Critical analysis of the evidence for current technologies in bone-healing and repair

TRPV4 Activator-Containing CMT-Hy Hydrogel Enhances Bone Tissue Regeneration In Vivo by Enhancing Mitochondrial Health

Treating different types of bone defects is difficult, complicated, time-consuming, and expensive. Here, we demonstrate that transient receptor potential cation channel subfamily V member 4 (TRPV4), a mechanosensitive, thermogated, and nonselective cation channel, is endogenously present in the mesenchymal stem cells (MSCs). TRPV4 regulates both cytosolic Ca2+ levels and mitochondrial health. Accordingly, the hydrogel made from a natural modified biopolymer carboxymethyl tamarind CMT-Hy and encapsulated with TRPV4-modulatory agents affects different parameters of MSCs, such as cell morphology, focal adhesion points, intracellular Ca2+, and reactive oxygen species- and NO-levels. TRPV4 also regulates cell differentiation and biomineralization in vitro. We demonstrate that 4α-10-CMT-Hy and 4α-50-CMT-Hy (the hydrogel encapsulated with 4αPDD, 10 and 50 nM, TRPV4 activator) surfaces upregulate mitochondrial health, i.e., an increase in ATP- and cardiolipin-levels, and improve the mitochondrial membrane potential. The same scaffold turned out to be nontoxic in vivo. 4α-50-CMT-Hy enhances the repair of the bone-drill hole in rat femur, both qualitatively and quantitatively in vivo. We conclude that 4α-50-CMT-Hy as a scaffold is suitable for treating large-scale bone defects at low cost and can be tested for clinical trials.

Sequential application of small molecule therapy enhances chondrogenesis and angiogenesis in murine segmental defect bone repair

The increasing incidence of physiologic/pathologic conditions that impair the otherwise routine healing of endochondral bone fractures and the occurrence of severe bone injuries necessitate novel approaches to enhance clinically challenging bone fracture repair. To promote the healing of nonunion fractures, we tested an approach that used two small molecules to sequentially enhance cartilage development and conversion to the bone in the callus of a murine femoral segmental defect nonunion model of bone injury. Systemic injections of smoothened agonist 21k (SAG21k) were used to stimulate chondrogenesis through the activation of the sonic hedgehog (SHH) pathway early in bone repair, while injections of the prolyl hydroxylase domain (PHD)2 inhibitor, IOX2, were used to stimulate hypoxia signaling-mediated endochondral bone formation. The expression of SHH pathway genes and Phd2 target genes was increased in chondrocyte cell lines in response to SAG21k and IOX2 treatment, respectively. The segmental defect responded to sequential systemic administration of these small molecules with increased chondrocyte expression of PTCH1, GLI1, and SOX9 in response to SAG and increased expression of hypoxia-induced factor-1α and vascular endothelial growth factor-A in the defect tissues in response to IOX2. At 6 weeks postsurgery, the combined SAG-IOX2 therapy produced increased bone formation in the defect with the bony union over the injury. Clinical significance: This therapeutic approach was successful in promoting cartilage and bone formation within a critical-size segmental defect and established the utility of a sequential small molecule therapy for the enhancement of fracture callus development in clinically challenging bone injuries.

Supramolecular Hydrogel Based on an Osteogenic Growth Peptide Promotes Bone Defect Repair

Current bone defect treatment strategies are associated with several risks and have major limitations. Therefore, it is necessary to develop an inexpensive growth factor delivery system that can be easily produced in large quantities and can promote long-term bone regeneration. An osteogenic growth peptide (OGP) is a 14 amino acid peptide with a short peptide sequence active fragment. In this study, we developed two OGP-based self-assembling supramolecular hydrogels (F- and G-sequence hydrogels) and investigated the in vitro and in vivo effects on proliferation and osteogenesis, including the mechanism of hydrogel-mediated bone defect repair. The hydrogels presented excellent biocompatibility and cell proliferation-promoting properties (1.5-1.7-fold increase). The hydrogels could effectively upregulate the expression of osteogenic factors, including RUNX2, BMP2, OCN, and OPN, to promote osteogenesis differentiation. Interestingly, 353 differentially expressed genes were identified in hBMSCs treated with hydrogels. The hydrogels were proved to be involved in the inflammatory pathways and folate-related pathways to mediate the osteogenesis differentiation. Furthermore, the therapeutic efficiency (bone volume/total volume, trabecular number, and bone mineral density) of hydrogels on bone regeneration in vivo was evaluated. The results showed that the hydrogels promoted bone formation in the early stage of bone defect healing. Taken together, this study was the first to develop and evaluate the properties of OGP-based self-assembling supramolecular hydrogels. Our study will provide inspiration for the development of delivering OGP for bone regeneration.

