Enhance Fracture Healing Research Articles

THU434 A Case Of An Atypical Femur Fracture Managed Medically With Teriparatide

Abstract Disclosure: S.V. Rupani: None. A. Kotwal: None. L. Graeff-Armas: None. Atypical femur fractures (AFFs) are atraumatic or low-trauma femur fractures located in the sub-trochanteric region or femoral shaft. AFFs represent around 0.5% of all femur fractures. The increased use of bisphosphonates has led to a rise in the incidence of AFFs as it has emerged as a potential complication. While the mechanism of bisphosphonate-related AFFs has yet to be elucidated, one proposed mechanism is that bisphosphonates can cause over-suppression of bone turnover. If over-suppression is a contributing factor, then hypothetically, anabolic therapy can help heal existing fractures and prevent impending fractures by reversing over-suppression. Numerous animal models have demonstrated that parathyroid hormone and teriparatide enhance fracture healing. However, clinical trials and meta-analyses on the effects of teriparatide in fracture healing have been equivocal. There have been both retrospective and prospective studies, along with anecdotal reports demonstrating the benefits of teriparatide in healing in AFFs. However, there have been no randomized controlled trials assessing the efficacy of teriparatide in AFFs. Based on this limited evidence, the American Society for Bone and Mineral Research recommends considering teriparatide in patients who have failed conservative therapy. We present a case of an incomplete AFF in the setting of short-term bisphosphonate use that was managed with teriparatide in addition to conservative measures. Our patient presented with a complete right AFF treated surgically and an incomplete left AFF that we managed medically with teriparatide. Repeat left femur imaging six months after starting teriparatide therapy showed interval callus formation consistent with a healed fracture. Right femur imaging also showed a healing proximal femoral shaft fracture status post intramedullary fixation. She completed twenty-five months of teriparatide therapy and did not sustain any interval fractures. Repeat imaging one year after completion of teriparatide therapy continued to show a stable healed left AFF, along with a healed right AFF. She is currently more than two years post-completion of teriparatide and has remained fracture free. This case highlights the role that teriparatide may have as an option for medical management in incomplete AFFs and to accelerate healing in complete AFFs that have been managed surgically. Furthermore, with therapeutic options for osteoporosis management limited in the post-AFF setting, teriparatide helps increase bone mineral density and reduce future fracture risk. Randomized controlled trials are needed to draw definite conclusions on the efficacy of teriparatide in managing AFFs. However, this is difficult given the rare occurrence of AFFs. Therefore, case reports like ours offer insight into when teriparatide may be helpful in managing AFFs. Presentation: Thursday, June 15, 2023

CD51 labels periosteal injury-responsive osteoprogenitors.

The periosteum is a critical source of skeletal stem and progenitor cells (SSPCs) that form callus tissue in response to injury. There is yet to be a consensus on how to identify SSPCs in the adult periosteum. The aim of this study was to understand how potential murine periosteal SSPC populations behave in vivo and in response to injury. We evaluated the in vivo differentiation potential of Sca1-CD51+ and Sca1+CD51+ cells following transplantation. In vitro, the Sca1+CD51+ population appears to be more primitive multipotent cells, but after transplantation, Sca1-CD51+ cells showed superior engraftment, expansion, and differentiation into chondrocytes and osteoblasts. Despite representing a clear population with flow cytometry, we identified very few Sca1+CD51+ cells histologically. Using a periosteal scratch injury model, we successfully mimicked the endochondral-like healing process seen in unstable fractures, including the expansion and osteochondral differentiation of αSMA+ cells following injury. CD51+ cells were present in the cambium layer of resting periosteum and expanded following injury. Sca1+CD51- cells were mainly localized in the outer periosteal layer. We found that injury increased colony-forming unit fibroblast (CFU-F) formation in the periosteum and led to rapid expansion of CD90+ cells. Several other populations, including Sca1-CD51+ and CD34+ cells, were expanded by day 7. Mice with enhanced fracture healing due to elevated Notch signaling mediated by NICD1 overexpression showed significant expansion of CD51+ and CD34hi cells in the early stages of healing, suggesting these populations contribute to more rapid healing. In conclusion, we demonstrate that periosteal injury leads to the expansion of various SSPC populations, but further studies are required to confirm their lineage hierarchy in the adult skeletal system. Our data indicate that CD51+ skeletal progenitor cells are injury-responsive and show good engraftment and differentiation potential upon transplantation.

