Experimental osteoporosis induced by ovariectomy and vitamin D deficiency does not markedly affect fracture healing in rats

Radiographic, Biomechanical and Histological Characterization of Femoral Fracture Healing in Aged CD-1 Mice

With a gradually increasing elderly population, the treatment of geriatric patients represents a major challenge for trauma and reconstructive surgery. Although, it is well established that aging affects bone metabolism, it is still controversial if aging impairs bone healing. Accordingly, we investigated fracture healing in young adult (3-4 months) and aged (16-18 months) CD-1 mice using a stable closed femoral fracture model. Bone healing was analyzed by radiographic, biomechanical and histological analysis at 1, 2, 3, 4 and 5 weeks after fracture. Our results demonstrated an increased callus diameter to femoral diameter ratio in aged animals at later time points of fracture healing when compared to young adult mice. Moreover, our biomechanical analysis revealed a significantly decreased bending stiffness at 3 and 4 weeks after fracture in aged animals. In contrast, at 5 weeks after fracture, the analysis showed no significant difference in bending stiffness between the two study groups. Additional histological analysis showed a delayed endochondral ossification in aged animals as well as a higher amounts of fibrous tissue at early healing time points. These findings indicate a delayed process of callus remodeling in aged CD-1 mice, resulting in a delayed fracture healing when compared to young adult animals. However, the overall healing capacity of the fractured femora was not affected by aging.

Early Retrieval of Spanning Plates Used for Fixation of Complex Fractures of the Distal Radius

Background  Spanning plates are being increasingly used for the treatment of complex fractures of the distal radius. The traditional recommendation is to leave the hardware in place for at least 12 weeks. Questions/Purpose  This study assesses the comparative outcomes of spanning plates removed at or before 10 weeks. We hypothesized that acceptable healing and functional outcomes can be achieved with earlier hardware removal to allow for earlier range of motion, rehabilitation, and return to function. Patients and Methods  All patients treated for a comminuted, intra-articular distal radius fracture with a temporary spanning plate were identified. Outcomes of bridge plates removed before 10 weeks were compared with plates removed after 12 weeks. Twenty patients in the short duration cohort were compared with 40 patients in the long duration cohort. Results  All fractures healed and there were 10 complications (4 short duration, 6 long duration) and 2 reoperations (1 short duration, 1 long duration) in the study population. There were no significant differences in final Quick-DASH scores (27.4 short duration, 20.9 long duration) or radiographic alignment. Mean values for wrist extension and ulnar deviation were significantly worse in the long duration cohort, although these differences are of unclear clinical significance. Conclusion  It may be safe to remove spanning bridge plates earlier than what is traditionally recommended. Plate removal at or before 10 weeks did not detract from healing or radiographic alignment. Prospective investigations assessing the optimal duration of fixation for this technique are needed. Level of Evidence  This is a Level IV study.

Lipid-nucleic acid nanoparticles of novel ionizable lipids for systemic BMP-9 gene delivery to bone-marrow mesenchymal stem cells for osteoinduction

Rational design of novel ionizable lipids for development of lipid-nucleic acid nanoparticles (LNP) is required for safe and effective systemic gene delivery for osteoporosis. LNPs require suitable characteristics for intravenous administration and effective accumulation in bone marrow for enhanced transfection. Hence, lipids with C18 tail and ionizable headgroup (Boc-His-ODA/BHODA and His-ODA/HODA) were synthesized and characterized physicochemically. LNPs were prepared with bone morphogenetic protein-9 gene (BHODA-LNP, HODA-LNP, and bone-homing peptide targeted HODA-LNP - HODA-LNPT). Thorough physicochemical (electrolyte stability, DNase I and serum stability) and biological (hemolysis, ROS induction, cytotoxicity and transfection) characterization was carried out followed by acute toxicity studies and therapeutic performance studies in ovariectomized rat model. Lipids with pH dependent ionization were successfully synthesized. LNPs thereof were ∼100 nm size with stability against electrolytes, DNase I and serum and exhibited low hemolytic potential demonstrating suitability for intravenous administration. LNPs exhibited minimal cytotoxicity, non-significant ROS induction and high transfection. In vivo studies demonstrated safety and improved bone regeneration in OVX rats with HODA-LNPT showing significantly better performance. Synthesized ionizable lipids offer safe and effective alternative for preparation of LNPs for gene delivery. Targeted BMP-9 LNP show potential for systemic osteoporosis treatment.

Mechanisms Underlying Normal Fracture Healing and Risk Factors for Delayed Healing

PURPOSE OF REVIEW

Substantial advances have been made in understanding the biological basis of fracture healing. Yet, it is unclear whether the presence of osteoporosis or prior or current osteoporosis therapy influences the healing process or is associated with impaired healing. This review discusses the normal process of fracture healing and the role of osteoporosis and patient-specific factors in relation to fracture repair.

RECENT FINDINGS

The definitive association of osteoporosis to impaired fracture healing remains inconclusive because of limited evidence addressing this point. eStudies testing anabolic agents in preclinical models of ovariectomized animals with induced fractures have produced mostly positive findings showing enhanced fracture repair. Prospective human clinical trials, although few in number and limited in design and to testing only one anabolic agent, have similarly yielded modestly favorable results. Interest is high for exploring currently available osteoporosis therapies for efficacy in fracture repair. Definitive data supporting their efficacy are essential in achieving approval for this indication.

A New Clinically Relevant T-Score Standard to Interpret Bone Status in a Sheep Model

Background

Osteoporosis is diagnosed by bone loss using a radiological parameter called T-score. Preclinical studies use DXA to evaluate bone status were the T-score is referenced on bone mineral density (BMD) values of the same animals before treatment. Clinically, the reference BMD represents values of an independent group of healthy patients around 30 years old. The present study established a clinically similar T-score standard to diagnose osteoporosis in a sheep model.

Material/Methods

We used 31 female merino land sheep (average 5.5 years old) to study osteoporosis. The following groups were compared using DXA measurement: 1) control; 2) ovariectomized (OVX); 3) OVX combined with a deficient diet (OVXD); and 4) OVXD combined with methylprednisolone administration (OVXDS). Further, an independent group of 32 healthy sheep (4–6 years old) were measured as an independent baseline. BMD was measured at 0 months, 3 months, and 8 months after treatment.

