Clinical Characteristics and Outcomes of Limb Fractures in Saudi Children.

BACKGROUND:  Children's bones are at high risk of fracture as they grow. The clinical characteristics of fractures in children differ from those in adults. Studying fractures in healthy children is critical for identifying cases of fragility fractures. The aim of this study was to assess the clinical characteristics of limb fractures as well as clinical indicators of fracture healing outcomes in healthy Saudi children seen in an emergency room. METHODS: A retrospective review of the treatment course of all pediatric fractures and related factors treated at King Abdullah Specialist Children's Hospital (KASCH) in Riyadh between 2016 and 2018 was conducted. Children with a primary bone disorder or chronic comorbidities known to affect bone health were excluded. RESULTS:  The study included 143 patients (mean age ± SD = 8.23 + 3.76 years), and 71% (n = 102) were males. Motor vehicle accidents (MVAs) were the most common mechanism of injury, accounting for 50 (35%) cases, followed by fall injuries, sports injuries, and pedestrian accidents at 45 (31.4%), 16 (11.2%), and 13 (9.1%), respectively. A total of 178 fractures were reported, with the femur (n = 75, 42.1%) being the most common of the reported fracture sites, followed by the forearm (n = 44, 24.7%). The most common type of fracture was transverse fracture (n = 96, 54% of patients). Vitamin D levels were measured in 53/143 cases. Of these, vitamin D deficiency was found in 38 (71.7%) patients. The average time for fracture healing was 32.9 ± 30.2 weeks. The mechanisms of injury, including MVAs and sports injuries, as well as femur and forearm fractures, were clinical factors that were independently associated with a longer duration of fracture healing time (p < 0.001), but age, gender, and vitamin D status were not associated with that outcome. CONCLUSION:  MVAs and fall injuries were the most common causes of fracture in our patients. MVAs and sports injuries were associated with prolonged healing time. Large prospective, multicenter, or field studies may be required to further explore clinical characteristics, outcomes, and environmental factors.

Mechanosensitive protein polycystin-1 promotes periosteal stem/progenitor cells osteochondral differentiation in fracture healing.

Background: Mechanical forces are indispensable for bone healing, disruption of which is recognized as a contributing cause to nonunion or delayed union. However, the underlying mechanism of mechanical regulation of fracture healing is elusive. Methods: We used the lineage-tracing mouse model, conditional knockout depletion mouse model, hindlimb unloading model and single-cell RNA sequencing to analyze the crucial roles of mechanosensitive protein polycystin-1 (PC1, Pkd1) promotes periosteal stem/progenitor cells (PSPCs) osteochondral differentiation in fracture healing. Results: Our results showed that cathepsin (Ctsk)-positive PSPCs are fracture-responsive and mechanosensitive and can differentiate into osteoblasts and chondrocytes during fracture repair. We found that polycystin-1 declines markedly in PSPCs with mechanical unloading while increasing in response to mechanical stimulus. Mice with conditional depletion of Pkd1 in Ctsk+ PSPCs show impaired osteochondrogenesis, reduced cortical bone formation, delayed fracture healing, and diminished responsiveness to mechanical unloading. Mechanistically, PC1 facilitates nuclear translocation of transcriptional coactivator TAZ via PC1 C-terminal tail cleavage, enhancing osteochondral differentiation potential of PSPCs. Pharmacological intervention of the PC1-TAZ axis and promotion of TAZ nuclear translocation using Zinc01442821 enhances fracture healing and alleviates delayed union or nonunion induced by mechanical unloading. Conclusion: Our study reveals that Ctsk+ PSPCs within the callus can sense mechanical forces through the PC1-TAZ axis, targeting which represents great therapeutic potential for delayed fracture union or nonunion.

Percutaneous Intramedullary Application of Stem Cells for Fifth Metatarsal Fractures Treated With a Cannulated Screw.

Non-union and refracture of fifth metatarsal fractures are common and devastating complications in the athletic population. Stem cell application at the fracture site, for biologic enhancement, is utilized to address this challenge. We present a simple technique to approach both the endosteum and the periosteum percutaneously, under a local anesthetic, in cases of cannulated screw intramedullary fixation.