Injectable hydrogel for sustained delivery of progranulin derivative Atsttrin in treating diabetic fracture healing

Hydrogels with long-term storage stability, controllable sustained-release properties, and biocompatibility have been garnering attention as carriers for drug/growth factor delivery in tissue engineering applications. Chitosan (CS)/Graphene Oxide (GO)/Hydroxyethyl cellulose (HEC)/β-glycerol phosphate (β-GP) hydrogel is capable of forming a 3D gel network at physiological temperature (37 °C), rendering it an excellent candidate for use as an injectable biomaterial. This work focused on an injectable thermo-responsive CS/GO/HEC/β-GP hydrogel, which was designed to deliver Atsttrin, an engineered derivative of a known chondrogenic and anti-inflammatory growth factor-like molecule progranulin. The combination of the CS/GO/HEC/β-GP hydrogel and Atsttrin provides a unique biochemical and biomechanical environment to enhance fracture healing. CS/GO/HEC/β-GP hydrogels with increased amounts of GO exhibited rapid sol-gel transition, higher viscosity, and sustained release of Atsttrin. In addition, these hydrogels exhibited a porous interconnected structure. The combination of Atsttrin and hydrogel successfully promoted chondrogenesis and osteogenesis of bone marrow mesenchymal stem cells (bmMSCs) in vitro. Furthermore, the work also presented in vivo evidence that injection of Atsttrin-loaded CS/GO/HEC/β-GP hydrogel stimulated diabetic fracture healing by simultaneously inhibiting inflammatory and stimulating cartilage regeneration and endochondral bone formation signaling pathways. Collectively, the developed injectable thermo-responsive CS/GO/HEC/βG-P hydrogel yielded to be minimally invasive, as well as capable of prolonged and sustained delivery of Atsttrin, for therapeutic application in impaired fracture healing, particularly diabetic fracture healing.

An angiogenic approach to osteoanabolic therapy targeting the SHN3-SLIT3 pathway.

Often, disorders of impaired bone formation involve not only a cell intrinsic defect in the ability of osteoblasts to form bone, but moreover a broader dysfunction of the skeletal microenvironment that limits osteoblast activity. Developing approaches to osteoanabolic therapy that not only augment osteoblast activity but moreover correct this microenvironmental dysfunction may enable both more effective osteoanabolic therapies and also addressing a broader set of indications where vasculopathy or other forms microenvironment dysfunction feature prominently. We here review evidence that SHN3 acts as a suppressor of not only the cell intrinsic bone formation activity of osteoblasts, but moreover of the creation of a local osteoanabolic microenvironment. Mice lacking Schnurri3 (SHN3, HIVEP3) display a very robust increase in bone formation, that is due to de-repression of ERK pathway signaling in osteoblasts. In addition to loss of SHN3 augmenting the differentiation and bone formation activity of osteoblasts, loss of SHN3 increases secretion of SLIT3 by osteoblasts, which in a skeletal context acts as an angiogenic factor. Through this angiogenic activity, SLIT3 creates an osteoanabolic microenvironment, and accordingly treatment with SLIT3 can increase bone formation and enhance fracture healing. These features both validate vascular endothelial cells as a therapeutic target for disorders of low bone mass alongside the traditionally targeted osteoblasts and osteoclasts and indicate that targeting the SHN3/SLIT3 pathway provides a new mechanism to induce therapeutic osteoanabolic responses.

Biological aspects to enhance fracture healing.

The ability to enhance fracture healing is paramount in modern orthopaedic trauma, particularly in the management of challenging cases including peri-prosthetic fractures, non-union and acute bone loss. Materials utilised in enhancing fracture healing should ideally be osteogenic, osteoinductive, osteoconductive, and facilitate vascular in-growth. Autologous bone graft remains the gold standard, providing all of these qualities. Limitations to this technique include low graft volume and donor site morbidity, with alternative techniques including the use of allograft or xenograft. Artificial scaffolds can provide an osteoconductive construct, however fail to provide an osteoinductive stimulus, and frequently have poor mechanical properties. Recombinant bone morphogenetic proteins can provide an osteoinductive stimulus; however, their licencing is limited and larger studies are required to clarify their role. For recalcitricant non-unions or high-risk cases, the use of composite graft combining the above techniques provides the highest chances of successfully achieving bony union.