Results

The same significance pattern between the treated groups and either baseline groups was seen. However, using an independent baseline changed the “clinical” interpretation of the data from an osteoporotic bone status (T-score <−2.5) after 3 months of OXDS treatment into an osteopenic bone status (T-score <−1.5 to −2.4).

Conclusions

Using an independent baseline enhanced the statistical significance and showed the clinical relevance. Furthermore, an independent baseline is a reliable alternative to use of a new control group for future experiments and thus reduces the number of animals needed by eliminating the need for a control and corresponding to clinical practice.

Calcium and vitamin-D deficiency marginally impairs fracture healing but aggravates posttraumatic bone loss in osteoporotic mice

Calcium and vitamin-D (Ca/VitD) deficiency is a major risk factor for osteoporosis. It may also contribute to the compromised bone healing frequently observed in osteoporotic patients, since calcium is essential for fracture-callus mineralization. Additionally, clinical data suggest systemic bone loss following fracture, which may aggravate osteoporosis and thus increase the risk for fragility fractures in osteoporotic patients further. However, the role of Ca/VitD in fracture healing and posttraumatic bone turnover has to date been poorly investigated. Here, we studied bone regeneration and posttraumatic bone turnover in C57BL/6 J mice with ovariectomy-induced osteoporosis. Mice were fed a standard or a Ca/VitD-deficient diet. Notably, fracture healing was only marginally disturbed in Ca/VitD-deficient mice. However, deficient mice displayed significantly increased serum parathyroid hormone levels and osteoclast activity, as well as reduced bone mass in the intact skeleton post-fracture, suggesting considerably enhanced calcium mobilization from the intact skeleton during bone regeneration. Ca/VitD supplementation initiated post-fracture prevented posttraumatic bone loss by reducing bone resorption and furthermore improved bone repair. These results imply that adequate Ca/VitD supply post-fracture is essential to provide sufficient calcium for callus-mineralization in order to prevent posttraumatic bone loss and to reduce the risk for secondary fractures in osteoporotic patients with Ca/VitD deficiency.

Effect of Obesity on Bone Healing After Foot and Ankle Long Bone Fractures

As obesity has become more common, fractures in the obese population have become more frequent. Concern exists regarding alterations in bone health and healing in obese patients. A matched case-control study was performed at 1 institution to evaluate whether an association exists between nonunion and a high body mass index in metatarsal and ankle fractures. A total of 48 patients with nonunion were identified, and control patients matched 2 to 1 (n = 96) were selected. The control patients were matched for age, sex, and fracture type. No association was identified between nonunion and the continuous body mass index (p = .23) or morbid obesity, with a body mass index of ≥40 kg/m² (p = .51). However, the results from both univariate and multivariate analysis suggested that patients with a current alcohol problem or a history of an alcohol problem might have a greater risk of nonunion. The odds ratio of a patient with a history of alcohol use experiencing nonunion was 2.7 (95% confidence interval 1.2 to 6.2). Further studies are warranted to confirm these findings.

Analysis of fracture healing in osteopenic bone caused by disuse: experimental study

Osteoporosis has become a serious global public health issue. Hence, osteoporotic fracture healing has been investigated in several previous studies because there is still controversy over the effect osteoporosis has on the healing process. The current study aimed to analyze two different periods of bone healing in normal and osteopenic rats. Sixty, 7-week-old female Wistar rats were randomly divided into four groups: unrestricted and immobilized for 2 weeks after osteotomy (OU2), suspended and immobilized for 2 weeks after osteotomy (OS2), unrestricted and immobilized for 6 weeks after osteotomy (OU6), and suspended and immobilized for 6 weeks after osteotomy (OS6). Osteotomy was performed in the middle third of the right tibia 21 days after tail suspension, when the osteopenic condition was already set. The fractured limb was then immobilized by orthosis. Tibias were collected 2 and 6 weeks after osteotomy, and were analyzed by bone densitometry, mechanical testing, and histomorphometry. Bone mineral density values from bony calluses were significantly lower in the 2-week post-osteotomy groups compared with the 6-week post-osteotomy groups (multivariate general linear model analysis, P<0.000). Similarly, the mechanical properties showed that animals had stronger bones 6 weeks after osteotomy compared with 2 weeks after osteotomy (multivariate general linear model analysis, P<0.000). Histomorphometry indicated gradual bone healing. Results showed that osteopenia did not influence the bone healing process, and that time was an independent determinant factor regardless of whether the fracture was osteopenic. This suggests that the body is able to compensate for the negative effects of suspension.

Immunolocalization of markers for bone formation during guided bone regeneration in osteopenic rats

Objective

The aim of this paper was to evaluate the repair of onlay autogenous bone grafts covered or not covered by an expanded polytetrafluoroethylene (e-PTFE) membrane using immunohistochemistry in rats with induced estrogen deficiency.

Material and Methods

Eighty female rats were randomly divided into two groups: ovariectomized (OVX) and with a simulation of the surgical procedure (SHAM). Each of these groups was again divided into groups with either placement of an autogenous bone graft alone (BG) or an autogenous bone graft associated with an e-PTFE membrane (BGM). Animals were euthanized on days 0, 7, 21, 45, and 60. The specimens were subjected to immunohistochemistry for bone sialoprotein (BSP), osteonectin (ONC), and osteocalcin (OCC).

Results

All groups (OVX+BG, OVX+BMG, SHAM+BG, and SHAM+BMG) showed greater bone formation, observed between 7 and 21 days, when BSP and ONC staining were more intense. At the 45-day, the bone graft showed direct bonding to the recipient bed in all specimens. The ONC and OCC showed more expressed in granulation tissue, in the membrane groups, independently of estrogen deficiency.

Conclusions

The expression of bone forming markers was not negatively influenced by estrogen deficiency. However, the markers could be influenced by the presence of the e-PTFE membrane.

Vitamin D in Foot and Ankle Fracture Healing: A Literature Review and Research Design

Vitamin D is a generic name for a group of essential vitamins, or secosteroids, important in calcium homeostasis and bone metabolism. Specifically, efficacy of vitamin D with regard to bone healing is in question. A literature review was performed, finding mostly large studies involving vitamin D effects on prevention of fractures and randomized animal model studies consisting of controlled fractures with vitamin D interventions. The prevention articles generally focus on at-risk populations, including menopausal women and osteoporotic patients, and also most often include calcium in the treatment group. Few studies look at vitamin D specifically. The animal model studies often focus more on vitamin D supplementation; however the results are still largely inconclusive. While recent case reports appear promising, the ambiguity of results on the topic of fracture healing suggests a need for more, higher level research. A novel study design is proposed to help determine the efficacy on vitamin D in fracture healing.

