Periosteal Response Research Articles

Effects of Aging on the Immune and Periosteal Response to Fracture in Mice.

Aging predisposes individuals to reduced bone mass and fragility fractures, which are costly and linked to high mortality. Understanding how aging affects fracture healing is essential for developing therapies to enhance bone regeneration in older adults. During the inflammatory phase of fracture healing, immune cells are recruited to the injury site as periosteal skeletal stem/progenitor cells (pSSPCs) rapidly proliferate and differentiate into osteochondral lineages, allowing for fibrocartilaginous callus formation and complete bone healing. Irrespective of age, how periosteal mesenchymal and immune cells interact during early fracture healing is incompletely understood, limiting our ability to potentially modulate these processes. To address this, we directly analyzed, in parallel, at a single-cell level, isolated murine CD45(+) and CD45(-) periosteal cells dissected from intact and fractured bones, collected three days after injury. Through comprehensive analysis, corroborated by bulk RNA-sequencing, flow cytometry, and histology, we found aging decreases pSSPCs proliferative, marked by a reduced expression of genes required for callus formation and an increased senescence signature. We found that the chemokine Cxcl9 was highly upregulated in aged intact Prrx1+ pSSPCs, predicted to interact with other pSSPCs directly, and associated with increased recruitment of CD8+ T cells at the fracture site three days after injury. Cell-to-cell communication analysis provided insight into the complexity of interactions among the many cell types regulating fracture healing and the impact of aging on these processes. Together, these results provide insight into age-induced alterations in fracture healing, informing the development of improved therapeutic approaches for fragility fractures.

Initial therapeutic evidence of a borosilicate bioactive glass (BSG) and Fe3O4 magnetic nanoparticle scaffold on implant-associated Staphylococcal aureus bone infection

Implant-associated Staphylococcus aureus (S. aureus) osteomyelitis is a severe challenge in orthopedics. While antibiotic-loaded bone cement is a standardized therapeutic approach for S. aureus osteomyelitis, it falls short in eradicating Staphylococcus abscess communities (SACs) and bacteria within osteocyte-lacuna canalicular network (OLCN) and repairing bone defects. To address limitations, we developed a borosilicate bioactive glass (BSG) combined with ferroferric oxide (Fe3O4) magnetic scaffold to enhance antibacterial efficacy and bone repair capabilities. We conducted comprehensive assessments of the osteoinductive, immunomodulatory, antibacterial properties, and thermal response of this scaffold, with or without an alternating magnetic field (AMF). Utilizing a well-established implant-related S. aureus tibial infection rabbit model, we evaluated its antibacterial performance in vivo. RNA transcriptome sequencing demonstrated that BSG + 5%Fe3O4 enhanced the immune response to bacteria and promoted osteogenic differentiation and mineralization of MSCs. Notably, BSG + 5%Fe3O4 upregulated gene expression of NOD-like receptor and TNF pathway in MSCs, alongside increased the expression of osteogenic factors (RUNX2, ALP and OCN) in vitro. Flow cytometry on macrophage exhibited a polarization effect towards M2, accompanied by upregulation of anti-inflammatory genes (TGF-β1 and IL-1Ra) and downregulation of pro-inflammatory genes (IL-6 and IL-1β) among macrophages. In vivo CT imaging revealed the absence of osteolysis and periosteal response in rabbits treated with BSG + 5%Fe3O4 + AMF at 42 days. Histological analysis indicated complete controls of SACs and bacteria within OLCN by day 42, along with new bone formation, signifying effective control of S. aureus osteomyelitis. Further investigations will focus on the in vivo biosafety and biological mechanism of this scaffold within infectious microenvironment.

