Regulation of VEGF expression by HIF-1α in the femoral head cartilage following ischemia osteonecrosis

Genetics and Epigenetics of Legg-Calvé-Perthes Disease

» Multifactorial Pathogenesis: Legg-Calvé-Perthes disease (LCPD) may result from a complex interplay of genetic, epigenetic, and environmental factors, culminating in avascular necrosis of the femoral head in children aged 4 to 10 years.» Genetic Contributions: Mutations in COL2A1 weaken cartilage integrity, and polymorphisms in IL6 drive inflammatory responses, exacerbating bone resorption and necrosis.» Role of Epigenetics: Epigenetic mechanisms, such as altered DNA methylation and miRNA dysregulation, may modulate disease progression by linking genetic susceptibility to environmental influences.» Environmental Amplifiers: Key environmental risk factors, including maternal smoking, low birth weight, and socioeconomic deprivation, may exacerbate the genetic and epigenetic predisposition to LCPD.» Future Directions: Advancements in genetic screening and epigenetic therapies, such as miRNA modulators and DNA methylation inhibitors, combined with preventive measures like improved prenatal care and reduced smoke exposure, may offer promising avenues for optimizing outcomes in LCPD.

Angiogenesis of Avascular Necrosis of the Femoral Head: A Classic Treatment Strategy

Avascular necrosis of the femoral head (ANFH) is a type of osteonecrosis due to the cessation of blood supply, characterized by persistent local pain and collapse of the joint. The etiology of ANFH is multifaceted, and while its precise pathogenesis remains elusive, it is currently widely believed that the femoral head is highly dependent on the vascular system. A large number of studies have shown that vascular injury is the initial factor in the onset of ANFH. In this review, we briefly introduced the process of angiogenesis and the blood supply to the femoral head, with a focus on summarizing the existing research on promoting angiogenesis for the treatment of ANFH. We conclude that providing alternative pathways through angiogenesis to resolve the problem of the obstructed free flow of the blood is an important means of treating ANFH. Moreover, we also looked forward to the mechanism of endothelial metabolism, which has not yet been studied in femoral head necrosis models, providing potential strategies for more effective use of angiogenesis for the treatment of femoral head necrosis.

Generation and characterization of mesenchymal stem cells from the affected femoral heads of dogs with Legg Calvé Perthes disease

Background

Canine Legg Calvé Perthes disease (LCPD) occurs during the growth period, and the cause of ischemic necrosis of the femoral head during growth remains unclear. If LCPD-affected femoral head-derived mesenchymal stem cells (LCPD-MSCs) can be generated, they can be used as a new tool for the pathophysiological analysis of canine LCPD.

Aim

To generate affected femoral head-derived mesenchymal stem cells (MSCs) from dogs with LCPD and investigate the mRNA expression levels of angiogenesis-related factors and osteogenic differentiation potency of LCPD-MSCs.

Methods

This study was performed using affected femoral heads from dogs diagnosed with LCPD and underwent femoral head and neck ostectomy. The necrotic tissue was harvested from the LCPD-affected femoral head and cultured statically (LCPD group, n = 6). Canine bone marrow-derived MSCs (BM-MSCs) were used as controls (control group, n = 6). First, the morphology of the cultured cells was observed, and the expression of CD29, CD34, CD44, CD45, CD90, and major histocompatibility complex class II was analyzed using flow cytometry. Additionally, the trilineage differentiation potency of the LCPD-affected head-derived adherent cells was examined. Furthermore, the expression levels of HIF1A, VEGFA, VEGFB, and PDGFB mRNAs and the bone differentiation potency of LCPD-affected head-derived adherent cells were investigated.

Results

LCPD-affected femoral head-derived adherent cells showed a fibroblast-like morphology, and the expression of cell surface antigens was similar to that of BM-MSCs. In addition, LCPD-affected femoral head-derived adherent cells showed the same trilineage differentiation potency as BM-MSCs and were consistent with MSC characteristics. Furthermore, the mRNA expression levels of angiogenesis-related factors could be objectively measured in LCPD-MSCs and those MSCs had bone differentiation potency.

Conclusion

In the present study, canine LCPD-MSCs were successfully generated, suggesting their usefulness as a tool for pathological analysis of LCPD in dogs.