LEVELS OF EVIDENCE

Therapeutic, Level IV: Systematic Review.

Impaired extracellular matrix structure resulting from malnutrition in ovariectomized mature rats

Bone loss is a symptom related to disease and age, which reflects on bone cells and ECM. Discrepant regulation affects cell proliferation and ECM localization. Rat model of osteoporosis (OVX) was investigated against control rats (Sham) at young and old ages. Biophysical, histological and molecular techniques were implemented to examine the underlying cellular and extracellular matrix changes and to assess the mechanisms contributing to bone loss in the context of aging and the widely used osteoporotic models in rats. Bone loss exhibited a compromised function of bone cells and infiltration of adipocytes into bone marrow. However, the expression of genes regulating collagen catabolic process and adipogenesis was chronologically shifted in diseased bone in comparison with aged bone. The data showed the involvement of Wnt signaling inhibition in adipogenesis and bone loss due to over-expression of SOST in both diseased and aged bone. Further, in the OVX animals, an integrin-mediated ERK activation indicated the role of MAPK in osteoblastogenesis and adipogenesis. The increased PTH levels due to calcium and estrogen deficiency activated osteoblastogenesis. Thusly, RANKL-mediated osteoclastogenesis was initiated. Interestingly, the data show the role of MEPE regulating osteoclast-mediated resorption at late stages in osteoporotic bone. The interplay between ECM and bone cells change tissue microstructure and properties. The involvement of Wnt and MAPK pathways in activating cell proliferation has intriguing similarities to oncogenesis and myeloma. The study indicates the importance of targeting both pathways simultaneously to remedy metabolic bone diseases and age-related bone loss.

Vitamin D and bone fracture healing

AIM: To examine whether vitamin D is of potential relevance in the healing process of fractures.

METHODS: The present narrative review examined the bulk of the evidence based literature on the topic of vitamin D and bone healing in key electronic data bases from 1980 onwards using the terms vitamin D and bone healing, callus, fracture healing. All data were examined carefully and categorized according to type of study. A summary of the diverse terms and approaches employed in the research, as well as the rationale for hypothesizing vitamin D has a role in fracture healing was detailed.

RESULTS: The results show very few human studies have been conducted to examine if vitamin D is effective at promoting post fracture healing, and the different animal models that have been studied provide no consensus on this topic. The terms used in the related literature, as well as the methods used to arrive at conclusions on this clinical issue are highly diverse, there is no standardization of either of these important terms and methodologies, hence no conclusive statements or clinical guidelines can be forthcoming. There is a strong rational for continuing to examine if vitamin D supplements should be administered post-fracture, and ample evidence vitamin D is an essential hormone for functioning in general, as well as bone health and muscle as this relates to bone density.

CONCLUSION: Whether those with low vitamin D levels can benefit from supplements if their nutritional practices do not cover recommended daily amounts, remains in question.

The role of vitamin D in human fracture healing: a systematic review of the literature

INTRODUCTION

Vitamin D is essential for bone mineralization and for the subsequent maintenance of bone quality. Mineralization is part of hard callus formation and bone remodelling, processes, which are part of fracture healing. We provide a comprehensive review of the literature to summarize and clarify if possible, the cellular effects of vitamin D and its clinical involvement in the process of fracture healing in human.

MATERIAL AND METHODS

We conducted a literature search in PubMed, Embase (OVID version), and Web of Science.

RESULTS

A total of 75 in vitro and 30 in vivo studies were found with inconsistent results about the cellular effect of vitamin D on fracture involved inflammatory cells, cytokines, growth factors, osteoblasts, osteoclasts and on the process of mineralization. With only five in vitro studies performed on material derived from a fracture site and one in vivo study in fracture patients, the exact cellular role remains unclear. Seven studies investigated the circulating vitamin D metabolites in fracture healing. Although it appears that 25(OH)D and 24,25(OH)2D3 are not affected by the occurrence of a fracture, this might not be the case with serum concentrations of 1,25(OH)2D3. The potential clinical effect of vitamin D deficiency is only described in one case series and three case controlled studies, where the results tend to show no effect of a vitamin D deficiency. No clinical studies were found investigating solely vitamin D supplementation. Two clinical studies found a positive effect of vitamin D supplementation and calcium, of increased bone mineral density or respectively increased fracture callus area at the fracture site. One study found indirect evidence that vitamin D and calcium promoted fracture healing.

CONCLUSION

Despite these results, and the presumed beneficial effect of vitamin D supplementation in deficient patients, clinical studies that address the effects of vitamin D deficiency or supplementation on fracture healing are scarce and remain inconclusive. We conclude that vitamin D has a role in fracture healing, but the available data are too inconsistent to elucidate how and in what manner.

Expression of muscarinic acetylcholine receptors M3 and M5 in osteoporosis

Background

Cholinergic signaling via muscarinic acetylcholine receptors (mAChR) is known to influence various physiological functions. In bone, M3 mAChR and M5 mAChR were identified on the membrane of osteoblast-like cells. M3 mAChR seems to be particularly relevant for bone physiology, as signaling via this receptor was reported to increase bone formation and decrease bone resorption. Thus, in the present study we investigated the relative mRNA expression of M3 and M5 mAChR in bones of a rat osteoporosis model.

Material/Methods

Osteoporosis was induced in Sprague-Dawley rats by bilateral ovariectomy and additional feeding of a diet deficient in calcium, vitamins C, D2, D3, and phosphorus, and free of soy and phytoestrogen. After a period of 3, 12, and 14 months, relative mRNA expression of M3 mAChR and M5 mAChR was analyzed in the 11^th thoracic vertebra by real-time RT-PCR.

Results

Relative mRNA expression of M3 mAChR was significantly reduced in bones of osteoporotic rats compared to sham operated animals that served as controls. Further, M3 mAChR mRNA expression was significantly down-regulated when comparing 14-month osteoporotic rats to 3-month osteoporotic rats. Relative M5 mAChR mRNA was expressed to a lesser extent than M3 mAChR and did not show significant differences in mRNA expression level between the experimental groups.

