poor fracture healing. Bisphosphate is a common anti-osteoporosis drug, but its application in fracture patients is still controversial because of its inhibitory effect on bone resorption.

METHOD

Studies were acquired from literature databases in accordance with established inclusion criteria. Standard mean difference (SMD) and 95% confidence intervals (Cls) were calculated to evaluate the effectiveness of the bisphosphonates treatment in fracture patients. Data analysis was conducted with the Review Manager 5.4.1 software.

RESULTS

A total of 16 studies involving 5022 patients obtained from selected databases were examined. As expected, bisphosphate had no significant effect on fracture healing time, but it could significantly increase BMD and prevent osteoporosis. Meanwhile, bisphosphate can inhibit both bone resorption and bone formation markers, resulting in low bone turnover state.

CONCLUSION

This meta-analysis showed that bisphosphonate have no significant effect on fracture healing time but they do increase the changes in BMD and reduce bone synthesis and resorption markers. Early application of bisphosphonates after injury in the appropriate patient population should be considered.

A novel mouse model to study fracture healing of the proximal femur

The majority of fractures, especially in elderly and osteoporotic patients, occurs in metaphyseal bone. However, only a few experimental models exist to study metaphyseal bone healing in mice. Currently used mouse models of metaphyseal fracture healing are either based on drill hole defects, lacking adequate biomechanical stimulation at the site of fracture and therefore endochondral ossification in the fracture callus, or are introduced into the distal part of the mouse femur stabilized by a locking plate, which is challenging due to the small specimen size. Therefore, the aim of the current study was to develop a new mouse model to study metaphyseal fracture healing of the proximal femur. We chose a combination between an open osteotomy and a closed intramedullary stabilization. A 24 G needle was inserted into the femur in a closed manner, then an osteotomy was made with a 0.4-mm Gigli wire saw between the third and the lesser trochanter of the femur using an open approach. Fractured femurs were analyzed using microcomputed tomography and histology at days 14 and 21 after surgery. No animals were lost due to surgery or anesthesia. All animals displayed normal limb loading and a physiological gait pattern within the first three days after fracture. We found robust endochondral ossification during the fracture healing process with high expression of late chondrocyte and early osteogenic markers at day 14 (d14). By day 21 (d21), all fractures had a bony bridging score of 3 or more, indicating successful healing. Callus volume significantly decreased from d14 to d21, whereas high numbers of osteoclasts appeared at the fracture callus until d21, indicating that callus remodeling had already started at d21. In conclusion, we successfully developed a novel mouse model to study endochondral fracture healing of the proximal femur. This model might be useful for future studies using transgenic animals to unravel molecular mechanisms of osteoporotic metaphyseal fracture healing.

Implementation of Endogenous and Exogenous Mesenchymal Progenitor Cells for Skeletal Tissue Regeneration and Repair

Harnessing adult mesenchymal stem/progenitor cells to stimulate skeletal tissue repair is a strategy that is being actively investigated. While scientists continue to develop creative and thoughtful ways to utilize these cells for tissue repair, the vast majority of these methodologies can ultimately be categorized into two main approaches: (1) Facilitating the recruitment of endogenous host cells to the injury site; and (2) physically administering into the injury site cells themselves, exogenously, either by autologous or allogeneic implantation. The aim of this paper is to comprehensively review recent key literature on the use of these two approaches in stimulating healing and repair of different skeletal tissues. As expected, each of the two strategies have their own advantages and limitations (which we describe), especially when considering the diverse microenvironments of different skeletal tissues like bone, tendon/ligament, and cartilage/fibrocartilage. This paper also discusses stem/progenitor cells commonly used for repairing different skeletal tissues, and it lists ongoing clinical trials that have risen from the implementation of these cells and strategies. Lastly, we discuss our own thoughts on where the field is headed in the near future.

Dose of alendronate directly increases trabeculae expansivity without altering bone volume in rat femurs

AIM

To evaluate the effects of sodium alendronate on bone repair in fractures created in appendicular bones.

METHODS

Wistar rats (n = 36) were allocated into three distinct groups: group C (control), group B1 (received 1 mg/kg of alendronate), and group B2 (received 3 mg/kg of alendronate). The rats underwent femoral transversal linear fracture surgery using stable internal fixation with a 2.0 mm plate and screw system. Each animal randomly received intraperitoneal applications of sodium alendronate at a dose corresponding to group B1 or B2 three times a week, while the control group received a 0.9% saline solution. Drug administration was performed until euthanasia at 45 d. The femurs were removed and each surgical piece was sent for radiographic, tomographic and microtomographic analysis. Data were submitted to descriptive and inferential statistical analysis (95% confidence interval).

