Skeletal Blood Flow in Bone Repair and Maintenance

Vascular architecture regulates mesenchymal stromal cell heterogeneity via P53-PDGF signaling in the mouse incisor

Mesenchymal stem cells (MSCs) reside in niches to maintain tissue homeostasis and contribute to repair and regeneration. Although the physiological functions of blood and lymphatic vasculature are well studied, their regulation of MSCs as niche components remains largely unknown. Using adult mouse incisors as a model, we uncover the role of Trp53 in regulating vascular composition through THBS2 to maintain mesenchymal tissue homeostasis. Loss of Trp53 in GLI1+ progeny increases arteries and decreases other vessel types. Platelet-derived growth factors from arteries deposit in the MSC region and interact with PDGFRA and PDGFRB. Significantly, PDGFRA+ and PDGFRB+ cells differentially contribute to defined cell lineages in the adult mouse incisor. Collectively, our results highlight Trp53's importance in regulating the vascular niche for MSCs. They also shed light on how different arterial cells provide unique cues to regulate MSC subpopulations and maintain their heterogeneity. Furthermore, they provide mechanistic insight into MSC-vasculature crosstalk.

Sequestration and Involucrum: Understanding Bone Necrosis and Revascularization in Pediatric Orthopedics

Sequestration, a condition where a section of bone becomes necrotic due to a loss of vascularity or thrombosis, can be a challenging complication of osteomyelitis. This review explores the pathophysiology of sequestration, highlighting the role of the periosteum in forming involucrum and creeping substitution which facilitate revascularization and bone formation. The authors also discuss the induced membrane technique, a two-stage surgical procedure for cases of failed healing of sequestration. Future directions include the potential use of prophylactic anticoagulation and novel drugs targeting immunocoagulopathy, as well as the development of advanced imaging techniques and single-stage surgical procedures.

Zhuang-Gu-Fang intervenes vasculogenic and osteogenic coupling in GK rats through Notch1/Noggin/VEGF pathway

Background

Zhuang-Gu-Fang (ZGF) has been proved to treat osteoporosis in ovariectomized rats by increasing osteogenic related factors Leptin, Ghrelin and Peptide YY(PYY). However, the mechanism of ZGF in the treatment of diabetic osteoporosis (DOP) remains unclear. The aim of this study was to explore the therapeutic effect of ZGF on DOP and its potential molecular mechanism.

Methods

Using GK rats as models, the pharmacodynamic effects of ZGF on bone loss were evaluated by hematoxylin-eosin (H&E) staining and micro-computed.tomography (micro-CT). The expression levels of CD31 and endomucin (Emcn) were detected by immunofluorescence to assess the role of ZGF in angiogenic osteogenic coupling. Finally, real-time quantitative PCR (RT-PCR) and Western Blot (WB)were used to detect the expression levels of osteogenic and angiogenesis-related genes and proteins Notch1, Noggin and vascular endothelial growth factor (VEGF).

Results

Administration of ZGF demonstrated a significant mitigation of bone loss attributable to elevated glucose levels. H&E staining and micro-CT showed that ZGF notably improved the integrity of the trabecular and cortical bone microarchitecture. Moreover, ZGF was found to augment the density of type H vessels within the bone tissue, alongside elevating the expression levels of Osterix, a transcription factor pivotal for bone formation. Furthermore, our findings suggest that ZGF facilitates the activation of the Notch1/Noggin/VEGF pathway, indicating a potential mechanism through which ZGF exerts its osteoprotective effects.

Conclusion

Our results suggest that ZGF potentially facilitates the formation of type H vessels through the Notch1/Noggin/VEGF pathway. This action not only enhances angiogenic-osteogenic coupling but also contributes to the improvement of bone structure and density. Consequently, ZGF emerges as a promising therapeutic agent for the prevention and management of DOP, offering a novel approach by leveraging angiogenesis-dependent osteogenesis.

NEST3D printed bone-mimicking scaffolds: assessment of the effect of geometrical design on stiffness and angiogenic potential

Tissue-engineered implants for bone regeneration require consideration regarding their mineralization and vascularization capacity. Different geometries, such as biomimetic designs and lattices, can influence the mechanical properties and the vascularization capacity of bone-mimicking implants. Negative Embodied Sacrificial Template 3D (NEST3D) printing is a versatile technique across a wide range of materials that enables the production of bone-mimicking scaffolds. In this study, different scaffold motifs (logpile, Voronoi, and trabecular bone) were fabricated via NEST3D printing in polycaprolactone to determine the effect of geometrical design on stiffness (10.44 ± 6.71, 12.61 ± 5.71, and 25.93 ± 4.16 MPa, respectively) and vascularization. The same designs, in a polycaprolactone scaffold only, or when combined with gelatin methacryloyl, were then assessed for their ability to allow the infiltration of blood vessels in a chick chorioallantoic membrane (CAM) assay, a cost-effective and time-efficient in ovo assay to assess vascularization. Our findings showed that gelatin methacrylolyl alone did not allow new chorioallantoic membrane tissue or blood vessels to infiltrate within its structure. However, polycaprolactone on its own or when combined with gelatin methacrylolyl allowed tissue and vessel infiltration in all scaffold designs. The trabecular bone design showed the greatest mineralized matrix production over the three designs tested. This reinforces our hypothesis that both biomaterial choice and scaffold motifs are crucial components for a bone-mimicking scaffold.

Idiosyncratic bone responses to blood flow restriction exercise: new insights and future directions

Applying blood flow restriction (BFR) during low-load exercise induces beneficial adaptations of the myotendinous and neuromuscular systems. Despite the low mechanical tension, BFR exercise facilitates a localized hypoxic environment and increase in metabolic stress, widely regarded as the primary stimulus for tissue adaptations. First evidence indicates that low-load BFR exercise is effective in promoting an osteogenic response in bone, although this has previously been postulated to adapt primarily during high-impact weight-bearing exercise. Besides studies investigating the acute response of bone biomarkers following BFR exercise, first long-term trials demonstrate beneficial adaptations in bone in both healthy and clinical populations. Despite the increasing number of studies, the physiological mechanisms are largely unknown. Moreover, heterogeneity in methodological approaches such as biomarkers of bone metabolism measured, participant and study characteristics, and time course of measurement renders it difficult to formulate accurate conclusions. Furthermore, incongruity in the methods of BFR application (e.g., cuff pressure) limits the comparability of datasets and thus hinders generalizability of study findings. Appropriate use of biomarkers, effective BFR application, and befitting study design have the potential to progress knowledge on the acute and chronic response of bone to BFR exercise and contribute toward the development of a novel strategy to protect or enhance bone health. Therefore, the purpose of the present synthesis review is to 1) evaluate current mechanistic evidence; 2) discuss and offer explanations for similar and contrasting data findings; and 3) create a methodological framework for future mechanistic and applied research.

Recent progress and treatment strategy of pectin polysaccharide based tissue engineering scaffolds in cancer therapy, wound healing and cartilage regeneration

Natural polymers and its mixtures in the form of films, sponges and hydrogels are playing a major role in tissue engineering and regenerative medicine. Hydrogels have been extensively investigated as standalone materials for drug delivery purposes as they enable effective encapsulation and sustained release of drugs. Biopolymers are widely utilised in the fabrication of hydrogels due to their safety, biocompatibility, low toxicity, and regulated breakdown by human enzymes. Among all the biopolymers, polysaccharide-based polymer is well suited to overcome the limitations of traditional wound dressing materials. Pectin is a polysaccharide which can be extracted from different plant sources and is used in various pharmaceutical and biomedical applications including cartilage regeneration. Pectin itself cannot be employed as scaffolds for tissue engineering since it decomposes quickly. This article discusses recent research and developments on pectin polysaccharide, including its types, origins, applications, and potential demands for use in AI-mediated scaffolds. It also covers the materials-design process, strategy for implementation to material selection and fabrication methods for evaluation. Finally, we discuss unmet requirements and current obstacles in the development of optimal materials for wound healing and bone-tissue regeneration, as well as emerging strategies in the field.

Extent of Abdominal Aortic Calcification Is Associated With Incident Rapid Weight Loss Over 5 Years: The Perth Longitudinal Study of Ageing Women

BACKGROUND

Abdominal aortic calcification (AAC), a marker of vascular disease, is associated with disease in other vascular beds including gastrointestinal arteries. We investigated whether AAC is related to rapid weight loss over 5 years and whether rapid weight loss is associated with 9.5-year all-cause mortality in community-dwelling older women.

METHODS

Lateral spine images from dual-energy x-ray absorptiometry (1998/1999) were used to assess AAC (24-point AAC scoring method) in 929 older women. Over 5 years, body weight was assessed at 12-month intervals. Rapid weight loss was defined as >5% decrease in body weight within any 12-month interval. Multivariable-adjusted logistic regression was used to assess AAC and rapid weight loss and Cox regression to assess the relationship between rapid weight loss and 9.5-year all-cause mortality.