Effectiveness of granulocyte colony stimulating factor to enhance healing on delayed union fracture model Sprague-Dawley rat

INTRODUCTION

Delayed union is a problem that can occur after fracture healing. Many studies were conducted based on the diamond concept approach to solve the problem of delayed union. Granulocyte-colony stimulating factor (G-CSF) is one of the various substances known to have a positive role in healing skeletal tissue or adjuvant regeneration. This study was conducted to see the effect of G-CSF in affecting delayed union fracture healing.

MATERIALS AND METHOD

The experimental study was conducted by randomized posttest only control group design on 24 experimental animals Sprague-Dawley white rats that had experienced delayed union models. The study compared the treatment group injected with subcutaneous G-CSF with a control group and was divided into four groups (n = 6). Harvest and follow-up histomorphometry and immunohistochemistry were performed in the second week and in the fourth week the histomorphometry analysis consisted of the percentage of immature bone area, cartilage, and fibrous area. The semiquantitative evaluation of immunohistochemistry with the expression of BMP-2 through the immunoreactive score (IRS).

RESULT

In the evaluation of histomorphometry and immunohistochemical parameters, there were significantly more woven bone area (p = 0,015), less fibrosis area (p = 0,002) and higher BMP 2 expression (p = 0,004) in treatment group week four compared to control. .

CONCLUSION

G-CSF was shown to increase the speed of healing in Sprague-Dawley rats on delayed union models evaluated from histomorphometry and immunohistochemical aspects.

Neuropeptide Y1 receptor antagonist but not neuropeptide Y itself increased bone mineral density when locally injected with hyaluronic acid in male Wistar rats

Background/aim

The nervous system controls bone mass via both the central (CNS) and the peripheral (PNS) nervous systems. Intriguingly, neuropeptide Y (NPY) signaling occurs in both. Less is known on how the PNS stimulated NPY signaling controls bone metabolism. The objective of this study was to evaluate whether NPY or NPY1 receptor antagonist changes local bone mineral density (BMD) when injected into a Wistar rat tibia.

Materials and methods

Tibial intramedullary area of 24 wild type male Wistar rats (average weight = 350 ± 50 g, average age = 4 ± 0.5 months) were injected with NPY (1 × 10-5 M and 1 × 10-6 M) and NPY1 receptor antagonist (1 × 10-4 M) dissolved in hyaluronic acid (HA) separately. Tibiae were collected after one and two weeks. BMD was measured with dual-energy X-ray absorptiometry (DXA) and micro quantitative computer tomography (QCT). Histological changes were analyzed with light microscopy, Goldner's Masson trichrome (MT), and hematoxylin-eosin staining.

Results

According to DXA, the mean BMD of NPY dose 1 (1 × 10-5 M) was significantly lower than that of the control (HA applied) group and not significantly but still lower than that of the NPY dose 2 and NPY1 antagonist applied groups. QCT results indicated the same pattern statistically insignificantly in the trabecular area but not in the cortex of the bones. Histologically, only NPY1 antagonist applied tibiae revealed young spongiosis bone trabeculae formed in the borderline of the cortical bones. HA was remarkably biocompatible and late degrading in the tissues.

Conclusion

Local administration of NPY and NPY1 antagonists may hold regulating potential of BMD and bone formation. NPY1 antagonist caused new bone formation in trabecular bone when applied locally. NPY dissolved in HA however can be used to suppress bone formation.

Nanocomposites drug delivery systems for the healing of bone fractures

The skeletal system is fundamental for the structure and support of the body consisting of bones, cartilage, and connective tissues. Poor fracture healing is a chief clinical problem leading to disability, extended hospital stays and huge financial liability. Even though most fractures are cured using standard clinical methods, about 10% of fractures are delayed or non-union. Despite decades of progress, the bone-targeted delivery system is still restricted due to the distinctive anatomical bone features. Recently, various novel nanocomposite systems have been designed for the cell-specific targeting of bone, enhancing drug solubility, improving drug stability and inhibiting drug degradation so that it can reach its target site without being removed in the systemic circulation. Such targeting systems could consist of biological compounds i.e. bone marrow stem cells (BMSc), growth factors, RNAi, parathyroid hormone or synthetic compounds, i.e. bisphosphonates (BPs) and calcium phosphate cement. Hydrogels and nanoparticles are also being employed for fracture healing. In this review, we discussed the normal mechanism of bone healing and all the possible drug delivery systems being employed for the healing of the bone fracture.

