Applicability of an active matrix metalloproteinase-8 point-of-care test in an oral and maxillofacial surgery clinic: a pilot study.

OBJECTIVES: Matrix metalloproteinases are enzymes that participate in numerous inflammatory responses and have been targeted as biomarkers in numerous pathologic states. The detection of active matrix metalloproteinase-8 (aMMP-8) using a mouthrinse point-of-care test (POCT) has emerged as a diagnostic marker for periodontitis and other systemic inflammatory states. The objective of this pilot study was to assess the applicability of aMMP-8 POCT in an oral and maxillofacial surgery clinic and to evaluate the relationship between aMMP-8 levels and different patient groups. MATERIALS AND METHODS: aMMP-8 POCT samples were collected from patients in an oral and maxillofacial surgery clinic during a one-month period. aMMP-8 levels were analyzed using a chairside lateral-flow immunotest and a digital reader. Clinically relevant patient variables were collected and descriptively evaluated. aMMP-8 levels over 20 ng/ml were considered to be elevated. RESULTS: A total of 115 patients were interviewed of which 112 agreed to the test (97.4%). Elevated aMMP-8 levels were observed in 58 (51.8%) patients. Bone loss was noted in 75 (67.0%) patients. Of these patients, aMMP-8 levels were elevated in 47 (62.7%) patients. Patients at an increased risk of infection had 35.5% higher aMMP-8 values on average compared to patients with no prior illnesses. CONCLUSION: aMMP-8 POCT provides a non-invasive and reliable method for measuring aMMP-8 levels. Future studies are warranted to assess the clinical relevance between elevated aMMP-8 levels and specific patient groups. CLINICAL RELEVANCE: The rapid availability of the test score allows an immediate impact on treatment planning.

Characteristics of Associated Injuries in Children and Teenagers With Craniofacial Fractures.

The incidence of pediatric craniofacial fractures and heterogeneity of fractures is known to increase with age. This study aimed to determine the occurrence of associated injuries (AIs) to craniofacial fractures and identify differences in patterns of and predictors for AIs in children and teenagers. A 6-year retrospective cross-sectional cohort study was designed and implemented. The study population included 397 patients aged 19 years or less diagnosed with craniofacial fracture at Helsinki University Hospital from 2013 to 2018. Boys (71.0%) and teenagers (64.7%) were predominated. Associated injuries were more common in teenagers than children. Teenagers had more often AI in 2 or more organ systems. Assault and intoxication by alcohol were observed only in teenagers and predominantly boys. A total of 27.0% of all patients sustained AIs. In 18.1%, brain injury was reported. In children, motor vehicle accident (MVA) was an independent predictor for AI. In teenagers, independent predictors for AI were female sex, isolated cranial fracture, combined cranial fracture, and high-energy trauma mechanism. Injury patterns and AI related to craniofacial fractures in the pediatric population are age-specific, requiring multidisciplinary collaboration in the diagnosis, treatment, and follow-up of such trauma. Predictors for AIs increase in complexity with age, and the role of sex as a predictor is evident in teenagers.

Maxillofacial injuries among ice hockey players: a retrospective study from a Finnish trauma Centre.

OBJECTIVE: Ice hockey players are at risk of a variety of injuries. In our investigation, we aimed to evaluate the types of facial fractures, injury mechanisms and need for surgical intervention in professional and recreational ice hockey players. MATERIAL AND METHODS: This retrospective study included all patients presenting to a tertiary trauma centre with any ice hockey-related facial fracture during the period from January 2013 to July 2020. The primary outcome variable was the need for surgical treatment, and the primary predictor variable was the injury mechanism. Demographic and clinically relevant variables were statistically evaluated and presented. RESULTS: Of 66 total patients, the most frequent fracture type was isolated mandible fracture (56.1%). Males were overrepresented (98.5%) in the patient population. Puck strikes were the most common mechanism of injury (74.2%). Surgical intervention was performed in nearly half of the patients (48.5%), and was significantly more common in younger patients (p = 0.006). Associated dental injuries were present in 27.3% of the cases and they were significantly associated with puck strikes (p = 0.027). CONCLUSIONS: Mandible fractures and puck strikes, the most common injury site and fracture mechanism respectively, sustained by ice-hockey players required surgical intervention in the majority of cases.