Leucine improves thiram-induced tibial dyschondroplasia and gut microbiota dysbiosis in broilers

Thiram, a commonly used agricultural insecticide and fungicide, has been found to cause tibial dyschondroplasia (TD) in broilers, leading to substantial economic losses in the poultry industry. In this study, we aimed to investigate the mechanism of action of leucine in mitigating thiram-induced TD and leucine effects on gut microbial diversity. Broiler chickens were randomly divided into five equal groups: control group (standard diet), thiram-induced group (thiram 80 mg/kg from day 3 to day 7), and different concentrations of leucine groups (0.3%, 0.6%, 0.9% leucine from day 8 to day 18). Performance indicator analysis and tibial parameter analysis showed that leucine positively affected thiram-induced TD broilers. Additionally, mRNA expressions and protein levels of HIF-1α/VEGFA and Ihh/PTHrP genes were determined via quantitative real-time polymerase chain reaction and western blot. The results showed that leucine recovered lameness disorder by downregulating the expression of HIF-1α, VEGFA, and PTHrP while upregulating the expression of Ihh. Moreover, the 16 S rRNA sequencing revealed that the leucine group demonstrated a decrease in the abundance of harmful bacteria compared to the TD group, with an enrichment of beneficial bacteria responsible for producing short-chain fatty acids, including Alistipes, Paludicola, CHKCI002, Lactobacillus, and Erysipelatoclostridium. In summary, the current study suggests that leucine could improve the symptoms of thiram-induced TD and maintain gut microbiota homeostasis.

A Molecular Troika of Angiogenesis, Coagulopathy and Endothelial Dysfunction in the Pathology of Avascular Necrosis of Femoral Head: A Comprehensive Review

Avascular necrosis of the femoral head (ANFH) is a painful disorder characterized by the cessation of blood supply to the femoral head, leading to its death and subsequent joint collapse. Influenced by several risk factors, including corticosteroid use, excessive alcohol intake, hypercholesterolemia, smoking and some inflammatory disorders, along with cancer, its clinical consequences are thrombus formation due to underlying inflammation and endothelial dysfunction, which collaborates with coagulopathy and impaired angiogenesis. Nonetheless, angiogenesis resolves the obstructed free flow of the blood by providing alternative routes. Clinical manifestations of early stage of ANFH mimic cysts or lesions in subchondral bone, vasculitis and transient osteoporosis of the hip, rendering it difficult to diagnose, complex to understand and complicated to cure. To date, the treatment methods for ANFH are controversial as no foolproof curative strategy is available, and these depend upon different severity levels of the ANFH. From an in-depth understanding of the pathological determinants of ANFH, it is clear that impaired angiogenesis, coagulopathy and endothelial dysfunction contribute significantly. The present review has set two aims, firstly to examine the role and relevance of this molecular triad (impaired angiogenesis, coagulopathy and endothelial dysfunction) in ANFH pathology and secondly to propose some putative therapeutic strategies, delineating the fact that, for the better management of ANFH, a combined strategy to curtail this molecular triangle must be composed rather than focusing on individual contributions.

Bone tissue engineering for treating osteonecrosis of the femoral head

Osteonecrosis of the femoral head (ONFH) is a devastating and complicated disease with an unclear etiology. Femoral head-preserving surgeries have been devoted to delaying and hindering the collapse of the femoral head since their introduction in the last century. However, the isolated femoral head-preserving surgeries cannot prevent the natural progression of ONFH, and the combination of autogenous or allogeneic bone grafting often leads to many undesired complications. To tackle this dilemma, bone tissue engineering has been widely developed to compensate for the deficiencies of these surgeries. During the last decades, great progress has been made in ingenious bone tissue engineering for ONFH treatment. Herein, we comprehensively summarize the state-of-the-art progress made in bone tissue engineering for ONFH treatment. The definition, classification, etiology, diagnosis, and current treatments of ONFH are first described. Then, the recent progress in the development of various bone-repairing biomaterials, including bioceramics, natural polymers, synthetic polymers, and metals, for treating ONFH is presented. Thereafter, regenerative therapies for ONFH treatment are also discussed. Finally, we give some personal insights on the current challenges of these therapeutic strategies in the clinic and the future development of bone tissue engineering for ONFH treatment.