Conclusions

M3 mAChR mRNA expression was reduced upon induction of osteoporosis and progression of disease was associated with further decrease of this receptor, indicating that M3 mAChR is involved in the development and regulation of osteoporosis.

Increased tartrate-resistant Acid phosphatase expression in osteoblasts and osteocytes in experimental osteoporosis in rats

Tartrate-resistant acid phosphatase (TRAP) is known as an osteoclast marker, but osteoblasts and osteocytes in the vicinity of bone remodeling sites also express TRAP. Cell culture studies suggest that osteoblasts endocytose osteoclastic TRAP for inactivation. To evaluate whether changes in osteoclast activity could alter TRAP expression in osteoblasts and/or osteocytes in vivo, we studied the ovariectomized and vitamin D-deficient rat (Ovx-D) and rats healing from rickets. Bone sections were analyzed for TRAP gene expression by in situ hybridization, TRAP protein by immunogold labeling, and TRAP enzyme activity using the fluorescent substrate ELF97. Osteoblasts and osteocytes close to intracortical remodeling sites and bone surfaces demonstrated TRAP, most prominently in cancellous bone and osteocytes. Intracellular TRAP was located to electron-dense vesicles with similar morphology in both cell types. Ovx-D increased osteoclast activity (p < 0.001) and ELF97⁺ osteocytes (p < 0.05) in cancellous bone, but no corresponding increase was observed in the osteocyte lacunar area. The level of TRAP⁺ vesicles in cortical osteoblasts (p < 0.01) in Ovx-D rats was also increased. Enhanced osteoclast activity was noted in healing rickets after 72 h (p < 0.05), but no differences in TRAP expression were detected in osteoblasts or osteocytes. Thus, increased osteoclast activity does not affect TRAP expression in osteoblasts and osteocytes, favoring the notion that increased TRAP in these cells is rather due to increased synthesis. Although the role of TRAP in osteoblasts and osteocytes remains elusive, we speculate that the function is related to the capability of the enzyme to regulate the phosphorylation of proteins known to be expressed by these cells.

Influence of diabetic state and vitamin D deficiency on bone repair in female mice

Type 1 diabetes is associated with an increased fracture risk, an impaired fracture healing, and an increased vitamin D insufficiency. However, the role of vitamin D in diabetic bone repair process remains unclear. We therefore examined the effects of vitamin D deficiency on the impaired bone repair in streptozotocin (STZ)-induced diabetes using female mice. Diabetes was induced by STZ injection into female mice after feeding with normal or vitamin D-deficient diet for 6weeks from the age of 4weeks. A femoral bone defect was induced in mice 4 weeks after induction of diabetes. The repair of damaged site on the femur was significantly delayed at days 7 and 10 after bone defect by diabetic state in mice, as assessed by quantitative computed tomography, while vitamin D deficiency did not affect the bone repair both in mice with normal and diabetic state. The decreases in bone mineral density (BMD) at cortical and trabecular bone by diabetic state were significantly augmented by vitamin D deficiency in tibia at the undamaged side in mice. Diabetic state blunted the levels of osteogenic and chondrogenic genes enhanced by vitamin D deficiency. Moreover, vitamin D deficiency significantly aggravated the decreases in osteocalcin and IGF-1 mRNA by diabetic state. In conclusion, our study showed that vitamin D deficiency aggravates the decrease in BMD by diabetic state in female mice, although vitamin D deficiency did not affect bone repair delayed by diabetic state.

Bone matrix, cellularity, and structural changes in a rat model with high-turnover osteoporosis induced by combined ovariectomy and a multiple-deficient diet

In estrogen-deficient, postmenopausal women, vitamin D and calcium deficiency increase osteoporotic fracture risk. Therefore, a new rat model of combined ovariectomy and multiple-deficient diet was established to mimic human postmenopausal osteoporotic conditions under nutrient deficiency. Sprague-Dawley rats were untreated (control), laparatomized (sham), or ovariectomized and received a deficient diet (OVX-Diet). Multiple analyses involving structure (micro-computed tomography and biomechanics), cellularity (osteoblasts and osteoclasts), bone matrix (mRNA expression and IHC), and mineralization were investigated for a detailed characterization of osteoporosis. The study involved long-term observation up to 14 months (M14) after laparotomy or after OVX-Diet, with intermediate time points at M3 and M12. OVX-Diet rats showed enhanced osteoblastogenesis and osteoclastogenesis. Bone matrix markers (biglycan, COL1A1, tenascin C, and fibronectin) and low-density lipoprotein-5 (bone mass marker) were down-regulated at M12 in OVX-Diet rats. However, up-regulation of matrix markers and existence of unmineralized osteoid were seen at M3 and M14. Osteoclast markers (matrix metallopeptidase 9 and cathepsin K) were up-regulated at M14. Micro-computed tomography and biomechanics confirmed bone fragility of OVX-Diet rats, and quantitative RT-PCR revealed a higher turnover rate in the humerus than in lumbar vertebrae, suggesting enhanced bone formation and resorption in OVX-Diet rats. Such bone remodeling caused disturbed bone mineralization and severe bone loss, as reported in patients with high-turnover, postmenopausal osteoporosis. Therefore, this rat model may serve as a suitable tool to evaluate osteoporotic drugs and new biomaterials or fracture implants.

Microstructural, densitometric and metabolic variations in bones from rats with normal or altered skeletal states

Background

High resolution μCT, and combined μPET/CT have emerged as non-invasive techniques to enhance or even replace dual energy X-ray absorptiometry (DXA) as the current preferred approach for fragility fracture risk assessment. The aim of this study was to assess the ability of µPET/CT imaging to differentiate changes in rat bone tissue density and microstructure induced by metabolic bone diseases more accurately than current available methods.

Methods

Thirty three rats were divided into three groups of control, ovariectomy and vitamin-D deficiency. At the conclusion of the study, animals were subjected to glucose (¹⁸FDG) and sodium fluoride (Na¹⁸F) PET/CT scanning. Then, specimens were subjected to µCT imaging and tensile mechanical testing.

Results

Compared to control, those allocated to ovariectomy and vitamin D deficiency groups showed 4% and 22% (significant) increase in ¹⁸FDG uptake values, respectively. DXA-based bone mineral density was higher in the vitamin D deficiency group when compared to the other groups (cortical bone), yet μCT-based apparent and mineral density results were not different between groups. DXA-based bone mineral density was lower in the ovariectomy group when compared to the other groups (cancellous bone); yet μCT-based mineral density results were not different between groups, and the μCT-based apparent density results were lower in the ovariectomy group compared to the other groups.