RESULTS

Mean±SD age of women was 75.0±2.6 years. During the initial 5 years, 366 (39%) women presented with rapid weight loss. Compared with women with low AAC (24-point AAC score 0-1), those with moderate (24-point AAC score 2-5: odds ratio, 1.36 [95% CI, 1.00-1.85]) and extensive (24-point AAC score 6+: odds ratio, 1.59 [95% CI, 1.10-2.31]) AAC had higher odds for presenting with rapid weight loss. Results remained similar after further adjustment for dietary factors (alcohol, protein, fat, and carbohydrates), diet quality, blood pressure, and cholesterol measures. The estimates were similar in subgroups of women who met protein intake (n=599) and physical activity (n=735) recommendations (extensive AAC: odds ratios, 1.81 [95% CI, 1.12-2.92] and 1.58 [95% CI, 1.02-2.44], respectively). Rapid weight loss was associated with all-cause mortality over the next 9.5 years (hazard ratio, 1.49 [95% CI, 1.17-1.89]; P=0.001).

CONCLUSIONS

AAC extent was associated with greater risk for rapid weight loss over 5 years in older women, a risk for all-cause mortality. Since the association was unchanged after taking nutritional intakes into account, these data support the possibility that vascular disease may play a role in the maintenance of body weight.

Targeting type H vessels in bone-related diseases

Blood vessels are essential for bone development and metabolism. Type H vessels in bone, named after their high expression of CD31 and Endomucin (Emcn), have recently been reported to locate mainly in the metaphysis, exhibit different molecular properties and couple osteogenesis and angiogenesis. A strong correlation between type H vessels and bone metabolism is now well-recognized. The crosstalk between type H vessels and osteoprogenitor cells is also involved in bone metabolism-related diseases such as osteoporosis, osteoarthritis, fracture healing and bone defects. Targeting the type H vessel formation may become a new approach for managing a variety of bone diseases. This review highlighted the roles of type H vessels in bone-related diseases and summarized the research attempts to develop targeted intervention, which will help us gain a better understanding of their potential value in clinical application.

Smokeless Tobacco Use is Associated With Worse Medical and Surgical Outcomes Following Total Hip Arthroplasty

BACKGROUND

Studies have demonstrated increased complication risk after total hip arthroplasty (THA) in patients who smoke cigarettes. It is unclear if smokeless tobacco use confers a similar impact. The purpose of this study was to (1) evaluate rates of postoperative complications after THA in smokeless tobacco users and people who smoke compared to matched controls, and (2) compare rates of postoperative complications in smokeless tobacco users versus patients who smoke.

METHODS

A retrospective cohort study was conducted using a large national database. For patients who underwent primary THA, smokeless tobacco users (n = 950) and people who smoke (n = 21,585) were matched 1:4 with controls (n = 3,800 and 86,340, respectively), and smokeless tobacco users (n = 922) were matched 1:4 with people who smoke (n = 3,688). Joint complication rates within 2 years and medical complications within 90 days postoperatively were compared using multivariable logistic regressions.

RESULTS

Within 90 days of primary THA, smokeless tobacco users demonstrated significantly higher rates of wound disruption, pneumonia, deep vein thrombosis, acute kidney injury (AKI), cardiac arrest, transfusion, readmission and longer length of stay compared to tobacco naïve controls. Within 2 years, smokeless tobacco users demonstrated significantly higher rates of prosthetic joint dislocations and overall joint-related complications compared to tobacco naïve controls.

CONCLUSION

Smokeless tobacco use is associated with higher rates of medical- and joint-related complications following primary THA. Smokeless tobacco use may be under-diagnosed in patients undergoing elective THA. Surgeons may consider delineating between smoking and smokeless tobacco use during preoperative counseling.

Multimodality imaging reveals angiogenic evolution in vivo during calvarial bone defect healing

The healing of calvarial bone defects is a pressing clinical problem that involves the dynamic interplay between angiogenesis and osteogenesis within the osteogenic niche. Although structural and functional vascular remodeling (i.e., angiogenic evolution) in the osteogenic niche is a crucial modulator of oxygenation, inflammatory and bone precursor cells, most clinical and pre-clinical investigations have been limited to characterizing structural changes in the vasculature and bone. Therefore, we developed a new multimodality imaging approach that for the first time enabled the longitudinal (i.e., over four weeks) and dynamic characterization of multiple in vivo functional parameters in the remodeled vasculature and its effects on de novo osteogenesis, in a preclinical calvarial defect model. We employed multi-wavelength intrinsic optical signal (IOS) imaging to assess microvascular remodeling, intravascular oxygenation (SO2), and osteogenesis; laser speckle contrast (LSC) imaging to assess concomitant changes in blood flow and vascular maturity; and micro-computed tomography (μCT) to validate volumetric changes in calvarial bone. We found that angiogenic evolution was tightly coupled with calvarial bone regeneration and corresponded to distinct phases of bone healing, such as injury, hematoma formation, revascularization, and remodeling. The first three phases occurred during the initial two weeks of bone healing and were characterized by significant in vivo changes in vascular morphology, blood flow, oxygenation, and maturity. Overall, angiogenic evolution preceded osteogenesis, which only plateaued toward the end of bone healing (i.e., four weeks). Collectively, these data indicate the crucial role of angiogenic evolution in osteogenesis. We believe that such multimodality imaging approaches have the potential to inform the design of more efficacious tissue-engineering calvarial defect treatments.

YBX1 promotes type H vessel-dependent bone formation in an m5C-dependent manner

RNA-binding proteins (RBPs) interact with RNA and ubiquitously regulate RNA transcripts during their life cycle, playing a fundamental role in the progression of angiogenesis-related diseases. In the skeletal system, endothelium-dependent angiogenesis is indispensable for bone formation. However, the role of RBPs in endothelium-dependent bone formation is unclear. Here, we show that RBP-Y-box-binding protein 1 (YBX1) was strongly reduced in the bone vasculature of ovariectomy (OVX) mice. Endothelial cell-specific deletion of Ybx1 impaired CD31-high, endomucin-high (CD31hiEMCNhi) endothelium morphology and resulted in low bone mass whereas Ybx1 overexpression promoted angiogenesis-dependent osteogenesis and ameliorated bone loss. Mechanistically, YBX1 deletion disrupted CD31, EMCN, and bone morphogenetic protein 4 (BMP4) stability in an m5C-dependent manner and blocked endothelium-derived BMP4 release, thereby inhibiting osteogenic differentiation of bone mesenchymal stromal cells. Administration of recombinant BMP4 protein restored impaired bone formation in Ybx1 deletion mice. Tail vein injection of CD31-modified polyethylene glycol-poly (lactic-co-glycolic acid) carrying sciadopitysin, a natural YBX1 agonist, pharmacologically partially reversed CD31hiEMCNhi vessels' decline and improved bone mass in both OVX and aging animals. These findings demonstrated the role of RBP-YBX1 in angiogenesis-dependent bone formation and provided a therapeutic approach for ameliorating osteoporosis.

In vivo depiction of cortical bone vascularization with ultra-high resolution-CT and deep learning algorithm reconstruction using osteoid osteoma as a model

PURPOSE

The purpose of this study was to evaluate the ability to depict in vivo bone vascularization using ultra-high-resolution (UHR) computed tomography (CT) with deep learning reconstruction (DLR) and hybrid iterative reconstruction algorithm, compared to simulated conventional CT, using osteoid osteoma as a model.

MATERIALS AND METHODS

Patients with histopathologically proven cortical osteoid osteoma who underwent UHR-CT between October 2019 and October 2022 were retrospectively included. Images were acquired with a 1024 × 1024 matrix and reconstructed with DLR and hybrid iterative reconstruction algorithm. To simulate conventional CT, images with a 512 × 512 matrix were also reconstructed. Two radiologists (R1, R2) independently evaluated the number of blood vessels entering the nidus and crossing the bone cortex, as well as vessel identification and image quality with a 5-point scale. Standard deviation (SD) of attenuation in the adjacent muscle and that of air were used as image noise and recorded.

RESULTS

Thirteen patients with 13 osteoid osteomas were included. There were 11 men and two women with a mean age of 21.8 ± 9.1 (SD) years. For both readers, UHR-CT with DLR depicted more nidus vessels (11.5 ± 4.3 [SD] (R1) and 11.9 ± 4.6 [SD] (R2)) and cortical vessels (4 ± 3.8 [SD] and 4.3 ± 4.1 [SD], respectively) than UHR-CT with hybrid iterative reconstruction (10.5 ± 4.3 [SD] and 10.4 ± 4.6 [SD], and 4.1 ± 3.8 [SD] and 4.3 ± 3.8 [SD], respectively) and simulated conventional CT (5.3 ± 2.2 [SD] and 6.4 ± 2.5 [SD], 2 ± 1.2 [SD] and 2.4 ± 1.6 [SD], respectively) (P < 0.05). UHR-CT with DLR provided less image noise than simulated conventional CT and UHR-CT with hybrid iterative reconstruction (P < 0.05). UHR-CT with DLR received the greatest score and simulated conventional CT the lowest score for vessel identification and image quality.