Mechanic-Driven Biodegradable Polyglycolic Acid/Silk Fibroin Nanofibrous Scaffolds Containing Deferoxamine Accelerate Diabetic Wound Healing

The extracellular matrix (ECM), comprising of hundreds of proteins, mainly collagen, provides physical, mechanical support for various cells and guides cell behavior as an interactive scaffold. However, deposition of ECM, especially collagen content, is seriously impaired in diabetic wounds, which cause inferior mechanical properties of the wound and further delay chronic wound healing. Thus, it is critical to develop ECM/collagen alternatives to remodel the mechanical properties of diabetic wounds and thus accelerate diabetic wound healing. Here, we firstly prepared mechanic-driven biodegradable PGA/SF nanofibrous scaffolds containing DFO for diabetic wound healing. In our study, the results in vitro showed that the PGA/SF-DFO scaffolds had porous three-dimensional nanofibrous structures, excellent mechanical properties, biodegradability, and biocompatibility, which would provide beneficial microenvironments for cell adhesion, growth, and migration as an ECM/collagen alternative. Furthermore, the data in vivo showed PGA/SF-DFO scaffolds can adhere well to the wound and have excellent biodegradability, which is helpful to avoid secondary damage by omitting the removal process of scaffolds. The finite element analysis results showed that the application of silk fibroin-based scaffolds could significantly reduce the maximum stress around the wound. Besides, PGA/SF-DFO scaffolds induced collagen deposition, re-vascularization, recovered impaired mechanical properties up to about 70%, and ultimately accelerated diabetic wound healing within 14 days. Thus, our work provides a promising therapeutic strategy for clinically chronic wound healing.

Bone Marrow Mesenchymal Stem Cells Overexpressing HIF-1α Prevented the Progression of Glucocorticoid-Induced Avascular Osteonecrosis of Femoral Heads in Mice

Glucocorticoid (GC)-induced avascular osteonecrosis of femoral head (AOFH) is a devastating complication, and no cures are currently available for it. Previous studies have demonstrated that implantation of bone marrow mesenchymal stem cells (BMMSCs) may prevent the progression of pre-collapse AOFH. Based on previous observations, we hypothesized that GCs induce AOFH via the COX-2 (cyclooxygenase-2)-PGE-2 (prostaglandin E2)-HIF-1α (hypoxia-inducible factor-1α) axis, and that modification of BMMSCs may improve the efficacy of their implantation. BMMSCs isolated from wild-type (WT) mice were treated with dexamethasone (Dex) and the results showed that Dex repressed the expression of COX-2. Femoral head samples harvested from both WT and COX-2 knock-out (COX-2^-/-) mice were subjected to micro-computed tomography and histological examinations. Compared with their WT littermates, COX-2^-/- mice had larger trabecular separations, diminished microvasculature, and reduced HIF-1α expression in their femoral heads. In vitro angiogenesis assays with tube formation and fetal metatarsal sprouting demonstrated that Dex repressed angiogenesis and PGE-2 antagonized its effects. An AOFH model was successfully established in C57BL/6J mice. In vitro experiment showed that BMMSCs infected with Lentivirus encoding HIF-1α (Lenti-HIF-1α) resulted in a robust increase in the production of HIF-1α protein. Implantation of BMMSCs overexpressing HIF-1α into femoral heads of AOFH mice significantly reduced osteonecrotic areas and enhanced bone repair, thus largely preserving the structural integrity of femoral heads. Our studies provide strong rationales for early intervention with core decompression and implantation of modified BMMSCs for GC-induced AOFH, which may spare patients from expensive and difficult surgical procedures.

Autophagy in Femoral Head Necrosis of Broilers Bone Metabolism Parameters and Autophagy-Related Gene Expression in Femoral Head Necrosis Induced by Glucocorticoid in Broilers

Objectives: In this study, the influence of methylprednisolone (MP) and 3-methyladenine (3-MA) on chondrocyte autophagy and bone quality were determined to investigate the mechanisms of femoral head necrosis in broilers.

Methods: Chickens were divided into four groups: control, MP, 3-MA, and 3-MA+MP groups. Blood and bone samples were collected for biochemistry assay and bone quality determination. Cartilage was separated from the femoral head for histopathological analysis and gene expression detection.