Prolonged Union in Conservative Treatment of Symphalangeal Toe Fractures: Case Series.

Background: Toe symphalangism is characterized by a fusion of the interphalangeal joint between the middle and distal phalanges. While typical lesser toe fractures heal well with conservative treatment, in our clinical experience, we encountered patients with symphalangeal toe fractures who experienced long-lasting pain and delayed radiographic union. Therefore, this study aimed to report radiographic outcomes following conservative treatment of symphalangeal fractures of the lesser toes. Methods: We retrospectively reviewed 14 patients with symphalangeal lesser toe fractures who were treated conservatively. We investigated the mechanism of injury and measured the time from the initial injury date to the complete radiographic union. The fracture gap distance was measured on an initial lateral radiograph. Results: Symphalangeal fractures involved the fourth toe in 4 patients (28.5%) and the fifth toe in 10 patients (71.4%). Regarding the mechanism of injury, 6 patients (42.9%) were injured by stubbing or bumping into the door, 5 patients (35.7%) were injured by tripping, 2 patients (14.3%) were injured by heavy objects falling directly on their toes, and 1 patient (2.3%) complained of pain after wearing pointed shoes for half a day. The mean time to complete union was 9.1 months, and the median period was 5.5 months (range, 0.8-29 months). The initial gap of the fracture was 0.60 mm (range, 0.30-1.04 mm). Conclusions: The results of our case series may help counsel patients in the outpatient clinic that prolonged healing time may be required for the union of symphalangeal toe fractures.

The impact of age and sex on the inflammatory response during bone fracture healing.

Inflammation is thought to be dysregulated with age leading to impaired bone fracture healing. However, broad analyses of inflammatory processes during homeostatic bone aging and during repair are lacking. Here, we assessed changes in inflammatory cell and cytokine profiles in circulation and in bone tissue to identify age- and sex-dependent differences during homeostasis and repair. During homeostatic aging, male mice demonstrated accumulation of CD4+ helper T cells and CD8+ cytotoxic T cells within bone while both pro-inflammatory "M1" and anti-inflammatory "M2" macrophage numbers decreased. Female mice saw no age-associated changes in immune-cell population in homeostatic bone. Concentrations of IL-1ß, IL-9, IFNγ, and CCL3/MIP-1α increased with age in both male and female mice, whereas concentrations of IL-2, TNFα, TNFR1, IL-4, and IL-10 increased only in female mice - thus we termed these "age-accumulated" cytokines. There were no notable changes in immune cell populations nor cytokines within circulation during aging. Sex-dependent analysis demonstrated slight changes in immune cell and cytokine levels within bone and circulation, which were lost upon fracture injury. Fracture in young male mice caused a sharp decrease in number of M1 macrophages; however, this was not seen in aged male mice nor in female mice of any age. Injury itself induced a decrease in the number of CD8+ T cells within the local tissue of aged male and of female mice but not of young mice. Cytokine analysis of fractured mice revealed that age-accumulated cytokines quickly dissipated after fracture injury, and did not re-accumulate in newly regenerated tissue. Conversely, CXCL1/KC-GRO, CXCL2/MIP-2, IL-6, and CCL2/MCP-1 acted as "fracture response" cytokines: increasing sharply after fracture, eventually returning to baseline. Collectively, we classify measured cytokines into three groups: (1) age-accumulated cytokines, (2) female-specific age-accumulated cytokines, and (3) fracture response cytokines. These inflammatory molecules represent potential points of intervention to improve fracture healing outcome.

Fueling recovery: The importance of energy coupling between angiogenesis and osteogenesis during fracture healing.

Approximately half of bone fractures that do not heal properly (non-union) can be accounted to insufficient angiogenesis. The processes of angiogenesis and osteogenesis are spatiotemporally regulated in the complex process of fracture healing that requires a substantial amount of energy. It is thought that a metabolic coupling between angiogenesis and osteogenesis is essential for successful healing. However, how this coupling is achieved remains to be largely elucidated. Here, we will discuss the most recent evidence from literature pointing towards a metabolic coupling between angiogenesis and osteogenesis. We will describe the metabolic profiles of the cell types involved during fracture healing as well as secreted products in the bone microenvironment (such as lactate and nitric oxide) as possible key players in this metabolic crosstalk.