The oldest fossil hominin from Italy: Reassessment of the femoral diaphysis from Venosa-Notarchirico in its Acheulean context

Venosa-Notarchirico is a musealized Lower Paleolithic site in southern Italy (Basilicata), where a human femoral shaft was discovered in 1985. The fossil specimen can be evaluated in the new light of excavations started in 2016, which provide a more updated and extensive picture of the site, including the crucial Ar/Ar date of 661-614 ka for the human specimen. This makes the fossil diaphysis from Venosa-Notarchirico (Vn-H1) the oldest fossil hominin found so far in the Italian peninsula, associated with the earliest evidence of genuine Acheulean in Europe. In this paper, we report a comparative morphometric analysis of this femur, as well as a paleopathological reappraisal of the periosteal alteration that affects the specimen, supported by an unpublished histological analysis. Vn-H1 represents the proximal two-thirds of a right femur lacking the epiphyseal region. We argue it belonged to an immature individual, possibly a juvenile (late adolescent). Its features suggest that the specimen may refer to an archaic (i.e., non-modern) human species, also showing morphological differences compared to fossil samples of the Neanderthal lineage. We also support the identification of a pathological condition affecting Vn-H1, particularly evident in some preserved portions of the mid-shaft as described here. Its etiology is discussed after differential diagnosis, which led us to suggest an alteration of inflammatory origin, viewed as a nonspecific periosteal response. This pathology may have been roughly concomitant with the death of the individual.

Sfrp4 is required to maintain Ctsk-lineage periosteal stem cell niche function.

We have previously reported that the cortical bone thinning seen in mice lacking the Wnt signaling antagonist Sfrp4 is due in part to impaired periosteal apposition. The periosteum contains cells which function as a reservoir of stem cells and contribute to cortical bone expansion, homeostasis, and repair. However, the local or paracrine factors that govern stem cells within the periosteal niche remain elusive. Cathepsin K (Ctsk), together with additional stem cell surface markers, marks a subset of periosteal stem cells (PSCs) which possess self-renewal ability and inducible multipotency. Sfrp4 is expressed in periosteal Ctsk-lineage cells, and Sfrp4 global deletion decreases the pool of PSCs, impairs their clonal multipotency for differentiation into osteoblasts and chondrocytes and formation of bone organoids. Bulk RNA sequencing analysis of Ctsk-lineage PSCs demonstrated that Sfrp4 deletion down-regulates signaling pathways associated with skeletal development, positive regulation of bone mineralization, and wound healing. Supporting these findings, Sfrp4 deletion hampers the periosteal response to bone injury and impairs Ctsk-lineage periosteal cell recruitment. Ctsk-lineage PSCs express the PTH receptor and PTH treatment increases the % of PSCs, a response not seen in the absence of Sfrp4. Importantly, in the absence of Sfrp4, PTH-dependent increase in cortical thickness and periosteal bone formation is markedly impaired. Thus, this study provides insights into the regulation of a specific population of periosteal cells by a secreted local factor, and shows a central role for Sfrp4 in the regulation of Ctsk-lineage periosteal stem cell differentiation and function.

Bacillus Calmette-Guérin Vaccine-Related Osteomyelitis in Immunocompetent Children in Saudi Arabia: A Narrative Review.

The Bacillus Calmette-Guérin (BCG) vaccine is the most frequently used live-attenuated vaccine worldwide. Since 2002, two BCG vaccination strains, Pasteur 1173 P2 and Tokyo 172-1, have been the mainstay of Saudi Arabian healthcare. In 2005, the Danish 1331 strain was first used as the principal strain in clinical trials. Children can develop osteomyelitis 4-24 months after immunization with the BCG vaccine, an uncommon but serious side effect in immunocompetent children. We conducted this study to review the epidemiology, diagnosis, clinical symptoms, laboratory analyses, imaging features, and management of BCG osteomyelitis in immunocompetent children. Long bone metaphyses and epiphyses are more frequently affected. The diagnosis of BCG osteomyelitis is difficult because the symptoms are vague and subtle, and the duration between presentation and vaccination may range from a few months to a year. Radiography and computed tomography scans for BCG osteomyelitis typically show a devastating lesion with an associated periosteal response. Magnetic resonance imaging frequently reveals a large interosseous abscess indicative of osteomyelitis. There are no current treatment guidelines for BCG osteomyelitis in Saudi Arabia, but antituberculous regimens, particularly isoniazid and rifampicin, have been found to be very effective in previous studies. Although older studies did not favor surgical intervention because of the risk of complications, a few studies performed minor surgical interventions and had good outcomes. As BCG osteomyelitis is an infrequent complication, especially in immunocompetent children, its diagnosis is time-consuming. Therefore, it is critical to inform healthcare workers of this possible complication to make the diagnosis more straightforward and avoid confusion with pyogenic osteomyelitis. As only a few cases have been reported, further studies in Saudi Arabia are required for evidence-based guidelines applicable to actual practice to be established.

