The Effectiveness of Human Parathyroid Hormone and Low-Intensity Pulsed Ultrasound on the Fracture Healing in Osteoporotic Bones

Low-intensity pulsed ultrasound regulates bone marrow mesenchymal stromal cells differentiation and inhibits bone loss by activating the IL-11-Wnt/β-catenin signaling pathway

BACKGROUND

Osteoporosis (OP) is a common metabolic bone disease. Low-intensity pulsed ultrasound (LIPUS) can effectively promote bone formation and fracture healing. The Wnt/β-catenin signaling pathway is crucial for regulating bone homeostasis and bone diseases, and its downregulation is one of the main mechanisms of osteoporosis pathogenesis. Interleukin-11 (IL-11), which is regulated by mechanical stress, is a key factor in bone remodeling. Here, we investigated the optimal intervention parameters for LIPUS, the relationships among LIPUS, IL-11, and the Wnt/β-catenin signaling pathway, and the effects of LIPUS on bone loss and potential molecular mechanisms in ovariectomized (OVX) mice.

METHODS

Bone marrow mesenchymal stromal cells (BMSCs) were subjected to LIPUS intervention for 0, 10, or 20 min to determine the optimal intervention time. The mediating role of IL-11 in LIPUS intervention was explored through IL-11 knockdown and overexpression. Finally, animal experiments were conducted to investigate the in vivo therapeutic effects of LIPUS.

RESULTS

The optimal intervention time for LIPUS was 20 min. LIPUS promoted IL-11 expression and upregulated the Wnt/β-catenin signaling pathway, thereby promoting osteogenic differentiation and inhibiting adipogenic differentiation of BMSCs. IL-11 mediates the regulation of the Wnt/β-catenin signaling pathway by LIPUS. Additionally, LIPUS effectively improved the bone microstructure in ovariectomized mice, inhibited bone loss, promoted IL-11 expression in bone tissue, and activated the Wnt/β-catenin signaling pathway in the femur.

CONCLUSION

Low-intensity pulsed ultrasound can regulate BMSCs differentiation and inhibit bone loss by promoting IL-11 expression and activating the Wnt/β-catenin signaling pathway.

Transcutaneous CO2 application combined with low-intensity pulsed ultrasound accelerates bone fracture healing in rats

BACKGROUND

Low-intensity pulsed ultrasound (LIPUS) is a non-invasive therapy that accelerates fracture healing. As a new treatment method for fracture, we recently reported that the transcutaneous application of CO2 accelerated fracture healing in association with promoting angiogenesis, blood flow, and endochondral ossification. We hypothesized that transcutaneous CO2 application, combined with LIPUS, would promote bone fracture healing more than the single treatment with either of them.

METHODS

Femoral shaft fractures were produced in 12-week-old rats. Animals were randomly divided into four groups: the combination of CO2 and LIPUS, CO2, LIPUS, and control groups. As the transcutaneous CO2 application, the limb was sealed in a CO2-filled bag after applying hydrogel that promotes CO2 absorption. Transcutaneous CO2 application and LIPUS irradiation were performed for 20 min/day, 5 days/week. At weeks 1, 2, 3, and 4 after the fractures, we assessed the fracture healing process using radiography, histology, immunohistochemistry, real-time PCR, and biomechanical assessment.

RESULTS

The fracture healing score using radiographs in the combination group was significantly higher than that in the control group at all time points and those in both the LIPUS and CO2 groups at weeks 1, 2, and 4. The degree of bone fracture healing in the histological assessment was significantly higher in the combination group than that in the control group at weeks 2, 3, and 4. In the immunohistochemical assessment, the vascular densities of CD31- and endomucin-positive microvessels in the combination group were significantly higher than those in the control and LIPUS groups at week 2. In the gene expression assessment, significant upregulation of runt-related transcription factor 2 (Runx2) and vascular endothelial growth factor (VEGF) was detected in the combination group compared to the LIPUS and CO2 monotherapy groups. In the biomechanical assessment, the ultimate stress was significantly higher in the combination group than in the LIPUS and CO2 groups.

CONCLUSION

The combination therapy of transcutaneous CO2 application and LIPUS had a superior effect in promoting fracture healing through the promotion of angiogenesis and osteoblast differentiation compared to monotherapy.