Treatment with Soluble Activin Type IIB Receptor Ameliorates Ovariectomy-Induced Bone Loss and Fat Gain in Mice.

INTRODUCTION: In postmenopausal osteoporosis, hormonal changes lead to increased bone turnover and metabolic alterations including increased fat mass and insulin resistance. Activin type IIB receptors bind several growth factors of the TGF-ß superfamily and have been demonstrated to increase muscle and bone mass. We hypothesized that ActRIIB-Fc treatment could improve bone and muscle mass, inhibit fat accumulation, and restore metabolic alterations in an ovariectomy (OVX) model of postmenopausal osteoporosis. MATERIALS AND METHODS: Female C57Bl/6 N mice were subjected to SHAM or OVX procedures and received intraperitoneal injections of either PBS or ActRIIB-Fc (5 mg/kg) once weekly for 7 weeks. Glucose and insulin tolerance tests (GTT and ITT, respectively) were performed at 7 and 8 weeks, respectively. Bone samples were analyzed with micro-computed tomography imaging, histomorphometry, and quantitative RT-PCR. RESULTS: Bone mass decreased in OVX PBS mice compared to the SHAM PBS group but ActRIIB-Fc was able to prevent these changes as shown by µCT and histological analyses. This was due to decreased osteoclast numbers and function demonstrated by histomorphometric and qRT-PCR analyses. OVX induced adipocyte hypertrophy that was rescued by ActRIIB-Fc, which also decreased systemic adipose tissue accumulation. OVX itself did not affect glucose levels in GTT but ActRIIB-Fc treatment resulted in impaired glucose clearance in both SHAM and OVX groups. OVX induced mild insulin resistance in ITT but ActRIIB-Fc treatment did not affect this. CONCLUSION: Our results reinforce the potency of ActRIIB-Fc as a bone-enhancing agent but also bring new insight into the metabolic effects of ActRIIB-Fc in normal and OVX mice.

Are the Elderly With Maxillofacial Injuries at Increased Risk of Associated Injuries?

PURPOSE: As the geriatric population continues to increase, more elderly patients with maxillofacial injuries are encountered in emergency rooms. It can be hypothesized that advanced age increases the risk of associated injuries (AIs). The purpose of the study was to estimate the frequency of AI and measure the association between age and risk for AI among a sample of patients with facial fractures. METHODS: A retrospective cohort study was designed and implemented. The study sample comprised patients aged 18 years or older who presented to the Töölö Trauma Centre, Helsinki University Hospital, Finland, between 2013 and 2018 for diagnosis and treatment of facial fractures. The primary outcome variable was the presence or absence of AI. AI was defined as any major injury outside the facial region, including injuries to brain, major vessels, internal organs or respiratory organs, and fractures. Secondary outcome variables were affected organ system (classified as brain, cranial bone, neck, upper extremity, lower extremity, chest, spine, and abdomen), number of affected organ systems (classified as 1 and ≥2), need for intensive care, and mortality. The primary predictor variable was age (adults vs elderly). Controlled variables were sex, mechanism of trauma, intoxication by alcohol, and type of facial fracture. Descriptive statistics, univariable, and multivariable logistic regression analysis were executed to measure the association between age groups and AI. P value less than .05 was set as the threshold for statistical significance. RESULTS: Of the total 2,682 patients, 1,931 (72.0%) were adults, and 751 (28.0%) were elderly. Elderly had a 1.6-fold risk (95% confidence interval [CI], 1.5-1.8; P < .001) of AIs as compared with adults. Moreover, after adjusting for mechanism of trauma and type of facial fracture, elderly had 1.8 times greater odds for injuries to 2 or more organ systems (95% CI, 1.3-2.5; P < .001), 2.2 times greater odds for brain injuries (95% CI, 1.6-2.9; P < .001), 2.3 times greater odds for neck injuries (95% CI, 1.5-3.6; P < .001), and 6.8 times greater odds for mortality (95% CI, 2.9-15.6; P < .001). CONCLUSION: Elderly patients have AIs significantly more frequently than younger adults. Age-specific features should be taken into consideration in the multiprofessional evaluation and treatment of facial fracture patients.

"A" stands for airway - Which factors guide the need for on-scene airway management in facial fracture patients?