Radiological evaluation for effect of NAC on tibia puncture fracture in dogs

The present study used N- acetyl cysteine NAC to study its effects on tibia bone defects in dogs. This study aimed to evaluate the effective use of N- acetylcysteine (NAC) on tibia puncture fracture in dogs. The dogs were divided into three groups (5 dogs for each one): Control group (treated with autogenous cartilage only), treated group 1(treated with autogenous cartilage mixed with NAC), and treated group 2 (treated with autogenous cartilage and NAC orally). Radiological assessment fourteen days postoperatively, there is no evidence of periosteal reaction in the radiological examination in the control group. While the radiological findings revealed evidence of periosteal response at the ridges of the bone gap in treated group one and radiological results showed evidence of more periosteal interaction at the edges of the bone gap in treated group two compared with the group one and control group, and the gap appeared cloudy in color. Twenty-eight days postoperatively showed that the bone gap seemed dark in the shade of bone gap in control groups. Twenty-eight days postoperatively in treated group one, radiographs showed a narrowing in the bone gap diameter as showed by radiological examination.

THE BIOLOGY OF PERIOSTEAL REACTIONS

<h3>BACKGROUND</h3> The periosteum is a thin membrane that covers almost all bony surfaces in the human body. This membrane is attached to the underlying bone through type I collagen fibers known as Sharpey's fibers. The periosteum is organized into an inner cellular layer with significant osteoblastic potential and an outer fibrous layer. This osteoblastic potential can be stimulated by both physiologic processes in growth and fracture repair and by pathologic conditions. The characteristics of the periosteal responses are modulated by factors such as the type of initiating stimulus, age, and anatomic site. <h3>CASE REPORT</h3> Through illustrative cases, we will discuss the biologic bases for periosteal responses and the association of these radiologic presentations with pathophysiologic situations such as in inflammation and malignancy. <h3>DISCUSSION/CONCLUSIONS</h3> This poster will review the gross and cellular anatomy of the periosteal membrane and a range of periosteal responses. An understanding of bone and periosteal biology serves as a foundation for a radiologist to recognize patterns of periosteal responses and to decipher the causative stimuli.

Imaging Method for Osteosarcoma Diagnosis and Clinical Staging Information Optimization

In order to better assist clinicians in the diagnosis and treatment of osteosarcoma, and our understanding of the advantages and disadvantages of different examination techniques of DR, CT and MRI, this article collects the pathological diagnosis of the PACS Medical system of Liaocheng People’s Hospital 2015 to 2018. 130 patients with osteosarcoma and imaging examination data, retrospectively analyzed the diagnostic and clinical staging information contained in DR, CT and MRI examination data of osteosarcoma patients, and detected the diagnosis and clinical staging information of osteosarcoma by comparing various examination methods ability to obtain the optimal imaging examination method that can provide complete diagnosis and clinical staging information of osteosarcoma, and is recommended as a routine clinical examination program. Finally, we conclude that: DR, CT, and MRI examinations have no significant differences in the detection capacity of osteosarcoma bone destruction, periosteal response, and periosteal triangle; MRI has less ability to detect tumor bone than DR and CT; DR has soft tissue. The ability to detect masses is inferior to CT and MRI. Among the single DR, CT or MRI examinations, CT examinations have the best comprehensive detection ability for all imaging diagnostic signs of osteosarcoma. MR examination has the best comprehensive display of clinical staging information such as infiltration range and infiltration boundary of osteosarcoma. Combined DR, CT, and MRI examinations are optimized imaging procedures that provide complete osteosarcoma diagnosis and clinical staging information.