Oral dehydroepiandrosterone supplementation enhances osteoporotic fracture healing in the OVX rats

Osteoporosis easily causes delayed fracture union, even non-union. It has been demonstrated that dehydroepiandrosterone (DHEA) supplementation can increase estrogen levels and improve bone mineral density (BMD) in the elderly, while the role of DHEA on fracture healing remains unknown. This study aimed to elucidate the impact of DHEA supplementation on osteoporotic fracture healing. Seventy-two female Sprague-Dawley rats were used. Forty-eight rats received ovariectomy (OVX), and the remaining rats received a sham OVX operation (sham group). A right transverse femoral osteotomy was performed in all rats at 12 weeks post-OVX. OVX rats were randomly allocated into 2 groups (n = 24 in each group): (i) ovariectomized rats (control group) and (ii) ovariectomized rats treated with DHEA (DHEA group, 5 mg/kg/day). The DHEA supplementation was initiated on the first day post-fracture for 3, 6, and 12 weeks. Fracture healing was evaluated by radiography, histology, biomechanical analysis, and dual-energy X-ray absorptiometry (DEXA). Serum biomarkers were analyzed using enzyme-linked immunosorbent assay (ELISA). At 3 and 6 weeks, radiographs revealed reduced calluses formation and lower radiographic scores in the control group than in other groups. The sham and DHEA groups showed higher BMD and bone mineral content (BMC) at the fracture site than the control group after fracture. Histological analysis revealed the fracture callus was remodeled better in the sham and DHEA groups than in the control group. At the early phase of healing, DHEA supplementation increased osteoblast number, callus area, and cartilage area than the control group. An increased bone area was observed in the DHEA group than in the control group at the late phase of healing. Additionally, improved biomechanical characteristics were observed in both the sham and DHEA groups than those in the control group post-fracture. ELISA showed higher levels of insulin-like growth factor-1 (IGF-1) and 17β-estradiol (E2) in the DHEA group than in the control group post-fracture. Furthermore, the DHEA group exhibited significantly elevated alkaline phosphatase (ALP) and osteocalcin (OC) levels compared to the control group at 6 and 12 weeks. The DHEA group and the control group did not exhibit a notable difference in TRAP-5b levels. The present study demonstrated that the DHEA treatment has a favorable impact on osteoporotic fracture healing by enhancing callus formation, consolidation, and strength in the OVX rats.

Osthole accelerates osteoporotic fracture healing by inducing the osteogenesis-angiogenesis coupling of BMSCs via the Wnt/β-catenin pathway

Osthole, a natural coumarin derivative, has been shown to have multiple pharmacological activities. However, its effect on osteoporotic fracture has not yet been examined. This research was designed to explore the unknown role and potential mechanism of osthole on osteoporotic fracture healing. We first evaluated the osteogenic and angiogenic abilities of osthole. Then angiogenesis-related assays were conducted to investigate the relationship between osteogenesis and angiogenesis, and further explore its molecular mechanism. After that, we established osteoporotic fracture model in ovariectomy-induced osteoporosis rats and treated the rats with osthole or placebo. Radiography, histomorphometry, histology, and sequential fluorescent labeling were used to evaluate the effect of osthole on osteoporotic fracture healing. In vitro research revealed that osthole promoted osteogenesis and up-regulated the expression of angiogenic-related markers. Further research found that osthole couldn't facilitate the angiogenesis of human umbilical vein endothelial cells in a direct manner, but it possessed the ability to induce the osteogenesis-angiogenesis coupling of bone marrow mesenchymal stem cells (BMSCs). Mechanistically, this was conducted through activating the Wnt/β-catenin pathway. Subsequently, using ovariectomy-induced osteoporosis tibia fracture rat model, we observed that osthole facilitated bone formation and CD31hiEMCNhi type H-positive capillary formation. Sequential fluorescent labeling confirmed that osthole could effectively accelerate bone formation in the fractured region. The data above indicated that osthole could accelerate osteoporotic fracture healing by inducing the osteogenesis-angiogenesis coupling of BMSCs via the Wnt/β-catenin pathway, which implied that osthole may be a potential drug for treating osteoporosis fracture.