Recent advances in bone-targeted therapy

The coordination between bone resorption and bone formation plays an essential role in keeping the mass and microstructure integrity of the bone in a steady state. However, this balance can be disturbed in many pathological conditions of the bone. Nowadays, the classical modalities for treating bone-related disorders are being challenged by severe obstacles owing to low tissue selectivity and considerable safety concerns. Moreover, as a highly mineralized tissue, the bone shows innate rigidity, low permeability, and reduced blood flow, features that further hinder the effective treatment of bone diseases. With the development of bone biology and precision medicine, one novel concept of bone-targeted therapy appears to be promising, with improved therapeutic efficacy and minimized systematic toxicity. Here we focus on the recent advances in bone-targeted treatment based on the unique biology of bone tissues. We summarize commonly used bone-targeting moieties, with an emphasis on bisphosphonates, tetracyclines, and biomimetic bone-targeting moieties. We also introduce potential bone-targeting strategies aimed at the bone matrix and major cell types in the bone. Based on these bone-targeting moieties and strategies, we discuss the potential applications of targeted therapy to treat bone diseases. We expect that this review will put together useful insights to help with the search for therapeutic efficacy in bone-related conditions.

Outcomes of Hindfoot Arthrodesis Supplemented With Bioactive Glass and Bone Marrow Aspirate: A Retrospective Radiographic Study

Foot and ankle surgeons continue to explore bone graft alternatives that will be comparable to the reference standard of autologous bone. The purpose of the present study was to consider the outcomes of hindfoot arthrodesis supplemented with bioactive glass in patients at risk of delayed union and nonunion. We performed a retrospective radiographic review of 29 consecutive patients (48 joints) who had undergone arthrodesis of ≥1 joint of the hindfoot (ankle, subtalar, talonavicular, calcaneocuboid). All patients included in the present study had a minimum of 1 documented risk factor for osseous nonunion (history of previous nonunion, trauma, smoking, diabetes, Charcot arthropathy, obesity, age >65 years at surgery). The patients were followed up for a minimum of 24 weeks or until radiographic healing had been achieved. We found 12 (25.0%) nonunions across all 48 joints supplemented with bioactive glass. We found 4 (16.7%) nonunions in the subtalar joint, 1 (11.1%) in the calcaneocuboid joint, and 1 (11.1%) in the talonavicular joint. We found that hindfoot arthrodesis procedures supplemented with bioactive glass resulted in an incidence of union comparable to that with autograft and other bone graft substitutes.

Can Clinical and Surgical Parameters Be Combined to Predict How Long It Will Take a Tibia Fracture to Heal? A Prospective Multicentre Observational Study: The FRACTING Study

BACKGROUND

Healing of tibia fractures occurs over a wide time range of months, with a number of risk factors contributing to prolonged healing. In this prospective, multicentre, observational study, we investigated the capability of FRACTING (tibia FRACTure prediction healING days) score, calculated soon after tibia fracture treatment, to predict healing time.

METHODS

The study included 363 patients. Information on patient health, fracture morphology, and surgical treatment adopted were combined to calculate the FRACTING score. Fractures were considered healed when the patient was able to fully weight-bear without pain.

RESULTS

319 fractures (88%) healed within 12 months from treatment. Forty-four fractures healed after 12 months or underwent a second surgery. FRACTING score positively correlated with days to healing: r = 0.63 (p < 0.0001). Average score value was 7.3 ± 2.5; ROC analysis showed strong reliability of the score in separating patients healing before versus after 6 months: AUC = 0.823.

CONCLUSIONS

This study shows that the FRACTING score can be employed both to predict months needed for fracture healing and to identify immediately after treatment patients at risk of prolonged healing. In patients with high score values, new pharmacological and nonpharmacological treatments to enhance osteogenesis could be tested selectively, which may finally result in reduced disability time and health cost savings.

Fracture-Targeted Delivery of β-Catenin Agonists via Peptide-Functionalized Nanoparticles Augments Fracture Healing

Despite several decades of progress, bone-specific drug delivery is still a major challenge. Current bone-acting drugs require high-dose systemic administration which decreases therapeutic efficacy and increases off-target tissue effects. Here, a bone-targeted nanoparticle (NP) delivery system for a β-catenin agonist, 3-amino-6-(4-((4-methylpiperazin-1-yl)sulfonyl)phenyl)-N-(pyridin-3-yl)pyrazine-2-carboxamide, a glycogen synthase kinase 3 beta (GSK-3β) inhibitor, was developed to enhance fracture healing. The GSK-3β inhibitor loading capacity was found to be 15 wt % within highly stable poly(styrene-alt-maleic anhydride)-b-poly(styrene) NPs, resulting in ∼50 nm particles with ∼ -30 mV surface charge. A peptide with high affinity for tartrate-resistant acid phosphatase (TRAP), a protein deposited by osteoclasts on bone resorptive surfaces, was introduced to the NP corona to achieve preferential delivery to fractured bone. Targeted NPs showed improved pharmacokinetic profiles with greater accumulation at fractured bone, accompanied by significant uptake in regenerative cell types (mesenchymal stem cells (MSCs) and osteoblasts). MSCs treated with drug-loaded NPs in vitro exhibited 2-fold greater β-catenin signaling than free drug that was sustained for 5 days. To verify similar activity in vivo, TOPGAL reporter mice bearing fractures were treated with targeted GSK-3β inhibitor-loaded NPs. Robust β-galactosidase activity was observed in fracture callus and periosteum treated with targeted carriers versus controls, indicating potent β-catenin activation during the healing process. Enhanced bone formation and microarchitecture were observed in mice treated with GSK-3β inhibitor delivered via TRAP-binding peptide-targeted NPs. Specifically, increased bone bridging, ∼4-fold greater torsional rigidity, and greater volumes of newly deposited bone were observed 28 days after treatment, indicating expedited fracture healing.