BACKGROUND: Numerous guidelines highlight the need for early airway management in facial trauma patients since specific fracture patterns may induce airway obstruction. However, the incidence of these hallmark injuries, including flail mandibles and posterior displacement of the maxilla, is contentious. We aim to evaluate specific trauma-related variables in facial fracture patients, which affect the need for on-scene versus in-hospital airway management. METHODS: This retrospective cohort study included all patients with any type of facial fracture, who required early airway management on-scene or in-hospital. The primary outcome variable was the site of airway management (on-scene versus hospital) and the main predictor variable was the presence of a traumatic brain injury (TBI). The association of fracture type, mechanism, and method for early airway management are also reported. Altogether 171 patients fulfilled the inclusion criteria. RESULTS: Of the 171 patients included in the analysis, 100 (58.5) had combined midfacial fractures or combination fractures of facial thirds. Altogether 118 patients (69.0%) required airway management on-scene and for the remaining 53 patients (31.0%) airway was secured in-hospital. A total of 168 (98.2%) underwent endotracheal intubation, whereas three patients (1.8%) received surgical airway management. TBIs occurred in 138 patients (80.7%), but presence of TBI did not affect the site of airway management. Younger age, Glasgow Coma Scale-score of eight or less, and oro-naso-pharyngeal haemorrhage predicted airway management on-scene, whereas patients who had fallen at ground level and in patients with facial fractures but no associated injuries, the airway was significantly more often managed in-hospital. CONCLUSIONS: Proper preparedness for airway management in facial fracture patients is crucial both on-scene and in-hospital. Facial fracture patients need proper evaluation of airway management even when TBI is not present.

Sports-based distribution of facial fractures - findings from a four-season country.

OBJECTIVE: The aim of this study was to elucidate the relationship between injury mechanisms and sports-related facial fractures, and to evaluate the changes in incidence rates of facial fractures sustained in sports-related events in a 30-year period. MATERIAL AND METHODS: This retrospective cohort study included all patients sports-related facial fractures admitted to a tertiary trauma centre during 2013-2018. Specific fracture types, sports, injury mechanisms as well as patient- and injury related variables are presented. The results underwent evaluated statistically with logistic regression analysis. RESULTS: Facial fractures occurred most frequently while playing ice hockey and football. Unilateral zygomatic-maxillary-orbital and isolated mandibular fractures accounted for 74.2% of all fracture types. In total, 99 patients (46.5%) required surgical intervention for their facial injuries. About 12.7% of patients sustained associated injuries in addition to facial fractures. Overall, the number of sports-related facial fractures has increased during the last three decades mostly due to the surging rates of ice hockey- and football-related facial fractures. CONCLUSIONS: Sport-related facial fractures have markedly increased in different sports disciplines during the past decades. The use of safety gear to protect the facial area should be enforced particularly in ice hockey.

Three-Dimensional Computer-Aided Analysis of 293 Isolated Blowout Fractures - Which Radiological Findings Guide Treatment Decision?

PURPOSE: Our study purpose was to clarify the extent of isolated unilateral orbital blowout fracture in relation to surgical treatment and other factors behind the treatment decision. The specific aim was to determine which computer-aided measurements based on radiological images associate with treatment choice. METHODS: A retrospective cohort study was implemented on patients with an isolated unilateral orbital blowout fracture. Computer-aided measurement of fracture extent was performed. The study variables included treatment as primary outcome (surgical vs nonsurgical), post-traumatic orbital volume difference (mL) compared to contralateral orbit, fracture area (mm2), fracture depth (mm) as predictor variables, and age, sex, injury mechanism, side and site of orbital fracture and positions of recti muscles as explanatory variables. Postoperative outcomes were reported. Logistic regression analysis was used to determine the risk factors for surgery. The statistical significance level was set at P < .05. RESULTS: Of 293 patients, 28.0% received surgical and 72.0% nonsurgical treatment. Volume difference, fracture area and fracture depth predicted surgical outcome (P < .001). In adjusted univariate regression analyses, fractures with moderate and severe displacement of recti muscles were more likely to receive surgical treatment than fractures with mild or no displacement (OR 6.15 and 30.75, respectively, P < .001). Isolated medial wall fractures were significantly less often (OR 0.05, P = .006) and patients with older age (OR 0.97, P = .013) slightly less often treated with surgery. Patients with preoperative symptoms had more often persisting postoperative symptoms than patients without preoperative symptoms. CONCLUSIONS: Positions of the recti muscles are an independent radiological factor guiding orbital blowout fracture treatment decision. The bony fracture extent is a combination of volume difference, fracture area and fracture depth which are strongly correlated to each other. A computer-aided method significantly facilitates the systematic evaluation of bone fragments, and the extent of orbital fractures.