Results: The results indicated that MP treatment significantly affected blood levels of alkaline phosphatase, high-density lipoprotein, calcium, phosphorus, bone alkaline phosphatase, and osteocalcin in broilers. Additionally, MP treatment significantly increased blood levels of cholesterol, low-density lipoprotein, triglyceride, carboxy-terminal telopeptide of type-I collagen, and tartrate-resistant acid phosphatase 5. MP treatment also significantly decreased the levels of bone parameters compared with these values in controls, inhibited the expression of collagen-2, aggrecan, and mammalian target of rapamycin, and increased the expression of beclin1 and microtubule-associated protein 1 light chain 3, hypoxia-inducible factor 1 alpha, phosphoinositide 3-kinase, protein kinase B and autophagy-related gene 5 of the femoral head. Furthermore, following co-treatment with 3-MA and MP, 3-MA mitigated the effects of MP.

Conclusions: Our findings demonstrated that autophagy may be involved in the pathogenesis of femoral head necrosis induced by MP in broilers, and this study provides new treatment and prevention ideas for femoral head necrosis caused by glucocorticoids.

Inhibition of miR-93-5p promotes osteogenic differentiation in a rabbit model of trauma-induced osteonecrosis of the femoral head

Trauma‐induced osteonecrosis of the femoral head (TIONFH) is characterized by femoral head collapse accompanied by degenerative changes of the hip. We previously reported that miR‐93‐5p expression is abnormally high in patients with TIONFH, but the role of miR‐93‐5p in the TIONFH process remains unclear. Herein, we investigated the role of miR‐93‐5p in TIONFH in a rabbit model. Bone marrow mesenchymal stem cells (BMSCs) were used for both in vivo and in vitro experiments. A rabbit model of TIONFH was injected with BMSCs transfected with miR‐93‐5p inhibitor. In addition, both an miR‐93‐5p mimic and negative control were transfected into BMSCs. Expression of miR‐93‐5p was significantly increased in the model group compared with control samples. An miR‐93‐5p inhibitor induced the expression of bone morphogenetic protein 2 (BMP‐2) and alkaline phosphatase. Furthermore, expression of osteogenesis‐related markers (BMP‐2, secreted phosphoprotein 1, RUNX family transcription factor 2 and Osterix) was higher in the miR‐93‐5p inhibitor group, as revealed by quantitative PCR and western blotting. In addition, in vitro experimentation revealed that an miR‐93‐5p mimic decreased BMP‐2 and TNF receptor superfamily member 11b expression, but increased receptor activator of nuclear factor‐kappaB ligand expression. In summary, the miR‐93‐5p inhibitor could promote osteogenic differentiation by increasing BMP‐2 expression during the development of TIONFH. Thus, miR‐93‐5p may have potential as a therapeutic target for TIONF treatment.

CD146+Mesenchymal stem cells treatment improves vascularization, muscle contraction and VEGF expression, and reduces apoptosis in rat ischemic hind limb

Peripheral arterial disease (PAD) is an increasingly common narrowing of the peripheral arteries that can lead to lower limb ischemia, muscle weakness and gangrene. Surgical vein or arterial grafts could improve PAD, but may not be suitable in elderly patients, prompting research into less invasive approaches. Mesenchymal stem cells (MSCs) have been proposed as potential therapy, but their effectiveness and underlying mechanisms in limb ischemia are unclear. We tested the hypothesis that treatment with naive MSCs (nMSCs) or MSCs expressing CD146 (^CD146+MSCs) could improve vascularity and muscle function in rat model of hind-limb ischemia. Sixteen month old Sprague-Dawley rats were randomly assigned to 4 groups: sham-operated control, ischemia, ischemia + nMSCs and ischemia+^CD146+MSCs. After 4 weeks of respective treatment, rat groups were assessed for ischemic clinical score, Tarlov score, muscle capillary density, TUNEL apoptosis assay, contractile force, and vascular endothelial growth factor (VEGF) mRNA expression. ^CD146+MSCs showed greater CD146 mRNA expression than nMSCs. Treatment with nMSCs or ^CD146+MSCs improved clinical and Tarlov scores, muscle capillary density, contractile force and VEGF mRNA expression in ischemic limbs as compared to non-treated ischemia group. The improvements in muscle vascularity and function were particularly greater in ischemia+^CD146+MSCs than ischemia + nMSCs group. TUNEL positive apoptotic cells were least abundant in ischemia+^CD146+MSCs compared with ischemia + nMSCs and non-treated ischemia groups. Thus, MSCs particularly those expressing CD146 improve vascularity, muscle function and VEGF expression and reduce apoptosis in rat ischemic limb, and could represent a promising approach to improve angiogenesis and muscle function in PAD.