Conclusion

PET and micro-CT provide an accurate three-dimensional measurement of the changes in bone tissue mineral density, as well as microstructure for cortical and cancellous bone and metabolic activity. As osteomalacia is characterized by impaired bone mineralization, the use of densitometric analyses may lead to misinterpretation of the condition as osteoporosis. In contrast, µCT alone and in combination with the PET component certainly provides an accurate three-dimensional measurement of the changes in both bone tissue mineral density, as well as microstructure for cortical and cancellous bone and metabolic activity.

Effects of multi-deficiencies-diet on bone parameters of peripheral bone in ovariectomized mature rat

Many postmenopausal women have vitamin D and calcium deficiency. Therefore, vitamin D and calcium supplementation is recommended for all patients with osteopenia and osteoporosis. We used an experimental rat model to test the hypothesis that induction of osteoporosis is more efficiently achieved in peripheral bone through combining ovariectomy with a unique multi-deficiencies diet (vitamin D depletion and deficient calcium, vitamin K and phosphorus). 14-week-old Sprague-Dawley rats served as controls to examine the initial bone status. 11 rats were bilaterally ovariectomized (OVX) and fed with multi-deficiencies diet. Three months later the treated group and the Sham group (n = 8) were euthanized. Bone biomechanical competence of the diaphyseal bone was examined on both, tibia and femur. Image analysis was performed on tibia via µCT, and on femur via histological analysis. Lower torsional stiffness indicated inferior mechanical competence of the tibia in 3 month OVX+Diet. Proximal metaphyseal region of the tibia showed a diminished bone tissue portion to total tissue in the µCT despite the increased total area as evaluated in both µCT and histology. Cortical bone showed higher porosity and smaller cross sectional thickness of the tibial diaphysis in the OVX+Diet rats. A lower ALP positive area and elevated serum level of RANKL exhibited the unbalanced cellular interaction in bone remodeling in the OVX+Diet rat after 3 month of treatment. Interestingly, more adipose tissue area in bone marrow indicated an effect of bone loss similar to that observed in osteoporotic patients. Nonetheless, the presence of osteoid and elevated serum level of PTH, BGP and Opn suggest the development of osteomalacia rather than an osteoporosis. As the treatment and fracture management of both osteoporotic and osteomalacia patients are clinically overlapping, this study provides a preclinical animal model to be utilized in local supplementation of minerals, drugs and growth factors in future fracture healing studies.

[Aspects of interest on vitamin D for the traumatologist and orthopaedic surgeon]

Vitamin D deficiency or insufficiency is a clinical problem particularly prevalent in elderly patients with low-energy fractures, particularly hip fractures, but has also been associated with stress fractures and high energy fractures. There is much evidence that supports the need to maintain adequate levels of vitamin D in the blood in order to; reduce the number of fragility fractures, furthering the consolidation of these, improve neuromuscular function of patients, prevent falls, prevent surgical infections, or improve the length of arthroplasties. However, it is rare for the orthopaedic surgeon to request the values of vitamin D in these patients and give the appropriate treatment It is recommended to maintain levels higher than 30-40ng/ml (75-100nmol/l) and increase vitamin D intake, in almost all cases, from 800 to 1,000IU/day to achieve these levels.

Implications of combined ovariectomy/multi-deficiency diet on rat bone with age-related variation in bone parameters and bone loss at multiple skeletal sites by DEXA

BACKGROUND

Osteoporosis is a multi-factorial, chronic, skeletal disease highly prevalent in post-menopausal women and is influenced by hormonal and dietary factors. Because animal models are imperative for disease diagnostics, the present study establishes and evaluates enhanced osteoporosis obtained through combined ovariectomy and deficient diet by DEXA (dual-energy X-ray absorptiometry) for a prolonged time period.

MATERIAL/METHODS

Sprague-Dawley rats were randomly divided into sham (laparotomized) and OVX-diet (ovariectomized and fed with deficient diet) groups. Different skeletal sites were scanned by DEXA at the following time points: M0 (baseline), M12 (12 months post-surgery), and M14 (14 months post-surgery). Parameters analyzed included BMD (bone mineral density), BMC (bone mineral content), bone area, and fat (%). Regression analysis was performed to determine the interrelationships between BMC, BMD, and bone area from M0 to M14.

RESULTS

BMD and BMC were significantly lower in OVX-diet rats at M12 and M14 compared to sham rats. The Z-scores were below -5 in OVX-diet rats at M12, but still decreased at M14 in OVX-diet rats. Bone area and percent fat were significantly lower in OVX-diet rats at M14 compared to sham rats. The regression coefficients for BMD vs. bone area, BMC vs. bone area, and BMC vs. BMD of OVX-diet rats increased with time. This is explained by differential percent change in BMD, BMC, and bone area with respect to time and disease progression.

CONCLUSIONS

Combined ovariectomy and deficient diet in rats caused significant reduction of BMD, BMC, and bone area, with nearly 40% bone loss after 14 months, indicating the development of severe osteoporosis. An increasing regression coefficient of BMD vs. bone area with disease progression emphasizes bone area as an important parameter, along with BMD and BMC, for prediction of fracture risk.

Delayed fracture healing in aged senescence-accelerated P6 mice

BACKGROUND

Osteoporosis is characterized by poor bone quality. However, it is still controversially discussed whether osteoporosis compromises fracture healing. Herein, we studied whether the course of healing of a femur fracture is affected by osteoporosis or age.

METHODS

Using the senescence-accelerated osteoporotic mouse, strain P6 (SAMP6), and a closed femur fracture model, we studied the process of fracture healing in 5- and 10-month-old animals, including biomechanical, histomorphometric, and protein biochemical analysis.

RESULTS

In five-month-old osteoporotic SAMP6 mice, bending stiffness, callus size, and callus tissue distribution as well as the concentrations of the bone formation marker osteocalcin and the bone resorption markers tartrate-resistant acid phosphatase form 5b (TRAP) and deoxypyridinoline (DPD) did not differ from that of non-osteoporotic, senescence-resistant, strain 1 (SAMR1) controls. In contrast, femur fractures in 10-month-old SAMP6 mice showed a significantly reduced bending stiffness and an increased callus size compared to fractures in age-matched SAMR1 controls. This indicates a delayed fracture healing in advanced age SAMP6 mice. The delay of fracture healing was associated with higher concentrations of TRAP and DPD. Significant differences in osteocalcin concentrations were not found between SAMP6 animals and SAMR1 controls.