Associated Injuries Are Common Among Patients With Bicycle-Related Craniofacial Fractures.

PURPOSE: Ample evidence exists on the relationship between bicycle injuries and craniofacial fractures. However, as the mechanism behind these injuries is often multifactorial, the presence of associated injuries (AIs) in this study population requires further examination. We hypothesized that patients with craniofacial fracture injured in bicycle accidents are at high risk of sustaining severe AIs, especially those of the head and neck region. PATIENTS AND METHODS: The investigators performed a retrospective study on all patients with bicycle-related craniofacial fracture admitted to a tertiary trauma centre during 2013 to 2018. The predictor variable was defined as any type of craniofacial fracture. The outcome variable was defined as any kind of AI. Other study variables included demographic and injury-related parameters. Variables were analyzed using bivariate and Firth's logistic regression analyses. RESULTS: A total of 407 patients were included in the analysis. Our results revealed that AIs were present in 150 (36.9%) patients; there were multiple AIs in 47 cases. Traumatic brain injuries followed by upper limb injuries were the most frequent AIs. Severe head and neck injuries were present in 20.1% of all patients with craniofacial fracture. AIs were observed in 57.4% of patients with combined midfacial fractures (P < .001). Helmet use had a protective effect against traumatic brain injuries (P < .001). CONCLUSIONS: Our results suggest that AIs are relatively common in this specific patient population. Close co-operation in multidisciplinary trauma centers allowing comprehensive evaluation and treatment can be recommended for patients with bicycle-related craniofacial fracture.

Craniofacial Fractures in Equine-Related Injuries: What Should a Maxillofacial Surgeon Expect?

ABSTRACT: Patients with equine-related injuries (ERI) have high rates of hospitalization and often require surgical treatment. This study aimed to clarify the injury profiles of patients sustaining ERI-related craniofacial fractures and their relationship with other severe head and neck injuries.This retrospective study included all patients with craniofacial fractures admitted to a tertiary trauma center during 2013 to 2018. Out of 3256 patients, a total of 39 patients were included in the study (1.2%). Demographic and clinically relevant variables were reported and statistically evaluated.Males represented only 7.7% of the study population. Isolated facial fractures were over-represented in this study population at 84.6% whereas only 7.7% of patients sustained isolated cranial fractures and 7.7% of patients sustained combined craniofacial fractures, respectively. Surgical intervention for craniofacial fractures was required in 48.7% of patients. In total, 17.9% of patients sustained severe head and neck injuries. Periods of unconsciousness and/or post-traumatic amnesia were seen in 41% of patients. Helmet use could only be confirmed in 17.9% of patients.As trauma mechanisms behind ERI are often multifactorial and patients are at a high risk of sustaining associated injuries, attentive examination, and exclusion of serious life-threatening injuries through a multi-disciplinary approach is imperative for this specific patient population.

Treatment with soluble activin type IIB-receptor improves bone mass and strength in a mouse model of Duchenne muscular dystrophy.