Local and targeted drug delivery for bone regeneration

While experimental bone regeneration approaches commonly employ cells, technological hurdles prevent translation of these therapies. Alternatively, emulating the spatiotemporal cascade of endogenous factors through controlled drug delivery may provide superior bone regenerative approaches. Surgically placed drug depots have clinical indications. Additionally, noninvasive systemic delivery can be used as needed for poorly healing bone injuries. However, a major hurdle for systemic delivery is poor bone biodistribution of drugs. Thus, peptides, aptamers, and phosphate-rich compounds with specificity toward proteins, cells, and molecules within the regenerative bone microenvironment may enable the design of targeted carriers with bone biodistribution greater than that achieved by drug alone. These carriers, combined with osteoregenerative drugs and/or stimuli-sensitive linkers, may enhance bone regeneration while minimizing off-target tissue effects.

Augmentation of bone healing in delayed and atrophic nonunion of fractures of long bones by partially decalcified bone allograft (decal bone)

BACKGROUND

Autograft from iliac crest is considered as gold standard for augmentation of bone healing in delayed and nonunion of fractures. Bone demineralized with 0.6N hydrochloric acid has shown to retain its osteoinductive capacity. We report the outcome of partially decalcified bone allograft (decal bone) in the treatment of delayed union and atrophic nonunions of bones.

MATERIALS AND METHODS

Twenty patients with clinicoradiological diagnosis of delayed union or atrophic nonunion of long bone fractures were included in this retrospective study. Patients at extreme of ages (<18 years and >60 years), pathological fractures, metabolic bone diseases, infected nonunion, hypertrophic nonunion and those having systemic illness like diabetes mellitus and on drugs that impair fracture healing were excluded from the study. Decal bone was prepared in the bone bank and maintained in department of orthopedics. Allografting was done in 20 patients of delayed union (9/20) and atrophic nonunion (11/20) of long bone fractures with mean age of 34 years (range 18-55 years). The bones involved were humerus (8/20), tibia (7/20) and femur (5/20). Fourteen patients underwent treatment in the form of internal fixation and allografting and six patients were operated with osteoperiosteal allografting.

RESULTS

Nineteen patients achieved union in mean time of 14.9 weeks range (range 8-20 weeks). Eight patients had serous discharge from the operative site that subsided in 11 days (range 4-21 days). One patient had pus discharge that required repeat debridement and antibiotics for 6 weeks. The fracture healed in 16 weeks.

CONCLUSION

The partially decalcified bone allograft is an effective modality for augmentation of bone healing without complication associated with autograft like donor site morbidity, increased blood loss and increase in the surgical time.

Can platelet-rich plasma (PRP) improve bone healing? A comparison between the theory and experimental outcomes

The increased concentration of platelets within platelet-rich plasma (PRP) provides a vehicle to deliver supra-physiologic concentrations of growth factors to an injury site, possibly accelerating or otherwise improving connective tissue regeneration. This potential benefit has led to the application of PRP in several applications; however, inconsistent results have limited widespread adoption in bone healing. This review provides a core understanding of the bone healing mechanisms, and corresponds this to the factors present in PRP. In addition, the current state of the art of PRP preparation, the key aspects that may influence its effectiveness, and treatment outcomes as they relate specifically to bone defect healing are presented. Although PRP does have a sound scientific basis, its use for bone healing appears only beneficial when used in combination with osteoconductive scaffolds; however, neither allograft nor autograft appear to be appropriate carriers. Aggressive processing techniques and very high concentrations of PRP may not improve healing outcomes. Moreover, many other variables exist in PRP preparation and use that influence its efficacy; the effect of these variables should be understood when considering PRP use. This review includes the essentials of what has been established, what is currently missing in the literature, and recommendations for future directions.