THE ROLE OF DENTIN MATRIX PROTEIN 1 (DMP1) IN LIPUS-ACCELERATED OSTEOPOROTIC FRACTURE HEALING

Osteoporotic fracture has become a major problem in ageing population and often requires prolonged healing time. Low Intensity Pulsed Ultrasound (LIPUS) can significantly enhance fracture healing through alteration of osteocyte lacuno-canalicular network (LCN). DMP1 in osteocytes is responsible for maintaining LCN and mineralisation. This study aims to investigate osteocyte-specific DMP1's role in enhanced osteoporotic fracture healing in response to mechanical stimulation.Bilateral ovariectomy was performed in 6-month-old female SD rats to induce osteoporosis. Metaphyseal fracture was created at left distal femur using oscillating micro-saw. Rats were randomised to groups: (1) DMP1 KD, (2) DMP1 KD + LIPUS, (3) Control, or (4) Control + LIPUS, where KD stands for knockdown by injection of shRNA into marrow cavity 2 weeks before surgery. Assessments included weekly radiography, microCT and immunohistochemistry on DMP1, E11, FGF23 and sclerostin.DMP1 KD significantly impaired LIPUS-accelerated fracture healing when comparing KD + LIPUS group to Control + LIPUS group. The X-ray relative opacity showed less tissue growth at all timepoints (Week 1, 3 & 6; p=0.000, 0.001 and 0.003 respectively) and the bone volume fraction was decreased after DMP1 KD at Week 3 (p=0.006). DMP1 KD also significantly altered the expression levels of osteocyte-specific DMP1, E11, FGF23 and sclerostin during healing process.The lower relative opacity and bone volume fraction in DMP1 KD groups indicated that knockdown of DMP1 was associated with poorer fracture healing process compared to non-knockdown groups. The similar results between knockdown group with and without LIPUS showed that blockage of DMP1 would negate LIPUS-induced enhancement on fracture healing.Acknowledgment: General Research Fund (Ref: 14113018)

Umbilical cord mesenchymal stem cells combined with secretome for treating congenital pseudarthrosis of the Tibia: a case series.

Most patients with congenital pseudoarthrosis of tibia (CPT) do not have promising outcomes despite multiple attempts using conventional surgeries. The combination of umbilical cord-derived mesenchymal stem cells and conditioned medium (secretome) contains major components pivotal for the enhancement of fracture healing. The purpose of this study was to address fracture healing in CPT cases that were treated using the combined implantation of umbilical-cord mesenchymal stem cells (UC-MSCs) and secretome. From 2016 to 2017, six patients with CPT who were treated by one senior pediatric orthopedic consultant at a single center (3 girls and 3 boys; mean age of 5.8years) were included in this case series. A combined procedure including resection of hamartomatous fibrotic tissue, implantation of MSCs and secretome, and fixation using a locking plate and screws was performed. Patients were followed up for a mean of 29months. Leg-length discrepancy, refracture rate, functional outcome, and radiological outcomes were assessed preoperatively, immediately postoperatively and at the final follow-up. Five out of 6 (83%) of the patients experienced primary union. One patient experienced refracture; however, 8months later, after another implantation and reconstruction were performed, union eventually occurred. Significant functional improvement was achieved after at least 1year of follow-up. This case series suggests that the combination of secretome and UC-MSCs is a potential treatment for CPT, it highlights the efficacy of the combined procedure in treating CPT and in achieving satisfying results. A larger number of subjects and longer follow-up are required for further study.

Circulating MiRNA-21-enriched extracellular vesicles promote bone remodeling in traumatic brain injury patients

Fracture combined with traumatic brain injury (TBI) is one of the most common and serious types of compound trauma in the clinic and is characterized by dysfunction of cellular communication in injured organs. Our prior studies found that TBI was capable of enhancing fracture healing in a paracrine manner. Exosomes (Exos), as small extracellular vesicles, are important paracrine vehicles for noncell therapy. However, whether circulating Exos derived from TBI patients (TBI-Exos) regulate the prohealing effects of fractures remains unclear. Thus, the present study aimed to explore the biological effects of TBI-Exos on fracture healing and reveal the potential molecular mechanism. TBI-Exos were isolated by ultracentrifugation, and the enriched miR-21-5 p was identified by qRT‒PCR analysis. The beneficial effects of TBI-Exos on osteoblastic differentiation and bone remodeling were determined by a series of in vitro assays. Bioinformatics analyses were conducted to identify the potential downstream mechanisms of the regulatory effect of TBI-Exos on osteoblasts. Furthermore, the role of the potential signaling pathway of TBI-Exos in mediating the osteoblastic activity of osteoblasts was assessed. Subsequently, a murine fracture model was established, and the effect of TBI-Exos on bone modeling was demonstrated in vivo. TBI-Exos can be internalized by osteoblasts, and in vitro, suppression of SMAD7 promoted osteogenic differentiation, whereas knockdown of miR-21-5 p in TBI-Exos strongly inhibited this bone-beneficial effect. Similarly, our results confirmed that preinjection of TBI-Exos led to enhanced bone formation, whereas knockdown of exosomal miR-21-5 p substantially impaired this bone-beneficial effect in vivo.