Langerhans cell histiocytosis of the shoulder girdle, pelvis and extremities: a review of radiographic and MRI features in 85 cases.

To describe the radiographic and MRI features of histologically proven Langerhans cell histiocytosis (LCH) of the bone. A retrospective review of the radiographic and MRI features of 85 histologically proven cases of skeletal LCH over a 12-year period. Clinical data recorded included age, gender and location. Radiographic features evaluated included Lodwick grading, cortical/periosteal response and matrix mineralisation. MRI features assessed included lesion size and T1-weighted signal intensity (T1W SI), nature of margin, hypointense rim, enhancement pattern, bone marrow and soft tissue oedema, soft tissue mass, fluid-fluid levels, the penumbra sign and the budding and bulging signs. The study included 85 patients, 54 males and 31 females with mean age of 13years (range 1-76years). The femur was the commonest bone involved (38.8%), followed by the scapula (9.4%), clavicle (8.2%), ilium (8.2%) and ischium (8.2%). The mean maximal lesion size was 40mm (range 16-85mm). The commonest radiographic appearance was of a lytic lesion with no appreciable sclerotic rim, an intact expanded cortex and either absent or laminated periosteal response. MRI demonstrated a hypointense rim (41.5%), the budding (31.7%) and bulging (36.6%) signs, eccentric extra-osseous mass (42.7%), prominent bone marrow (95.3%) and soft tissue oedema (84.1%). Rarer features included haemorrhage (2.4%), the penumbra sign (3.5%) and fluid-fluid levels (2.4%). Thirteen of 25 post-contrast studies showed peripheral/rim enhancement with central necrosis. LCH classically presents as a moderately aggressive lytic bone lesion on radiography, with prominent reactive bone and soft tissue oedema being a characteristic feature on MRI.

The differentiation between aneurysmal bone cyst and telangiectatic osteosarcoma: a clinical, radiographic and MRI study

Aneurysmal bone cyst (ABC) and telangiectatic osteosarcoma (TOS) share several clinical and imaging features, including young presentation, long bone involvement, lytic appearance on radiography and fluid-fluid levels on MRI. Therefore, they may be difficult to differentiate. The aim of this study is to identify clinical, radiological and MRI features which aid differentiation of the two lesions. Retrospective review of all histologically confirmed ABC and TOS over an 11-year period. Data recorded include age at presentation, sex, skeletal location and various radiographic and MRI features. This retrospective study included 183 patients, 92 males and 91 females. Mean age at presentation of 18.4years (range 1-70years); 152 cases of ABC and 31 TOS. No significant difference between age and sex. TOS was significantly less likely to involve the axial skeleton; no difference related to location within the bone. Radiographic findings significantly favouring ABC included a less aggressive pattern of bone destruction, a purely lytic appearance, an expanded but intact cortex, no periosteal response and no soft tissue mass. MRI features significantly favouring ABC included smaller tumour size (maximum mean dimension 46mm compared to 95mm for TOS), absence of soft tissue mass, > 2/3 of the lesion filled with fluid levels and thin septal enhancement following contrast. Several radiographic and MRI features aid in the differentiation between ABC and TOS. Lesions with a geographic Type 1A or IB pattern of bone destruction which are completely filled with FFLs on MRI can confidently be diagnosed as ABC.

A PDGFRβ-PI3K signaling axis mediates periosteal cell activation during fracture healing.