Early application of pulsed electromagnetic field in the treatment of postoperative delayed union of long-bone fractures: a prospective randomized controlled study

BACKGROUND

Pulsed electromagnetic field (PEMF) is reported to be an effective adjunct for the management of nonunion long-bone fractures. Most studies implement PEMF treatment after 6 months or longer of delayed union or nonunion following fracture treatment. Despite these variations in treatment, the early application of PEMF following a diagnosis of a postoperative delayed union has not been specifically analyzed. In this study, the outcomes of postoperative delayed union of long-bone fractures treated with an early application of PEMF were evaluated as compared with a sham-treated control group.

METHODS

In this prospective, randomized controlled study, a total of 58 long-bone fracture patients, who presented with delayed union of between 16 weeks and 6 months, were randomly split into two groups and subjected to an early application of PEMF or sham treatment. Clinical and radiological assessments were performed to evaluate the healing status. Treatment efficacy was assessed at three month intervals.

RESULTS

Patients in the PEMF group showed a higher rate of union than those in the control group after the first three months of treatment, but this difference failed to achieve statistical significance. At the end of the study, PEMF treatment conducted for an average of 4.8 months led to a success rate of 77.4%. This was significantly higher than the control, which had an average duration of 4.4 months and a success rate of 48.1%. The total time from operation to the end of the study was a mean of 9.6 months for patients in the PEMF group.

CONCLUSIONS

Fracture patients treated with an early application of PEMF achieved a significantly increased rate of union and an overall reduced suffering time compared with patients that receive PEMF after the 6 months or more of delayed union, as described by others.

Mesenchymal stem cells facilitate fracture repair in an alcohol-induced impaired healing model

OBJECTIVES

Clinical studies have shown alcohol to be a risk factor for traumatic orthopaedic injuries and for nonunion. Data from animal studies suggest that alcohol exposure inhibits fracture healing. This report presents a novel rodent model of impaired fracture healing caused by repeated alcohol exposure. Using this model, we examined the regenerative effects of an intravenously administered population of isolated and expanded mesenchymal stem cells (MSCs) on fracture healing.

METHODS

Bone marrow-derived MSC were isolated from transgenic green fluorescent protein C57BL/6 mice, and culture expanded using a lineage depletion protocol. Adult wild-type C57BL/6 mice were subjected to a 2-week binge alcohol exposure paradigm (3 days during which they received daily intraperitoneal injections of a 20% alcohol/saline solution followed by a 4-day rest period and another binge cycle for 3 consecutive days). At completion of the second binge cycle, mice were subjected to a mid-shaft tibia fracture while intoxicated. Twenty-four hours after the fracture, animals were administered an intravenous transplant of green fluorescent protein-labeled MSC. Two weeks after the fracture, animals were euthanized and injured tibiae were collected and subjected to biomechanical, histologic, and microcomputed tomography analysis.

RESULTS

Pre-injury binge alcohol exposure resulted in a significant impairment in biomechanical strength and decrease in callus volume. MSC transplants restored both fracture callus volume (P < 0.05) and biomechanical strength (P < 0.05) in animals with alcohol-impaired healing. In vivo imaging demonstrated a time-dependent MSC migration to the fracture site.

CONCLUSIONS

These data suggest that a 2-week binge alcohol exposure significantly impairs fracture healing in a murine tibia fracture model. Intravenously administered MSC were capable of specifically homing to the fracture site and of normalizing biomechanical, histologic, and microcomputed tomography parameters of healing in animals exposed to alcohol. Understanding MSC recruitment patterns and functional contributions to fracture repair may lead to their use in patients with impaired fracture healing and nonunion.

Cigarette smoking influences the clinical and occupational outcome of patients with tibial shaft fractures

Tibial shaft fracture is one of the most common types of bone fracture in young patients. In this prospective clinical cohort study, we investigated the effects of cigarette smoking on the clinical, functional, psychosocial and occupational outcomes after isolated lower-leg fracture. We examined 85 patients, including 61 men and 24 women, with a collective mean age of 46 years (range: 18-84 years). Thirty-nine patients had never smoked (G1) and 45 patients were current or previous smokers (G2). The G2 group displayed a significantly increased risk for delayed union or nonunion (G1=3 patients, G2=18 patients; P=0.0007) and increased time required for fracture healing (mean times: G1=11.9 weeks, G2=17.4 weeks; p=0.003) and a markedly increased time out of work (mean times: G1=16.1 weeks, G2=21.5 weeks; p=0.1177 (not significant)). The 18 negatively affected patients in G2 displayed a significant increase in the time required for fracture healing and time out of work (26 weeks (p=0.02) and 31 weeks (p=0.03), respectively). G2 group members had a 3- to 18-fold higher risk of impaired bone healing. The mean Short Form 36 (SF-36) was similar in both groups. The physical-function scores were G1=49.6 and G2=48.6; the mental scores were G1=52.7 and G2=52.8. These findings indicate that smoking significantly increases the risk of impaired fracture healing, which has clinical and occupational consequences for the affected patients. Based on our data, we developed a score to estimate the individual risk of impaired fracture healing. These types of patients must be informed and closely monitored to determine the need for timely re-intervention with additional therapy, such as BMP s or ultrasound.