CONCLUSION

UHR-CT with DLR shows less noise than UHR-CT with hybrid iterative reconstruction and significantly improves cortical bone vascularization depiction compared to simulated conventional CT.

Cornus officinalis: a potential herb for treatment of osteoporosis

Osteoporosis (OP) is a systemic metabolic skeletal disorder characterized by a decline in bone mass, bone mineral density, and deterioration of bone microstructure. It is prevalent among the elderly, particularly postmenopausal women, and poses a substantial burden to patients and society due to the high incidence of fragility fractures. Kidney-tonifying Traditional Chinese medicine (TCM) has long been utilized for OP prevention and treatment. In contrast to conventional approaches such as hormone replacement therapy, TCM offers distinct advantages such as minimal side effects, low toxicity, excellent tolerability, and suitability for long-term administration. Extensive experimental evidence supports the efficacy of kidney-tonifying TCM, exemplified by formulations based on the renowned herb Cornus officinalis and its bioactive constituents, including morroniside, sweroside, flavonol kaempferol, Cornuside I, in OP treatment. In this review, we provide a comprehensive elucidation of the underlying pathological principles governing OP, with particular emphasis on bone marrow mesenchymal stem cells, the homeostasis of osteogenic and osteoclastic, and the regulation of vascular and immune systems, all of which critically influence bone homeostasis. Furthermore, the therapeutic mechanisms of Cornus officinalis-based TCM formulations and Cornus officinalis-derived active constituents are discussed. In conclusion, this review aims to enhance understanding of the pharmacological mechanisms responsible for the anti-OP effects of kidney-tonifying TCM, specifically focusing on Cornus officinalis, and seeks to explore more efficacious and safer treatment strategies for OP.

Recent advancement in vascularized tissue-engineered bone based on materials design and modification

Bone is one of the most vascular network-rich tissues in the body and the vascular system is essential for the development, homeostasis, and regeneration of bone. When segmental irreversible damage occurs to the bone, restoring its vascular system by means other than autogenous bone grafts with vascular pedicles is a therapeutic challenge. By pre-generating the vascular network of the scaffold in vivo or in vitro, the pre-vascularization technique enables an abundant blood supply in the scaffold after implantation. However, pre-vascularization techniques are time-consuming, and in vivo pre-vascularization techniques can be damaging to the body. Critical bone deficiencies may be filled quickly with immediate implantation of a supporting bone tissue engineered scaffold. However, bone tissue engineered scaffolds generally lack vascularization, which requires modification of the scaffold to aid in enhancing internal vascularization. In this review, we summarize the relationship between the vascular system and osteogenesis and use it as a basis to further discuss surgical and cytotechnology-based pre-vascularization strategies and to describe the preparation of vascularized bone tissue engineered scaffolds that can be implanted immediately. We anticipate that this study will serve as inspiration for future vascularized bone tissue engineered scaffold construction and will aid in the achievement of clinical vascularized bone.

Core-Shell NiS@SrTiO3 Nanorods on Titanium for Enhanced Osseointegration via Programmed Regulation of Bacterial Infection, Angiogenesis, and Osteogenesis

Developing bone implants with dynamic self-adjustment of antibacterial, angiogenic, and osteogenic functions in line with a bone regenerative cascade is highly required in orthopedics. Herein, a unique core-shell nanorods array featuring a thin layer of NiS coated on each SrTiO3 nanorod (NiS@SrTiO3) was in situ constructed on titanium (Ti) through a two-step hydrothermal treatment. Under near-infrared (NIR) irradiation, the photoresponsive effect of NiS layer in synergy with the physical perforation of SrTiO3 nanorods initially enabled in vitro antibacterial rates of 96.5% to Escherichia coli and 93.1% to Staphylococcus aureus. With the degradation of the NiS layer, trace amounts of Ni ions were released, which accelerated angiogenesis by upregulating the expression of vascular regeneration-related factors, while the gradual exposure of SrTiO3 nanorods could simultaneously enhance the surface hydrophilicity in favor of cell adhesion and slowly release Sr ions to promote the proliferation and differentiation of MC3T3-E1 cells. The in vivo assessment verified not only the satisfactory antibacterial effect but also the superior osteogenic ability of the NiS@SrTiO3/Ti group with the aid of NIR irradiation, finally promoting the osseointegration of the Ti implant. The modification method endowing Ti implant with antibacterial, angiogenic, and osteogenic functions provides a new strategy to improve the long-term reliability of Ti-based devices.

What Do We Know About Hair Growth Induced by Wounding and Its Therapeutic Applications?

BACKGROUND

Many studies have reported the role of hair follicles (HFs) in the wound healing response, and vice versa, the creation of superficial injuries may stimulate hair growth, which has encouraged new treatments for hair loss.

OBJECTIVE

To review the phenomenon of wound-induced hair growth and the usefulness of therapeutic procedures based on skin wounding in androgenetic alopecia (AGA).

METHODS

A literature search was conducted to review cases of localized hypertrichosis induced by wounds and the role of microneedling, fractional laser, and scalp threading as monotherapy for AGA.

RESULTS

Localized hypertrichosis has been extensively reported after bone fractures, burn injury, chronic venous ulcer, etc. Only 2 cases of wound-induced hair neogenesis in humans have been reported. As monotherapy for AGA, 1 of 3 studies of microneedling, 4 of 6 of fractional lasers, and 2 of 3 studies of scalp threading show good efficacy.

CONCLUSION

Certain types of wounds seem to stimulate localized hair growth in humans, but the underlying mechanism is unclear. Reports on wound-induced HF neogenesis in humans are anecdotal and questions remain as to whether this is a true phenomenon in humans. Further clinical studies are needed before recommending wound-induced hair growth procedures as therapies for AGA.

External mechanical loading overrules cell-cell mechanical communication in sprouting angiogenesis during early bone regeneration

Sprouting angiogenesis plays a key role during bone regeneration. For example, insufficient early revascularization of the injured site can lead to delayed or non-healing. During sprouting, endothelial cells are known to be mechano-sensitive and respond to local mechanical stimuli. Endothelial cells interact and communicate mechanically with their surroundings, such as outer-vascular stromal cells, through cell-induced traction forces. In addition, external physiological loads act at the healing site, resulting in tissue deformations and impacting cellular arrangements. How these two distinct mechanical cues (cell-induced and external) impact angiogenesis and sprout patterning in early bone healing remains however largely unknown. Therefore, the aim of this study was to investigate the relative role of externally applied and cell-induced mechanical signals in driving sprout patterning at the onset of bone healing. To investigate cellular self-organisation in early bone healing, an in silico model accounting for the mechano-regulation of sprouting angiogenesis and stromal cell organization was developed. Computer model predictions were compared to in vivo experiments of a mouse osteotomy model stabilized with a rigid or a semirigid fixation system. We found that the magnitude and orientation of principal strains within the healing region can explain experimentally observed sprout patterning, under both fixation conditions. Furthermore, upon simulating the selective inhibition of either cell-induced or externally applied mechanical cues, external mechanical signals appear to overrule the mechanical communication acting on a cell-cell interaction level. Such findings illustrate the relevance of external mechanical signals over the local cell-mediated mechanical cues and could be used in the design of fracture treatment strategies for bone regeneration.

Anti-inflammatory and pro-regenerative effects of a monoterpene glycoside on experimental periodontitis in a rat model of diabetes

OBJECTIVE

Paeoniflorin (Pae) is a monoterpene glycoside with immune-regulatory effects. Several studies have already demonstrated the impact of Pae on periodontitis, but its effect on diabetic periodontitis is unclear. In this study, our aim was to test the hypothesis that Pae had a strong anti-inflammatory effect that prevented bone loss in diabetic periodontitis.

METHODS

Thirty male Wistar albino rats were randomly divided into control (healthy, n = 10), periodontitis (PD) + diabetes (DM; n = 10), and PD + DM + Pae (n = 10) groups. Ligature-induced periodontitis was created by placing 4-0 silk ligatures around the lower first molars on both sides of the mandibulae. Experimental DM was created via an injection of 50 mg/kg and streptozotocin (STZ). Hyperglycemia was confirmed by the blood glucose levels of rats (>300 mg/dL). The bone mineral density (BMD), trabecular number, trabecular thickness, and bone loss were measured by micro-CT. The expression levels of IL-1β, IL-6, and TNF-α were measured in tissue homogenates by ELISA.

RESULTS

The PD + DM + Pae group had significantly less alveolar crest resorption when compared to the PD + DM group. There was also a significant difference between the PD + DM + Pae group compared to PD + DM group in trabecular thickness, BMD, and the number of trabeculae. Pae application led to a statistically significant decrease in IL-1β, IL-6, and TNF-α levels in diabetic periodontitis.