BACKGROUND: Inhibition of activin/myostatin pathway has emerged as a novel approach to increase muscle mass and bone strength. Duchenne muscular dystrophy (DMD) is a neuromuscular disorder that leads to progressive muscle degeneration and also high incidence of fractures. The aim of our study was to test whether inhibition of activin receptor IIB ligands with or without exercise could improve bone strength in the mdx mouse model for DMD. METHODS: Thirty-two mdx mice were divided to running and non-running groups and to receive either PBS control or soluble activin type IIB-receptor (ActRIIB-Fc) once weekly for 7 weeks. RESULTS: Treatment of mdx mice with ActRIIB-Fc resulted in significantly increased body and muscle weights in both sedentary and exercising mice. Femoral µCT analysis showed increased bone volume and trabecular number (BV/TV +80%, Tb.N +70%, P < 0.05) in both ActRIIB-Fc treated groups. Running also resulted in increased bone volume and trabecular number in PBS-treated mice. However, there was no significant difference in trabecular bone structure or volumetric bone mineral density between the ActRIIB-Fc and ActRIIB-Fc-R indicating that running did not further improve bone structure in ActRIIB-Fc-treated mice. ActRIIB-Fc increased bone mass also in vertebrae (BV/TV +20%, Tb.N +30%, P < 0.05) but the effects were more modest. The number of osteoclasts was decreased in histological analysis and the expression of several osteoblast marker genes was increased in ActRIIB-Fc treated mice suggesting decreased bone resorption and increased bone formation in these mice. Increased bone mass in femurs translated into enhanced bone strength in biomechanical testing as the maximum force and stiffness were significantly elevated in ActRIIB-Fc-treated mice. CONCLUSIONS: Our results indicate that treatment of mdx mice with the soluble ActRIIB-Fc results in a robust increase in bone mass, without any additive effect by voluntary running. Thus ActRIIB-Fc could be an attractive option in the treatment of musculoskeletal disorders.

The complex role of Rcor2: Regulates mesenchymal stromal cell differentiation in vitro but is dispensable in vivo.

Recent research has revealed several important pathways of epigenetic regulation leading to transcriptional changes in bone cells. Rest Corepressor 2 (Rcor2) is a coregulator of Lysine-specific histone demethylase 1 (Lsd1), a demethylase linked to osteoblast activity, hematopoietic stem cell differentiation and malignancy of different neoplasms. However, the role of Rcor2 in osteoblast differentiation has not yet been examined in detail. We have previously shown that Rcor2 is highly expressed in mesenchymal stromal cells (MSC) and particularly in the osteoblastic lineage. The role of Rcor2 in osteoblastic differentiation in vitro was further characterized and we demonstrate here that lentiviral silencing of Rcor2 in MC3T3-E1 cells led to a decrease in osteoblast differentiation. This was indicated by decreased alkaline phosphatase and von Kossa stainings as well as by decreased expression of several osteoblast-related marker genes. RNA-sequencing of the Rcor2-downregulated MC3T3-E1 cells showed decreased repression of Rcor2 target genes, as well as significant upregulation of majority of the differentially expressed genes. While the heterozygous, global loss of Rcor2 in vivo did not lead to a detectable bone phenotype, conditional deletion of Rcor2 in limb-bud mesenchymal cells led to a moderate decrease in cortical bone volume. These findings were not accentuated by challenging bone formation by ovariectomy or tibial fracture. Furthermore, a global deletion of Rcor2 led to decreased white adipose tissue in vivo and decreased the capacity of primary cells to differentiate into adipocytes in vitro. The conditional deletion of Rcor2 led to decreased adiposity in fracture callus. Taken together, these results suggest that epigenetic regulation of mesenchymal stromal cell differentiation is mediated by Rcor2, which could thus play an important role in defining the MSC fate.

Occipital condyle fracture-A rare but severe injury in cranial fracture patients.

We clarified occurrence, severity, and associated injuries of occipital condyle fractures (OCFs) in a cranial fracture population. Retrospective data of cranial fracture patients were analyzed. The outcome variable was presence of OCF in cranial fracture patients. Predictor variables were type of associated injury, Glasgow Coma Scale (GCS) value under 6, and death during hospital care. In addition, occurrence of OCF was assessed according to cranial fracture subtypes. Explanatory variables were age, sex, injury mechanism, involvement of alcohol, and high-energy injury. Treatment and outcome of OCFs were analyzed. Of 637 cranial fracture patients, 19 (3.0%) sustained an OCF, eight of whom had no other cranial fractures. In the multivariate adjusted model, increased risk for OCF was detected in patients with cervical injuries (OR 18.66, 95% CI 5.52, 63.12; p < 0.001) and facial fractures (OR 5.99, 95% CI 1.01, 35.45; p = 0.049). Patients with fractures not extending to the skull base were less likely to have OCF (OR 0.01, 95% CI 0.001, 0.25; p = 0.004), and fractures localized solely to the base of the skull offered a protective effect for OCF (OR 0.19, 95% CI 0.06, 0.58; p = 0.003). All OCFs were treated non-operatively with a cervical collar without complications. OCF patients typically sustain other severe injuries, particularly cervical injuries and facial fractures. Careful screening for associated injuries is therefore crucial when examining a patient with OCF. The classification scheme of Mueller et al. seems to be useful in guiding the treatment of OCFs, at least type 1 and 2 fractures.