The role of stem cells in fracture healing and nonunion

Nonunion and large bone defects present a therapeutic challenge to the surgeon and are often associated with significant morbidity. These defects are expensive to both the health care system and society. However, several surgical procedures have been developed to maximise patient satisfaction and minimise health-care-associated and socioeconomic costs. Integrating recent evidence into the diamond concept leads to one simple conclusion that not only provides us with answers to the "open questions" but also simplifies our entire understanding of bone healing. It has been shown that a combination of neo-osteogenesis and neovascularisation will restore tissue deficits, and that the optimal approach includes a biomaterial scaffold, cell biology techniques, a growth factor and optimisation of the mechanical environment. Further prospective, controlled, randomised clinical studies will determine the effectiveness and economic benefits of treatment with mesenchymal stem cells, not in comparison to other conventional surgical approaches but in direct conjunction with them.

Current methods of diagnosis and treatment of scaphoid fractures

Fractures of the scaphoid bone mainly occur in young adults and constitute 2-7% of all fractures. The specific blood supply in combination with the demanding functional requirements can easily lead to disturbed fracture healing. Displaced scaphoid fractures are seen on radiographs. The diagnostic strategy of suspected scaphoid fractures, however, is surrounded by controversy. Bone scintigraphy, magnetic resonance imaging and computed tomography have their shortcomings. Early treatment leads to a better outcome. Scaphoid fractures can be treated conservatively and operatively. Proximal scaphoid fractures and displaced scaphoid fractures have a worse outcome and might be better off with an open or closed reduction and internal fixation. The incidence of scaphoid non-unions has been reported to be between 5 and 15%. Non-unions are mostly treated operatively by restoring the anatomy to avoid degenerative wrist arthritis.

Osteoblastic differentiation and stress response of human mesenchymal stem cells exposed to alternating current electric fields

BACKGROUND

Electric fields are integral to many biological events, from maintaining cellular homeostasis to embryonic development to healing. The application of electric fields offers substantial therapeutic potential, while optimal dosing regimens and the underlying mechanisms responsible for the positive clinical impact are poorly understood.

METHODS

The purpose of this study was to track the differentiation profile and stress response of human bone marrow derived mesenchymal stem cells (hMSCs) undergoing osteogenic differentiation during exposure to a 20 mV/cm, 60 kHz electric field. Morphological and biochemical changes were imaged using endogenous two-photon excited fluorescence (TPEF) and quantitatively assessed through eccentricity calculations and extraction of the redox ratio from NADH, FAD and lipofuscin contributions. Real time reverse transcriptase-polymerase chain reactions (RT-PCR) were used to track osteogenic differentiation markers, namely alkaline phosphatase (ALP) and collagen type 1 (col1), and stress response markers, such as heat shock protein 27 (hsp27) and heat shock protein 70 (hsp70). Comparisons of collagen deposition between the stimulated hMSCs and controls were examined through second harmonic generation (SHG) imaging.

RESULTS

Quantitative differences in cell morphology, as described through an eccentricity ratio, were found on days 2 and days 5 (p < 0.05) in samples exposed to the electric field. A delayed but two fold increase in ALP and col1 transcript was detected by week 2 (p < 0.05) in differentiating hMSCs exposed to an electric field in comparison to the nonstimulated controls. Upregulation in stress marker, hsp27, and type 1 collagen deposition were correlated with this response. Increases in NADH, FAD, and lipofuscin were traced in the stimulation group during the first week of field exposure with differences statistically significant on day 10 (p < 0.05). Changes in hsp27 expression correlate well with changes in lipofuscin detected in the stimulation group, suggesting a connection with oxidative stress. Both differentiation factors and electrical stimulation improved hMSC differentiation potential to bone based on calcium deposition on day 28.

CONCLUSIONS

Electrical stimulation is a useful tool to improve hMSC osteogenic differentiation, while heat shock proteins may reveal underlying mechanisms, and optical non-invasive imaging may be used to monitor the induced morphological and biochemical changes.

The indications and use of bone morphogenetic proteins in foot, ankle, and tibia surgery

Tissue engineering is an area of rapid growth. Tissue engineering in orthopedic surgery involves the use of growth factors, mesenchymal stem cells, and scaffolds, individually or in combination, toward the growth and restoration of various musculoskeletal tissues, such as ligaments, tendons, muscles, nerves, and bone. These advances are constantly evolving in foot and ankle surgery as well. Bone morphogenetic proteins (BMPs) have played an integral role in the advancement of tissue engineering strategies across multiple orthopedic subspecialities and have proved to play a role in the development of bone and musculoskeletal tissues. BMPs have recently been applied in several areas of foot and ankle surgery, including acute fracture augmentation, nonunions, and arthrodesis, with promising results. This article reviews the key aspects of clinical translation of strategies in tissue engineering as well as current applications and results of BMP use in tibia, foot, and ankle surgery. Future applications of BMP and novel materials in foot and ankle surgery are also reviewed.