CD47 is Required for Mesenchymal Progenitor Proliferation and Fracture Repair.

CD47 is a ubiquitous and pleiotropic cell-surface receptor. Disrupting CD47 enhances injury repair in various tissues but the role of CD47 has not been studied in bone injuries. In a murine closed-fracture model, CD47-null mice showed decreased callus bone volume, bone mineral content, and tissue mineral content as assessed by microcomputed tomography 10 days post-fracture, and increased fibrous volume as determined by histology. To understand the cellular basis for this phenotype, mesenchymal progenitors (MSC) were harvested from bone marrow. CD47-null MSC showed decreased large fibroblast colony formation (CFU-F), significantly less proliferation, and fewer cells in S-phase, although osteoblast differentiation was unaffected. However, consistent with prior research, CD47-null endothelial cells showed increased proliferation relative to WT cells. Similarly, in a murine ischemic fracture model, CD47-null mice showed reduced fracture callus bone volume and bone mineral content relative to WT. Consistent with our In vitro results, in vivo EdU labeling showed decreased cell proliferation in the callus of CD47-null mice, while staining for CD31 and endomucin demonstrated increased endothelial cell mass. Finally, WT mice administered a CD47 morpholino, which blocks CD47 protein production, showed a callus phenotype similar to that of non-ischemic and ischemic fractures in CD47-null mice, suggesting the phenotype was not due to developmental changes in the knockout mice. Thus, inhibition of CD47 during bone healing reduces both non-ischemic and ischemic fracture healing, in part, by decreasing MSC proliferation. Furthermore, the increase in endothelial cell proliferation and early blood vessel density caused by CD47 disruption is not sufficient to overcome MSC dysfunction.

Impact of osteoporosis and osteoporosis medications on fracture healing: a narrative review.

Antiresorptive medications do not negatively affect fracture healing in humans. Teriparatide may decrease time to fracture healing. Romosozumab has not shown a beneficial effect on human fracture healing. BACKGROUND: Fracture healing is a complex process. Uncertainty exists over the influence of osteoporosis and the medications used to treat it on fracture healing. METHODS: Narrative review authored by the members of the Fracture Working Group of the Committee of Scientific Advisors of the International Osteoporosis Foundation (IOF), on behalf of the IOF and the Société Internationale de Chirurgie Orthopédique et de Traumatologie (SICOT). RESULTS: Fracture healing is a multistep process. Most fractures heal through a combination of intramembranous and endochondral ossification. Radiographic imaging is important for evaluating fracture healing and for detecting delayed or non-union. The presence of callus formation, bridging trabeculae, and a decrease in the size of the fracture line over time are indicative of healing. Imaging must be combined with clinical parameters and patient-reported outcomes. Animal data support a negative effect of osteoporosis on fracture healing; however, clinical data do not appear to corroborate with this. Evidence does not support a delay in the initiation of antiresorptive therapy following acute fragility fractures. There is no reason for suspension of osteoporosis medication at the time of fracture if the person is already on treatment. Teriparatide treatment may shorten fracture healing time at certain sites such as distal radius; however, it does not prevent non-union or influence union rate. The positive effect on fracture healing that romosozumab has demonstrated in animals has not been observed in humans. CONCLUSION: Overall, there appears to be no deleterious effect of osteoporosis medications on fracture healing. The benefit of treating osteoporosis and the urgent necessity to mitigate imminent refracture risk after a fracture should be given prime consideration. It is imperative that new radiological and biological markers of fracture healing be identified. It is also important to synthesize clinical and basic science methodologies to assess fracture healing, so that a convergence of the two frameworks can be achieved.

PPARγ inhibition promotes osteogenic differentiation of bone marrow mesenchymal stem cells and fracture healing.