Methods to accelerate fracture healing - a narrative review from a clinical perspective

Bone regeneration is a complex pathophysiological process determined by molecular, cellular, and biomechanical factors, including immune cells and growth factors. Fracture healing usually takes several weeks to months, during which patients are frequently immobilized and unable to work. As immobilization is associated with negative health and socioeconomic effects, it would be desirable if fracture healing could be accelerated and the healing time shortened. However, interventions for this purpose are not yet part of current clinical treatment guidelines, and there has never been a comprehensive review specifically on this topic. Therefore, this narrative review provides an overview of the available clinical evidence on methods that accelerate fracture healing, with a focus on clinical applicability in healthy patients without bone disease. The most promising methods identified are the application of axial micromovement, electromagnetic stimulation with electromagnetic fields and direct electric currents, as well as the administration of growth factors and parathyroid hormone. Some interventions have been shown to reduce the healing time by up to 20 to 30%, potentially equivalent to several weeks. As a combination of methods could decrease the healing time even further than one method alone, especially if their mechanisms of action differ, clinical studies in human patients are needed to assess the individual and combined effects on healing progress. Studies are also necessary to determine the ideal settings for the interventions, i.e., optimal frequencies, intensities, and exposure times throughout the separate healing phases. More clinical research is also desirable to create an evidence base for clinical guidelines. To make it easier to conduct these investigations, the development of new methods that allow better quantification of fracture-healing progress and speed in human patients is needed.

Study of Injectable Hydrogel Based on ALN/nHA Promoting Osteogenesis and Inhibiting Osteoclasts in Osteoporotic Bone Defects Repair

Osteoporotic bone defects cannot withstand surgery with more significant trauma due to bone fragility, while systemic drug therapy has formidable adverse effects. Consequently, the present study introduces an innovatively devised injectable double-crosslinked hydrogel, as a potential therapeutic avenue for addressing varied shapes of osteoporotic bone defects via a minimally invasive approach. The injectable hydrogel is formed by the formation of Schiff base bonds between oxidized sodium alginate (OSA) and carboxymethyl chitosan, and the polymerization of gelatin methacrylate by UV light crosslinking. Additionally, alendronate sodium (ALN) is loaded into the hydrogel through Schiff base formation with OSA, and nanohydroxyapatite (nHA) is incorporated into the hydrogel via blending. The hydrogel demonstrates excellent injectability, and the nHA improves the mechanical properties of hydrogel and can promote bone formation. In addition, the hydrogel can sustain the release of ALN, which has the effect of inhibiting osteoclasts. Cell studies indicate that the hydrogel can promote the differentiation of osteoblasts and inhibit the activity of osteoclast, so as to obtain better osteogenic effect. Therefore, the injectable hydrogel can be used to repair osteoporotic bone defects through a minimally invasive, simple treatment modality.

Low-intensity pulsed ultrasound and parathyroid hormone improve muscle atrophy in estrogen deficiency mice

Due to aging and long-term estrogen deficiency, postmenopausal women suffer muscle atrophy (MA), which is characterized by decreased muscle mass and muscle quality. Low-intensity pulsed ultrasound (LIPUS) is an acoustic wave inducing biological effects mainly by the mechanical stimulation and used as a non-invasive physical therapy for muscle repair. Parathyroid hormone (PTH) is an 84-amino-acid polypeptide, and its bioactive fragment [PTH (1-34)] has potential application in the treatment of MA. We speculate that the combination of physical therapy (i.e., the LIPUS) and regulatory hormone (i.e., the PTH) would be more effective in the treatment of MA. The objective of this study was to evaluate the individual and combined effects of LIPUS and PTH therapy on MA in estrogen deficiency mice. Seventy 8-week-old female C57BL/6J mice were used in this study and the MA model was induced by an intraperitoneal injection of 4-vinylcyclohexene diepoxide (VCD) for 20 consecutive days. The VCD-induced MA mice were randomly divided into MA, LIPUS, PTH and LIPUS + PTH (Combined) groups (n = 10/group). In the LIPUS group, the mice were treated by LIPUS in bilateral quadriceps muscles for 20 min, five times a week for 6 weeks. In the PTH group, the mice received subcutaneous injection of PTH (1-34) (80 ug/kg/d) five times a week, for 6 weeks. In the Combined group, the PTH was administrated 30 min before each LIPUS session. Hematoxylin-eosin (H&E) staining, serum biochemical analysis and quantitative real-time polymerase chain reaction (qRT-PCR) were applied to evaluate the therapeutic effects of related treatments. The results showed that the MA mice had a disordered estrus cycle, significantly decreased muscle mass and myofibers cross-sectional area (CSA). After treatments, LIPUS, PTH and Combined groups had a significantly increased CSA, compared with the MA mice without treatment. In addition, Combined group had a significantly increased mRNA expression of Pax7, MyoD and MyoG, compared with LIPUS and PTH monotherapy groups. Our findings indicated that the combination of LIPUS and PTH treatment improves muscle regeneration ability, which might have potential for treating MA in postmenopausal women.