Phases 1-3 clinical trials using adult stem cells in osteonecrosis and nonunion fractures

Nonunion fractures and aseptic bone necrosis are two pathological conditions having some impairment of the cellular part of the repair: a reduction of MSC and of the osteoblastic activation. Both are good candidates for cell-based therapies using stem cells. We made a review of the published human trials. Only autologous bone marrow aspirate implantation was until now used. In Nonunion, a direct injection—15 to 150 ml—was made in 4 case series studies. In another, the bone marrow aspirate was concentrated before injection. The results were good. In bone necrosis, only one level 1 study was published. The results at 24 months were positive in terms of reduction of the necrosis and appearance of collapse. In 3 case series studies, a treatment with concentrated bone marrow aspirates was deemed useful with good results in 76 to 96%. These results are interesting but need confirmation by controlled studies.

Bone marrow stromal cells contribute to bone formation following infusion into femoral cavities of a mouse model of osteogenesis imperfecta

Currently, there are conflicting data in literature regarding contribution of bone marrow stromal cells (BMSCs) to bone formation when the cells are systemically delivered in recipient animals. To understand if BMSCs contribute to bone cell phenotype and bone formation in osteogenesis imperfecta bones (OI), MSCs marked with GFP were directly infused into the femurs of a mouse model of OI (oim). The contribution of the cells to the cell phenotype and bone formation was assessed by histology, immunohistochemistry and biomechanical loading of recipient bones. Two weeks following infusion of BMSCs, histological examination of the recipient femurs demonstrated presence of new bone when compared to femurs injected with saline which showed little or no bone formation. The new bone contained few donor cells as demonstrated by GFP fluorescence. At 6 weeks following cell injection, new bone was still detectable in the recipient femurs but was enhanced by injection of the cells suspended in pepsin solubilized type I collagen. Immunofluorescence and immunohistochemical staining showed that donor GFP positive cells in the new bone were localized with osteocalcin expressing cells suggesting that the cells differentiated into osteoblasts in vivo. Biomechanical loading to failure in three point bending, revealed that, femurs infused with BMSCs in PBS or in soluble type I collagen were biomechanically stronger than those injected with PBS or type I collagen alone. Taken together, the results indicate that transplanted cells differentiated into osteoblasts in vivo and contributed to bone formation in vivo; we also speculate that donor cells induced differentiation or recruitment of endogenous cells to initiate reparative process at early stages following transplantation.

In vitro: osteoclastic activity studies on surfaces of 3D printed calcium phosphate scaffolds

Various biomaterials have been developed for the use as bone substitutes for bone defects. To optimize their integration and functionality, they should be adapted to the individual defect. Rapid prototyping is a manufacturing method to tailor materials to the 3D geometry of the defect. Especially 3D printing allows the manufacture of implants, the shape of which can be designed to fit the bone defect using anatomical information obtained from the patient. 3D printing of calcium phosphates, which are well established as bone substitutes, involves a sintering step after gluing the granules together by a binder liquid. In this study, we analyzed if and how these 3D printed calcium phosphate surfaces can be resorbed by osteoclast-like cells. On 3D printed scaffold surfaces consisting of pure HA and β-TCP as well as a biphasic mixture of HA and TCP the osteoclastic cell differentiation was studied. In this regard, cell proliferation, differentiation, and activation were analyzed with the monocytic cell line RAW 264.7. The results show that osteoclast-like cells were able to resorb calcium phosphate surfaces consisting of granules. Furthermore, biphasic calcium phosphate ceramics exhibit, because of their osteoclastic activation ability, the most promising surface properties to serve as 3D printed bone substitute scaffolds.

Biological basis for the use of autologous bone marrow stromal cells in the treatment of congenital pseudarthrosis of the tibia

The study was designed to establish the biological basis for the use of autologous bone-marrow stromal cells (MSC) in order to improve the curing opportunities of congenital pseudarthrosis of the tibia (CPT). The investigation was planned by taking into account that the pathophysiology of bone healing mainly depends on the osteogenic potential of the resident cells, although several factors play a crucial role in restoring the normal bone structure. Bone marrow samples were collected from the lesion site (P) and the iliac crest (IC) of 7 patients affected by CPT and type 1 neurofibromatosis (NF1+) and 6 patients affected by CPT without NF1 (NF1-). Four patients without CPT served as control group. Biochemical, functional and molecular assays showed that the ability to generate bone-forming cells was higher in IC-MSC than in P-MSC, but lower in CPT patients than in control group. We evaluated whether host factors, such as autologous serum and the microenvironment surrounding the pseudarthrosis lesion, could impair the osteogenic differentiation of IC-MSC. Autologous serum was less effective than FBS in promoting the IC-MSC differentiation, but the damage was more evident in NF1- than in NF1+ patients. Additionally, the supernatant of osteoblast cultures obtained from bone fragments close to the lesion site favoured the differentiation of IC-MSC in NF1- patients. In summary, our results suggest that MSC transplantation could be a promising strategy for the therapy of CPT. Further studies are warranted to confirm the clinical effectiveness in comparison to standard surgical treatment.