RESULTS

Quantitative evaluations of bone neoformation did not show differences among the groups in the radiographic (P = 0.341), microtomographic (P = 0.581) and tomographic evaluations (P = 0.171). In the qualitative microtomographic analysis, a smaller distance was observed between the internal bone trabeculae in the groups that used alendronate (P = 0.05). On the other hand, group B2 had a higher amount of bone trabeculae per unit length when compared to the other groups (P = 0.04).

CONCLUSION

It is likely that the use of alendronate did not have a direct influence on the amount of bone neoformation, however it did influence the bone quality in a dose-dependent manner, ultimately affecting the distance and quantity of the trabeculae.

Dual modulation of bone formation and resorption with zoledronic acid-loaded biodegradable magnesium alloy implants improves osteoporotic fracture healing: An in vitro and in vivo study

Osteoporotic fracture (OPF) remains a major clinical challenge for skeletal regeneration. Impaired osteogenesis and excessive remodeling result in prolonged and poor quality of fracture healing. To augment bone formation and inhibit excessive resorption simultaneously, we constructed a biodegradable magnesium-based implant integrated with the anti-catabolic drug zoledronic acid (ZA); this implant exhibits controllable, sustained release of magnesium degradation products and ZA in vitro. The extracts greatly stimulate the osteogenic differentiation of rat-bone marrow-derived mesenchymal stem cells (rBMSCs), while osteoclastogenesis is inhibited by ZA. Implantation of intramedullary nails to fix femur fracture in ovariectomy-induced osteoporotic rats for up to 12 weeks demonstrates magnesium implants alone can enhance OPF repair through promoting callus formation compared to conventional stainless steel, while the combinatory treatment with local ZA release from implant coating further increases bone regeneration rate and callus size, remarkably improves bone quality and mechanical strength and suppresses osteoclasts and bone remodeling, due to the synergistic effect of both agents. The slow and uniform degradation of the implant ensures a steady decrease in bending force, which meets clinical requirements. In summary, biodegradable magnesium-based implants can locally co-deliver magnesium degradation products and zoledronic acid in a controlled manner, and can be superior alternatives for the reconstruction of osteoporosis-related fracture.

STATEMENT OF SIGNIFICANCE

Management of osteoporotic fracture has posed a major challenge in orthopedics, as the imbalance between diminished osteogenesis and excessive bone remodeling often leads to delayed and compromised fracture repair. Among various efforts expended on augmenting osteoporotic fracture healing, herein we reported a new strategy by engineering and utilizing a biodegradable magnesium-based implant integrated with local drug delivery, specifically, zoledronic acid (ZA)-loaded polylactic acid/brushite bilayer coating on a biodegradable Mg-Nd-Zn-Zr alloy (denoted as Mg/ZA/CaP), aiming to combine the favorable properties of Mg and zoledronic acid for simultaneous modulation of bone formation and bone resorption. In vitro and in vivo studies demonstrated its superior treatment efficacy along with adequate degradation. It stimulated new bone formation while suppressing remodeling, ascribed to the local release of magnesium degradation products and zoledronic acid. To our knowledge, the enhanced fracture repair capability of Mg-based implants was for the first time demonstrated in an osteoporotic fracture animal model. This innovative biodegradable Mg-based orthopedic implant presents great potential as a superior alternative to current internal fixation devices for treating osteoporotic fracture.

Effects of single or combination therapy of teriparatide and anti-RANKL monoclonal antibody on bone defect regeneration in mice

OBJECTIVE

The purpose of this study is to investigate the effects of a single or combination therapy of teriparatide (TPTD) and anti-RANKL Ab (anti-murine receptor activator of nuclear factor κB ligand monoclonal antibody) on the regeneration of both cancellous and cortical bone.