A Numerical Study on Mechanical Effects of Low-Intensity Pulsed Ultrasound on Trabecular Bone and Osteoblasts

The lack of sufficient mechanical stimulation to the human bone, results in disuse osteoporosis. Low-intensity pulsed ultrasound (LIPUS) promotes fracture healing and the treatment of disuse osteoporosis, but its biomechanical mechanism remains unknown. Simulative research on the mechanical effects of LIPUS on disuse trabecular bone and osteoblasts have been performed. The von Mises stress of disuse trabecular bone and osteoblasts obviously increased under LIPUS irradiation. The average von Mises stress of osteoblasts were two orders of magnitude higher under the irradiation of simulant LIPUS than that without LIPUS irradiation, and the von Mises stress of osteoblasts was positively correlated with the amplitude of sound pressure excitation. The results showed that LIPUS irradiation could obviously improve the mechanical micro-environment of trabecular bone and osteoblasts to alleviate the lack of mechanical stimulation. The results of the research can reveal the biomechanical mechanism of LIPUS in the treatment of disuse osteoporosis to some extent and provide theoretical guidance for clinical treatment of disuse osteoporosis through physical methods.

Clinical Efficacy and Safety of Zoledronic Acid Combined with PVP/PKP in the Treatment of Osteoporotic Vertebral Compression Fracture: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Objective

We conducted this meta-analysis to provide better evidence of the efficacy and safety of zoledronic acid (ZA) combined with percutaneous vertebroplasty/kyphoplasty (PVP/PKP) on osteoporotic vertebral compression fracture (OVCF) and proposed a protocol for its application in clinical practice.

Methods

All randomized controlled trials (RCTs) of ZA combined with PVP or PKP compared to individual PVP/PKP for the management of patients with OVCFs were included in this study. Electronic database searches were conducted from database inception to November 2020, including the Cochrane Library, PubMed, Web of Science, and Embase. The pooled data were analyzed using RevMan 5.3 software.

Results

Seven RCTs with 929 subjects were finally included. All included studies reported visual analog scores (VAS), and no statistically significant differences were identified at follow-ups of 3 d and 1 w (P > 0.05). In contrast, significant differences were observed at the 1 mo, 3 mo, 6 mo, and 12 mo follow-ups (P < 0.05). Two trials reported the Cobb angle and vertebral body height (VBH), including 182 subjects without significant differences at the 12 mo follow-up (P > 0.05). In addition, significant differences in the bone mineral density (BMD), β-isomerized C-terminal telopeptide of type I collagen (β-CTX), N-terminal propeptide of type I collagen (PINP), and N-terminal molecular fragment (N-MID) levels were observed between the two groups (P < 0.05). All trials reported side effects. Significant differences in recurrent fractures, fever, flu-like symptoms, and arthralgia or myalgia were identified (P < 0.05); however, no significant difference in postoperative leakage was detected (P > 0.05).

Conclusion

Compared to PVP/PKP alone, an additional ZA injection had advantages of long-term analgesic effects with improved bone metabolism indexes. Moreover, combination therapy significantly prevented complications and drug reactions were well tolerated. Overall, this systematic review revealed that ZA combined with PVP/PKP was an effective, safe, and comprehensive therapy for patients with OVCFs.