This study aimed to explore the effects of peroxisome proliferator-activated receptor γ (PPARγ) inhibition on fracture healing of nonunion and the underlying mechanisms. Bone marrow mesenchymal stem cells (BMSCs) were treated with PPARγ antagonist GW9662 (5 µM, 10 µM). Alkaline phosphatase (ALP) staining and Alizarin Red S was used to assess early stage of osteogenesis and osteogenic differentiation. GW9662 (1 mg/kg/day) were administered intraperitoneally into the rats with bone fracture. Bone healing processes in the rat femur fracture model were recorded and assessed by radiographic methods on Weeks 8, 14, and 20 postoperation. Osteogenesis and angiogenesis at the fracture sites were evaluated by radiographic and histological methods on postoperative Week 20. GW9662 treatment increased ALP activity and Alp mRNA expression in rat BMSCs. Moreover, GW9662 administration increased matrix mineralization and mRNA and protein levels of Bmp2 and Runx2 in the BMSCs. In addition, GW9662 treatment improved radiographic score in the fracture rats and increased osteogenesis-related proteins, including type I collagen, osteopontin, and osteoglycin, in the bone tissues of the fracture sites. In conclusion, PPARγ inhibition promotes osteogenic differentiation of rat BMSCs, as well as improves the fracture healing of rats through Bmp2/Runx2 signaling pathway in the rat model of bone fracture.

Preventing Atrophic Long-Bone Nonunion: Retrospective Analysis at a Level I Trauma Center.

Background: Among the risk factors for nonunion are unchangeable patient factors such as the type of injury and comorbidities, and factors that can be influenced by the surgeon such as fracture treatment and the postoperative course. While there are numerous studies analyzing unchangeable factors, there is poor evidence for factors that can be affected by the physician. This raises the need to fill the existing knowledge gaps and lay the foundations for future prevention and in-depth treatment strategies. Therefore, the goal of this study was to illuminate knowledge about nonunion in general and uncover the possible reasons for their development; Methods: This was a retrospective analysis of 327 patients from 2015 to 2020 from a level I trauma center in Germany. Information about patient characteristics, comorbidities, alcohol and nicotine abuse, fracture classification, type of osteosynthesis, etc., was collected. Matched pair analysis was performed, and statistical testing performed specifically for atrophic long-bone nonunion; Results: The type of osteosynthesis significantly affected the development of nonunion, with plate osteosynthesis being a predictor for nonunion. The use of wire cerclage did not affect the development of nonunion, nor did the use of NSAIDs, smoking, alcohol, osteoporosis and BMI; Conclusion: Knowledge about predictors for nonunion and strategies to avoid them can benefit the medical care of patients, possibly preventing the development of nonunion.

Zinc finger protein 36 like 2-histone deacetylase 1 axis is involved in the bone responses to mechanical stress.

The molecular mechanism underlying the promotion of fracture healing by mechanical stimuli remains unclear. The present study aimed to investigate the role of zinc finger protein 36 like 2 (ZFP36L2)-histone deacetylase 1 (HDAC1) axis on the osteogenic responses to moderate mechanical stimulation. Appropriate stimulation of fluid shear stress (FSS) was performed on MC3T3-E1 cells transduced with ZFP36L2 and HDAC1 recombinant adenoviruses, aiming to validate the influence of mechanical stress on the expression of ZFP36L2-HDAC1 and the osteogenic differentiation and mineralization. The results showed that moderate FSS stimulation significantly upregulated the expression of ZFP36L2 in MC3T3-E1 cells (p < 0.01). The overexpression of ZFP36L1 markedly enhanced the levels of osteogenic differentiation markers, including bone morphogenetic protein 2 (BMP2), runt-related transcription factor 2 (RUNX2), alkaline phosphatase (ALP), Osterix, and collagen type I alpha 1 (COL1A1) (p < 0.01). ZFP36L2 accelerated the degradation of HDAC1 by specifically binding to its 3' UTR region, thereby fulfilling its function at the post-transcriptional regulatory gene level and promoting the osteogenic differentiation and mineralization fate of cells. Mechanical unloading notably diminished/elevated the expression of ZFP36L2/HDAC1, decreased bone mineral density and bone volume fraction, hindered the release of osteogenic-related factors and vascular endothelial growth factor in callus tissue (p < 0.01), and was detrimental to fracture healing. Collectively, proper stress stimulation plays a crucial role in facilitating osteogenesis through the promotion of ZFP36L2 and subsequent degradation of HDAC1. Targeting ZFP36L2-HDAC1 axis may provide promising insights to enhance bone defect healing.