CONCLUSION

In conclusion, the present study indicates that fracture healing in osteoporotic SAMP6 mice is not affected in five-month-old animals, but delayed in animals with an age of 10 months. This is most probably due to the increased osteoclast activity in advanced age SAMP6 animals.

Effect of host sex and sex hormones on muscle-derived stem cell-mediated bone formation and defect healing

Muscle-derived stem cells (MDSCs) are known to exhibit sexual dimorphism, by donor sex, of osteogenic, chondrogenic, and myogenic differentiation potential in vitro. Moreover, host sex differences in the myogenic capacity of MDSCs in vivo are also observed. This study investigated the role of host sex and host sex hormones in MDSC-mediated bone formation and healing. Using unaltered male, castrated male, unaltered female, and ovariectomized female mice, both MDSC-mediated ectopic bone formation and cranial defect healing were examined. Male hosts, whether unaltered or castrated, form significantly larger volumes of MDSC-mediated ectopic bone than female hosts (either unaltered or ovariectomized), and no differences in ectopic bone volume were found between hosts of the same sex. In a cranial defect healing model, similar results were found-unaltered and castrated male hosts display larger volumes of bone formed when compared with unaltered and ovariectomized female hosts. However, in this healing model, some volume differences were found between hosts of the same sex. In both models, these differences were attributed to varying rates of endochondral bone formation in male and female hosts.

Bone healing around titanium implants in two rat colitis models

OBJECTIVE

Crohn's disease is a chronic inflammatory process that has recently been associated with a higher risk of early implant failure. Herein we provide information on the impact of colitis on peri-implant bone formation using preclinical models of chemically induced colitis.

METHODS

Colitis was induced by intrarectal instillation of 2,4,6-trinitro-benzene-sulfonic-acid (TNBS). Colitis was also induced by feeding rats dextran-sodium-sulfate (DSS) in drinking water. One week after disease induction, titanium miniscrews were inserted into the tibia. Four weeks after implantation, peri-implant bone volume per tissue volume (BV/TV) and bone-to-implant contacts (BIC) were determined by histomorphometric analysis.

RESULTS

Cortical histomorphometric parameters were similar in the control (n = 10), DSS (n = 10) and TNBS (n = 8) groups. Cortical BV/TV was 92.2 ± 3.7%, 92.0 ± 3.0% and 92.6 ± 2.7%. Cortical BIC was 81.3 ± 8.8%, 83.2 ± 8.4% and 84.0 ± 7.0%, respectively. No significant differences were observed when comparing the medullary BV/TV and BIC (19.5 ± 6.4%, 16.2 ± 5.6% and 15.4 ± 9.0%) and (48.8 ± 12.9%, 49.2 ± 6.2 and 41.9 ± 11.7%), respectively. Successful induction of colitis was confirmed by loss of body weight and colon morphology.

CONCLUSIONS

The results suggest bone regeneration around implants is not impaired in chemically induced colitis models. Considering that Crohn's disease can affect any part of the gastrointestinal tract including the mouth, our model only partially reflects the clinical situation.

Impact of dietary vitamin D on osseointegration in the ovariectomized rat

AIM

Vitamin D deficiency is highly prevalent in the population and associated with impaired peri-implant bone regeneration. Yet, there is a gap in understanding the impact of vitamin D supplementation on the process of osseointegration. In this study, the effect of vitamin D supplementation on peri-implant bone regeneration was investigated.

METHODS

Fifty ovariectomized Sprague-Dawley rats were divided into three groups. The depletion group was fed a vitamin D-free diet for 8 weeks. The repletion group received vitamin D-free diet for 6 weeks, before animals were switched to standard diet containing 2400 IU/kg vitamin D. The control group was fed the standard diet. Two titanium mini-implants were placed in the tibia. All groups remained on their previous diet until sacrifice. Blood sample testing and histomorphometric analysis were performed.

RESULTS

Vitamin D depletion caused a significant reduction in 25-hydroxvitamin D in rat serum that returned to control levels in the repletion group. This vitamin deficiency was associated with a decrease in bone-to-implant contact in the cortical area, which was leveled to controls in the repletion group. No significant changes by vitamin D depletion were noticed in the medullar compartment. Moreover, also the peri-implant bone area and the mineral apposition rate remained unchanged upon vitamin D depletion.

CONCLUSION

These results indicate that vitamin D deficiency has a negative impact on cortical peri-implant bone formation in ovariectomized rats, which can be compensated by vitamin D supplementation. This study provides first insight into the potential beneficial effect of vitamin D supplementation in implant dentistry.

Bone repair in osteoporotic bone: postmenopausal and cortisone-induced osteoporosis

Although osteoporosis has been the subject of a considerable number of publications in recent years, very few studies have investigated the effects of osteoporosis on the process of tissue repair. Most of the studies are based on animal data, using the ovariectomized rat model, and in most cases, fractures were obtained by femoral osteotomy. This model is imperfect in several aspects to fit with postmenopausal osteoporosis which is a complex, multifactorial disorder. Furthermore, a surgically induced fracture is not exactly the same as a fracture which occurs as a result of bone fragility. However, and despite contradictory results in some of the studies, in ovariectomized rats a delay in bone consolidation has been reported in the model, associated locally with a decrease in bone mineral density and mechanical resistance. Very few human data are available, which confirm the existence of a delay in consolidation subsequent to femoral fractures in aged patients compared to young patients.

Is supplementation of vitamin d beneficial for fracture healing? A short review of the literature

There has been a surge of interest regarding the benefits of vitamin D supplementation to prevent fractures. But can it also make them heal more quickly once they have occurred-that is, is supplementation of vitamin D beneficial for fracture healing? We found 13 studies that met our inclusion criteria, 11 of these were performed in animals. Two animal studies showed negative, 2 neutral, and 7 positive results. One clinical case series in humans was inconclusive in our opinion, and one randomized double-blind placebo-controlled trial showed that supplementation of vitamin D3 and calcium in elderly women with reduced bone mass and a proximal humerus fracture had a positive influence on bone healing. The major weakness of the latter study is low number of participants. A clear statement on the benefits of vitamin D for fracture healing awaits further trials, but all types of fractures in elderly individuals indicate the need for secondary prevention and the implementation of appropriate guidelines concerning falls, vitamin D, and osteoporosis.