Cervical spine injuries in facial fracture patients - injury mechanism and fracture type matter.

Evidence supports the notion that craniofacial fractures are significant predictors of cervical spine injuries (CSIs), but some debate remains on the injury mechanism of co-existing CSIs in craniofacial fractures and the relationship between CSI and specific facial fractures. In this retrospective study, we aim to assess the incidence rates of specific facial fracture types as well as other important variables and their relationship with CSIs. The primary outcome variable, CSI, and several predictor variables, including facial fracture type, were evaluated with logistic regression analyses. Of 2919 patients, the total CSI incidence rate was 3.0%. Rates of CSI in patients with isolated mandibular fractures (OR 0.26 CI 0.10, 0.63; p = 0.006) were lower than those previously reported, whereas isolated nasal fractures were strongly associated with CSI (OR 2.67 CI 1.36, 5.22; p = 0.004). Patients with concomitant cranial injuries were twice as likely to have CSI (OR 2.00, CI 1.22, 3.27; p = 0.006). Even though there is a strong occurrence rate of CSIs in patients with cranial injuries, clinicians should be aware that patients presenting with isolated facial fractures are at significant risk for sustaining CSIs also.

Multiple targets identified with genome wide profiling of small RNA and mRNA expression are linked to fracture healing in mice.

Long-bone fracture is a common injury and its healing process at the fracture site involves several overlapping phases, including inflammation, migration of mesenchymal progenitors into the fracture site, endochondral ossification, angiogenesis and finally bone remodelling. Increasing evidence shows that small noncoding RNAs are important regulators of chondrogenesis, osteogenesis and fracture healing. MicroRNAs are small single-stranded, non-coding RNA-molecules intervening in most physiological and biological processes, including fracture healing. Angiogenin-cleaved 5' tRNA halves, also called as tiRNAs (stress-induced RNAs) have been shown to repress protein translation. In order to gain further understanding on the role of small noncoding RNAs in fracture healing, genome wide expression profiles of tiRNAs, miRNAs and mRNAs were followed up to 14 days after fracture in callus tissue of an in vivo mouse model with closed tibial fracture and, compared to intact bone and articular cartilage at 2 months of age. Total tiRNA expression level in cartilage was only approximately one third of that observed in control D0 bone. In callus tissue, 11 mature 5'end tiRNAs out of 191 tiRNAs were highly expressed, and seven of them were differentially expressed during fracture healing. When comparing the control tissues, 25 miRNAs characteristic to bone and 29 miRNAs characteristic to cartilage tissue homeostasis were identified. Further, a total of 54 out of 806 miRNAs and 5420 out of 18,700 mRNAs were differentially expressed (DE) in callus tissue during fracture healing and, in comparison to control bone. They were associated to gene ontology processes related to mesenchymal tissue development and differentiation. A total of 581 miRNA-mRNA interactions were identified for these 54 DE miRNAs by literature searches in PubMed, thereby linking by Spearman correlation analysis 14 downregulated and 28 upregulated miRNAs to 164 negatively correlating and 168 positively correlating miRNA-mRNA pairs with chondrogenic and osteogenic phases of fracture healing. These data indicated that tiRNAs and miRNAs were differentially expressed in fracture callus tissue, suggesting them important physiological functions during fracture healing. Hence, the data provided by this study may contribute to future clinical applications, such as potential use as biomarkers or as tools in the development of novel therapeutic approaches for fracture healing.

Mesenchymal Cell-Derived Juxtacrine Wnt1 Signaling Regulates Osteoblast Activity and Osteoclast Differentiation.