Bone growth stimulation for foot and ankle nonunions

During the last few decades, electrical current stimulation has gone from an investigational modality to an accepted method of treatment to assist with bone healing. This article provides an overview of electrical bone stimulation for nonunions in the foot and ankle.

Low-intensity pulsed ultrasound: Fracture healing

Annually, millions of people across the world are inflicted with bone fracture injuries. Untimely healing is a significant burden in terms of socioeconomic costs, personal costs, and patients' quality of life. Low-intensity pulsed ultrasound (LIPUS) has gained much attention as a potential adjunctive therapy for accelerating fresh fracture healing, but its efficacy remains controversial. This paper is presented in two parts a literature review followed by a systematic review. The literature review highlights the physiology of fracture healing and the influence LIPUS exerts on cells and molecules involved in this healing process. In part two, we present a systematic review of randomized controlled trials (RCTs) assessing the clinical effectiveness of LIPUS in accelerating the time to fracture healing. The electronic databases we searched for the systematic review are as follows: MEDLINE (from 1996 to November 2008), EMBASE (from 1996 to November 2008), and Healthstar (from 1966 to October 2008). A two-step screening process was used to assess the eligibility of studies yielded by our search. The first step was a review of titles and abstracts for the selection of studies that met the following criteria: (i) inclusion of skeletally mature patients with a fresh fracture, (ii) a minimum of two treatment arms with at least one arm receiving LIPUS treatment and another arm receiving placebo, (iii) random allocation of patients to the different treatment arms, (iv) radiological assessment of time to fracture healing, and (v) publication in the English language. In the second step, selected articles were reviewed in full text. Eligible trials were all scored independently by two reviewers for methodological reporting quality using the 15-item CLEAR NPT checklist (Checklist to Evaluate the Report of a Nonpharmacological Trial). We identified a total of seventy seven studies, nine of which met our inclusion criteria after the initial screening. Of these nine trials, seven were included for the final review. The types of fractures studied among these seven trials included lateral malleolar, radial, and tibial fractures. Three of the seven trials found that LIPUS significantly reduces healing time compared to placebo, whereas the other four did not find a statistically significant difference. There is a substantial level of inconsistency in the findings of several RCTs evaluating the efficacy of LIPUS as an adjunct for fracture healing. Although LIPUS has proven to be effective in certain trials for accelerating fracture healing, no definitive statement can be made regarding its universal use for all fracture types and methods of fracture care. Future high-quality RCTs with larger sample sizes may help to elucidate the specific indications that warrant or dismiss the need for LIPUS therapy.

Global burden of trauma: Need for effective fracture therapies

Orthopedic trauma care and fracture management have advanced significantly over the last 50 years. New developments in the biology and biomechanics of the musculoskeletal system, fixation devices, and soft tissue management have greatly influenced our ability to care for musculoskeletal injuries. Many therapies and treatment modalities have the potential to transform future orthopedic treatment by decreasing invasive procedures and providing shorter healing times. Promising results in experimental models have led to an increase in clinical application of these therapies in human subjects. However, for many modalities, precise clinical indications, timing, dosage, and mode of action still need to be clearly defined. In order to further develop fracture management strategies, predict outcomes and improve clinical application of newer technologies, further research studies are needed. Together with evolving new therapies, the strategies to improve fracture care should focus on cost effectiveness. This is a great opportunity for the global orthopedic community, in association with other stakeholders, to address the many barriers to the delivery of safe, timely, and effective care for patients with musculoskeletal injuries in developing countries.

Tissue engineering for bone defect healing: an update on a multi-component approach

The need for an interdisciplinary approach in order to establish new therapeutic strategies for the therapy of bone defects has been acknowledged by the scientific community for many years. This awareness makes itself felt when looking at the multitude of approaches--ranging from cell-based to scaffold-based strategies and also including the use of osteogenic growth factors and genetic engineering--that are currently being combined to assess their potential to develop effective concepts for the treatment of extensive loss of osseous tissue. With a strong focus on the preclinical research in this field, the goal of this review is to give an update on the multi-component approaches that are currently being investigated in tissue engineering of bone.