Dual Role of Caveolin-1 in β-Catenin Signaling During Fracture Healing Induced by Low-Intensity Pulsed Ultrasound in Rabbits

We did this research to observe the effect of LIPUS on long bone fracture repair and caveolin-1, β-catenin signaling expression in the radius defects of rabbits, to explore its possible molecular mechanisms. 24 male New Zealand rabbits with bilateral radial bone defects were divided into 4 groups randomly, n = 6. The right side had daily LIPUS exposure for 20 minutes, while the left received sham treatment. After 7, 14, 21, 28 days, respectively, fracture healing was observed by X-ray imaging and Dual Energy X-ray Absorptiometry (DXA) scan, specimens were harvested for histology, immunohistochemistry, and gene expression analysis. We found that LIPUS brought forward endochondral ossification, increased the bone callus size without changes in Bone Mineral Density (BMD). The caveolin-1 expression increased first then decreased, while the β-catenin kept growing during the process. These demonstrated that caveolin-1 participated in fracture healing accelerated by LIPUS, which was speculated to play a dual role in β-catenin signaling expression.

Effectiveness of low-intensity pulsed ultrasound on osteoarthritis of the temporomandibular joint: A review

Loading is indispensable for the growth, development, and maintenance of joint tissues, including mandibular condylar cartilage, but excessive loading or reduced host adaptive capacity can considerably damage the temporomandibular joint (TMJ), leading to temporomandibular joint osteoarthritis (TMJ-OA). TMJ-OA, associated with other pathological conditions and aging processes, is a highly degenerative disease affecting the articular cartilage. Many treatment modalities for TMJ-OA have been developed. Traditional clinical treatment includes mainly nonsurgical options, such as occlusal splints. However, non-invasive therapy does not achieve joint tissue repair and regeneration. Growing evidence suggests that low-intensity pulsed ultrasound (LIPUS) accelerates bone fracture healing and regeneration, as well as having extraordinary effects in terms of soft tissue repair and regeneration. The latter have received much attention, and various studies have been performed to evaluate the potential role of LIPUS in tissue regeneration including that applied to articular cartilage. The present article provides an overview of the status of LIPUS stimulation used to prevent the onset and progression of TMJ-OA and enhance the tissue regeneration of mandibular condylar cartilage. The etiology and management of TMJ-OA are explained briefly, animal models of TMJ-OA are described, and the effectiveness of LIPUS on cell metabolism and tissue regeneration in the TMJ is discussed.

Effects of Intermittent Administration of Parathyroid Hormone and Parathyroid Hormone-Related Protein on Fracture Healing: A Narrative Review of Animal and Human Studies

Intermittent administration of parathyroid hormone (PTH) stimulates skeletal remodeling and is a potent anabolic agent in bone. PTH‐related protein (PTHrP) is anabolic acting on the same PTH1 receptor and is in therapeutic use for osteoporosis. The body of literature for PTH actions in fracture healing is emerging with promising yet not entirely consistent results. The objective of this review was to perform a literature analysis to extract up‐to‐date knowledge on the effects of intermittent PTH and PTHrP therapy in bone fracture healing. A literature search of the PubMed database was performed. Clinical case studies and articles related to “regeneration,” “implant,” and “distraction osteogenesis” were excluded. A narrative review was performed to deliberate the therapeutic potential of intermittent PTH administration on fracture healing. A smaller number of studies centered on the use of PTHrP or a PTHrP analog were also reviewed. Animal studies clearly show that intermittent PTH therapy promotes fracture healing and revealed the strong therapeutic potential of PTH. Human subject studies were fewer and not as consistent as the animal studies yet provide insight into the potential of intermittent PTH administration on fracture healing. Differences in outcomes for animal and human studies appear to be attributed partly to variable doses, fracture sites, age, remodeling patterns, and bone architectures, although other factors are involved. Future studies to examine the dose, timing, and duration of PTH administration will be necessary to further delineate the therapeutic potential of PTH for fracture healing in humans. © 2019 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.

Periodontal tissue regeneration after low-intensity pulsed ultrasound stimulation with or without intra-marrow perforation in two-wall intra-bony defects-A pilot study in dogs

AIM

To evaluate the effects of low-intensity pulsed ultrasound (LIPUS) with/without intra-marrow perforation (IMP) on periodontal healing in two-wall intra-bony defects in dogs.