Effects of long-term plate fixation with different fixation modes on the radial cortical bone in dogs

The aim of this study was to examine the effect of long-term locking plate fixation on the cortical bone of the canine radius. Locking compression plates were fixed to the left and right radius in dogs (n = 3). The left radius was fixed with a locking head screw (Locking Plate group, LP). The locking compression plate was compressed periosteally in the right radius using a cortex screw (Compression Plate group, CP). Radial bones from dogs that were euthanized for other purposes were collected as an untreated control group (Control group). After euthanasia at 36 weeks following plate fixation, radial bones were evaluated for bone mineral density and underwent histological analysis. Bone metabolic markers were analyzed by quantitative polymerase chain reaction (qPCR). Statistical analyses were performed for comparisons between groups. The LP group showed no significant difference in bone mineral density after plate fixation, whereas the CP group showed significantly lower bone mineral density. Histological analysis indicated that the number of osteoclasts and rate of empty lacunae increased significantly in the CP group relative to the Control and LP groups. qPCR analysis indicated increased expression of inflammatory cytokines, such as tumor necrosis factor-alpha, interleukin-6, and tumor necrosis factor ligand superfamily member 11 in the CP group, whereas Runt-related transcription factor 2, an osteoblast marker, was similar in all groups. The expression of hypoxia-inducible factor-1α in the CP group was also increased relative to that in the Control and LP groups. Thus, locking plate fixation is a biologically superior fixation method that does not cause implant-induced osteoporosis in the bone in the long term.

Combined Pharmacotherapy with Alendronate and Desferoxamine Regulate the Bone Resorption and Bone Regeneration for Preventing Glucocorticoids-Induced Osteonecrosis of the Femoral Head

Background

Osteonecrosis of the femoral head (ONFH) is a challenge for surgeons and is still without effective treatment method. This study is aimed at evaluating the combined pharmacotherapy with alendronate and desferoxamine for preventing glucocorticoid-induced osteonecrosis of the femoral head (GIOFH) and evaluating the efficacy of the combined medicine in regulating the bone resorption and bone regeneration.

Materials and Methods

Thirty-six rats were randomly assigned to three groups: group A received alendronate and desferoxamine (n = 12), group B received alendronate only (n = 12), and group C acted as the control group received placebo (n = 12). All rats induced the GIOFH using methylprednisolone combined with lipopolysaccharide. Eight weeks later, all rats were killed and their tissues were subjected to radiographic and histological analyses.

Results

According to the results, alendronate administration improved the trabecular thickness and separation in micro-CT analysis but had no significant evidence in increasing the bone area and decreasing the ratio of osteocyte lacunae in histological analysis when compared with the control group. Meanwhile, the alendronate group had more OCs, but less OCN and VEGF levels along with decreased p-AKT, HIF-1α, RANKL, and NFATc1 expressions than the control group. For comparison, alendronate combined with DFO further improved the bone volume, trabecular number, trabecular separation, and trabecular thickness with lower ratio of osteocyte lacunae and OC number, higher expression of OCN and VEGF and upregulated signal factors of HIF-1α and β-catenin, and decreased RANKL and NFATc1.

Conclusion

Combined pharmacotherapy with alendronate and desferoxamine provide significant effects in regulating the bone resorption and bone regeneration for preventing GIOFN.

Desferoxamine protects against glucocorticoid-induced osteonecrosis of the femoral head via activating HIF-1α expression

Glucocorticoid-induced osteonecrosis of the femoral head (GIOFH) is one of the most common complications of glucocorticoid administration. By chelating Fe²⁺ , desferoxamine (DFO) was reported to be able to activate the HIF-1α/VEGF pathway and promote angiogenesis. In the present study, we examined whether DFO administration could promote angiogenesis and bone repair in GIOFH. GIOFH was induced in rats by methylprednisolone in combination with lipopolysaccharide. Bone repair was assessed by histologic analysis and microcomputed tomography (micro-CT). Vascularization was assessed by Microfil perfusion and micro-CT analysis. Immunohistochemical staining was performed to analyze the expression of HIF-1α, VEGF, and CD31. Our in vivo study revealed that DFO increased HIF-1α/VEGF expression and promoted angiogenesis and osteogenesis in GIOFH. Moreover, our in vitro study revealed that DFO restored dexamethone-induced HIF-1α downregulation and angiogenesis inhibition. Besides, our in vitro study also demonstrated that DFO could protect bone marrow-derived stem cells from dexamethone-induced apoptosis and mitochondrial dysfunction by promoting mitophagy and mitochondrial fission. In summary, our data provided useful information for the development of novel therapeutics for management of GIOFH.

