Site Of Bone Injury Research Articles

CD90's role in vascularization and healing of rib fractures: insights from Dll4/notch regulation.

Vascularization after rib fracture is a crucial physiological process that is essential for the repair and healing of the rib. Studies have shown that CD90 plays a critical role in regulating rib fracture healing, but the underlying mechanism of its role has not been fully elucidated. CD90 adenovirus knockout mice were used to construct a rib injury model. The bone healing was observed by micro-CT. CD31/EMCN immunofluorescence staining was performed on bone tissue to observe the density of H-shaped and L-shaped blood vessels at the site of bone injury. CD31 and EMCN dual-stained single cells from the rib fracture sites were detected by flow cytometry. The periosteal stem cells transfected with CD90 or Notch1 overexpression and silencing vector were co-cultured with osteoblast MC3T3-E1 in osteogenic induction medium. Moreover, bone microvascular endothelial cells were extracted from the rib injury and co-cultured with the periosteal stem cells transfected with CD90. CCK-8 was used to detect cell viability, RT-qPCR and Western blot were used to detect Notch1, Notch2, Notch3, Notch4, CD31, HIF-1α, CD90, RUNX2, OCN and OPN expression. Alkaline phosphatase (ALP) staining and alizarin red staining were used to observe mineralized nodules. Immunofluorescence staining was used to detect the expression of Dll4, Notch, and CD90 in each group of cells. The angiogenesis experiment was conducted to observe cellular vascular formation. Compared with the Adsh-NC group, the bone healing in the Adsh-CD90 group was significantly impaired, with a marked reduction in the number and volume of blood vessels at the rib fracture site, as evidenced by CD31/EMCN immunofluorescence staining, which showed a reduction in the number of H type vessels at the site of bone injury. It was found that CD90 depletion can inhibit the signaling of Dll4/Notch in the rib fracture site. Furthermore, we found that overexpression of Notch1 reverses the impairment of tubule formation in bone microvascular endothelial cells caused by CD90 suppression.r.Dll4 protein reverses the inhibitory effect of CD90 deletion on periosteal stem cells and MC3T3-E1 cell viability and osteogenesis. In the end, we found that overexpression of Notch1 and CD90 can promote angiogenesis of bone microvascular endothelial cells and Notch pathway activation. CD90 can affect vascular formation in mouse rib fractures, and CD90 may be regulated by Dll4/Notch.

Alendronate-functionalized polymeric micelles target icaritin to bone for mitigating osteoporosis in a rat model

Formulating drugs into nanoparticles that target sites of disease can lead to strong therapeutic effects with lower doses of drugs and lower rates of off-target adverse effects. Few ways to target drugs to bone have been described, hampering the treatment of osteoporosis. Here we exploit the ability of alendronate to bind tightly to hydroxyapatite in bone as a tactic to target polymeric micelles loaded with the plant flavonoid icaritin to osteoporotic lesions. The traditional Chinese medicine icaritin, from Herba Epimedii, has previously been shown to inhibit adipogenesis and enhance osteogenesis by bone mesenchymal stem cells, but the compound on its own persists only briefly in the bloodstream. Our delivery system led to stronger inhibition of adipogenesis and activation of osteogenesis in a rat model of osteoporosis than when the icaritin-loaded micelles lacked alendronate. These results establish the feasibility of using alendronate to target osteogenic phytomolecules to sites of bone injury, which may guide the development of effective therapies against osteoporosis and, by extension, other bone disorders.

Artificial periosteum promotes bone regeneration through synergistic immune regulation of aligned fibers and BMSC-recruiting phages