Bone quality assessment in patients with healing mandibular fracture sites: a computed tomography investigation.

The objective of this retrospective study was to assess the bone quality of healing mandibular fracture sites by measuring the Hounsfield units (HU) on computed tomographic (CT) images obtained presurgery and postsurgery in patients treated with rigid internal fixation (RIF). The HU values of healing fracture sites were compared to those of corresponding nonfractured (control) sites on the opposing side and cervical vertebrae sites in the same patients. In total, 31 patients with 45 mandibular fractures treated with RIF underwent presurgical and postsurgical CT examinations. The scans performed after surgery (1, 3, 6, 12, or 18 months) were taken only when there was a need for radiographic evaluation due to a complaint of discomfort from the patient or when the surgeon needed to verify the postsurgical outcome, and each patient underwent only a single postsurgical CT. At the presurgical CT examination, the HU values were lower in the fracture sites than in the control sites. At 3 months postsurgery, the HU values in the fracture sites had increased as the mandibular bone healed. At 6 months postsurgery, the HU values in the fracture sites were higher than those of the control sites. At 12 and 18 months postsurgery, the HU values of both sites were similar. The HU values of the cervical vertebrae remained constant with time. These results suggest that, in patients who have been treated with RIF for mandibular bone fracture, HU values measured by CT vary across time, expressing the physiologic bone healing process.

Clavicle fracture and triathlon performance: a case report.

BACKGROUND: Collarbone fracture is a common injury, particularly among athletes involved in contact sports and participating in endurance activities. Conventional treatment requires surgery and postoperative immobilization, resulting in an average return-to-sport timeframe of approximately 13 weeks. This case challenges the established treatment protocols, aiming to expedite recovery and enable a quicker resumption of high-intensity athletic activities. CASE PRESENTATION: A 24-year-old Caucasian athlete completed a Half-Ironman Triathlon (70.3) merely three weeks post-collarbone fracture. Utilizing Extracorporeal Magneto-Transduction Therapy (EMTT) alongside surgical intervention, the patient achieved accelerated healing and remarkable performance outcomes without encountering any adverse effects. CONCLUSIONS: The integration of EMTT into the treatment paradigm for bone fractures alters the traditional understanding of recovery timelines and rehabilitation strategies. This case highlights the potential benefits of electromagnetic wave therapy in expediting the healing process and enabling athletes to resume high-level sports activities at an earlier stage.

Advances in the role and mechanism of fibroblasts in fracture healing.

With the development of social population ageing, bone fracture has become a global public health problem due to its high morbidity, disability and mortality. Fracture healing is a complex phenomenon involving the coordinated participation of immigration, differentiation and proliferation of inflammatory cells, angioblasts, fibroblasts, chondroblasts and osteoblasts which synthesize and release bioactive substances of extracellular matrix components, Mortality caused by age-related bone fractures or osteoporosis is steadily increasing worldwide as the population ages. Fibroblasts play an important role in the process of fracture healing. However, it is not clear how the growth factors and extracellular matrix stiffness of the bone-regeneration microenvironment affects the function of osteoblasts and fibroblasts in healing process. Therefore, this article focuses on the role of fibroblasts in the process of fracture healing and mechanisms of research progress.

Unraveling IGFBP3-mediated m6A modification in fracture healing.

BACKGROUND: This study investigates the role of IGFBP3-mediated m6A modification in regulating the miR-23a-3p/SMAD5 axis and its impact on fracture healing, aiming to provide insights into potential therapeutic targets. METHODS: Utilizing fracture-related datasets, we identified m6A modification-related mRNA and predicted miR-23a-3p as a regulator of SMAD5. We established a mouse fracture healing model and conducted experiments, including Micro-CT, RT-qPCR, Alizarin Red staining, and Alkaline phosphatase (ALP) staining, to assess gene expression and osteogenic differentiation. RESULTS: IGFBP3 emerged as a crucial player in fracture healing, stabilizing miR-23a-3p through m6A modification, leading to SMAD5 downregulation. This, in turn, inhibited osteogenic differentiation and delayed fracture healing. Inhibition of IGFBP3 partially reversed through SMAD5 inhibition, restoring osteogenic differentiation and fracture healing in vivo. CONCLUSION: The IGFBP3/miR-23a-3p/SMAD5 axis plays a pivotal role in fracture healing, highlighting the relevance of m6A modification. IGFBP3's role in stabilizing miR-23a-3p expression through m6A modification offers a potential therapeutic target for enhancing fracture healing outcomes.