CONCLUSION

Systemic application of Pae suppressed inflammation caused by PD and DM, leading to reduced bone loss and enhanced bone quality.

The Mechanisms and Efficacy of Photobiomodulation Therapy for Arthritis: A Comprehensive Review

Rheumatoid arthritis (RA) and osteoarthritis (OA) have a significant impact on the quality of life of patients around the world, causing significant pain and disability. Furthermore, the drugs used to treat these conditions frequently have side effects that add to the patient's burden. Photobiomodulation (PBM) has emerged as a promising treatment approach in recent years. PBM effectively reduces inflammation by utilizing near-infrared light emitted by lasers or LEDs. In contrast to photothermal effects, PBM causes a photobiological response in cells, which regulates their functional response to light and reduces inflammation. PBM's anti-inflammatory properties and beneficial effects in arthritis treatment have been reported in numerous studies, including animal experiments and clinical trials. PBM's effectiveness in arthritis treatment has been extensively researched in arthritis-specific cells. Despite the positive results of PBM treatment, questions about specific parameters such as wavelength, dose, power density, irradiation time, and treatment site remain. The goal of this comprehensive review is to systematically summarize the mechanisms of PBM in arthritis treatment, the development of animal arthritis models, and the anti-inflammatory and joint function recovery effects seen in these models. The review also goes over the evaluation methods used in clinical trials. Overall, this review provides valuable insights for researchers investigating PBM treatment for arthritis, providing important references for parameters, model techniques, and evaluation methods in future studies.

Biomaterials combined with ADSCs for bone tissue engineering: current advances and applications

In recent decades, bone tissue engineering, which is supported by scaffold, seed cells and bioactive molecules (BMs), has provided new hope and direction for treating bone defects. In terms of seed cells, compared to bone marrow mesenchymal stem cells, which were widely utilized in previous years, adipose-derived stem cells (ADSCs) are becoming increasingly favored by researchers due to their abundant sources, easy availability and multi-differentiation potentials. However, there is no systematic theoretical basis for selecting appropriate biomaterials loaded with ADSCs. In this review, the regulatory effects of various biomaterials on the behavior of ADSCs are summarized from four perspectives, including biocompatibility, inflammation regulation, angiogenesis and osteogenesis, to illustrate the potential of combining various materials with ADSCs for the treatment of bone defects. In addition, we conclude the influence of additional application of various BMs on the bone repair effect of ADSCs, in order to provide more evidences and support for the selection or preparation of suitable biomaterials and BMs to work with ADSCs. More importantly, the associated clinical case reports and experiments are generalized to provide additional ideas for the clinical transformation and application of bone tissue engineering loaded with ADSCs.

Activatable Semiconducting Polymer Nanoinducers Amplify Oxidative Damage via Sono-Ferroptosis for Synergistic Therapy of Bone Metastasis

Bone metastases are secondary malignant tumors that commonly occur after the spread of advanced cancer cells. We herein report the activatable semiconducting polymer nanoinducers (ASPNFP) that can amplify oxidative damage via sono-ferroptosis for bone metastasis treatment. ASPNFP are constructed by encapsulating plasma amine oxidase-based semiconducting polymer nanoparticles (SPNP) and Fe3O4 nanoparticles into singlet oxygen (1O2)-responsive nanocarriers. ASPNFP generate 1O2 under ultrasound (US) irradiation via a sonodynamic effect to destroy the stability of 1O2-responsive nanocarriers, allowing US-triggered releases of SPNP and Fe3O4 nanoparticles. SPNP decompose polyamines in tumor cells to produce acrolein and hydrogen peroxide (H2O2), in which H2O2 promotes Fenton reaction mediated by Fe3O4 nanoparticles for inducing enhanced ferroptosis and generation of hydroxyl radicals (•OH). The generated acrolein, 1O2, and •OH can simultaneously amplify the oxidative damage. ASPNFP thus mediate an amplified sono-ferroptosis effect to inhibit the growth of bone metastasis and restrict tumor metastasis.

Computed Tomography Bone Imaging: Pushing the Boundaries in Clinical Practice

Bone microarchitecture has several clinical implications over and above estimating bone strength. Computed tomography (CT) analysis mainly uses high-resolution peripheral quantitative CT and micro-CT, research imaging techniques, most often limited to peripheral skeleton assessment. Ultra-high-resolution (UHR) CT and photon-counting detector CT, two commercially available techniques, provide images that can approach the spatial resolution of the trabeculae, bringing bone microarchitecture analysis into clinical practice and improving depiction of bone vascularization, tumor matrix, and cortical and periosteal bone. This review presents bone microarchitecture anatomy, principles of analysis, reference measurements, and an update on the performance and potential clinical applications of these new CT techniques. We also share our clinical experience and technical considerations using an UHR-CT device.

Verteporfin attenuates trauma-induced heterotopic ossification of Achilles tendon by inhibiting osteogenesis and angiogenesis involving YAP/β-catenin signaling

Heterotopic ossification occurs as a pathological ossification condition characterized by ectopic bone formation within soft tissues following trauma. Vascularization has long been established to fuel skeletal ossification during tissue development and regeneration. However, the feasibility of vascularization as a target of heterotopic ossification prevention remained to be further clarified. Here, we aimed to identify whether verteporfin as a widely used FDA-approved anti-vascularization drug could effectively inhibit trauma-induced heterotopic ossification formation. In the current study, we found that verteporfin not only dose dependently inhibited the angiogenic activity of human umbilical vein endothelial cells (HUVECs) but also the osteogenic differentiation of tendon stem cells (TDSCs). Moreover, YAP/β-catenin signaling axis was downregulated by the verteporfin. Application of lithium chloride, an agonist of β-catenin, recovered TDSCs osteogenesis and HUVECs angiogenesis that was inhibited by verteporfin. In vivo, verteporfin attenuated heterotopic ossification formation by decelerating osteogenesis and the vessels densely associated with osteoprogenitors formation, which could also be readily reversed by lithium chloride, as revealed by histological analysis and Micro-CT scan in a murine burn/tenotomy model. Collectively, this study confirmed the therapeutic effect of verteporfin on angiogenesis and osteogenesis in trauma-induced heterotopic ossification. Our study sheds light on the anti-vascularization strategy with verteporfin as a candidate treatment for heterotopic ossification prevention.

Skeletal-Vascular Interactions in Bone Development, Homeostasis, and Pathological Destruction

Bone is a highly vascularized organ that not only plays multiple roles in supporting the body and organs but also endows the microstructure, enabling distinct cell lineages to reciprocally interact. Recent studies have uncovered relevant roles of the bone vasculature in bone patterning, morphogenesis, homeostasis, and pathological bone destruction, including osteoporosis and tumor metastasis. This review provides an overview of current topics in the interactive molecular events between endothelial cells and bone cells during bone ontogeny and discusses the future direction of this research area to find novel ways to treat bone diseases.

Angiogenesis coupled with osteogenesis in a bone tissue engineering scaffold enhances bone repair in osteoporotic bone defects

Increased life expectancy has resulted in an increase in osteoporosis incidence worldwide. The coupling of angiogenesis and osteogenesis is indispensable for bone repair. Although traditional Chinese medicine (TCM) exerts therapeutic effects on osteoporosis, TCM-related scaffolds, which focus on the coupling of angiogenesis and osteogenesis, have not yet been used for the treatment of osteoporotic bone defects.Panax notoginsengsaponin (PNS), the active ingredient ofPanax notoginseng, was added to a poly (_L-lactic acid) (PLLA) matrix. Osteopractic total flavone (OTF), the active ingredient ofRhizoma Drynariae, was encapsulated in nano-hydroxyapatite/collagen (nHAC) and added to the PLLA matrix. Magnesium (Mg) particles were added to the PLLA matrix to overcome the bioinert character of PLLA and neutralize the acidic byproducts generated by PLLA. In this OTF-PNS/nHAC/Mg/PLLA scaffold, PNS was released faster than OTF. The control group had an empty bone tunnel; scaffolds containing OTF:PNS = 100:0, 50:50, and 0:100 were used as the treatment groups. Scaffold groups promoted new vessel and bone formation, increased the osteoid tissue, and suppressed the osteoclast activity around osteoporotic bone defects. Scaffold groups upregulated the expression levels of angiogenic and osteogenic proteins. Among these scaffolds, the OTF-PNS (50:50) scaffold exhibited a better capacity for osteogenesis than the OTF-PNS (100:0 and 0:100) scaffolds. Activation of the bone morphogenic protein (BMP)-2/BMP receptor (BMPR)-1A/runt-related transcription factor (RUNX)-2signaling pathway may be a possible mechanism for the promotion of osteogenesis. Our study demonstrated that the OTF-PNS/nHAC/Mg/PLLA scaffold could promote osteogenesis via the coupling of angiogenesis and osteogenesis in osteoporotic rats with bone defects, and activating theBMP-2/BMPR1A/RUNX2signaling pathway may be an osteogenesis-related mechanism. However, further experiments are necessary to facilitate its practical application in the treatment of osteoporotic bone defects.