Given the crucial role of periosteum in bone repair, the use of artificial periosteum to induce spontaneous bone healing instead of using bone substitutes has become a potential strategy. Also, the proper transition from pro-inflammatory signals to anti-inflammatory signals is pivotal for achieving optimal repair outcomes. Hence, we designed an artificial periosteum loaded with a filamentous bacteriophage clone named P11, featuring an aligned fiber morphology. P11 endowed the artificial periosteum with the capacity to recruit bone marrow mesenchymal stem cells (BMSCs). The artificial periosteum also regulated the immune microenvironment at the bone injury site through the synergistic effects of biochemical factors and topography. Specifically, the inclusion of P11 preserved inflammatory signaling in macrophages and additionally facilitated the migration of BMSCs. Subsequently, aligned fibers stimulated macrophages, inducing alterations in cytoskeletal and metabolic activities, resulting in the polarization into the M2 phenotype. This progression encouraged the osteogenic differentiation of BMSCs and promoted vascularization. In vivo experiments showed that the new bone generated in the AP group exhibited the most efficient healing pattern. Overall, the integration of biochemical factors with topographical considerations for sequential immunomodulation during bone repair indicates a promising approach for artificial periosteum development. Statement of significanceThe appropriate transition of macrophages from a pro-inflammatory to an anti-inflammatory phenotype is pivotal for achieving optimal bone repair outcomes. Hence, we designed an artificial periosteum featuring an aligned fiber morphology and loaded with specific phage clones. The artificial periosteum not only fostered the recruitment of BMSCs but also achieved sequential regulation of the immune microenvironment through the synergistic effects of biochemical factors and topography, and improved the effect of bone repair. This study indicates that the integration of biochemical factors with topographical considerations for sequential immunomodulation during bone repair is a promising approach for artificial periosteum development.

The reciprocity of skeletal muscle and bone: an evolving view from mechanical coupling, secretory crosstalk to stem cell exchange.

Introduction: Muscle and bone constitute the two main parts of the musculoskeletal system and generate an intricately coordinated motion system. The crosstalk between muscle and bone has been under investigation, leading to revolutionary perspectives in recent years. Method and results: In this review, the evolving concept of muscle-bone interaction from mechanical coupling, secretory crosstalk to stem cell exchange was explained in sequence. The theory of mechanical coupling stems from the observation that the development and maintenance of bone mass are largely dependent on muscle-derived mechanical loads, which was later proved by Wolff's law, Utah paradigm and Mechanostat hypothesis. Then bone and muscle are gradually recognized as endocrine organs, which can secrete various cytokines to modulate the tissue homeostasis and remodeling to each other. The latest view presented muscle-bone interaction in a more direct way: the resident mesenchymal stromal cell in the skeletal muscle, i.e., fibro-adipogenic progenitors (FAPs), could migrate to the bone injury site and contribute to bone regeneration. Emerging evidence even reveals the ectopic source of FAPs from tissue outside the musculoskeletal system, highlighting its dynamic property. Conclusion: FAPs have been established as the critical cell connecting muscle and bone, which provides a new modality to study inter-tissue communication. A comprehensive and integrated perspective of muscle and bone will facilitate in-depth research in the musculoskeletal system and promote novel therapeutic avenues in treating musculoskeletal disorders.

Factors influencing magnetic resonance imaging changes associated with pelvic bone injury after high-intensity focused ultrasound ablation of uterine fibroids: a retrospective case-control study.

The application of high-intensity focused ultrasound (HIFU) in the treatment of uterine fibroids is becoming increasingly widespread, and postoperative collateral thermal damage to adjacent tissue has become a prominent subject of discussion. However, there is limited research related to bone injury. Therefore, the aim of this study was to investigate the potential factors influencing unintentional pelvic bone injury after HIFU ablation of uterine fibroids with magnetic resonance imaging (MRI). A total of 635 patients with fibroids treated with HIFU in the First Affiliated Hospital of Chongqing Medical University were enrolled. All patients underwent contrast-enhanced MRI (CE-MRI) pre- and post-HIFU. Based on the post-treatment MRI, the patients were divided into two groups: pelvic bone injury group and non-injury group, while the specific site of pelvic bone injury of each patient was recorded. The univariate and multivariate analyses were used to assess the correlations between the factors of fibroid features and treatment parameters and pelvic bone injury, and to further analyze the factors influencing the site of injury. Signal changes in the pelvis were observed on CE-MRI in 51% (324/635) of patients after HIFU. Among them, 269 (42.4%) patients developed sacral injuries and 135 (21.3%) had pubic bone injuries. Multivariate analyses showed that patients with higher age [P=0.003; odds ratio (OR), 1.692; 95% confidence interval (CI): 1.191-2.404], large anterior side-to-skin distance of fibroid (P<0.001; OR, 2.297; 95% CI: 1.567-3.365), posterior wall fibroid (P=0.006; OR, 1.897; 95% CI: 1.204-2.989), hyperintensity on T2-weighted imaging (T2WI, P=0.003; OR, 2.125; 95% CI: 1.283-3.518), and large therapeutic dose (TD, P<0.001; OR, 3.007; 95% CI: 2.093-4.319) were at higher risk of postoperative pelvic bone injury. Further analysis of the factors influencing the site of the pelvic bone injury showed that some of the fibroid features and treatment parameters were associated with it. Moreover, some postoperative pain-related adverse events were associated with the pelvic bone injury. Post-HIFU treatment, patients may experience pelvic injuries to the sacrum, pubis, or a combination of both, and some of them experienced adverse events. Some fibroid features and treatment parameters are associated with the injury. Taking its influencing factors into full consideration preoperatively, slowing down treatment, and prolonging intraoperative cooling phase can help optimize treatment decisions for HIFU.

