Targeting endothelial PDGFR-ß facilitates angiogenesis-associated bone formation through the PAK1/NICD axis.

The intricate orchestration of osteoporosis (OP) pathogenesis remains elusive. Mounting evidence suggests that angiogenesis-driven osteogenesis serves as a crucial foundation for maintaining bone homeostasis. This study aimed to explore the potential of the endothelial platelet-derived growth factor receptor-ß (PDGFR-ß) in mitigating bone loss through its facilitation of H-type vessel formation. Our findings demonstrate that the expression level of endothelial PDGFR-ß is reduced in samples obtained from individuals suffering from OP, as well as in ovariectomy mice. Depletion of PDGFR-ß in endothelial cells ameliorates angiogenesis-mediated bone formation in mice. The regulatory influence of endothelial PDGFR-ß on H-type vessels is mediated through the PDGFRß-P21-activated kinase 1-Notch1 intracellular domain signaling cascade. In particular, the endothelium-specific enhancement of PDGFR-ß facilitates H-type vessels and their associated bone formation in OP. Hence, the strategic targeting of endothelial PDGFR-ß emerges as a promising therapeutic approach for the management of OP in the near future.

Injectable Ozone-Rich Nanocomposite Hydrogel Loaded with D-Mannose for Anti-Inflammatory and Cartilage Protection in Osteoarthritis Treatment.

Osteoarthritis (OA) is a dynamic condition characterized by cartilage damage and synovial inflammation. Ozone (O3) shows potential therapeutic effects owing to its anti-inflammatory properties; however, its high reactivity and short half-life substantially limit its effectiveness in OA treatment. In this study, an ozone-rich thermosensitive nanocomposite hydrogel loaded with D-mannose is developed for OA treatment. Briefly, O3 is encapsulated in nanoparticles (NPs) composed of perfluorotributylamine and fluorinated hyaluronic acid to improve its stability. Next, D-mannose is conjugated with α-amino of the hydroxypropyl chitin (HPCH) via Schiff base to prepare MHPCH. These nanoparticles are encapsulated in MHPCH to produce O3 NPs@MHPCH. In vitro cell experiments demonstrate that the O3 NPs@MHPCH treatment significantly reduced VEGF and inflammation levels, accompanied by a decrease in inflammatory factors such as IL-1ß, IL-6, TNF-α, and iNOS. Furthermore, O3 NPs@MHPCH promotes the expression of collagen II and aggrecan and stimulates chondrocyte proliferation. Additionally, in vivo studies show that O3 NPs@MHPCH significantly alleviated OA by reducing synovial inflammation, cartilage destruction, and subchondral bone remodeling. O3 NPs@MHPCH offers a promising option for improving the efficacy of O3 therapy and reducing the risk of synovial inflammation and cartilage degeneration in OA.

Specific inhibition of FAK signaling attenuates subchondral bone deterioration and articular cartilage degeneration during osteoarthritis pathogenesis.

Osteoarthritis (OA), a disease of the entire joint, is characterized by abnormal bone remodeling and coalescent degradation of articular cartilage. We have previously found that elevated levels of H-type vessels in subchondral bone correlate with OA and that focal adhesion kinase (FAK) is critical for H-type vessel formation in osteoporosis. However, the potential role of FAK in OA remains unexplored. Here, we demonstrate that the p-FAK level was dramatically elevated in subchondral bone following anterior cruciate ligament transection (ACLT) in rats. Specific inhibition of FAK signaling with Y15 in subchondral bone resulted in the suppression of subchondral bone deterioration and this effect was mediated by H-type vessel-induced ectopic bone formation. Further, articular cartilage degeneration was also alleviated after Y15 treatment. In vitro, the p-FAK level was significantly elevated in mesenchymal stem cells (MSCs) from vehicle-treated ACLT rats as compared to that in MSCs from sham controls and Y15-treated ACLT rats. Elevated p-FAK level in MSCs promoted vascular endothelial growth factor (VEGF) expression, as demonstrated from the high VEGF level in the blood, subchondral bone, and conditioned medium (CM) of MSCs from vehicle-treated ACLT rats. The CM of MSCs from vehicle-treated ACLT rats might promote the angiogenesis of endothelial cells and the catabolic response of chondrocytes through the FAK-growth factor receptor-bound protein 2-mitogen-activated protein kinase-mediated expression of VEGF. The effect of the CM from MSCs of Y15-treated ACLT rats or that treated with a VEGF-neutralizing antibody on vessel formation and the catabolic response was lowered. Thus, the specific inhibition of FAK signaling may be a promising avenue for the prevention or early treatment of OA.