Increased osteoblast and osteoclast activity in female senescence-accelerated, osteoporotic SAMP6 mice during fracture healing

BACKGROUND

Previous studies have shown that fracture healing depends on gender and that in females, ovariectomy-induced osteoporosis impairs the healing process. There is no information, however, whether the alteration of fracture healing in osteoporosis also depends on gender.

MATERIALS AND METHODS

Therefore, we herein studied fracture healing in female and male senescence-accelerated osteoporotic mice, strain P6 (SAMP6), including biomechanical, histomorphometric, and protein biochemical analysis.

RESULTS

Bending stiffness was reduced in male and female SAMP6 mice compared with senescence-resistant strain 1 (SAMR1) controls. This was associated with elevated serum concentrations of tartrate-resistent acid phosphatase form 5b (TRAP) in both female and male SAMP6 mice. Callus size, however, was significantly larger in female SAMP6 mice compared with male SAMP6 mice and female SAMR1 controls. This indicates a delayed remodeling process in female SAMP6 mice. The delay of callus remodeling in female SAMP6 mice was associated with a significantly higher osteoprotegerin (OPG) callus tissue expression and increased serum concentrations of osteocalcin (OC) and deoxypyridinoline (DPD), indicating elevated osteoblast and osteoclast activities.

CONCLUSION

The present study shows that remodeling during fracture healing in female, but not in male, SAMP6 mice is delayed, most probably due to an increased osteoblast and osteoclast activity.

Effects of calcium supplements on fracture healing in a rat osteoporotic model

Fracture healing is a complex process, which is further complicated if the bone is osteoporotic. Calcium is one of the important minerals in bone and has been found to prevent osteoporosis but its role in fracture healing of osteoporotic bone is still unclear. We carried out a study on the effects of calcium supplementation on the late phase healing of fractured osteoporotic bone using an ovariectomized rat model. Twenty-four female Sprague-Dawley rats were divided into three groups: sham-operated (SO), ovariectomized-control (OVXC), and ovariectomized + calcium supplements (Ca). The right femurs of all the rats were fractured at mid-epiphysis and a K-wire was inserted for internal fixation. After 2 months of treatment, the rats were sacrificed and the femora were dissected out for radiological and biomechanical assessment. As expected, osteoporosis resulted in impaired healing as shown by the poor radiological and biomechanical properties of the OVXC group. CT scans showed significantly lower callus volumes in the SO and Ca groups compared to the OVXC group. Radiological scoring of fracture healing and callus staging of the SO and Ca groups were better than the OVXC group. However, the biomechanical parameters of the Ca group were significantly lower than the SO group and similar to the OVXC group. Therefore, calcium supplements may appear to improve fracture healing of osteoporotic bone but failed to improve strength.

Gene expression and distribution of key bone turnover markers in the callus of estrogen-deficient, vitamin D-depleted rats

An experimental rat model was used to test the hypothesis that in osteoporosis (OP) the molecular composition of the extracellular matrix in the fracture callus is disturbed. OP was induced at 10 weeks of age by ovariectomy and a vitamin D(3)-deficient diet, and sham-operated animals fed normal diet served as controls. Three months later a closed tibial fracture was made and stabilized with an intramedullary nail. After 3 and 6 weeks of healing, the animals were killed and the fracture calluses examined with global gene expression, in situ mRNA expression, and ultrastructural protein distribution of four bone turnover markers: osteopontin, bone sialoprotein, tartrate-resistant acid phosphatase, and cathepsin K. Global gene expression showed a relatively small number of differently regulated genes, mostly upregulated and at 3 weeks. The four chosen markers were not differently regulated, and only minor differences in the in situ mRNA expression and ultrastructural protein distribution were detected. Gene expression and composition of fracture calluses are not generally disturbed in experimental OP.

Influence of defective bone marrow osteogenesis on fracture repair in an experimental model of senile osteoporosis

Bone marrow osteogenesis in senile osteoporotic bone is impaired and, as such, may have significant implications on the successful outcome of fracture repair. Here we utilize a well-established murine model of senile osteoporosis, the P6 strain of senescence-accelerated mice (SAMP6), to investigate fracture healing in aged osteoporotic bone. A femoral osteotomy was created in SAMP6 and in non-osteoporotic age-matched control R1 senescence-resistant mice (SAMR1). The course of fracture healing was evaluated over a period of 42 days using quantitative microCT and histological analysis. The differentiation capabilities of bone mesenchymal progenitor cells derived from SAMP6 and SAMR1 mice was examined, and their osteogenic potential determined. Although preliminary in vitro analysis confirmed that bone marrow-derived stem cells (BMSC) isolated from SAMP6 mice had a reduced osteogenic capacity, no significant deficit in fracture repair as determined by quantitative microCT could be detected. This was supported by histology assessment, where complete bridging of the fracture gap was evident by day 28 and was fully healed day 42 in both SAMP6 and SAMR1 mice. Further in vitro studies revealed that periosteal-derived progenitor cells (PDPC) isolated from SAMP6 mice had an osteogenic potential comparable to that observed in SAMR1 mice. In conclusion, fracture healing in SAMP6 mice is not detrimentally affected by impairment of BMSC osteogenesis, suggesting that bone marrow-mediated repair processes are dispensable for normal bone healing in this senile osteoporotic fracture model. Furthermore, the influence of PDPC in the repair process may partly explain the absence of any detectable deficits in fracture repair in SAMP6 mice.

Evidence for anti-osteoporosis therapy in acute fracture situations--recommendations of a multidisciplinary workshop of the International Society for Fracture Repair

The International Society for Fracture Repair convened a multidisciplinary workshop to assess the current evidence around the interaction between anti-osteoporosis drugs and the healing of incident fractures, with a view to making recommendations for clinical practice. The consensus was that there is no evidence-based reason to withhold anti-resorptive therapy while a fracture heals, whether or not the patient was taking such therapy when the fracture occurred. The workshop also considered existing models of service provision for secondary prevention and concluded that the essential ingredient for reliable delivery is the inclusion of a dedicated coordinator role. Several unresolved issues were defined as subjects for further research, including the question of whether continuous long-term administration of anti-resorptives may impair bone quality. The rapidly changing area requires re-assessment of drugs and their interaction with fracture healing in the near future.