Highlights of recent clinically relevant papers

Equine Veterinary EducationVolume 35, Issue 6 p. 282-283 RESEARCH HIGHLIGHTS Highlights of recent clinically relevant papers Sue Wright, Corresponding Author Sue Wright [email protected] orcid.org/0000-0002-5513-8571 EVE Editorial Office Email: [email protected]Search for more papers by this author Sue Wright, Corresponding Author Sue Wright [email protected] orcid.org/0000-0002-5513-8571 EVE Editorial Office Email: [email protected]Search for more papers by this author First published: 03 May 2023 https://doi.org/10.1111/eve.13797Read the full textAboutPDF ToolsExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL No abstract is available for this article. References Fouquet, G., Abbas, G., Johnson, J.P., Pompermayer, E., Harel, C., Aldous, E. et al. (2022) Ultrasound-guided injection technique of the equine cervical nerve roots. Frontiers of Veterinary Science. Available from: https://doi.org/10.3389/fvets.2022.992208 eCollection 2022. Kolding, S.A., Sørensen, J.N., Kramer, J., McCracken, M.J., Reed, S.K. & Keegan, K.G. (2023) Prevalence and clinical significance of increasing head height asymmetry as a measure of forelimb lameness in horses when trotting in a straight line after palmar digital nerve block. Equine Veterinary Journal. Available from: https://doi.org/10.1111/evj.13921 Melly, V., Ortved, K.F., Manzi, T.J., Richardson, D.W., Stefanovski, D. & Wulster, K.B. (2023) Identification of a previously unreported site of subchondral bone injury in the dorsodistolateral calcaneus in thoroughbred racehorses. Equine Veterinary Journal. Available from: https://doi.org/10.1111/evj.13928 Miglinci, L., Reicher, P., Nell, B., Koch, M., Jindra, C. & Brandt, S. (2023) Detection of equine papillomaviruses and gamma-herpesviruses in equine squamous cell carcinoma. Pathogens, 12(2), 179. Available from: https://doi.org/10.3390/pathogens12020179 Wanstrath, M.A., Bauck, A.G., Smith, A.D. & Freeman, D.E. (2022) Surgical enlargement of the epiploic foramen in horses. Veterinary Radiology & Ultrasound, 52, 308– 314. Available from: https://doi.org/10.1111/vsu.13927 Wolkowski, D.D., McCarthy, R.D., Schoonover, M.J., Taylor, J.D. & Eastman, T.G. (2022) Effects of intra-articular injection of an acellular equine liquid amniotic allograft in healthy equine joints. Veterinary Surgery, 52, 62– 68. Available from: https://doi.org/10.1111/vsu.13918 Volume35, Issue6June 2023Pages 282-283 ReferencesRelatedInformation

Identification of a Specific Phage as Growth Factor Alternative Promoting the Recruitment and Differentiation of MSCs in Bone Tissue Regeneration.