A distinct "repair" role of regulatory T cells in fracture healing.

Regulatory T cells (Tregs) suppress immune responses and inflammation. Here, we described the distinct nonimmunological role of Tregs in fracture healing. The recruitment from the circulation pool, peripheral induction, and local expansion rapidly enriched Tregs in the injured bone. The Tregs in the injured bone displayed superiority in direct osteogenesis over Tregs from lymphoid organs. Punctual depletion of Tregs compromised the fracture healing process, which leads to increased bone nonunion. In addition, bone callus Tregs showed unique T-cell receptor repertoires. Amphiregulin was the most overexpressed protein in bone callus Tregs, and it can directly facilitate the proliferation and differentiation of osteogenic precursor cells by activation of phosphatidylinositol 3-kinase/protein kinase B signaling pathways. The results of loss- and gain-function studies further evidenced that amphiregulin can reverse the compromised healing caused by Treg dysfunction. Tregs also enriched in patient bone callus and amphiregulin can promote the osteogenesis of human pre-osteoblastic cells. Our findings indicate the distinct and nonredundant role of Tregs in fracture healing, which will provide a new therapeutic target and strategy in the clinical treatment of fractures.

Biomechanical Effects of Mechanical Stress on Cells Involved in Fracture Healing.

Fracture healing is a complex staged repair process in which the mechanical environment plays a key role. Bone tissue is very sensitive to mechanical stress stimuli, and the literature suggests that appropriate stress can promote fracture healing by altering cellular function. However, fracture healing is a coupled process involving multiple cell types that balance and limit each other to ensure proper fracture healing. The main cells that function during different stages of fracture healing are different, and the types and molecular mechanisms of stress required are also different. Most previous studies have used a single mechanical stimulus on individual mechanosensitive cells, and there is no relatively uniform standard for the size and frequency of the mechanical stress. Analyzing the mechanisms underlying the effects of mechanical stimulation on the metabolic regulation of signaling pathways in cells such as in bone marrow mesenchymal stem cells (BMSCs), osteoblasts, chondrocytes, and osteoclasts is currently a challenging research hotspot. Grasping how stress affects the function of different cells at the molecular biology level can contribute to the refined management of fracture healing. Therefore, in this review, we summarize the relevant literature and describe the effects of mechanical stress on cells associated with fracture healing, and their possible signaling pathways, for the treatment of fractures and the further development of regenerative medicine.

Schnurri-3 controls osteogenic fate of Adipoq-lineage progenitors in bone marrow.

Background: Recently, the osteogenic potential of Adiponectin-labeled adipogenic lineage progenitors (Adipoq-lineage progenitors) in bone marrow has been observed to support bone maintenance and repair. However, little is known about the function of Schnurri-3 (SHN3, also known as HIVEP3) in other mesenchymal lineage cells, apart from its negative regulation of bone formation on osteoblasts. Method: In this study, we used single-cell RNA sequencing (scRNA-seq) profiling to demonstrate that Adipoq-lineage progenitors express higher levels of Shn3 compared to other mesenchymal cell populations in mice and humans. To investigate the role of SHN3 in Adipoq-lineage progenitors, we generated a murine model specifically harboring a Shn3-deficient allele in Adipoq-expressing cells. Information of mice body weight was collected weekly to generate body weight curve. Bone phenotype was analyzed using micro-CT and histomorphometric studies. To eliminate the role of peripheral adipose tissue on bone, we collected adipose wet weight, performed intraperitoneal glucose tolerance tests and intraperitoneal insulin tolerance tests, and conducted a fat-transplantation study. Osteoblast and osteoclast functions were assessed through toluidine blue staining and TRAP staining, respectively. We further investigated the effect of Shn3 depletion on the differentiation of Adipoq-lineage progenitors through immunostaining and in vitro differentiation assays. Finally, we evaluated whether Shn3 deficiency in Adipoq-lineage progenitors affects the fracture healing process by generating bi-cortical femoral fracture models. Results: Depletion of Shn3 in Adipoq-lineage progenitors resulted in a significant increase in trabecular bone mass and bone formation in vivo, without disrupting whole-body energy metabolism and skeletal development. Consistent with these findings, both cell-lineage tracing and functional assays revealed that Shn3 ablation effectively shifted the cell fate of Adipoq-lineage progenitors towards an osteogenic phenotype in the bone marrow. Furthermore, in vivo studies demonstrated that the lack of Shn3 in Adipoq-lineage progenitors also enhanced bone fracture healing under pathological conditions. Conclusion: Overall, our findings provide a novel strategy for targeting the osteoanabolic potential of bone marrow Adipoq-lineage progenitors as a potential treatment for bone loss-related disorders. Translational potential of this article: We have identified a novel gene target that directs the cell fate of a previously identified non-osteogenic cell population under physiological conditions. This study not only expands the therapeutic value of Shn3 ablation in treating osteoporotic or traumatic bone diseases but also provides new insights into the contribution of bone marrow Adipoq-lineage progenitors to osteogenesis. Thus, this article further supports Shn3 silencing as a valuable approach to treat osteopenia and accelerate fracture healing (see graphical abstract).