MATERIALS AND METHODS

Two-wall intra-bony defects (5 mm wide, 5 mm deep) were created at the distal and mesial aspects of mandibular premolars in four beagle dogs (four defects per dog). The 16 defects were divided into four treatment groups: IMP, LIPUS, IMP + LIPUS (IMP/LIPUS) and control (open flap debridement). The LIPUS and IMP/LIPUS sites received daily LIPUS exposure for 3 weeks starting 1 week after surgery. The animals were euthanized 4 weeks after surgery for histologic evaluation.

RESULTS

There was significantly greater new bone formation at LIPUS (2.93 ± 0.74 mm) and IMP/LIPUS (3.18 ± 0.52 mm) sites than at control sites (1.65 ± 0.46 mm). New bone area at LIPUS (6.36 ± 2.28 mm² ) and IMP/LIPUS (6.13 ± 1.25 mm² ) sites was significantly greater than that at control sites (2.15 ± 1.75 mm² ). New cementum length at LIPUS sites (4.09 ± 0.75 mm) was significantly greater than that at control (2.29 ± 1.02 mm) and IMP (2.41 ± 0.41 mm) sites. No significant difference was observed between LIPUS and IMP/LIPUS sites in any histomorphometric parameter.

CONCLUSIONS

These findings suggest that LIPUS effectively promotes periodontal regeneration in two-wall intra-bony defects in dogs.

Acceleration of Bone Defect Healing and Regeneration by Low-Intensity Ultrasound Radiation Force in a Rat Tibial Model

The objective was to evaluate the effect of low-intensity pulsed ultrasound (LIPUS)-induced acoustic radiation force on trabecular bone defect repair and healing in a rat tibial model. A uniform surgical defect, 3.5 mm in diameter, was generated in the proximal bilateral tibial region of rats (N = 20). LIPUS was applied to the defects in the left tibia for 20 min every day for 2 wk. Contralateral defects in the right tibia served as a control without active LIPUS treatment. The micro-computed tomography data revealed that LIPUS-treated tibia exhibited higher bone volume/total volume, connectivity density, trabecular number, and bone mineral density and significantly lower trabecular separation. Histomorphometry analysis indicated a similar trend. Mechanical testing data revealed that LIPUS treatment significantly increased bone stiffness relative to that of the control group. Short-term (2-wk) LIPUS therapy initiated trabecular bone repair and regeneration in large trabecular bone defects, whereas cortical bone remained in the initial non-mineralization stage.

Acceleration of Fracture Healing in Experimental Model: Platelet-Rich Fibrin or Hyaluronic Acid?

In this study, we compared the bone-healing effects of the local application of platelet-rich fibrin (PRF) and hyaluronic acid (HA) to bilateral tibial fractures in rats. Twenty-three adult male Sprague-Dawley rats were used. Twenty-two animals were randomly allocated to a control group (n = 6) and 2 study groups: PRF (n = 8) and HA (n = 8). The 23rd rat was used as a donor to obtain PRF. Each group was divided into 2 subgroups for histomorphometric and radiologic assessments at 2 and 6 weeks. Foreign body reaction, necrosis, inflammation, new bone formation, and fibrosis were investigated as bone healing parameters in terms of histopathologic analysis. The difference between the groups for these parameters was evaluated. The radiologic evaluation was performed by comparing the 3-dimensional reconstruction images of the fracture sites between the study and control groups. Histomorphometric evaluation showed that at 2 weeks postoperatively, the control group showed lesser bone formation (26.1 ± 6.6%) when compared to the study (HA: 54.7 ± 9.7%; PRF: 75.3 ± 19.2%) groups and PRF group showed highest total ossification. At 6 weeks postoperatively the PRF group showed lesser total ossification (50.7 ± 28.2%) when compared to control (76.3 ± 21.7%) and HA group. The HA (88.8 ± 13.3%) showed highest total ossification. In the control group, fibrosis was more prominent at week 6, whereas in the HA and PRF groups the amount of ossification increased. In contrast to histopathologic healing, radiologic bone healing did not differ significantly among the study and control groups 2 weeks after surgery, whereas at 6 weeks, the results of radiologic bone formation were in accordance with those of histopathologic bone healing.