Inefficient use and loss of exogenously implanted mesenchymal stem cells (MSCs) are major concerns in MSCs-based bone tissue engineering. It is a promising approach to overcome the above issues by recruiting and regulation of endogenous MSCs. However, there are few substances that can recruit MSCs effectively and specifically to the site of bone injury. In this study, we identified a phage clone (termed P11) with specific affinity for MSCs through phage display biopanning, and further investigated the effects of P11 on the cytological behavior of MSCs and macrophages. The results showed that P11 could bind MSCs specifically and promote the proliferation and migration of MSCs. Meanwhile, P11 could polarize macrophages to the M1 phenotype and significantly changed their morphology, which further enhanced the chemotaxis of MSCs. Additionally, RNA-seq results revealed that P11 could promote the secretion of osteogenesis-related markers in MSCs through the TPL2-MEK-ERK signaling pathway. Altogether, P11 has great potential to be used as growth factor alternatives in bone tissue engineering, with the advantages of cheaper and stable activity. Our study also advances the understanding of the effects of phages on macrophages and MSCs, and provides a new idea for the development in the field of phage-based tissue engineering.

Endocrine modulation of brain-skeleton axis driven by neural stem cell-derived perilipin 5 in the lipid metabolism homeostasis for bone regeneration

Factors released from the nervous system always play crucial roles in modulating bone metabolism and regeneration. How the brain-driven endocrine axes maintain bone homeostasis, especially under metabolic disorders, remains obscure. Here, we found that neural stem cells (NSCs) residing in the subventricular zone participated in lipid metabolism homeostasis of regenerative bone through exosomal perilipin 5 (PLIN5). Fluorescence-labeled exosomes tracing and histological detection identified that NSC-derived exosomes (NSC-Exo) could travel from the lateral ventricle into bone injury sites. Homocysteine (Hcy) led to osteogenic and angiogenic impairment, whereas the NSC-Exo were confirmed to restore it. Mecobalamin, a clinically used neurotrophic drug, further enhanced the protective effects of NSC-Exo through increased PLIN5 expression. Mechanistically, NSC-derived PLIN5 reversed excessive Hcy-induced lipid metabolic imbalance and aberrant lipid droplet accumulation through lipophagy-dependent intracellular lipolysis. Intracerebroventricular administration of mecobalamin and/or AAV-shPlin5 confirmed the effects of PLIN5-driven endocrine modulations on new bone formation and vascular reconstruction in hyperhomocysteinemic and high-fat diet models. This study uncovered a novel brain-skeleton axis that NSCs in the mammalian brain modulated bone regeneration through PLIN5-driven lipid metabolism modulation, providing evidence for lipid- or bone-targeted medicine development.

Osteogenic differentiation and proliferation potentials of human bone marrow and umbilical cord-derived mesenchymal stem cells on the 3D-printed hydroxyapatite scaffolds

Mesenchymal stem cells (MSCs) are a promising candidate for bone repair. However, the maintenance of MSCs injected into the bone injury site remains inefficient. A potential approach is to develop a bone-liked platform that incorporates MSCs into a biocompatible 3D scaffold to facilitate bone grafting into the desired location. Bone tissue engineering is a multistep process that requires optimizing several variables, including the source of cells, osteogenic stimulation factors, and scaffold properties. This study aims to evaluate the proliferation and osteogenic differentiation potentials of MSCs cultured on 2 types of 3D-printed hydroxyapatite, including a 3D-printed HA and biomimetic calcium phosphate-coated 3D-printed HA. MSCs from bone marrow (BM-MSCs) and umbilical cord (UC-MSCs) were cultured on the 3D-printed HA and coated 3D-printed HA. Scanning electron microscopy and immunofluorescence staining were used to examine the characteristics and the attachment of MSCs to the scaffolds. Additionally, the cell proliferation was monitored, and the ability of cells to differentiate into osteoblast was assessed using alkaline phosphatase (ALP) activity and osteogenic gene expression. The BM-MSCs and UC-MSCs attached to a plastic culture plate with a spindle-shaped morphology exhibited an immunophenotype consistent with the characteristics of MSCs. Both MSC types could attach and survive on the 3D-printed HA and coated 3D-printed HA scaffolds. The MSCs cultured on these scaffolds displayed sufficient osteoblastic differentiation capacity, as evidenced by increased ALP activity and the expression of osteogenic genes and proteins compared to the control. Interestingly, MSCs grown on coated 3D-printed HA exhibited a higher ALP activity and osteogenic gene expression than those cultured on the 3D-printed HA. The finding indicated that BM-MSCs and UC-MSCs cultured on the 3D-printed HA and coated 3D-printed HA scaffolds could proliferate and differentiate into osteoblasts. Thus, the HA scaffolds could provide a suitable and favorable environment for the 3D culture of MSCs in bone tissue engineering. Additionally, biomimetic coating with octacalcium phosphate may improve the biocompatibility of the bone regeneration scaffold.