S100 Calcium Binding Protein A9 Represses Angiogenic Activity and Aggravates Osteonecrosis of the Femoral Head

Ischemic damage aggravation of femoral head collapse is a prominent pathologic feature of osteonecrosis of the femoral head (ONFH). In this regard, S100 calcium binding protein A9 (S100A9) is known to deteriorate joint integrity, however, little is understood about which role S100A9 may play in ONFH. In this study, a proteomics analysis has revealed a decrease in the serum S100A9 level in patients with ONFH upon hyperbaric oxygen therapy. Serum S100A9 levels, along with serum vascular endothelial growth factor (VEGF), soluble vascular cell adhesion molecule-1 (sVCAM-1), interleukin-6 (IL-6), and tartrate-resistant acid phosphatase 5b levels were increased in patients with ONFH, whereas serum osteocalcin levels were decreased as compared to healthy controls. Serum S100A9 levels were increased with the Ficat and Arlet stages of ONFH and correlated with the patients with a history of being on glucocorticoid medication and alcohol consumption. Osteonecrotic tissue showed hypovasculature histopathology together with weak immunostaining for vessel marker CD31 and von Willrbrand factor (vWF) as compared to femoral head fracture specimens. Thrombosed vessels, fibrotic tissue, osteocytes, and inflammatory cells displayed strong S100A9 immunoreactivity in osteonecrotic lesion. In vitro, ONFH serum and S100A9 inhibited the tube formation of vessel endothelial cells and vessel outgrowth of rat aortic rings, whereas the antibody blockade of S100A9 improved angiogenic activities. Taken together, increased S100A9 levels are relevant to the development of ONFH. S100A9 appears to provoke avascular damage, ultimately accelerating femoral head deterioration through reducing angiogenesis. This study provides insight into the molecular mechanism underlying the development of ONFH. Here, analysis also highlights that serum S100A9 is a sensitive biochemical indicator of ONFH.

Vasculature submucosal changes at early stages of osteonecrosis of the jaw (ONJ)

Osteonecrosis of the jaw (ONJ), a rare, but potentially severe side effect of anti-resorptive medications, presents as exposed bone in the maxillofacial region lasting for at least 8 weeks. While clinical experience and animal models concur in finding that systemic antiresorptive treatment in conjunction with local risk factors, such as tooth extraction or dental disease may lead to ONJ development, the subclinical molecular changes that precede bone exposure remain poorly understood. The identification of these changes is not only important in understanding disease pathophysiology, but could provide potential for treatment development. Here, we evaluated the early stages of ONJ utilizing a model of experimental periodontitis (EP) in mice treated with two different types of antiresorptives, targeting potential changes in vasculature, hypoxia, oxidative stress, and apoptosis. Antiresorptive treatment in animals with EP increased levels of empty osteocytic lacunae and increased ONJ prevalence compared to Veh animals. The arteriole and venule network seen around EP areas was diminished in animals treated with antiresorptives. Higher levels of vascular endothelial growth factor A (VEGF-A) and vascular cell adhesion protein-1 (VCAM-1) were observed 1-week following EP in treated animals. Finally, levels of hypoxia, oxidative stress, and apoptosis remained high in antiresorptive treated animals with EP through the duration of the experiment. Together, our data point to subclinical vasculature organizational disturbances that subsequently affect levels of hypoxia, oxidative stress, and apoptosis in the area of developing ONJ.

Promoting vascularization for tissue engineering constructs: current strategies focusing on HIF-regulating scaffolds

INTRODUCTION

Vascularization remains one of the greatest yet unmet challenges in tissue engineering. When engineered tissues are scaled up to therapeutically relevant dimensions, their demand of oxygen and nutrients can no longer be met by diffusion. Thus, there is a need for perfusable vascular structures. Hypoxia-inducible factors (HIF) act as transcriptional oxygen sensors and regulate a multitude of genes involved in adaptive processes to hypoxia, including angiogenesis. Thus, targeting HIFs is a promising strategy to induce vascularization of engineered tissues.