BMP-6 promotes type 2 immune response during enhancement of rat mandibular bone defect healing.

Bone morphogenetic proteins (BMPs) are used as key therapeutic agents for the treatment of difficult fractures. While their effects on osteoprogenitors are known, little is known about their effects on the immune system. We used permutations of BMP-6 (B), vascular endothelial growth factor (V), and Hedgehog signaling pathway activator smoothened agonist (S), to treat a rat mandibular defect and investigated healing outcomes at week 8, in correlation with the cellular landscape of the immune cells in the fracture callus at week 2. Maximum recruitment of immune cells to the fracture callus is known to occur at week 2. While the control, S, V, and VS groups remained as nonunions at week 8; all BMP-6 containing groups - B, BV, BS and BVS, showed near-complete to complete healing. This healing pattern was strongly associated with significantly higher ratios of CD4 T (CD45+CD3+CD4+) to putative CD8 T cells (CD45+CD3+CD4-), in groups treated with any permutation of BMP-6. Although, the numbers of putative M1 macrophages (CD45+CD3-CD11b/c+CD38high) were significantly lower in BMP-6 containing groups in comparison with S and VS groups, percentages of putative - Th1 cells or M1 macrophages (CD45+CD4+IFN-γ+) and putative - NK, NKT or cytotoxic CD8T cells (CD45+CD4-IFN-γ+) were similar in control and all treatment groups. Further interrogation revealed that the BMP-6 treatment promoted type 2 immune response by significantly increasing the numbers of CD45+CD3-CD11b/c+CD38low putative M2 macrophages, putative - Th2 cells or M2 macrophages (CD45+CD4+IL-4+) cells and putative - mast cells, eosinophils or basophils (CD45+CD4-IL-4+ cells). CD45- non-haematopoietic fractions of cells which encompass all known osteoprogenitor stem cells populations, were similar in control and treatment groups. This study uncovers previously unidentified regulatory functions of BMP-6 and shows that BMP-6 enhances fracture healing by not only acting on osteoprogenitor stem cells but also by promoting type 2 immune response.

Enhancing Tibial and Fibular Fracture Healing: A Case Report on the Value of Dynamization

Background: Tibial and fibular fractures, commonly resulting from high-energy traumas such as road traffic accidents, present difficulties in their management due to displacement, instability, and the requirement for surgical intervention. Case presentation: We present a 27-year-old male patient with a tibial and fibular fracture managed with intramedullary nail fixation and subsequent dynamization. The aim is to highlight the clinical significance of dynamization in addressing delayed healing and non-union in fractures. Clinical assessment and radiographic evaluation were performed to diagnose the tibial and fibular fractures. The patient underwent intramedullary nail fixation followed by dynamization. The utilization of intramedullary nail fixation demonstrated consistent outcomes with established literature. However, delayed healing and non-union were observed. The introduction of dynamization after failed healing attempts led to significant improvements in callus formation and fracture healing. Conclusions: This case emphasizes the value of dynamization as a strategy to enhance fracture healing, particularly in cases of delayed union or non-union. Dynamization represents a promising adjunctive approach in orthopedic fracture management.

Modulating macrophage polarization for the enhancement of fracture healing, a systematic review.