(Digital Presentation) Electrodeposition of Thin Films of Femn Alloys for Biodegradable Scaffolds Fabrication

Biodegradable metallic scaffolds are interesting biomaterials for applications in temporary implants for bone regeneration because of their good mechanical properties. In addition, the need for a second surgery to remove the implant is reduced if biodegradable metals are used. Fe has adequate mechanical properties for scaffolds manufacture and suitable biocompatibility. However, Fe shows slow biodegradation rates for the application and, therefore, different approaches have been developed such as the development of alloys or by reducing the thickness of the Fe strut in the scaffold. FeMn alloys are considered ideal materials, as they are not ferromagnetic. In addition, additive manufacturing technologies (3D printing) are considered appropriate to manufacture these scaffolds due to the ability to obtain complicated geometries and customized parts for a specific bone injury site. Electrodeposition is also an interesting technique because it allows the deposition of thinner strut walls of Fe (or alloys) with high purity, in addition to providing a good surface finishing. The aim of the first part of this work is to electrodeposit thin films of FeMn alloys and to evaluate its microstructure and mechanical properties. The thin films were electrodeposited potentiostatically from sulfate electrolytes with different concentrations of FeSO4 and MnSO4. The effect of deaeration, substrate material and electrodeposition potential were evaluated. The microstructure of the electrodeposited films was characterized by SEM/EDX and XRD. The surface finishing was evaluated by AFM and the mechanical properties by microhardness measurements.

Gravity-based patterning of osteogenic factors to preserve bone structure after osteochondral injury in a large animal model

Chondral and osteochondral repair strategies are limited by adverse bony changes that occur after injury. Bone resorption can cause entire scaffolds, engineered tissues, or even endogenous repair tissues to subside below the cartilage surface. To address this translational issue, we fabricated thick-shelled poly(D,L-lactide-co-glycolide) microcapsules containing the pro-osteogenic agents triiodothyronine and β-glycerophosphate, and delivered these microcapsules in a large animal model of osteochondral injury to preserve bone structure. We demonstrate that the developed microcapsules ruptured in vitro under increasing mechanical loads, and readily sink within a liquid solution, enabling gravity-based patterning along the osteochondral surface. In a large animal, these mechanically-activated microcapsules (MAMCs) were assessed through two different delivery strategies. Intra-articular injection of control MAMCs enabled fluorescent quantification of MAMC rupture and cargo release in a synovial joint setting over time in vivo. This joint-wide injection also confirmed that the MAMCs do not elicit an inflammatory response. In the contralateral hindlimbs, chondral defects were created, MAMCs were patterned in situ, and nanofracture (Nfx), a clinically utilized method to promote cartilage repair, was performed. The Nfx holes enabled marrow-derived stromal cells to enter the defect area and served as repeatable bone injury sites to monitor over time. Animals were evaluated one and two weeks after injection and surgery. Analysis of injected MAMCs showed that bioactive cargo was released in a controlled fashion over two weeks. A bone fluorochrome label injected at the time of surgery displayed maintenance of mineral labeling in the therapeutic group, but resorption in both control groups. Alkaline phosphatase (AP) staining at the osteochondral interface revealed higher AP activity in defects treated with therapeutic MAMCs. Overall, this study develops a gravity-based approach to pattern bioactive factors along the osteochondral interface, and applies this novel biofabrication strategy to preserve bone structure after osteochondral injury.