AREAS COVERED

Here we review current vascularization strategies and summarize the present knowledge regarding activation of HIF signaling by ions, iron chelating agents, α-Ketoglutarate (αKG) analogues, and the lipid-lowering drug simvastatin to induce angiogenesis. Specifically, we focus on the incorporation of HIF-activating agents into biomaterials and scaffolds for controlled release.

EXPERT OPINION

Vascularization of tissue constructs through activation of upstream regulators of angiogenesis offers advantages but also suffers from drawbacks. HIFs can induce a complete angiogenic program; however, this program appears to be too slow to vascularize larger constructs before cell death occurs. It is therefore crucial that HIF-activation is combined with cell protective strategies and prevascularization techniques to obtain fully vascularized, vital tissues of therapeutically relevant dimensions.

Hypoxia promotes maintenance of the chondrogenic phenotype in rat growth plate chondrocytes through the HIF-1α/YAP signaling pathway

The Hippo‑yes‑associated protein (YAP) signaling pathway was previously identified to serve an important role in controlling chondrocyte differentiation and post‑natal growth. Growth plate cartilage tissue is avascular, and hypoxia‑inducible factor (HIF)‑1α is essential for chondrocytes to maintain their chondrogenic phenotype in a hypoxic environment. In the present study, the role of hypoxia and HIF‑1α in the regulation of YAP in chondrocytes was investigated. The data demonstrated that hypoxia promoted the maintenance of the chondrogenic phenotype, HIF‑1α expression and YAP activation in chondrocytes in a time‑dependent manner. Hypoxia promoted YAP activation in a Hippo‑independent manner. Inhibiting the expression of HIF‑1α decreased the activation of YAP and downregulated the expression of sex‑determining region‑box 9 protein (SOX9) under hypoxic conditions, while the upregulation of HIF‑1α by cobalt chloride promoted the expression and nuclear translocation of YAP and upregulated the expression of SOX9 and collagen II chain under normoxic conditions. In addition, inhibition of YAP expression under hypoxia did not affect the expression of the HIF‑1α signaling pathway, but inhibited the up‑regulation of SOX9 expression caused by hypoxia. In addition, reoxygenation following hypoxia inhibited the activation of YAP caused by hypoxia in chondrocytes, whereas the upregulation of SOX9 and collagen II chain also appeared to be inhibited. In conclusion, the results of the present study demonstrated that hypoxia promoted YAP activation via HIF‑1α. Therefore, the HIF‑1α/YAP signaling axis may serve an important role in controlling growth plate chondrocyte differentiation and the maintenance of the chondrogenic phenotype in growth plate chondrocytes.

Tibial dyschondroplasia is closely related to suppression of expression of hypoxia-inducible factors 1α, 2α, and 3α in chickens

Tibial dyschondroplasia (TD) cases has not been reported in Tibetan chickens (TBCs), but it is commonly seen in commercial broilers characterized by lameness. The underlying mechanism remains unclear. Hypoxia-inducible factors (HIFs) are important regulators of cellular adaptation to hypoxic conditions. In this study, we investigated the role of HIF-1α, -2α, and -3α in hypoxia and thiram-induced TD and their effect on tibial growth plate development in Arbor Acres chickens (AACs) and TBCs. RNA and protein expression levels of HIF-1α, -2α, and -3α were determined by using quantitative reverse transcriptase polymerase chain reaction and western blotting analyses, respectively. Interestingly, the results showed that HIF-1α, -2α, and -3α expressions in the tibial growth plate of TBCs were upregulated by hypoxia and the change was more significant in TBCs than in AACs. However, these factors were downregulated in thiram-induced TD. To further clarify the effect of thiram on tibial growth plate in commercial broilers, AACs were observed to exhibit more pronounced changes in their growth plate that that in TBCs. Taken together, these results demonstrate that HIF-1α, -2α, and -3α may be important in tibial growth plate development and in the prevention of TD. The present study contributes novel insights on a therapeutic target for poultry TD.