BackgroundAll fracture repairs start with the innate immune system with the inflammatory response known as the inflammatory stage guided and driven by the secretion of chemokine by the ruptured tissue, followed by the sequential recruitment of neutrophils, monocytes and macrophages. These innate immune cells would infiltrate the fracture site and secrete inflammatory cytokines to stimulate recruitment of more immune cells to arrive at the fracture site coordinating subsequent stages of the repair process. In which, subsidence of pro-inflammatory M1 macrophage and transformation to anti-inflammatory M2 macrophages promotes osteogenesis that marks the start of the anabolic endochondral stage.MethodsLiterature search was performed on Pubmed, Embase, and Web of Science databases (last accessed 15th April 2021) using “macrophage AND fracture”. Review was performed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guideline.ResultsEleven pre-clinical animal studies out of 429 articles were included in this systematic review according to our inclusion and exclusion criteria. All of which investigated interventions targeting to modulate the acute inflammatory response and macrophage polarization as evident by various markers in association with fracture healing outcomes.ConclusionThis systematic review summarizes attempts to modulate the innate immune response with focuses on promoting macrophage polarization from M1 to M2 phenotype targeting the enhancement of fracture injury repair. Methods used to achieve the goal may include applications of damage-associated molecular pattern (DAMP), pathogen-associated molecular pattern (PAMP) or mechanical stimulation that hold high translational potentials for clinical application in the near future.

Integrative approach to fracture healing: A review

It is said that first sign of civilization in human history was a femur that had been broken and then healed with the care of the loved ones. Such deep is the association of mankind and fractures. Since time immemorial, fracture patients are taking varied therapies to enhance fracture healing. Some are evidence based, some are not. With renewed interest in complementary and alternative medicine; it becomes wise to make primary care physicians aware of the viewpoints of dietician, homeopathy doctor and an ayurveda doctor on the medicines prescribed by them for fracture cases. A physician should be aware of different treatment methodologies to have an intelligent discussion with a curious patient. Dieticians emphasize on a healthy balanced diet. Ayurveda physicians focus on shali rice and clarified butter; while homeopathy physicians vouch on Symphytum.

Toll-like receptor 9 (TLR9) gene deletion-mediated fracture healing in type II diabetic osteoporosis associates with inhibition of the nuclear factor-kappa B (NF-κB) signaling pathway

ABSTRACT Diabetes is characterized by increased fracture risk. Evidence from in vivo studies is lacking for anti-fracture strategies in diabetes. Our microarray analyses predicted association of Toll-like receptor 9 (TLR9) with both diabetes and osteoporosis, which was the focus of this work in a murine model of type II diabetic osteoporosis (T2DOP). A T2DOP model with fracture was established in TLR9 knockout (TLR9−/−) mice, which were then treated with the NF-κB signaling pathway inhibitor (PDTC) and activator (TNF-α). The obtained data suggested that TLR9 knockout augmented regeneration of bone tissues and cartilage area in the callus, and diminished fibrous tissues in T2DOP mice. Moreover, TLR9 depletion significantly affected bone mineral density (BMD), bone volume/tissue volume (BV/TV), connectivity density, trabecular number, trabecular separation and trabecular thickness, thus promoting fracture recovery. Bone morphology and structure were also improved in response to TLR9 depletion in T2DOP mice. TLR9 depletion inactivated NF-κB signaling in T2DOP mice. PDTC was found to enhance fracture healing in T2DOP mice, while TNF-α negated this effect. Collectively, these data indicate that TLR9 depletion may hold anti-fracture properties, making it a potential therapeutic target for T2DOP. Abbreviations: Diabetic osteoporosis (DOP); bone mineral density (BMD); Toll-like receptors (TLRs); type 2 diabetes (T2D); Toll-like receptor 9 (TLR9); nuclear factor-kappaB (NF-κB); streptozotocin (STZ); type 2 diabetic osteoporosis (T2DOP); Gene Expression Omnibus (GEO); Kyoto encyclopedia of genes and genomes (KEGG); pyrrolidine dithiocarbamate (PDTC); computed tomography (CT); Hematoxylin–eosin (HE); bone morphogenetic protein 7 (BMP7); analysis of variance (ANOVA);

Age-associated callus senescent cells produce TGF-β1 that inhibits fracture healing in aged mice.