A Multifunctional Composite Hydrogel That Rescues the ROS Microenvironment and Guides the Immune Response for Repair of Osteoporotic Bone Defects (Adv. Funct. Mater. 27/2022)

Osteoporotic Defect Repair In article number 2201067, Chaoyong Liu, Bin Li, Fengxuan Han, and co-workers describe a multifunctional composite hydrogel approach, which enables effective repair of osteoporotic bone defects by rescuing the ROS microenvironment and guiding the immune response of the bone injury site. The findings provide a novel platform for repair of osteoporotic bone defects based on integrated bone microenviroment regulation.

Pathological differences in the bone healing processes between tooth extraction socket and femoral fracture

Despite various reports on the bone healing processes of tooth extraction socket and long bone fracture, the differences of pathological changes during these healing processes remain elusive. This study aims to elucidate the underlying mechanisms behind the pathophysiology of bone regeneration between the tooth extraction socket and femoral fractures through a comparative study. Eight-week-old male mice were used in the experiments. The maxillary first molar was extracted, and intramedullary nailing femoral fracture (semistabilized fracture repair) was performed in the femur. Pathological changes in these bone injuries were investigated by micro-CT, histology, immunohistochemistry, and RT-PCR until day 7 post operation. Pathological changes in drill hole injury created in cortical bone of femur were also examined. Micro-CT analyses revealed increases in mineralized tissues in both the tooth extraction socket and femoral fracture. Histological examinations revealed that tooth socket was repaired by intramembranous ossification, and intramedullary nailing femoral fracture was healed by endochondral ossification. Immunohistochemical investigation revealed that tooth socket healing associated with Sp7-positive cells but not Sox9, aggrecan, and type II collagen, while femoral fracture models exhibited positive signals for all antibodies. RT-PCR analyses revealed the expression of Sp7, Col1a1, and Col2a1 in tooth socket healing, and the expression of Sp7, Col1a1, Runx2, Sox9, Acan, Col2a1, and Col10a1 in intramedullary nailing femoral fracture. Drill hole injury was repaired primarily by intramembranous ossification when the periosteum was removed before making the hole. The present study demonstrated that the absence of cartilage appearance during tooth extraction socket healing indicates it as distinctly different pathological features from the healing processes of semistabilized femoral fracture. This study contributes to the understanding of the molecular and cellular characteristics of bone healing among the different sites of bone injury.

Clinical profile and outcome of traumatic brain injury in children: record-based descriptive study

Background: Paediatric head injury is considered to be a major public health problem and is often associated with significant morbidity and mortality in severe cases. The present study aimed to explore the demographics, mechanism of injury and clinical aspects of injury in children in a peripheral hospital attached to tertiary care centre.Methods: Electronic medical records of all paediatric patients aged ≤12 years with traumatic brain injury admitted during one-year period from January to December 2018 were reviewed. Epidemiological and clinical data of paediatric patients with traumatic brain injury (TBI) were analysed using SPSS version 20.Results: The medical records of 203 paediatric patients with TBI were analysed. The majority of the injury occurred in patients belonging to age-group 1-6 years. The number of male children outnumbered (58.1%) that of female children (41.9%). Fall from height was the most common mode of injury, followed by fall from a staircase. As per the Glasgow coma scale, 4% patients had severe head injury. Vomiting and headache was the most common symptom at admission (50.2%), a subdural hematoma was the most common lesion seen on computed tomography scans; frontal bone was the most common site of skull bone injury. Cutaneous injuries associated with contused lacerated wounds were the most common external injuries, 92.1% completely recovered with conservative management.Conclusions: Increasing incidence of paediatric trauma suggests the need for supervision during play and identification of environmental risk factors for such injuries. Parental advice and supervision is recommended to prevent accidental falls.

The Therapeutic Potential of Hematopoietic Stem Cells in Bone Regeneration.