The role of EGFR signaling in age-related osteoporosis in mouse cortical bone.

So far, there has been no effective cure for osteoporotic cortical bone, the most significant change in long bone structure during aging and the main cause of bone fragility fractures, because its underlying molecular and cellular mechanisms remain largely unknown. We used 3- and 15-mo-old mice as well as 15-mo-old mice treated with vehicle and gefitinib to evaluate structural, cellular, and molecular changes in cortical bone. We found that the senescence of osteoprogenitors was increased, whereas the expression of phosphorylated epidermal growth factor receptor (EGFR) on the endosteal surface of cortical bone down-regulated in middle-aged 15-mo-old mice compared with young 3-mo-old mice. Further decreasing EGFR signaling by gefitinib treatment in middle-aged mice resulted in promoted senescence of osteoprogenitors and accelerated cortical bone degeneration. Moreover, inhibiting EGFR signaling suppressed the expression of enhancer of zeste homolog 2 (Ezh2), the repressor of cell senescence-inducer genes, through ERK1/2 pathway, thereby promoting senescence in osteoprogenitors. Down-regulated EGFR signaling plays a physiologically significant role during aging by reducing Ezh2 expression, leading to the senescence of osteoprogenitors and the decline in bone formation on the endosteal surface of cortical bone.-Liu, G., Xie, Y., Su, J., Qin, H., Wu, H., Li, K., Yu, B., Zhang, X. The role of EGFR signaling in age-related osteoporosis in mouse cortical bone.

Health Care Costs of Post-traumatic Osteomyelitis in China: Current Situation and Influencing Factors.

BACKGROUND: Currently, very limited information is available regarding the economic burdens of patients with extremity post-traumatic osteomyelitis (OM). This study aimed to investigate direct health care costs and utilization for inpatients with extremity post-traumatic OM and analyze its constituent ratios and influencing factors in Southern China. METHODS: We searched in the electronic medical record system for inpatients who had received surgical interventions at our department between 2013 and 2016 for extremity post-traumatic OM. Data of direct health care costs incurred during their hospitalizations were collected in six main categories (service, diagnosis, treatment, materials, pharmaceuticals, and miscellaneous expenses). In addition, data of total medical costs for contemporaneous inpatients with non-post-traumatic OM were also collected as controls. RESULTS: A total of 278 post-traumatic OM and 10,420 controls were included. The median cost for the post-traumatic OM inpatients was $10,504 US dollars, 4.8-fold higher than that for those with non-post-traumatic OM ($2189, P < 0.001). The direct cost in the category of materials accounted for the largest proportion (61%), followed by that in pharmaceuticals (12%) and treatment (11%). The median number of hospital admissions for post-traumatic OM patients was 1 time, with a median length-of-stay of 22 d. The most influencing factors for the health care costs of the post-traumatic OM inpatients were use of an external fixator ($16,016 for those who used versus $4956 for those who did not, P < 0.001), external fixator type ($19,563 for ring fixator versus $14,966 for rail fixator, P < 0.001), infection site ($13,755 for tibia, $14,216 for femur and $5673 for calcaneus, P < 0.001), and infection-associated injury type ($12,890 for infection after open fracture versus $8087 for infection after closed fracture, P = 0.001). CONCLUSIONS: An unexpectedly large proportion of the direct health care costs for inpatients with extremity post-traumatic OM went to cover an external fixator, with expenses for pharmaceuticals and treatment accounting for only a little more than the tenth of the total health care costs. Use of external fixator, external fixator type, infection site, and infection-associated injury type directly influenced the health care costs.