Comparison of the effects of once-weekly and once-daily rhPTH (1-34) injections on promoting fracture healing in rodents

To compare the efficacy of once-weekly and once-daily subcutaneous injections of teriparatide (recombinant human parathyroid hormone 1-34) on fracture healing, 50 adult male Sprague-Dawley rats were subjected to a unilateral tibia fracture and received internal fixation with a Kirschner needle. Based on the injection dose and frequency, the rats were randomly divided into five groups (n = 10 each): subcutaneous injections of saline or 10 µg/kg/w, 20 µg/kg/w, 10 µg/kg/d, and 20 µg/kg/d teriparatide. Four weeks later, the rats were euthanatized, and the fractured tibiae were assessed using X-rays, dual-energy X-ray absorptiometry, micro-computed tomography, the three-point bending biomechanics test, and histology. Compared to the saline control group, either daily or weekly subcutaneous injections of teriparatide significantly increased bone mass, improved the bone microarchitecture, and promoted fracture healing (p < 0.05). There were no significant differences in bone mineral density (BMD), bone microstructure or bone strength between the 20 µg/kg/w and 10 µg/kg/d groups (p > 0.05). Teriparatide 20 µg weekly injections promoted bone fracture healing to the same extent as teriparatide 10 µg daily injections, which can dramatically decrease the cumulative dosage of teriparatide injections. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1145-1152, 2018.

Evaluation of the effects of photobiomodulation on vertebras in two rat models of experimental osteoporosis

The aim of this study was to evaluate the effects of photobiomodulation (PBM) on cancellous bone in rat models of ovariectomized induced osteoporosis (OVX-D) and glucocorticoid-induced osteoporosis (GIOP). The experiment comprised of nine groups. A group of healthy rats was used for baseline evaluations. The OVX-D rats were further divided into groups as follows: control rats with osteoporosis, OVX-D rats that received alendronate (1 mg/kg 60 days), OVX-D rats treated with pulsed wave laser (890 nm, 80 Hz, 900 s, 0.0061 W/cm2, 5.5 J/cm2, three times a week, 60 days), and OVX-D rats treated with alendronate + pulsed laser. Dexamethasone was administered to the remaining rats that were split into four groups: control, alendronate-treated rats, laser-treated rats, and GIOP rats treated with alendronate + laser. T12, L1, L2, and L3 vertebrae were subjected to laser. Results of the current study demonstrated that OVX-D and GIOP significantly decreased some stereological parameters, and type 1 collagen gene expression compared to the healthy group. There was a significant increase in osteoclast number in both OVX-D and glucocorticoid administration compared to the healthy group. However, the detrimental effect of the OVX-D procedure on bone was more serious than glucocorticoid administration. Results showed that laser alone had a detrimental effect on trabecular bone volume, and cortical bone volume in groups GIOP and OVX-D compared to those in the healthy group. Alendronate significantly improved total vertebral bone volume, trabecular bone volume, and cortical bone volume, in GIOP and OVX-D groups compared to the laser-treated groups. Furthermore, the alendronate + laser in OVX-D rats and GIOP rats produced significantly increased osteoblast number and type 1 collagen gene expression and caused a significant decrease in osteoclast number compared to the controls.

Effect of parathyroid hormone on healing in osteoporotic fractures via a phospholipase C-independent pathway

Objective

This study was performed to investigate the effect of parathyroid hormone (PTH) on healing in osteoporotic fractures via a phospholipase C (PLC)-independent pathway and explore the mechanism of PTH-mediated bone formation.

Methods

Ninety-six 12-week-old C57BL/6J female mice underwent bilateral ovariectomy. One month later, the lower third of the femur was fractured and the mice were treated using saline, PTH(1-28), PTH(1-34), zoledronic acid (ZA), PTH(1-28)+ZA, and PTH(1-34)+ZA. The mice were killed at weeks 2 and 4 in each group. Biomechanical testing and micro-computed tomography were performed.

Results

The formation and strength of the callus increased in all but the saline group. The mice treated with PTH(1-34) showed a significantly higher ultimate bending force, bending rigidity, bone mineral density, percent bone volume, and trabecular thickness than those treated with PTH(1-28). The PTH(1-34)+ZA group demonstrated the greatest improvements in the ultimate bending force, bending rigidity, bone mineral density, and relative bone volume.

Conclusions

PTH can promote fracture healing and callus hardness in ovariectomized mice by increasing callus formation and reconstructing trabecular bone via a PLC-independent pathway. PTH combined with ZA has a cumulative effect on the healing of fractures in ovariectomized mice.