The repair process of bone fractures is a complex biological mechanism requiring the recruitment and in situ functionality of stem/stromal cells from the bone marrow (BM). BM mesenchymal stem/stromal cells have been widely explored in multiple bone tissue engineering applications, whereas the use of hematopoietic stem cells (HSCs) has been poorly investigated in this context. A reasonable explanation is the fact that the role of HSCs and their combined effect with other elements of the hematopoietic niches in the bone-healing process is still elusive. Therefore, in this review we intend to highlight the influence of HSCs in the bone repair process, mainly through the promotion of osteogenesis and angiogenesis at the bone injury site. For that, we briefly describe the main biological characteristics of HSCs, as well as their hematopoietic niches, while reviewing the biomimetic engineered BM niche models. Moreover, we also highlighted the role of HSCs in translational in vivo transplantation or implantation as promoters of bone tissue repair. Impact statement The ability of bone to natural self-heal depends on the size and stabilization level of the tissue fracture, and it is impaired in several pathophysiological conditions. Considering that the available treatment options have demonstrated limited regenerative performance, the hematopoietic stem cells (HSCs) co-cultured in different tissue engineering strategies have emerged as a powerful tool to promote effective bone regeneration and healing. Here, we reviewed the most important biomimetic bone-marrow hematopoietic niches and showed the regenerative potential of these cells, both in vitro and in translational in vivo transplantation/implantation approaches. This knowledge encourages the development of new HSC-related bone regenerative therapies.

Enhancement and mechanisms of MC3T3-E1 osteoblast-like cell adhesion to albumin through calcium exposure.

Serum albumin is the most prominent protein in blood, and it aids in bone fracture healing, though the manner through which enhanced healing occurs is not well understood. This study investigates the influence of calcium on the bioactivity of albumin due to the prevalence of calcium at bone injury sites. Bovine serum albumin (BSA) was exposed to varying concentrations of calcium, adsorbed to tissue culture polystyrene, and the subsequent BSA-coated surfaces were evaluated with calcium titration, and cell adhesion, viability, and binding inhibition studies. Calcium-modified BSA improved overall MC3T3-E1 osteoblast-like cell adhesion, although high calcium concentrations induced cell death. Inhibiting specific integrins revealed that without calcium exposure, cell binding to BSA was primarily mediated by integrins that typically bind to the GFOGER sequence of collagen. As calcium exposure increases, the primary binding interaction transitioned to integrins known to bind RGD. However, cell binding to calcium-modified BSA was not completely eliminated during the inhibition studies indicating additional unidentified binding interactions occur. Overall, these results suggest that the exposure to calcium induces conformational changes that affect the cell-binding bioactivity of BSA, which may explain the beneficial impact of albumin in bone tissue.

Evaluation of usage of silicon-doped hydroxyapatite ceramics for treatment of fragmented bone fractures in dogs

None of the methods of osteosynthesis provides the consolidation of bone fragments which have lost contact with soft tissues. It makes extremely difficult treating of this type fractures. Bone defect between the fragments and absence of a primary biological matrix complicates revascularization, causes long-term life of the connective tissue and cells of cartilaginous phenotype in the fracture zone. It is leads to a long-term consolidation of the fracture. Composites of hydroxyapatite and calcium phosphates are considered as bioactive and therefore the most promising for bone defects replacing. The aim of this investigation was clinical, radiological and hematological evaluation using of silicon-doped ceramics for fragmented bone fractures in dogs. For study was chosen dogs with accidental fragmented fractures of tubular bones which treated by extracortical osteosynthesis method. Animal was divided into two groups. A bone defects were filled with ceramics (GTlKg-3) for experimental animal group (n = 7), while no filling of bone defects in control animal group(n = 7) was performed. Protocol of anesthesia included medetomidine, butorphanol tartrate and epidural anesthesia with 2 % lidocaine solution. Animals of the control group began to lean on the injured limb from the 12–15th day after surgery, while the animal of research group from the 8-9th day. Complete limb repair in dogs of the control group occurred on the 38–42th day, but such period for experimental group animals was shorter – 25–27th day after the osteosynthesis. X-ray investigation (60th day) of experimental group dogs showed new formed bone tissue with osteosclerotic zones without a periosteal reaction, bone tissue, with a normal view of the epiphyseal areas and the bone marrow cavity. This is evidence of localized reparative osteogenesis (within bone trauma only), and completed fracture consolidation. At the same time in cases of the control group we found lower X-ray density of new bone, periosteum was thickened with excessive proliferation of the endosteum, especially below the site of bone injury. Thus, in case the absence of hydroxyapatite matrix in bone defects there were compensatory increasing proliferation of periosteum and endoosteum. Fragmented fractures of tubular bones in dogs have occurred by erythrocytopenia, that quickly disappear due to the reparative osteogenesis in dog of experimental group. These animals have had leukocytosis increasing due to the first three days after osteosynthesis as a reaction to the implantation of a calcium-phosphorus composite material. Dogs of control group have had second wave of leukocytosis increasing on forty-second day associated with elongated remodeling process. Areparative osteogenesis can be accelerated in 1.5 times in case of replacement of bone defects with silicon doped hydroxyapatite ceramics. It is possibility realized thru moderate reduction of active phase of inflammation and acceleration of proliferative phase, mainly from endosteum side with early mineralization of bone regenerate. The dynamics of hematology parameters is a typical for the tubular bone consolidation that indicates about moderate inflammation and demonstrate biological tolerance of silicon-doped hydroxyapatite ceramics.