Litsea glutinosa extract promotes fracture healing and prevents bone loss via BMP2/SMAD1 signaling.

Estrogen deficiency is one of the main causes for postmenopausal osteoporosis. Current osteoporotic therapies are of high cost and associated with serious side effects. So there is an urgent need for cost-effective anti-osteoporotic agents. Anti-osteoporotic activity of Litsea glutinosa extract (LGE) is less explored. Moreover, its role in fracture healing and mechanism of action is still unknown. In the present study we explore the osteoprotective potential of LGE in osteoblast cells and fractured and ovariectomized (Ovx) mice models. Alkaline phosphatase (ALP), MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) and mineralization assays revealed that LGE treatment increased osteoblast cell differentiation, viability and mineralization. LGE treatment at 0.01 µg increased the expression of BMP2, PSMAD, RUNX2 and type 1 col. LGE also mitigated RANKL-induced osteoclastogenesis. Next, drill hole injury Balb/C mice model was treated with LGE for 12 days. Micro-CT analysis and Calcein labeling at the fracture site showed that LGE (20 mg/kg) enhanced new bone formation and bone regeneration, also increased expression of BMP2/SMAD1 signaling genes at fracture site. Ovx mice were treated with LGE for 1 month. µCT analysis indicated that the treatment of LGE at 20 mg/kg dose prevented the alteration in bone microarchitecture and maintained bone mineral density and bone mineral content. Treatment also increased bone strength and restored the bone turnover markers. Furthermore, in bone samples, LGE increased osteogenesis by enhancing the expression of BMP2/SMAD1 signaling components and decreased osteoclast number and surface. We conclude that LGE promotes osteogenesis via modulating the BMP2/SMAD1 signaling pathway. The study advocates the therapeutic potential of LGE in osteoporosis treatment.

Temporal dynamics of immune-stromal cell interactions in fracture healing.

Bone fracture repair is a complex, multi-step process that involves communication between immune and stromal cells to coordinate the repair and regeneration of damaged tissue. In the US, 10% of all bone fractures do not heal properly without intervention, resulting in non-union. Complications from non-union fractures are physically and financially debilitating. We now appreciate the important role that immune cells play in tissue repair, and the necessity of the inflammatory response in initiating healing after skeletal trauma. The temporal dynamics of immune and stromal cell populations have been well characterized across the stages of fracture healing. Recent studies have begun to untangle the intricate mechanisms driving the immune response during normal or atypical, delayed healing. Various in vivo models of fracture healing, including genetic knockouts, as well as in vitro models of the fracture callus, have been implemented to enable experimental manipulation of the heterogeneous cellular environment. The goals of this review are to (1): summarize our current understanding of immune cell involvement in fracture healing (2); describe state-of-the art approaches to study inflammatory cells in fracture healing, including computational and in vitro models; and (3) identify gaps in our knowledge concerning immune-stromal crosstalk during bone healing.