High cholesterol inhibits tendon-related gene expressions in tendon-derived stem cells through reactive oxygen species-activated nuclear factor-κB signaling.

Clinical studies have indicated that increased serum cholesterol levels raised the risk of tendinopathy in hypercholesterolemia, but the effect of cholesterol on tendon-derived stem cells (TDSCs) and its underlying mechanism have not been studied. The purpose of this study is to investigate the association between cholesterol and tendinopathy in vitro and in vivo, and its underlying molecular mechanism as well. In TDSCs, the effect of cholesterol was assessed by quantitative polymerase chain reaction, western blot analysis, and immunofluorescence staining. Intracellular levels of reactive oxygen species (ROS) was detected, using flow cytometry. The link between nuclear factor (NF)-κB signaling and the effect of cholesterol was evaluated using a representative IκB kinase (IKK) inhibitor, BAY 11-7082. In addition, Achilles tendons from apolipoprotein E mice fed with a high-fat diet were histologically assessed using hematoxylin and eosin staining and immunohistochemistry. We found that high cholesterol apparently lowered the expression of tendon cell markers (collagen 1, scleraxis, tenomodulin), and elevated ROS levels via the NF-κB pathway both in vitro and in vivo. The ROS scavenger N-acetylcysteine (NAC) and BAY 11-7082 reversed the inhibiting effect of cholesterol on the tendon-related gene expressions of TDSCs. Moreover, NAC blocked cholesterol-induced phosphorylation of IκBα and p65. Significant histological alternation in vivo was shown in Achilles tendon in the hypercholesterolemic group. These results indicated that high cholesterol may inhibit the tendon-related gene expressions in TDSCs via ROS-activated NF-кB signaling, implying pathogenesis of tendinopathy in hypercholesterolemia and suggesting a new mechanism underlying hypercholesterolemia-induced tendinopathy.

G-CSF partially mediates bone loss induced by Staphylococcus aureus infection in mice.

Bone loss in Staphylococcus aureus (S. aureus) osteomyelitis poses a serious challenge to orthopedic treatment. The present study aimed to elucidate how S. aureus infection in bone might induce bone loss. The C57BL/6 mice were injected with S. aureus (106 CFU/ml, 100 µl) or with the same amount of vehicle (control) via the tail vein. Microcomputed tomography (microCT) analysis showed bone loss progressing from week 1 to week 5 after infection, accompanied by a decreased number of osteocalcin-positive stained osteoblasts and the suppressed mRNA expression of Runx2 and osteocalcin. Transcriptome profiles of GSE30119 were downloaded and analyzed to determine the differences in expression of inflammatory factors between patients with S. aureus infected osteomyelitis and healthy controls, the data showed significantly higher mRNA expression of granulocyte colony-stimulating factor (G-CSF) in the whole blood from patients with S. aureus infection. Enzyme-linked immunosorbent assay (ELISA) analysis confirmed an increased level of G-CSF in the bone marrow and serum from S. aureus infected mice, which might have been due to the increased amount of F4/80+ macrophages. Interestingly, G-CSF neutralizing antibody treatment significantly rescued the bone loss after S. aureus infection, as evidenced by its roles in improving BV/TV and preserving osteocalcin- and osterix-positive stained cells. Importantly, we found that G-CSF level was significantly up-regulated in the serum from osteomyelitis patients infected by S. aureus Together, S. aureus infection might suppress the function of osteoblastic cells and induce progressive bone loss by up-regulating the level G-CSF, suggesting a therapeutic potential for G-CSF neutralization in combating bone loss in S. aureus osteomyelitis.

Systematic Review of Heel Puncture-Related Osteomyelitis of the Calcaneus in Newborn Infants.