Human genetic evidence demonstrates that WNT1 mutations cause osteogenesis imperfecta (OI) and early-onset osteoporosis, implicating WNT1 as a major regulator of bone metabolism. However, its main cellular source and mechanisms of action in bone remain elusive. We generated global and limb bud mesenchymal cell-targeted deletion of Wnt1 in mice. Heterozygous deletion of Wnt1 resulted in mild trabecular osteopenia due to decreased osteoblast function. Targeted deletion of Wnt1 in mesenchymal progenitors led to spontaneous fractures due to impaired osteoblast function and increased bone resorption, mimicking the severe OI phenotype in humans with homozygous WNT1 mutations. Importantly, we showed for the first time that Wnt1 signals strictly in a juxtacrine manner to induce osteoblast differentiation and to suppress osteoclastogenesis, in part via canonical Wnt signaling. In conclusion, mesenchymal cell-derived Wnt1, acting in short range, is an essential regulator of bone homeostasis and an intriguing target for therapeutic interventions for bone diseases. © 2019 The Authors. Journal of Bone and Mineral Research Published by Wiley Periodicals, Inc.

Soluble activin type IIB receptor improves fracture healing in a closed tibial fracture mouse model.

Fractures still present a significant burden to patients due to pain and periods of unproductivity. Numerous growth factors have been identified to regulate bone remodeling. However, to date, only the bone morphogenetic proteins (BMPs) are used to enhance fracture healing in clinical settings. Activins are pleiotropic growth factors belonging to the TGF-ß superfamily. We and others have recently shown that treatment with recombinant fusion proteins of activin receptors greatly increases bone mass in different animal models by trapping activins and other ligands thus inhibiting their signaling pathways. However, their effects on fracture healing are less known. Twelve-week old male C57Bl mice were subjected to a standardized, closed tibial fracture model. Animals were divided into control and treatment groups and were administered either PBS control or a soluble activin type IIB receptor (ActRIIB-Fc) intraperitoneally once a week for a duration of two or four weeks. There were no significant differences between the groups at two weeks but we observed a significant increase in callus mineralization in ActRIIB-Fc-treated animals by microcomputed tomography imaging at four weeks. Bone volume per tissue volume was 60%, trabecular number 55% and bone mineral density 60% higher in the 4-week calluses of the ActRIIB-Fc-treated mice (p<0.05 in all). Biomechanical strength of 4-week calluses was also significantly improved by ActRIIB-Fc treatment as stiffness increased by 64% and maximum force by 45% (p<0.05) compared to the PBS-injected controls. These results demonstrate that ActRIIB-Fc treatment significantly improves healing of closed long bone fractures. Our findings support the previous reports of activin receptors increasing bone mass but also demonstrate a novel approach for using ActRIIB-Fc to enhance fracture healing.

Impaired osteoclast homeostasis in the cystatin B-deficient mouse model of progressive myoclonus epilepsy.

Progressive myoclonus epilepsy of Unverricht-Lundborg type (EPM1) is an autosomal recessively inherited disorder characterized by incapacitating stimulus-sensitive myoclonus and tonic-clonic epileptic seizures with onset at the age of 6 to 16 years. EPM1 patients also exhibit a range of skeletal changes, e.g., thickened frontal cranial bone, arachnodactyly and scoliosis. Mutations in the gene encoding cystatin B (CSTB) underlie EPM1. CSTB is an inhibitor of cysteine cathepsins, including cathepsin K, a key enzyme in bone resorption by osteoclasts. CSTB has previously been shown to protect osteoclasts from experimentally induced apoptosis and to modulate bone resorption in vitro. Nevertheless, its physiological function in bone and the cause of the bone changes in patients remain unknown. Here we used the CSTB-deficient mouse (Cstb-/-) model of EPM1 to evaluate the contribution of defective CSTB protein function on bone pathology and osteoclast differentiation and function. Micro-computed tomography of hind limbs revealed thicker trabeculae and elevated bone mineral density in the trabecular bone of Cstb-/- mice. Histology from Cstb-/- mouse bones showed lower osteoclast count and thinner growth plates in long bones. Bone marrow-derived osteoclast cultures revealed lower osteoclast number and size in the Cstb-/- group. Cstb-/- osteoclasts formed less and smaller resorption pits in an in vitro assay. This impaired resorptive capacity was likely due to a decrease in osteoclast numbers and size. These data imply that the skeletal changes in Cstb-/- mice and in EPM1 patients are a result of CSTB deficiency leading to impaired osteoclast formation and consequently compromised resorptive capacity. These results suggest that the role of CSTB in osteoclast homeostasis and modulation of bone metabolism extends beyond cathepsin K regulation.