Insufficient and delayed fracture healing remain significant public health problems with limited therapeutic options. Phosphoinositide 3-kinase (PI3K) signaling, a major pathway involved in regulation of fracture healing, promotes proliferation, migration, and differentiation of osteoprogenitors. We have recently reported that knock-in mice with a global increase in PI3K signaling (gCblYF) show enhanced femoral fracture healing characterized by an extraordinary periosteal response to injury. Interestingly, of all growth factor receptors involved in fracture healing, PI3K directly binds only to PDGFR. Given these findings, we hypothesized a PDGFR-PI3K interaction is necessary for mediating robust periosteal cell activation following fracture. In this study, we isolated primary periosteal cells from gCblYF mice to analyze cross-talk between the PDGFRβ and PI3K signaling pathways. We found PDGFRβ signaling contributes to robust Akt phosphorylation in periosteal cells in comparison with other growth factor signaling pathways. Additionally, we performed femoral fractures on gCblYF mice with a conditional removal of PDGFRβ in mesenchymal progenitors using inducible alpha smooth muscle actin (αSMA) CreERT2 mice. Our studies showed that depletion of PDGFRβ signaling within these progenitors in the early phase of fracture healing significantly abrogates PI3K-mediated periosteal activation and proliferation three days after fracture. Combined, these results suggest that PDGFRβ signaling through PI3K is necessary for robust periosteal activation in the earliest phases of fracture healing.

Changes in the Structure and Mechanical Properties of the Bone after Puncture Cryoablation: Experimental Study

Purpose of the study — to evaluate possible impact of cryoablation on a healthy bone and to identify probable causes of postoperative fractures.Materials and Methods. The authors performed cryoablation of the femur in the experiment on 8 mature rabbits of Soviet Chinchilla (SC) breed with a follow up for up to two months. Anitrogenous cryoprobe of 1.5 mm in diameter was introduced into the femur through a perforation hole. The bone was completely frozen up to -180°С in two cycles with continuous thermometry. Pathomorfological examinations were performed after 7 and 55 days along with assessment of bone hardness. Preparation of material stipulated sawing the bone at the fracture site along the bone axis. One half-bone was used for histological examination, and another one — for measuring mechanical properties by local pressing of a diamond indenter onto the bone at certain applied force. The distance between measurement points along the bone was 250 μm. Statistical processing included variance significance analysis using t-test.Results. The authors reported bone fractures at the site of cryodestruction in all animals in one week after the procedure. Statistical analysis of the measurements and histological examination demonstrated that freezing of the entire bone diameter up to -180°С results in its complete destruction. Strength reduction around the fracture site corresponded to the temperature distribution area in the range from -9ºС to -15ºС. However, areas of cooling below -40ºС exhibited some bone segments with normal hardness. Mosaic pattern of strength reduction is explained by microcirculation disorders. Histology confirmed thrombosis of intraosseous blood vessels in the area of cryotherapy. The first focal signs of osteomalacia emerged by the end of the first week after cryoablation. Subsequently, the bone preserved its regenerative properties, but by the end of the second month after the procedure the histogenesis was still not completed and the bone did not regain its strength.Conclusion. The authors believe that a limited number of cases, the specific features of the angioarchitecture of animal bones and their ability to produce a heavy periosteal response do not allow to apply obtained quantitative outcomes of the present study to clinical situations. However, complete freezing of the entire bone diameter inevitably results in fracture formation.

Periosteal Reactions and Its Significance

The periosteum covering the bony cortex consists of an outer and inner layer. The inner layer of the periosteum is the site of separation and subperiosteal haemorrhage because it's less adherent. When the bone is insulted, it results in periosteal reaction. There are different variables that affect the periosteal response appearance like the rapidity of the phase of the disease, intensity, duration of the injury and age of the patient. The appearance and the pattern of periosteal reaction aids the imaging characterization of bone lesions and assesses their aggressiveness and their differential diagnosis, but not specific for a particular diagnosis. This article outlines the forms and patterns of periosteal responses that can guide to the diagnosis of underlying disease process.