INTRODUCTION: Heel puncture (HP) in neonates can result in osteomyelitis if done non-aseptically or with incorrect technique. This study summarizes clinical experience with heel puncture-related osteomyelitis of the calcaneus (HP-CO) in newborns. METHODS: We systematically reviewed studies that examined HP-CO in newborn patients using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Our search included the PubMed, Embase, and Cochrane Library databases until December 31, 2023. We used the National Institutes of Health (NIH) assessment scale to evaluate the quality of our analyzed studies. RESULTS: This study analyzed 15 neonatal calcaneal osteomyelitis (CO) cases due to HP conducted in six countries from 1976 to 2016. The average age of the cases was 8.87 ± 6.13 days, with an average birth weight of 2367.27 ± 947.59 g. The infants had undergone an average of 9.00 ± 8.90 HP, with 93.33% exhibiting swelling. Staphylococcus aureus was present in 80% of cases. Beta-lactam antibiotics were used, with satisfactory outcomes in 53.33% of cases. However, in seven cases, three patients had flatfoot due to calcaneal deformity, and other complications were observed in some patients after 7-8 years. CONCLUSIONS: This study offers valuable insights into a rare condition, including its epidemiology, clinical and laboratory characteristics, and treatment options for infants with HP-CO. To prevent the risk of osteomyelitis in this vulnerable group of patients, increasing awareness and maintaining strict aseptic techniques is necessary. We recommend that infants presenting with tenderness, redness, purulent discharge, erythema, or fever and with a history of repeated HP and swollen ankles should be evaluated for suspicion of osteomyelitis. A graphical abstract is avilable for this article.

Zwitterion-Lubricated Hydrogel Microspheres Encapsulated with Metformin Ameliorate Age-Associated Osteoarthritis.

Chondrocyte senescence and reduced lubrication play pivotal roles in the pathogenesis of age-related osteoarthritis (OA). In the present study, highly lubricated and drug-loaded hydrogel microspheres are designed and fabricated through the radical polymerization of sulfobetaine (SB)-modified hyaluronic acid methacrylate using microfluidic technology. The copolymer contains a large number of SB and carboxyl groups that can provide a high degree of lubrication through hydration and form electrostatic loading interactions with metformin (Met@SBHA), producing a high drug load for anti-chondrocyte senescence. Mechanical, tribological, and drug release analyses demonstrated enhanced lubricative properties and prolonged drug dissemination of the Met@SBHA microspheres. RNA sequencing (RNA-seq) analysis, network pharmacology, and in vitro assays revealed the extraordinary capacity of Met@SBHA to combat chondrocyte senescence. Additionally, inducible nitric oxide synthase (iNOS) has been identified as a promising protein modulated by Met in senescent chondrocytes, thereby exerting a significant influence on the iNOS/ONOO-/P53 pathway. Notably, the intra-articular administration of Met@SBHA in aged mice ameliorated cartilage senescence and OA pathogenesis. Based on the findings of this study, Met@SBHA emerges as an innovative and promising strategy in tackling age-related OA serving the dual function of enhancing joint lubrication and mitigating cartilage senescence.

Endothelial PDGF-BB/PDGFR-ß signaling promotes osteoarthritis by enhancing angiogenesis-dependent abnormal subchondral bone formation.

The mechanisms that coordinate the shift from joint homeostasis to osteoarthritis (OA) remain unknown. No pharmacological intervention can currently prevent the progression of osteoarthritis. Accumulating evidence has shown that subchondral bone deterioration is a primary trigger for overlying cartilage degeneration. We previously found that H-type vessels modulate aberrant subchondral bone formation during the pathogenesis of OA. However, the mechanism responsible for the elevation of H-type vessels in OA is still unclear. Here, we found that PDGFR-ß expression, predominantly in the CD31hiEmcnhi endothelium, was substantially elevated in subchondral bones from OA patients and rodent OA models. A mouse model of OA with deletion of PDGFR-ß in endothelial cells (ECs) exhibited fewer H-type vessels, ameliorated subchondral bone deterioration and alleviated overlying cartilage degeneration. Endothelial PDGFR-ß promotes angiogenesis through the formation of the PDGFR-ß/talin1/FAK complex. Notably, endothelium-specific inhibition of PDGFR-ß by local injection of AAV9 in subchondral bone effectively attenuated the pathogenesis of OA compared with that of the vehicle-treated controls. Based on the results from this study, targeting PDGFR-ß is a novel and promising approach for the prevention or early treatment of OA.