Cellular senescence plays an important role in human diseases, including osteoporosis and osteoarthritis. Senescent cells (SCs) produce the senescence-associated secretory phenotype to affect the function of neighboring cells and SCs themselves. Delayed fracture healing is common in the elderly and is accompanied by reduced mesenchymal progenitor cells (MPCs). However, the contribution of cellular senescence to fracture healing in the aged has not to our knowledge been studied. Here, we used C57BL/6J 4-month-old young and 20-month-old aged mice and demonstrated a rapid increase in SCs in the fracture callus of aged mice. The senolytic drugs dasatinib plus quercetin enhanced fracture healing in aged mice. Aged callus SCs inhibited the growth and proliferation of callus-derived MPCs (CaMPCs) and expressed high levels of TGF-β1. TGF-β–neutralizing Ab prevented the inhibitory effects of aged callus SCs on CaMPCs and promoted fracture healing in aged mice, which was associated with increased CaMPCs and proliferating cells. Thus, fracture triggered a significant cellular senescence in the callus cells of aged mice, which inhibited MPCs by expressing TGF-β1. Short-term administration of dasatinib plus quercetin depleted callus SCs and accelerated fracture healing in aged mice. Senolytic drugs represent a promising therapy, while TGF-β1 signaling is a molecular mechanism for fractures in the elderly via SCs.

Correlation Between Traumatic Brain Injuries and Callus Formation in Long bone Fractures.

Orthopaedic aphorism teaches that fractures of long bones when associated with head injuries frequently heal with excessive callus and at a faster rate than normal. However, the evidence on this subject is flimsy and the aphorism remains unsubstantiated. Numerous studies have been conducted evaluating the possible humoral and other factors involved leading to excess callus formation in patients with a head injury. This study was designed to evaluate the effects of a traumatic head injury on bone healing in adults with a diaphyseal fracture of the lower limb. Fiveteen patients with a closed fracture of tibia or femur and associated head injury (cases) and 15 patients with a closed fracture of tibia or femur without an associated head injury (controls) were included in the study. All patients were evaluated in terms of various serum parameters, including IL-6, growth hormone, PTH, LDH, prolactin levels, and ALP. Head injuries were graded as mild, moderate, or severe. Ventilatory support if required was noted. Serum prolactin was repeated at 5weeks. Patients were followed up with serial radiographs, and the volume of callus formed was calculated and compared. The mean value of growth hormone, interleukin-6 levels, and prolactin levels at 5weeks were found to be higher in patients with head injuries, and the difference was highly significant (p = 0.001). The severity of head injury also correlated proportionately with the spike in IL-6 levels. There was more pronounced callus formation in patients with head injury group when compared to the controls. This difference was significant at all intervals. There was higher volume of callus noted at the end of 6months in patients with severe head injury (GCS < 7) when compared to patients with moderate head injury (GCS > 7). The patients with severe head injury were naturally under ventilator support for a prolonged period compared to those with moderate head injury. It was thus indiscernible if the excess callus observed is due to the humoral cascade or as an effect of prolonged ventilation. Patients with head injuries show elevated parathyroid hormone levels, growth hormone levels at the time of injury, and elevated prolactin levels 5weeks after the trauma-all of which might contribute to enhanced osteogenesis. Interleukin-6 levels are also elevated and the levels correlate to severity of head injury. Head injury triggers a humoral cascade invloving interleukin-6, parathyroid hormoe, growth hormone, and prolactin that contributes to enhanced fracture healing.

The Effects of TMP Treatment and High Fat Diet on Bone Fracture Healing

Delayed and impaired bone fracture healing are associated with diabetic populations. This is a challenging problem for orthopaedic surgeons especially in the US where the percentage of type 2 diabetic patients continues to climb at an alarming rate. Limited treatment options exist for orthopaedic surgeons to improve fracture healing, and the most commonly used therapies involve placement of proteins (bone morphogenetic protein), graft tissue, or demineralized bone matrix at the fracture site. We have previously demonstrated that local administration of the main megakaryocyte growth factor, thrombopoietin, enhances bone healing. Here we demonstrate the utility of systemically administering thrombopoietin mimetic peptides (TMPs) to improve impaired fracture healing in a mouse model of type 2 diabetes. Briefly, 120 male mice on a C57BL/6 background were placed on a low fat diet (LFD) or high fat diet (HFD) for 12 weeks prior to undergoing a surgically created femoral fracture. Mice were treated with 33 nmol/kg of TMP or saline immediately after surgery and daily for the following week. Mice were euthanized at 1, 2, and 4 weeks post-surgery (n=10/group). Here, we confirmed that HFD resulted in impaired fracture healing. We also showed accelerated bone union and increased callus formation in TMP treated mice compared to saline groups, irrespective of diet (p&lt;0.05). Among TMP groups that were fed either a HFD or LFD, the HFD TMP group showed greater improvements in bone healing compared to the HFD saline control mice. Further study on TMP should include alternative routes of administration and providing treatment when a surgical repair appears to be deteriorating. Although there is more to be understood about the clinical importance and mechanism by which systemic TMP treatment enhances fracture healing, these data appear promising.