Steady-State Piperacillin Concentrations in the Proximity of an Orthopedic Implant: A Microdialysis Porcine Study

Implant-associated osteomyelitis is one of the most feared complications following orthopedic surgery. Although the risk is low, sufficient antibiotic protection of the implant surface is important. The aim of this study was to assess steady-state piperacillin concentrations in the proximity of an orthopedic implant. Time above the minimal inhibitory concentration (fT>MIC) was evaluated for MIC of 8 (low target) and 16 μg/mL (high target). Six female pigs received an intravenous bolus infusion of 4 g/0.5 g piperacillin/tazobactam over 30 min every 6 h. Steady state was assumed achieved in the third dosing interval (12-18 h). Microdialysis catheters were placed in a cannulated screw in the proximal tibial cancellous bone, in cancellous bone next to the screw, and in cancellous bone on the contralateral tibia. Dialysates were collected from time 12 to 18 h and plasma samples were collected as reference. For the low piperacillin target (8 µg/mL), comparable mean fT>MIC across all the investigated compartments (mean range: 54-74%) was found. For the high target (16 µg/mL), fT>MIC was shorter inside the cannulated screw (mean: 16%) than in the cancellous bone next to the screw and plasma (mean range: 49-54%), and similar between the two cancellous bone compartments. To reach more aggressive piperacillin fT>MIC targets in relation to the implant, alternative dosing regimens such as continuous infusion may be considered.

Sequential Therapy for Bone Regeneration by Cerium Oxide-Reinforced 3D-Printed Bioactive Glass Scaffolds

Rational design of multifunctional biomaterials with customized architecture and on demand bioactivity is of great significance for bone tissue engineering (BTE) in modern society. Herein, a versatile therapeutic platform has been established by integrating cerium oxide nanoparticles (CeO₂ NPs) into bioactive glass (BG) to fabricate three-dimensional (3D)-printed scaffolds, achieving a sequential therapeutic effect against inflammation and promoting osteogenesis toward bone defect. The antioxidative activity of CeO₂ NPs plays a crucial role in alleviating the oxidative stress upon formation of bone defects. Subsequently, CeO₂ NPs exert a promotion effect on the proliferation and osteogenic differentiation of rat osteoblasts through enhancing mineral deposition and alkaline phosphatase and osteogenic gene expression. Strikingly, the incorporation of CeO₂ NPs bestows on the BG scaffolds greatly reinforced mechanical properties, improved biocompatibility, adequate cell adhesion, elevated osteogenic capability, and multifunctional performance in a single platform. In vivo studies on the treatment of rat tibial defect confirmed the better osteogenic properties of CeO₂-BG scaffolds compared with pure BG scaffolds. Additionally, the employment of the 3D printing technique creates a proper porous microenvironment around the bone defect, which further facilitates the cell in-growth and new bone formation. This report provides a systematic study on CeO₂-BG 3D-printed scaffolds prepared by simple ball milling method, achieving sequential and integral treatment in BTE based on a single platform.

Penetration of Vancomycin into Noninfected Bone in Patients Undergoing Total Joint Arthroplasty Evaluated by a Minimal Physiologically Based Population Pharmacokinetic Modeling Approach

Arthroplasty is a healthcare priority and represents high volume, high cost surgery. Periprosthetic joint infection (PJI) results in significant mortality, thus it is vital that the risk for PJI is minimized. Vancomycin is recommended for surgical prophylaxis in total joint arthroplasty (TJA) by current clinical practice guidelines endorsed by the Infectious Diseases Society of America. This study aimed to develop a new assay to determine vancomycin concentrations in serum and bone, and a minimal physiologically based population PK (mPBPK) model to evaluate vancomycin bone penetration in noninfected patients. Eleven patients undergoing TJA received 0.5-2.0 g intravenous vancomycin over 12-150 min before surgery. Excised bone specimens and four blood samples were collected per patient. Bone samples were pulverized under liquid nitrogen using a cryogenic mill. Vancomycin concentrations in serum and bone were analyzed by liquid chromatography-tandem mass spectrometry and subjected to mPBPK modeling. Vancomycin serum and bone concentrations ranged from 9.30 to 86.6 mg/L, and 1.94-37.0 mg/L, respectively. Average bone to serum concentration ratio was 0.41 (0.16-1.0) based on the collected samples. The population mean total body clearance was 2.12L/h/kg^0.75. Inclusion of total body weight as a covariate substantially decreased interindividual variability in clearance. The bone/blood partition coefficient (K_pbone) was estimated at 0.635, reflecting the average bone/blood concentration ratio at steady-state. The model predicted median ratio of vancomycin area under the curve (AUC) for bone/AUC for serum was 44%. Observed vancomycin concentrations in bone were overall consistent with perfusion-limited distribution from blood to bone. An mPBPK model overall well described vancomycin concentrations in serum and bone.

A Novel Computational Biomechanics Framework to Model Vascular Mechanopropagation in Deep Bone Marrow

The mechanical stimuli generated by body exercise can be transmitted from cortical bone into the deep bone marrow (mechanopropagation). Excitingly, a mechanosensitive perivascular stem cell niche is recently identified within the bone marrow for osteogenesis and lymphopoiesis. Although it is long known that they are maintained by exercise-induced mechanical stimulation, the mechanopropagation from compact bone to deep bone marrow vasculature remains elusive of this fundamental mechanobiology field. No experimental system is available yet to directly understand such exercise-induced mechanopropagation at the bone-vessel interface. To this end, taking advantage of the revolutionary in vivo 3D deep bone imaging, an integrated computational biomechanics framework to quantitatively evaluate the mechanopropagation capabilities for bone marrow arterioles, arteries, and sinusoids is devised. As a highlight, the 3D geometries of blood vessels are smoothly reconstructed in the presence of vessel wall thickness and intravascular pulse pressure. By implementing the 5-parameter Mooney-Rivlin model that simulates the hyperelastic vessel properties, finite element analysis to thoroughly investigate the mechanical effects of exercise-induced intravascular vibratory stretching on bone marrow vasculature is performed. In addition, the blood pressure and cortical bone bending effects on vascular mechanoproperties are examined. For the first time, movement-induced mechanopropagation from the hard cortical bone to the soft vasculature in the bone marrow is numerically simulated. It is concluded that arterioles and arteries are much more efficient in propagating mechanical force than sinusoids due to their stiffness. In the future, this in-silico approach can be combined with other clinical imaging modalities for subject/patient-specific vascular reconstruction and biomechanical analysis, providing large-scale phenotypic data for personalized mechanobiology discovery.

Smokeless Tobacco Use is Associated With Worse Outcomes Following Total Knee Arthroplasty

BACKGROUND

Studies have demonstrated increased complication risk after total knee arthroplasty (TKA) in patients who smoke cigarettes, but it is unclear if smokeless tobacco use confers a similar impact. The purpose of this study was to (1) evaluate rates of postoperative complications after TKA in smokeless tobacco users and smokers as compared to matched controls, and (2) compare rates of postoperative complications in smokeless tobacco users versus smokers to determine if one is associated with significantly higher rates of postoperative complications.

METHODS

A retrospective cohort study was conducted using a national database. For patients who underwent primary TKA, smokeless tobacco users (n = 1,535) and smokers (n = 28,953) were matched at a 1:4 with controls (n = 6,140 and 115,812, respectively), and smokeless tobacco users (n = 1,481) were matched at a 1:4 with smokers (n = 5,924). Rates of joint complications within 2 years and medical complications within 90 days postoperatively were compared using multivariable logistic regressions.

RESULTS

After primary TKA, compared to controls, smokeless tobacco users demonstrated significantly higher rates of aseptic loosening/mechanical failure within 2 years, longer lengths of stay, and higher rates of urinary tract infection, pneumonia, deep vein thrombosis, and acute kidney injury within 90 days. Compared to smokers, smokeless tobacco users demonstrated significantly lower rates of aseptic revision and lower rates of wound disruption.

CONCLUSION

Smokeless tobacco use is associated with higher rates of both medical and joint complications following primary TKA. However, smoking is associated with higher risk for complications than smokeless tobacco use.

LEVEL OF EVIDENCE

Level III.