Strontium ranelate enhances callus strength more than PTH 1-34 in an osteoporotic rat model of fracture healing

Treatment of an underlying disease is often initiated after the occurrence of an osteoporotic fracture. Our aim was to investigate whether teriparatide (PTH 1-34) and strontium ranelate affect fracture healing in ovariectomized (OVX) rats when provided for the first time after the occurrence of an osteoporotic fracture. We combined the model of an OVX rat with a closed diaphyseal fracture. Sixty Sprague Dawley rats were randomly assigned to four groups. Fracture healing in OVX rats after treatment with pharmacological doses of strontium ranelate and PTH 1-34 was compared with OVX and sham-treated control groups. After 28 days, the femur was excised and scanned by micro computed tomography and the callus evaluated, after which biomechanical torsional testing was performed and torque and toughness until reaching the yield point were analyzed. Only treatment with strontium ranelate led to a significant increase in callus resistance compared to the OVX control rats, whereas both PTH 1-34 and strontium ranelate increased the bone volume/tissue volume ratio of the callus. The PTH 1-34-increased trabecular bone volume within the callus was even higher compared to sham. As for the callus tissue volume, the increase induced by strontium ranelate was significant, contrary to the changes induced by PTH. Callus in strontium ranelate-treated animals is more resistant to torsion compared with OVX control rats. To our knowledge, this is the first report of the enhancement of fracture healing by strontium ranelate. Because both treatments enhance bone and tissue volume within the callus, there may be a qualitative difference between the calluses of PTH 1-34- and strontium ranelate-treated OVX rats. The superior results obtained with strontium ranelate compared to PTH in terms of callus resistance could be the consequence of a better quality of the new bone formed within the callus.

Can rhBMP-2 containing collagen sponges enhance bone repair in ovariectomized rats?: a preliminary study

With an aging population the frequency of postmenopausal fractures is increasing. Methods to enhance the repair of osteoporotic bone repair therefore become more important to reduce the society burden of care. We asked if absorbable collagen sponges containing recombinant human bone morphogenetic protein-2 (rhBMP-2) have the potential to enhance bone repair. We randomly assigned 40 rats into the ovariectomy and sham operation groups. A segmental defect was created in the right tibia 12 weeks after ovariectomy. rhBMP-2-containing absorbable collagen sponges were implanted into the defect in half of the animals in each group. We analyzed radiographs and histological sections and performed three-point bending tests to assess repair. Radiological scores in the rhBMP-2 applied rats were higher than those in controls at the end of 8 weeks after tibial osteotomy. The specimens failed under higher loads in the rhBMP-2-applied groups and histology revealed a higher fracture healing score, including callus formation, bone union, marrow changes, and cortex remodeling. We observed no adverse tissue responses such as fibrous connective tissue formation and inflammatory cellular infiltration. rhBMP-2 in absorbable collagen sponges enhanced bone repair in segmental tibial defects of ovariectomized rats. The sponges with rhBMP-2 appeared to enhance bone repair.

Comparison of radiographic fracture healing in the distal radius for patients on and off bisphosphonate therapy

PURPOSE

To compare healing rates of distal radius fractures in patients on bisphosphonate therapy at the time of injury to rates in those not on bisphosphonate therapy.

METHODS

A total of 196 consecutive patients treated for distal radius fractures were included in this study. Patients currently on bisphosphonate therapy at the time of injury (bisphosphonate group, n = 43) were compared to the remaining patient group (control group, n = 153). Demographic information was recorded from the patients' medical records, and radiographs were reviewed to determine fracture healing. Patients were further stratified according to age, gender, fracture complexity, type of treatment, and comorbidities. Univariate and multivariate regression were used to identify factors associated with time to radiographic fracture union.

RESULTS

The mean time to union was 55 (+/-17) days in the bisphosphonate group versus 49 (+/-14) days in the control group. Bisphosphonate use and surgical treatment were associated with a longer time to radiographic union. Bisphosphonate use was associated with increased healing times when individually controlling for age, gender, fracture complexity, or comorbidities. Bisphosphonate use was also associated with longer time to healing after adjusting for age, gender, and treatment type. Surgical fracture fixation was associated with a longer time to healing after adjusting for bisphosphonate use.

CONCLUSIONS

Current bisphosphonate use and surgical treatment were both associated with longer times to radiographic union of distal radius fractures. However, the small differences in healing times (<1 week) are not considered clinically relevant. Although further studies are needed to better define the effects of bisphosphonate therapy on fracture healing, our results suggest that bisphosphonate therapy can be continued after distal radius fractures without notable deleterious effects.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic III.

Shortcomings of DXA to assess changes in bone tissue density and microstructure induced by metabolic bone diseases in rat models

The aim of this study is to demonstrate the deficiencies of dual-energy X-ray absorptiometry (DXA), compared with quantitative computed tomography, to reflect and differentiate between changes in bone mineral density and microstructure that contribute to a well-defined finding of altered skeletal state for both osteoporosis and renal osteodystrophy induced by chronic renal insufficiency.

INTRODUCTION

The aim of this study is to demonstrate the deficiencies of dual-energy X-ray absorptiometry (DXA), compared with quantitative CT, to reflect and differentiate between changes in bone mineral density and microstructure that contribute to a well-defined finding of altered skeletal state for both osteoporosis and renal osteodystrophy induced by chronic renal insufficiency.

METHODS

Forty-five female Sprague-Dawley rats were divided into three equal groups: control, ovariectomy, and nephrectomy. Following euthanasia, femurs were excised, divided into diaphyseal and distal metaphyseal sections, and subjected to DXA and micro-CT imaging and mechanical testing.

RESULTS

Ovariectomy does not affect the structural and mechanical properties of cortical bone material, but partial nephrectomy does adversely affect these properties. Both are verified by DXA and micro-CT imaging and mechanical testing. Meanwhile, nephrectomy does not affect trabecular bone microstructure or equivalent density, yet ovariectomy affects the trabecular microstructure. DXA is unable to detect changes in trabecular bone microstructure in relation to changes in their mechanical properties.

DISCUSSION

Dual energy X-ray absorptiometry measures the average bone mineral content in a 2D projected area and cannot differentiate whether the changes occur in the bone microstructure or equivalent bone tissue density. In contrast, micro-CT provides an accurate measurement of the changes in both equivalent bone tissue mineral density and microstructure for cancellous and cortical bone.