METHODS

Nine-week-old mice underwent bone defect surgery on the left femoral metaphysis (cancellous-bone healing model) and right femoral mid-diaphysis (cortical-bone healing model). After surgery, the mice were assigned to 1 of 4 groups to receive 1) saline (5 times a week; CNT group), 2) TPTD (40μg/kg 5 times a week; TPTD group), 3) anti-RANKL Ab (5mg/kg once; Ab group), or 4) a combination of TPTD and anti-RANKL Ab (COMB group). The following analyses were performed: Time-course microstructural analysis of healing in both cancellous and cortical bone in the bone defect, the volumetric bone mineral density of the tibia with micro-computed tomography, histological, histomorphometrical, and biomechanical analysis of regenerated bone.

RESULTS

Regeneration of cancellous bone volume in the COMB group was the highest among the 4 groups, and this combined administration prompted medullary callus formation in the early phase of bone regeneration. On the other hand, regeneration of cortical bone volume in the COMB group was significantly higher than in the Ab group and was almost same as in the TPTD group. Histological analysis showed remaining woven bones, cartilage matrix, and immature lamellar bone in the COMB and Ab groups. However, biomechanical analysis showed that hardness and Young's modulus of regenerated cortical bone in the COMB group was not lower than in both the CNT and TPTD groups. Volumetric bone mineral density in the tibia was significantly increased in the COMB group compared with the other 3 groups.

CONCLUSION

In the early phase of bone regeneration, the combination of TPTD and anti-RANKL Ab accelerates regeneration of cancellous bone in bone defects and increases cancellous bone mass in the tibia more effectively than either agent does individually, but these additive effects are not observed in the regeneration of cortical bone.

Decisive differences in the bone repair processes of the metaphysis and diaphysis in young mice

Fractures are common traumatic injuries that mainly occur in the metaphyses of long bones such as the proximal humerus, distal radius, and proximal femur. However, most studies of fracture repair processes have focused on the diaphyseal region. In this study, we compared the bone repair processes of the metaphysis and the diaphysis of the mouse tibia. Bone apertures were formed in the tibial metaphysis and diaphysis. At indicated times after surgery, samples were collected, and the healing process was investigated using micro-computed tomography, as well as histological, immunohistochemical, and mRNA expression analyses. In the metaphysis, cartilage formation was not detected on the periosteal side. The bone aperture was filled with newly formed bone produced from bone marrow at day 7. In the case of the diaphysis, cartilage was formed around the aperture at day 4 and sequentially replaced by bone on the periosteal side. The bone aperture was filled with newly formed bone at day 14. In the bone marrow, expression of the osteogenic markers such as alkaline phosphatase, osteocalcin, and type I collagen, appeared earlier with metaphyseal injury than with diaphyseal injury. The mRNA expression of chondrogenesis markers was markedly upregulated in the diaphysis compared with that in the metaphysis on the periosteal side. These results indicate differences in the bone repair processes of the two regions, suggesting functional heterogeneity of the periosteum and bone marrow mesenchymal cells in response to bone fractures.

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Fractures occur mainly in the metaphyses of long bones, but most studies of fracture repair have focused on the diaphysis.

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We compared the bone repair processes of the metaphysis and the diaphysis of the mouse tibia.

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In the metaphysis, cartilage was not detected by histology and newly formed bone was produced from the bone marrow on day 7.

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In the diaphysis, cartilage was formed on day 4 and replaced with newly formed bone by day 14.

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Expression of osteogenic and chondrogenic markers also differed between the two regions of bone during the repair process.

Isolated metaphyseal injury influences unrelated bones

Background and purpose - Fracture healing involves different inflammatory cells, some of which are not part of the traditional bone field, such as B-cells and cytotoxic T-cells. We wanted to characterize bone healing by flow cytometry using 15 different inflammatory cell markers in a mouse model of metaphyseal injury, and incidentally discovered a previously unknown general skeletal reaction to trauma. Material and methods - A bent needle was inserted and twisted to traumatize the cancellous bone in the proximal tibia of C57/Bl6 female mice. This is known to induce vivid bone formation locally in the marrow compartment. Cells were harvested from the injured region, the uninjured contralateral tibia, and the humerus. The compositions of the immune cell populations were compared to those in untraumatized control animals. Results - Tibial metaphyseal injury led to substantial changes in the cell populations over time. Unexpectedly, similar changes were also seen in the contralateral tibia and in the humerus, despite the lack of local trauma. Most leukocyte subsets were affected by this generalized reaction. Interpretation - A relatively small degree of injury to the proximal tibia led to systemic changes in the immune cell populations in the marrow of unrelated bones, and probably in the entire skeleton. The few changes that were specific for the injury site appeared to relate to modulatory functions.