Type H vessel/platelet-derived growth factor receptor β+ perivascular cell disintegration is involved in vascular injury and bone loss in radiation-induced bone damage

Collapse of the microvascular system is a prerequisite for radiation-induced bone loss. Since type H vessels, a specific bone vessel subtype surrounded by platelet-derived growth factor receptor β⁺ (PDGFRβ⁺ ) perivascular cells (PVCs), has been recently identified to couple angiogenesis and osteogenesis, we hypothesize that type H vessel injury initiates PDGFRβ⁺ PVC dysfunction, which contributes to the abnormal angiogenesis and osteogenesis after irradiation. In this study, we found that radiation led to the decrease of both type H endothelial cell (EC) and PDGFRβ⁺ PVC numbers. Remarkably, results from lineage tracing showed that PDGFRβ⁺ PVCs detached from microvessels and converted the lineage commitment from osteoblasts to adipocytes, leading to vascular injury and bone loss after irradiation. These phenotype transitions above were further verified to be associated with the decrease in hypoxia-inducible factor-1α (HIF-1α)/PDGF-BB/PDGFRβ signalling between type H ECs and PDGFRβ⁺ PVCs. Pharmacological blockade of HIF-1α/PDGF-BB/PDGFRβ signalling induced a phenotype similar to radiation-induced bone damage, while the rescue of this signalling significantly alleviated radiation-induced bone injury. Our findings show that the decrease in HIF-1α/PDGF-BB/PDGFRβ signalling between type H ECs and PDGFRβ⁺ PVCs after irradiation affects the homeostasis of EC-PVC coupling and plays a part in vascular damage and bone loss, which has broad implications for effective translational therapies.

Examination of human osteoarchaeological remains as a feasible source of polar and apolar metabolites to study past conditions

Metabolomics is a modern tool that aids in our understanding of the molecular changes in organisms. Archaeological science is a branch of archaeology that explores different archaeological materials using modern analytical tools. Human osteoarchaeological material are a frequent finding in archaeological contexts and have the potential to offer information about previous human populations, which can be illuminating about our current condition. Using a set of samples comprising different skeletal elements and bone structures, here we explore for the first time the possibility of extracting metabolites from osteoarchaeological material. Here, a protocol for extraction and measurement of extracted polar and less-polar/apolar metabolites by ultra-high performance liquid chromatography hyphenated to high resolution mass spectrometry is presented to measure the molecules separated after a reversed phase and hydrophilic interaction liquid chromatography column. Molecular information was obtained, showing that osteoarchaeological material is a viable source of molecular information for metabolomic studies.

Bone Healing Gone Wrong: Pathological Fracture Healing and Non-Unions-Overview of Basic and Clinical Aspects and Systematic Review of Risk Factors

Bone healing is a multifarious process involving mesenchymal stem cells, osteoprogenitor cells, macrophages, osteoblasts and -clasts, and chondrocytes to restore the osseous tissue. Particularly in long bones including the tibia, clavicle, humerus and femur, this process fails in 2-10% of all fractures, with devastating effects for the patient and the healthcare system. Underlying reasons for this failure are manifold, from lack of biomechanical stability to impaired biological host conditions and wound-immanent intricacies. In this review, we describe the cellular components involved in impaired bone healing and how they interfere with the delicately orchestrated processes of bone repair and formation. We subsequently outline and weigh the risk factors for the development of non-unions that have been established in the literature. Therapeutic prospects are illustrated and put into clinical perspective, before the applicability of biomarkers is finally discussed.

Substance P-Mediated Vascular Protection Ameliorates Bone Loss

Estrogen deficiency causes bone loss via diverse pathological cellular events. The involvement of the vasculature in bone formation has been widely studied, and type H vasculature has been found to be closely related to bone healing. Ovariectomy- (OVX-) induced estrogen deficiency reduces type H vessel density and promotes reduction of bone density. Analysis of early events after OVX showed that estrogen deficiency preferentially induces oxidative stress, which might provoke endothelial dysfunction and reduce angiogenic factors systemically and locally. The instability of the vascular potential is expected to promote bone loss under estrogen deficiency. Substance P (SP) is an endogenous neuropeptide that controls inflammation and prevents cell death under pathological conditions. SP can elevate nitric oxide production in endothelial cells and inhibit endothelial dysfunction. This study is aimed at investigating the preventive effects of systemically injected SP on OVX-induced vascular loss and osteoporosis onset. SP was systemically administered to OVX rats twice a week for 4 weeks, immediately after OVX induction. OVX conditions could decrease antioxidant enzyme activity, type H vessels, and angiogenic growth factors in the bone marrow, followed by inflammation and bone loss. However, pretreatment with SP could block type H vessel loss, accompanied by the enrichment of nitric oxide and sustained angiogenic factors. SP-mediated early vascular protection inhibits bone density reduction. Altogether, this study suggests that early administration of SP can block osteoporosis development by modulating oxidative stress and protecting the bone vasculature and angiogenic paracrine potential at the initial stage of estrogen deficiency.

Ginsenoside Rg1 interferes with the progression of diabetic osteoporosis by promoting type H angiogenesis modulating vasculogenic and osteogenic coupling

Ginsenoside Rg1 (Rg1) has been demonstrated to have antidiabetic and antiosteoporotic activities. The aim of this study was to investigate the protective effect of Rg1 against diabetic osteoporosis and the underlying mechanism. In vitro, we found that Rg1 increased the number of osteoprogenitors and alleviated high glucose (HG) induced apoptosis of osteoprogenitors by MTT assays and flow cytometry. qRT‒PCR and western blot analysis suggested that Rg1 can also promote the secretion of vascular endothelial growth factor (VEGF) by osteoprogenitors and promote the coupling of osteogenesis and angiogenesis. Rg1 can also promote the proliferation of human umbilical vein endothelial cells (HUVECs) cultured in high glucose, enhance the angiogenic ability of endothelial cells, and activate the Notch pathway to promote endothelial cells to secrete the osteogenesis-related factor Noggin to regulate osteogenesis, providing further feedback coupling of angiogenesis and osteogenesis. Therefore, we speculated that Rg1 may have similar effects on type H vessels. We used the Goto-Kakizaki (GK) rat model to perform immunofluorescence staining analysis on two markers of type H vessels, Endomucin (Emcn) and CD31, and the osteoblast-specific transcription factor Osterix, and found that Rg1 stimulates type H angiogenesis and bone formation. In vivo experiments also demonstrated that Rg1 promotes VEGF secretion, activates the Noggin/Notch pathway, increases the level of coupling between type H vessels and osteogenesis, and improves the bone structure of GK rats. All of these data reveal that Rg1 is a promising candidate drug for treating diabetic osteoporosis as a potentially bioactive molecule that promotes angiogenesis and osteointegration coupling.

3D-Printing for Critical Sized Bone Defects: Current Concepts and Future Directions

The management and definitive treatment of segmental bone defects in the setting of acute trauma, fracture non-union, revision joint arthroplasty, and tumor surgery are challenging clinical problems with no consistently satisfactory solution. Orthopaedic surgeons are developing novel strategies to treat these problems, including three-dimensional (3D) printing combined with growth factors and/or cells. This article reviews the current strategies for management of segmental bone loss in orthopaedic surgery, including graft selection, bone graft substitutes, and operative techniques. Furthermore, we highlight 3D printing as a technology that may serve a major role in the management of segmental defects. The optimization of a 3D-printed scaffold design through printing technique, material selection, and scaffold geometry, as well as biologic additives to enhance bone regeneration and incorporation could change the treatment paradigm for these difficult bone repair problems.

Prediction Criteria for the Formation of Refracture after Union of a Long Bone Fracture on the Basis of Hemodynamic Changes in the Tissues of the Area of Damage

We studied hemodynamic changes in the area of leg bone fracture and determined the prognostic criteria for refracture formation after achieved union. In Wistar rats (n=18), shin bone fracture with external fixation of the fragments was modeled. The union was formed 35 days after osteosynthesis, the device was removed at this term. In 5 cases, a refracture was formed after the termination of fixation. Hemodynamics and local temperature in the tissues in the area of injury were recorded before the start of the experiment and on days 21 and 35 of fixation. In rats with refracture after union, the blood circulation in the area of damage was characterized by a pronounced hypertonicity of the arteries of both large and small diameters, obstruction of venous outflow, and local hyperthermia. This hemodynamics in tissues in the area of damage can serve as an informative criterion for predicting the course of reparative osteogenesis.

Dexamethasone loaded injectable, self-healing hydrogel microspheresbased on UPy-functionalized Gelatin/ZnHAp physical network promotes bone regeneration

Biopolymer-based injectable hydrogels provide great potential as bone tissue engineering (BTE) scaffolds on account of biocompatibility, and pore interconnectivity that enables delivery of cells and/or signaling molecules for bone repair. Recently, Gelatin hydrogels based on H-bonds were considered in response to concerns around the chemical crosslinking agents. In this study, a self-healing gelatin hydrogel with remarkable compressive and self-healing properties was prepared via formation of quadruple hydrogen bonds between ureidopyrimidinon functional groups, which were substituted on NH₂ groups of gelatin(GelUPy). Degree of substitution controls properties of the resulting hydrogel from a shape- memory hydrogel (100% substitution), to a hydrogel (about 80%), to this self-healing hydrogel (about 40%). We report a strategy that adopts an emulsion synthesis approach to delivery of dexamethasone and Ca/Zn ions from injectable self-healing GelUPy hydrogel (GelUPy-ZnHApUPy-DEX), to induce osteogenic differentiation of adipose-derived stem cells, in vitro, and enhance bone regeneration in a cranial bone defect in a rat model. We show that key properties of the composite hydrogels, including mechanical properties, and release behavior of DEX are a match to the requirements of BTE. Overall, our results demonstrate that this self-healing gelatin approach is a promising strategy to enhance bone regeneration through a minimally invasive procedure.