Preparation and characteristics of a novel oxygen-releasing coating for improved cell responses in hypoxic environment.

Affected by environmental factors such as oxygen deficiency, the secretion of growth factor was abnormal in bone injury sites, resulting in the poor responses of osteoblasts and prolonging the healing process. Herein, in this study, we reported an in situ oxygen-releasing porous titanium coating that combines the dual degradability of poly(lactic-co-glycolic acid) with the self-releasing oxygen capacity of the CaO2 core. The resulting formulation exhibited stable oxygen-releasing capacity as well as the ability to promote proliferation and differentiation of the MC3T3 cell line under hypoxia conditions. According to these results, oxygen-releasing coatings based on improved cellular microenvironment may be a promising bone repair material that would reduce the incidence of difficult bone healing in the future.

Guided bone regeneration with a gelatin layer and adenoviral delivery of c-myb enhances bone healing in rat tibia.

Aim: Bone healing becomes problematic during certain states, such as trauma. This study verifies whether the application of c-myb with gelatin promotes bone healing during bone injuries. Materials & methods: A biodegradable membrane was modified with adenoviral vector c-myb (Ad/c-myb) and gelatin and applied in the bone injury site of rat tibia. Results:c-myb enhanced osteogenic differentiation and mineralization in bone marrow stromal cellsafter induction with osteogenic media. In vivo examination of rat tibia after application of the biodegradable membrane with Ad/c-myb and a gelatin layer demonstrated increased bone volume, bone mineral density, new bone formation and osteogenic molecules, compared with Ad/LacZ. Conclusion:c-myb has the potential to assist bone healing and may be applicable to the treatment of bone during injury.

An Improved Methodology to Evaluate Cell and Molecular Signals in the Reparative Callus During Fracture Healing.

Approximately 5% to 10% of all bone fractures do not heal completely, contributing to significant patient suffering and medical costs. Even in healthy individuals, fracture healing is associated with significant downtime and loss of productivity. However, no pharmacological treatments are currently available to promote efficient bone healing. A better understanding of the underlying molecular mechanisms is crucial for developing novel therapies to hasten healing. The early reparative callus that forms around the site of bone injury is a fragile tissue consisting of shifting cell populations held together by loose connective tissue. The delicate callus is challenging to section and is vulnerable to disintegration during the harsh steps of immunostaining, namely, decalcification, deparaffinization, and antigen retrieval. Here, we describe an improved methodology for processing early-stage fracture calluses and immunofluorescence labeling of the sections to visualize the temporal (timing) and spatial (location) patterns of cellular and molecular events that regulate bone healing. This method has a short turnaround time from sample collection to microscopy as it does not require lengthy decalcification. It preserves the structural integrity of the fragile callus as the method does not entail deparaffinization or harsh methods of antigen retrieval. Our method can be adapted for high-throughput screening of drugs that promote efficacious bone healing.