Conventional Radiography and MRI Diagnosis of Bone Tumors Developed at the Knee

Abstract Introduction. It is known that bone tumors have a predilection to develop for a certain skeletal bone segment. Also, bone tumors have a predilection for certain age groups. The knee is a common site for bone tumors. Purpose. Presentation of diagnostic parameters of conventional radiography as the first technique in the detection and characterization of bone tumors developed at the knee level and the criteria for differentiation of the malignant substrate from the benign (the type of bone destruction, the type of periosteal response, poorly defined margins) one. The value of MRI is also presented and illustrated as a unique imaging technique that allows the direct visualization of bone marrow with high spatial resolution for local staging of bone tumors. Material and method. The present study aimed to investigate the radiographic and MRI imaging characteristics of bone tumors developed at the knee joint, which were retrospectively analyzed (October 2007 and November 2017) in a selected group of 91 patients. The limit of age between 11 and 67 years, 73(70%) men, 18 (30%) women. Examination protocol: complete clinical examination, radiographic knee examination in anteroposterior and lateral incidents. MRI standard protocol, native, and post paramagnetic contrast. Results. Conventional Radiographic and MRI have been detected and characterized a number of 55 (67%) primary malignant bone tumors confirmed by histopathological diagnosis, ranging from 8 histopathological types and 37 (33%) cases of benign tumors with 9 histopathological types. Conclusions. Radiological examination is the first investigation in the evaluation of knee bone tumors, suggesting the malignant nature expressed by the badly defined margin, bone destruction, discontinuous peristaltic reaction, and extension to the soft parts. MRI is a unique imaging technique that allows direct visualization of bone marrow with high spatial resolution and best tool for local staging of bone tumors.

The research progress of periosteal histologic features and response mode

One of the biggest pending issues in clinical medicine is the bone injury caused by trauma, cancer, deformity, etc. Research suggests that the periosteum around epiphysis is a dense connective issue membrane. It has a dynamic structure and not looks like what it is seemingly. It provides favorable living environment for stem cells with regeneration potential. Besides, it also plays an important role in bone nutrition, cell supply, pain sensation and growth repair. Therefore, deep study in periosteum structure and function, as well as in periosteum response mode will benefit the clinical application of bone defect repair. Key words: Bone injury; Bone defect repair; Osteogenesis; Periosteum; Periosteal reaction

Microdamage induced by in vivo Reference Point Indentation in mice is repaired by osteocyte-apoptosis mediated remodeling

Reference Point Indentation (RPI) is a technology that is designed to measure mechanical properties that relate to bone toughness, or its ability to resist crack growth, in vivo. Independent of the mechanical parameters generated by RPI, its ability to initiate and propagate microcracks in bone is itself an interesting issue. Microcracks have a crucial biological relevance in bone, are central to its ability to maintain homeostasis. In healthy tissues, a process of targeted remodeling routinely repairs microcracks in a process mediated by osteocyte apoptosis. However, in diseases such as osteoporosis this process becomes deficient and microcracks can accumulate. Small animal models such are crucial for the study of such diseases, but it is technically challenging to create microcracks in these animals without causing outright failure. Therefore we sought to use RPI as a focal microdamage placement tool, to introduce microcracks to mouse long bones and investigate whether the same pathway mediates their repair as that described in other microdamage systems. We first used SEM to confirm that microdamage is formed RPI in mouse bone. Then, since RPI is carried out transdermally, we sought to confirm that no periosteal response occurred at the indented region. We then used a pan-caspase inhibitor (QVD) to determine whether osteocyte apoptosis plays the same pivotal role in microdamage repair in this model, as has been demonstrated in others. In conclusion, we validated that the microdamage-apoptosis-remodeling pathway is maintained with this method of microdamage induction in mice. We show that RPI can be used as a reliable and reproducible microdamage placement tool in living mouse long bones without inducing a periosteal response. We also used a caspase inhibitor, to block osteocyte apoptosis and thus abrogate the remodeling response to microdamage. This demonstrates that the well described microdamage repair system, involving targeted remodeling mediated by osteocyte apoptosis, is conserved in this novel mouse model using an in vivo RPI loading system.