Restoration of the Knee Medial Collateral Ligament and Complete Soft-tissue Coverage After Medial Open-Wedge High Tibial Osteotomy

High tibial osteotomy (HTO) is used in the treatment of knee osteoarthritis. This surgical procedure is indicated in patients with medial osteoarthritis who are relatively young and active and have a good range of motion. In most medial open-wedge HTO cases, the fascia, medial collateral ligament (MCL), and part of the knee joint capsule are carefully separated and moved to expose the osteotomy site, but many patients experience postoperative swelling and pain in the affected limb due to bleeding from the osteotomy site and MCL failure. We have developed a method of osteotomy followed by a restoration of the MCL to its anatomic position and complete soft-tissue coverage of the osteotomy. This Technical Note aims to provide a comprehensive description of the employment of a soft-tissue envelope for the MOW-HTO protection.

Association of adenosine signaling gene signature with estrogen receptor-positive breast and prostate cancer bone metastasis

Bone metastasis is a common and devastating consequence of several major cancer types, including breast and prostate. Osteocytes are the predominant bone cell, and through connexin (Cx) 43 hemichannels release ATP to the bone microenvironment that can be hydrolyzed to adenosine. Here, we investigated how genes related to ATP paracrine signaling are involved in two common bone-metastasizing malignancies, estrogen receptor positive (ER⁺) breast and prostate cancers. Compared to other sites, bone metastases of both cancer types expressed higher levels of ENTPD1 and NT5E, which encode CD39 and CD73, respectively, and hydrolyze ATP to adenosine. ADORA3, encoding the adenosine A3 receptor, had a similar expression pattern. In primary ER⁺ breast cancer, high levels of the triplet ENTPD1/NT5E/ADORA3 expression signature was correlated with lower overall, distant metastasis-free, and progression-free survival. In ER⁺ bone metastasis biopsies, this expression signature is associated with lower survival. This expression signature was also higher in bone-metastasizing primary prostate cancers than in those that caused other tumor events or did not lead to progressive disease. In 3D culture, a non-hydrolyzable ATP analog inhibited the growth of breast and prostate cancer cell lines more than ATP did. A3 inhibition also reduced spheroid growth. Large-scale screens by the Drug Repurposing Hub found ER⁺ breast cancer cell lines were uniquely sensitive to adenosine receptor antagonists. Together, these data suggest a vital role for extracellular ATP degradation and adenosine receptor signaling in cancer bone metastasis, and this study provides potential diagnostic means for bone metastasis and specific targets for treatment and prevention.

Update on MRI findings of osteomyelitis of long bones in the adult population

OBJECTIVES

To evaluate the usefulness of new and established MRI signs of osteomyelitis in long bones in adults.

METHODS

All patient records over a 9-year period with clinical or MRI suspicion for osteomyelitis were retrospectively reviewed, using strict criteria for proof of infection. Two musculoskeletal radiologists independently reviewed the MRIs of proven osteomyelitis.

RESULTS

Out of 45 MRIs of confirmed osteomyelitis, 2 MRIs (4%) did not show confluent low-signal intensity on T1-weighted images, but all showed confluent high-signal intensity on T2-weighted images. Central hypoenhancing regions of marrow without abscess formation were found in 15-18/35 (43-51%) cases where gadolinium was given. We often found multiple foci of marrow replacement in the same bone. The areas of marrow involvement often had an irregular contour. Penumbra sign, marrow fat globules, and sequestra were uncommon.

CONCLUSION

Multiple foci of bone marrow signal abnormalities, an irregular contour of marrow abnormality, and central marrow hypoenhancement without abscess are common signs of osteomyelitis of long bones in adults. Confluent low T1-signal intensity is not always present.

Microfluidic evidence of synergistic effects between mesenchymal stromal cell-derived biochemical factors and biomechanical forces to control endothelial cell function

A functional vascular system is a prerequisite for bone repair as disturbed angiogenesis often causes non-union. Paracrine factors released from human bone marrow derived mesenchymal stromal cells (BMSCs) have angiogenic effects on endothelial cells. However, whether these paracrine factors participate in blood flow dynamics within bone capillaries remains poorly understood. Here, we used two different microfluidic designs to investigate critical steps during angiogenesis and found pronounced effects of endothelial cell proliferation as well as chemotactic and mechanotactic migration induced by BMSC conditioned medium (CM). The application of BMSC-CM in dynamic cultures demonstrates that bioactive factors in combination with fluidic flow-induced biomechanical signals significantly enhanced endothelial cell migration. Transcriptional analyses of endothelial cells demonstrate the induction of a unique gene expression profile related to tricarboxylic acid cycle and energy metabolism by the combination of BMSC-CM factors and shear stress, which opens an interesting avenue to explore during fracture healing. Our results stress the importance of in vivo - like microenvironments simultaneously including biochemical, biomechanical and oxygen levels when investigating key events during vessel repair. STATEMENT OF SIGNIFICANCE: Our results demonstrate the importance of recapitulating in vivo - like microenvironments when investigating key events during vessel repair. Endothelial cells exhibit enhanced angiogenesis characteristics when simultaneous exposing them to hMSC-CM, mechanical forces and biochemical signals simultaneously. The improved angiogenesis may not only result from the direct effect of growth factors, but also by reprogramming of endothelial cell metabolism. Moreover, with this model we demonstrated a synergistic impact of mechanical forces and biochemical factors on endothelial cell behavior and the expression of genes involved in the TCA cycle and energy metabolism, which opens an interesting new avenue to stimulate angiogenesis during fracture healing.

Concentrations of co-administered vancomycin and meropenem in the internal dead space of a cannulated screw and in cancellous bone adjacent to the screw - Evaluated by microdialysis in a porcine model

BACKGROUND

Cannulated screws are often used in the management of open lower extremity fractures. These fractures exhibit broad contamination profiles, necessitating empirical Gram-positive and Gram-negative antibiotic coverage. To ensure full antibiotic protection of the cannulated screw and the bone tissue, it is generally accepted that target tissue antibiotic concentrations, as a minimum, reach and remain above relevant epidemiological cut-off minimal inhibitory concentrations (T>MIC) for a sufficient amount of time.

METHODS

8 female pigs were included. Microdialysis catheters were placed in the internal dead space of a cannulated screw placed in tibial cancellous bone, in tibial cancellous bone adjacent to the screw (mean distance to the screw: 3 mm), and in cancellous bone on the contralateral tibia. Following single-dose simultaneous intravenous administrations of vancomycin (1000 mg) and meropenem (1000 mg), microdialysates and plasma were dynamically sampled over 8 h. The applied MIC targets ranged from 1 to 4 µg/mL for vancomycin and 0.125-2 µg/mL for meropenem RESULTS: For both drugs, and for all MIC targets investigated (except for the high vancomycin target: 4 µg/mL), the internal dead space of the cannulated screw had the shortest T>MIC. At the low MIC targets T>MIC ranged between 88 and 449 min across sampling sites for vancomycin (1 µg/mL), and 148-406 min for meropenem (0.125 µg/mL). For the high MIC targets, T>MIC ranged between 3 and 446 min for vancomycin (4 μg/mL) and 17-181 min for meropenem (2 μg/mL). Vancomycin displayed longer T>MIC (2 and 4 μg/mL), higher area under the concentration time curve (AUC_0-last) and peak drug concentration in the proximal tibial cancellous bone without a screw nearby. For meropenem, only the cancellous bone AUC_0-last was significantly higher on the side with no screw.

CONCLUSION

We found short T>MIC, particularly for the high MIC targets for vancomycin and meropenem, both inside the cannulated screw and in cancellous bone adjacent to the screw. The presence of a cannulated screw impaired the penetration of especially vancomycin into cancellous bone adjacent to the screw. More aggressive or different vancomycin and meropenem approaches may be considered to encompass contaminating differences and to ensure a theoretically more sufficient antibiotic protection of cannulated screws when used in the management of open lower extremity fractures.