Dual-Targeted Nanoplatform Regulating the Bone Immune Microenvironment Enhances Fracture Healing.

The immune system and skeletal system are closely linked. Macrophages are one of the most important immune cells for bone remodeling, playing a prohealing role mainly through M2 phenotype polarization. Baicalein (5,6,7-trihydroxyflavone, BCL) has been well documented to have a noticeable promotion effect on M2 macrophage polarization. However, due to the limitations in targeted delivery to macrophages and the toxic effect on other organs, BCL has rarely been used in the treatment of bone fractures. In this study, we developed mesoporous silica and Fe3O4 composite-targeted nanoparticles loaded with BCL (BCL@MMSNPs-SS-CD-NW), which could be magnetically delivered to the fracture site. This induced macrophage recruitment in a targeted manner, polarizing them toward the M2 phenotype, which was demonstrated to induce mesenchymal stem cells (MSCs) toward osteoblastic differentiation. The mesoporous silicon nanoparticles (MSNs) were prepared with surface sulfhydrylation and amination modification, and the mesoporous channels were blocked with β-cyclodextrin. The outer layer of the mesoporous silicon was added with an amantane-modified NW-targeting peptide to obtain the targeted nanosystem. After entering macrophages, BCL could be released from nanoparticles since the disulfide linker could be cleaved by intracellular glutathione (GSH), resulting in the removal of cyclodextrin (CD) gatekeeper, which is a key element in the pro-bone-remodeling functions such as anti-inflammation and induction of M2 macrophage polarization to facilitate osteogenic differentiation. This nanosystem passively accumulated in the fracture site, promoting osteogenic differentiation activities, highlighting a potent therapeutic benefit with high biosafety.

Implantable Electrical Stimulation at Dorsal Root Ganglions Accelerates Osteoporotic Fracture Healing via Calcitonin Gene-Related Peptide.

The neuronal engagement of the peripheral nerve system plays a crucial role in regulating fracture healing, but how to modulate the neuronal activity to enhance fracture healing remains unexploited. Here it is shown that electrical stimulation (ES) directly promotes the biosynthesis and release of calcitonin gene‐related peptide (CGRP) by activating Ca2+/CaMKII/CREB signaling pathway and action potential, respectively. To accelerate rat femoral osteoporotic fracture healing which presents with decline of CGRP, soft electrodes are engineered and they are implanted at L3 and L4 dorsal root ganglions (DRGs). ES delivered at DRGs for the first two weeks after fracture increases CGRP expression in both DRGs and fracture callus. It is also identified that CGRP is indispensable for type‐H vessel formation, a biological event coupling angiogenesis and osteogenesis, contributing to ES‐enhanced osteoporotic fracture healing. This proof‐of‐concept study shows for the first time that ES at lumbar DRGs can effectively promote femoral fracture healing, offering an innovative strategy using bioelectronic device to enhance bone regeneration.

Current Modalities for Fracture Healing Enhancement.

Previously, most fractures have been treated through bone reduction and immobilization. With an increase in the patients' need for an early return to their normal function, development in surgical techniques and materials have accelerated. However, delayed union or non-union of the fracture site sometimes inhibits immediate return to normal life. To enhance fracture healing, diverse materials and methods have been developed. This is a review on the current modalities of fracture healing enhancement, which aims to provide a comprehensive knowledge regarding fracture healing for researchers and health practitioners.

Locking screw augmentation in hypertrophic nonunion of tibia: a novel surgical technique.

Nonunion is a common complication in long bone diaphyseal fracture. Hypertrophic nonunion is commonly caused by mechanical instability due to high strain at the fracture site whereas atrophic nonunion is mainly caused by biological impairment. Multiple surgical techniques have been reported to treat hypertrophic nonunion of long bones but there is no consensus about what is the best choice. We present our surgical option in hypertrophic nonunion of lower limb. We performed a locking cortical screw augmentation technique in fractures previously fixed with plate and screws in order to increase plate stability and to enhance fracture healing process. Radiographic evaluations carried out three months after surgery showed that the fracture line is radiographically filled by bone callus. No pain, no limp, no signs of infection or implant failure were reported. Locking cortical screw augmentation could represent a valid technique to reduce micromovements and to increase the stability at the fracture site with the possibility of early weight bearing and good clinical outcome.