Loss of Cbl-PI3K interaction modulates the periosteal response to fracture by enhancing osteogenic commitment and differentiation

The periosteum contains multipotent skeletal progenitors that contribute to bone repair. The signaling pathways regulating the response of periosteal cells to fracture are largely unknown. Phosphatidylinositol-3 Kinase (PI3K), a prominent lipid kinase, is a major signaling protein downstream of several factors that regulate osteoblast differentiation. Cbl is an E3 ubiquitin ligase and a major adaptor protein that binds to the p85 regulatory subunit and modulates PI3K activity. Substitution of tyrosine 737 to phenylalanine (Y737F) in Cbl abolishes the interaction between Cbl and p85 subunit without affecting the Cbl's ubiquitin ligase function. Here, we investigated the role of PI3K signaling during the very early stages of fracture healing using OsterixRFP reporter mice. We found that the absence of PI3K regulation by Cbl resulted in robust periosteal thickening, with increased proliferation of periosteal cells. While the multipotent properties of periosteal progenitors to differentiate into chondrocytes and adipocytes did not change, osteogenic differentiation in the absence of Cbl-PI3K interaction was highly augmented. The increased stability and nuclear localization of Osterix observed in periosteal cells lacking Cbl-PI3K interaction may explain this enhanced osteogenic differentiation since the expression of Osterix transcriptional target genes including osteocalcin and BSP are increased in YF cells. Overall, our findings highlight a hitherto unexplored and novel role for Cbl and PI3K in modulating the osteogenic response of periosteal cells during the early stages of fracture repair.

Loss of scleraxis in mice leads to geometric and structural changes in cortical bone, as well as asymmetry in fracture healing.

Scleraxis (Scx) is a known regulator of tendon development, and recent work has identified the role of Scx in bone modeling. However, the role of Scx in fracture healing has not yet been explored. This study was conducted to identify the role of Scx in cortical bone development and fracture healing. Scx green fluorescent protein-labeled (ScxGFP) reporter and Scx-knockout (Scx-mutant) mice were used to assess bone morphometry and the effects of fracture healing on Scx localization and gene expression, as well as callus healing response. Botulinum toxin (BTX) was used to investigate muscle unloading effects on callus shape. Scx-mutant long bones had structural and mechanical defects. Scx gene expression was elevated and bmp4 was decreased at 24 h after fracture. ScxGFP+ cells were localized throughout the healing callus after fracture. Scx-mutant mice demonstrated disrupted callus healing and asymmetry. Asymmetry of Scx-mutant callus was not due to muscle unloading. Wild-type littermates (age matched) served as controls. This is the first study to explore the role of Scx in cortical bone mechanics and fracture healing. Deletion of Scx during development led to altered long bone properties and callus healing. This study also demonstrated that Scx may play a role in the periosteal response during fracture healing.-McKenzie, J. A., Buettmann, E., Abraham, A. C., Gardner, M. J., Silva, M. J., Killian, M. L. Loss of scleraxis in mice leads to geometric and structural changes in cortical bone, as well as asymmetry in fracture healing.

In vitro rabbit periosteal cell proliferation and response to stimulus in microfluidic culture system

In vitro rabbit periosteal cell proliferation and response to stimulus in microfluidic culture system

Tumeur d’Ewing de localisation mandibulaire. À propos d’un cas

Ewing sarcoma is the second most common primary malignant bone cancer in children and adolescents. Clinical presentation is usually dominated by local pain and a palpable mass. These symptoms justify imaging investigations: the first one, when an osseous lesion is suspected, is usually a conventional radiograph in two planes. Ewing sarcoma appears as a poorly defined osteolytic lesion that may frequently be associated with cortical erosion or laminar periosteal response ("onion skin"). However, this aspect is not pathognomonic and the definitive diagnosis is made by biopsy. Absence of pain or an unusual localization can lead to misdiagnosis. We report the case of a 7-year-old boy with Ewing sarcoma located in the mandible with a clinical picture including progressive mandibular swelling but no pain.