Similarities Between Disuse and Age-Induced Bone Loss

Disuse and aging are known risk factors associated with low bone mass and quality deterioration, resulting in increased fracture risk. Indeed, current and emerging evidence implicate a large number of shared skeletal manifestations between disuse and aging scenarios. This review provides a detailed overview of current preclinical models of musculoskeletal disuse and the clinical scenarios they seek to recapitulate. We also explore and summarize the major similarities between bone loss after extreme disuse and advanced aging at multiple length scales, including at the organ/tissue, cellular, and molecular level. Specifically, shared structural and material alterations of bone loss are presented between disuse and aging, including preferential loss of bone at cancellous sites, cortical thinning, and loss of bone strength due to enhanced fragility. At the cellular level bone loss is accompanied, during disuse and aging, by increased bone resorption, decreased formation, and enhanced adipogenesis due to altered gap junction intercellular communication, WNT/β-catenin and RANKL/OPG signaling. Major differences between extreme short-term disuse and aging are discussed, including anatomical specificity, differences in bone turnover rates, periosteal modeling, and the influence of subject sex and genetic variability. The examination also identifies potential shared mechanisms underlying bone loss in aging and disuse that warrant further study such as collagen cross-linking, advanced glycation end products/receptor for advanced glycation end products (AGE-RAGE) signaling, reactive oxygen species (ROS) and nuclear factor κB (NF-κB) signaling, cellular senescence, and altered lacunar-canalicular connectivity (mechanosensation). Understanding the shared structural alterations, changes in bone cell function, and molecular mechanisms common to both extreme disuse and aging are paramount to discovering therapies to combat both age-related and disuse-induced osteoporosis. © 2022 American Society for Bone and Mineral Research (ASBMR).

Biocompatible silane adhesion layer on titanium implants improves angiogenesis and osteogenesis

Silane adhesion layer strategy has been widely used to covalently graft biomolecules to the titanium implant surface, thereby conferring the implant bioactivity to ameliorate osseointegration. However, few researchers pay attention to the effects of silanization parameters on biocompatibility and biofunctionality of the silane adhesion layers. Accordingly, the present study successfully fabricated the silane adhesion layers with different thickness, intactness, and surface morphologies by introducing 3-aminopropyltriethoxysilane on the alkali-treated titanium surface in time-varied processing of silanization. The regulatory effects of the silane adhesion layers on angiogenesis and osteogenesis were assessed in vitro. Results showed that the prolonged silanization processing time increased the thickness and intactness of the silane adhesion layer and significantly improved its biocompatibility. Notably, the silane adhesion layer prepared after 12 h of silanization exhibited a brain-like surface morphology and benefited the adhesion and proliferation of endothelial cells (ECs) and osteoblasts (OBs). Moreover, the layer promoted angiogenesis via stimulating vascular endothelial growth factor (VEGF) secretion and nitric oxide (NO) production of ECs. Simultaneously, it improved osteogenesis by enhancing alkaline phosphatase (ALP) activity, collagen secretion, and extracellular matrix mineralization of OBs. This work systematically investigated the biocompatibility and biofunctionality of the modified silane adhesion layers, thus providing valuable references for their application in covalently grafting biomolecules on the titanium implant surface.

Total flavonoids of Rhizoma Drynariae enhances CD31hiEmcnhi vessel formation and subsequent bone regeneration in rat models of distraction osteogenesis by activating PDGF‑BB/VEGF/RUNX2/OSX signaling axis

Total flavonoids of Rhizoma Drynariae (TFRD), extracted from the kidney-tonifying Traditional Chinese medicine Rhizoma Drynariae, can be effective in treating osteoporosis, bone fractures and defects. However, the pharmacological effects of TFRD on the specific vessel subtype CD31^hiEmcn^hi during distraction osteogenesis (DO) remains unclear. The present study aimed to investigate the effects of TFRD on CD31^hiEmcn^hi vessels in a rat model of DO. In the present study, tibial DO models were established using 60 rats with a distraction rate of 0.2 mm per day for 20 days. Co-immunofluorescence staining of CD31 and endomucin (Emcn) was conducted to determine CD31^hiEmcn^hi vessels. Radiographic, angiographic and histological analyses were performed to assess bone and vessel formation. Tube formation, alkaline phosphatase (ALP) and Von Kossa staining assays were performed to test angiogenesis of endothelial precursor cells (EPCs) and osteogenesis of bone marrow-derived mesenchymal stem cells (BMSCs). Additionally, expression levels of platelet-derived growth factor (PDGF)-BB, VEGF, runt-related transcription factor 2 (RUNX2) and Osterix (OSX) were determined by western blotting and reverse transcription-quantitative PCR. The in vivo assays demonstrated that TFRD markedly promoted CD31^hiEmcn^hi vessel formation during DO, whereas PDGF-BB neutralizing antibody suppressed vessel formation. Furthermore, the ALP, Von Kossa staining and tube formation assays indicated that TFRD notably elevated the angiogenic capacity of EPCs and osteogenic capacity of BMSCs under stress conditions, which was significantly suppressed by blocking PDGF-BB. The protein and mRNA levels of PDGF-BB, VEGF, RUNX2 and OSX were upregulated by TFRD, but downregulated by blocking PDGF-BB. Thus, TFRD could facilitate CD31^hiEmcn^hi vessel formation and subsequently enhance angiogenic-osteogenic coupling to regenerate bone defects during DO via the PDGF-BB/VEGF/RUNX2/OSX signaling axis, which indicated that CD31^hiEmcn^hi vessels could be a potential novel therapeutic target for DO, and TFRD may represent a promising drug for promoting bone regeneration in DO by increasing CD31^hiEmcn^hi vessels.

Mechanisms of dermal bone repair after predatory attack in the giant stem-group teleost Leedsichthys problematicus Woodward, 1889a (Pachycormiformes)

Leedsichthys problematicus is a suspension-feeding member of the Mesozoic clade Pachycormiformes (stem-group Teleostei), and the largest known ray-finned fish (Actinopterygii). As in some larger fish, the skeleton is poorly ossified, but the caudal fin (tail) is well-preserved. Bony calluses have been found here, on the dermal fin rays, and when sectioned, show evidence of bone repair in response to damage. As part of this repair, distinctive tissue changes are observed, including the deposition of woven bone onto broken bone fragments and the surface of the lepidotrichium, after resorption of the edges of these fragments and the lepidotrichial surface itself. Within the woven bone are many clear elongate spaces, consistent with their interpretation as bundles of unmineralized collagen (Sharpey's fibres). These normally provide attachment within dermal bones, and here attach new bone to old, particularly to resorbed surfaces, identified by scalloped reversal lines. Haversian systems are retained in the old bone, from which vasculature initially invaded the callus, hence bringing stem cells committed to forming bone onto the surfaces of the damaged area. These observations provide strong evidence of a vital response through survival of a predatory attack by a large marine reptile, coeval with Leedsichthys in the Jurassic seas.

De novo dual functional 3D scaffold using computational simulation with controlled drug release

A novel and facile synthesis is made of cotton-like three-dimensional (3D) fibrous scaffold containing spatiotemporally defined patterns of simvastatin (SIM) optimized for angiogenesis-coupled osteogenesis. Herein, we demonstrate the 3D fiber deposition mechanism in detail during the electrospinning process via computer simulation. The 3D fibrous scaffolds were functionalized with hydroxyapatite nanoparticles (HA - NPs) to induce the biomineralization process mimicking the natural apatite layer. The morphology, physiochemical properties, biomimetic mineralization, and drug release of the as-fabricated 3D fibrous scaffolds of simvastatin-loaded poly (ɛ-caprolactone) poly (glycerol-sebacate) hydroxyapatite nanoparticles (3D - PGHS) were investigated. The effects of simvastatin on the osteogenic differentiation of human mesenchymal stem cells (hMSCs) and angiogenesis in human umbilical vein endothelial cells (HUVECs) were assessed. The results showed that the 3D - PGHS both enhanced the expression of osteogenic markers including ALP, RUNX2, and COLA1 in hMSCs, and promoted the migration and tube formation of HUVECs. This finding demonstrates the potential of 3D scaffold-loaded SIM as a putative point-of-care therapy for tightly controlled tissue regeneration.

Exosomes derived from magnesium ion-stimulated macrophages inhibit angiogenesis

Angiogenesis, an essential prerequisite to osteogenesis in bone repair and regeneration, can be mediated by immunoregulation of macrophages. Magnesium and its alloys are promising biodegradable bone implant materials and can affect immunoregulation of macrophages by the degradation products (magnesium ions. Nevertheless, the mechanism of macrophage-derived exosomes stimulated by Mg ions in immunoregulation is still not well understood. Herein, 10-50 mM magnesium ions are shown to inhibit the macrophage viability and proliferation in a dose-dependent manner, but a high concentration results in macrophage apoptosis. The exosomes secreted by macrophages from magnesium ion stimulation inhibit angiogenesis of endothelial cells, as manifested by the suppressed cell viability, proliferation, migration, and tube formation, which arise at least partially from exosome-mediated downregulation of endothelial nitric oxide and the vascular endothelial growth factor. The findings reported in this paper suggest that the bio-functionality of biodegradable magnesium alloys must be considered from the perspective of immunoregulation of macrophage-derived exosomes. Our results also suggest potential cancer therapy by inhibiting tumor-associated angiogenesis.