Small non-coding RNAs-based bone regulation and targeting therapeutic strategies

Small non-coding RNAs, which are 20-25 nucleotide ribonucleic acids, have emerged as an important transformation in the biological evolution over almost three decades. microRNAs (miRNAs) and short interfering RNAs (siRNAs) are two significant categories of the small RNAs that exert important effects on bone endocrinology and skeletology. Therefore, clarifying the expression and function of these important molecules in bone endocrine physiology and pathology is of great significance for improving their potential therapeutic value for metabolism-associated bone diseases. In the present review, we highlight the recent advances made in understanding the function and molecular mechanism of these small non-coding RNAs in bone metabolism, especially their potentially therapeutic values in bone-related diseases.

Downregulated SOX9 mediated by miR-206 promoted cell apoptosis in Legg-Calvé-Perthes disease

Legg-Calvé-Perthes disease (LCPD) commonly onsets in adolescents, and threatens their health. However, the potential mechanism underlying LCPD remains unclear. MicroRNA (miR)-206 and SRY-box 9 (SOX9) serve an important role in chondrocytes; however, their role in LCPD remains ambiguous. In the present study, whether miR-206 and SOX9 mediated cell apoptosis in dexamethasone (DEX)-induced LCPD was investigated. The chondrocytes of the LCPD and normal control group were isolated from clinical tissues. Reverse transcription-quantitative polymerase chain reaction was used to evaluate the expression of miR-206 and SOX9 mRNA. Western blotting was used to measure the protein level of SOX9. A combination of Annexin V-fluorescein isothiocyanate flow cytometry was used to assess cell apoptosis. The association between miR-206 and SOX9 was detected using a luciferase reporter assay. miR-206 was overexpressed while SOX9 was downregulated in chondrocytes treated with DEX obtained from patients with LCPD. miR-206 targeted SOX9 to regulate its expression. Overexpression of miR-206 promoted cell apoptosis in TC28, while it was reversed by SOX9 overexpression. TC28 cells pretreated with DEX significantly promoted cell apoptosis, while cells transfected with miR-206 inhibitor significantly reversed the effect; however, downregulated SOX9 abolished the effects of miR-206 inhibitor. SOX9 mediated by miR-206 possibly contributed to the pathogenesis of LCPD. The results of the present study suggest that miR-206 and SOX9 function as important therapeutic targets for the future of clinical therapy.

Tibial dyschondroplasia is highly associated with suppression of tibial angiogenesis through regulating the HIF-1α/VEGF/VEGFR signaling pathway in chickens

Tibial dyschondroplasia (TD) is an intractable poultry problem that is characterized by the appearance of non-vascularized and non-mineralized cartilage masses in tibial growth plates (TGPs). However, the role of angiogenesis inhibition in the occurrence of TD remains unknown. In this study, we found that, compared to low-altitude Arbor Acres chickens (AACs), high-altitude Tibetan chickens showed higher tibial vascular distributions that were accompanied by up-regulation of hypoxia-inducible factor-1α (HIF-1α), vascular endothelial growth factor A (VEGFA) and VEGF receptors. These observations provide insights into hypoxia-induced angiogenesis, which may be related to the absence of TD in high-altitude native Tibetan chickens. Importantly, hypoxia experiments also showed that during hypoxia, tibial angiogenesis was enhanced, which was due to pro-angiogenic factor up-regulation (including VEGFA, VEGFR1, VEGFR2, and IL-8), in AACs. Moreover, we observed that thiram-induced TD could strongly inhibit tibial angiogenesis in the hypertrophic zone through coordinated down-regulation of HIF-1α and pro-angiogenic factors, leading to a disruption in the blood supply to the TGP. Taken together, these findings reveal that the occurrence of TD is highly associated with inhibition of tibial angiogenesis through down-regulated expression of HIF-1α, VEGFA and VEGF receptors, which results in suppression of TGP development.

Three-year outcomes of intracapsular femoral neck fractures fixed with sliding hip screws in adults aged under sixty-five years

INTRODUCTION

Intracapsular femoral neck fractures remain associated with high rates of post-traumatic femoral head necrosis, non-union, and revision surgery.

AIM

Our aim was to identify factors associated with revision surgery in intracapsular femoral neck fractures treated with sliding hip screws (SHS) in adults aged <65 years.

PATIENTS AND METHODS

Consecutive admissions were identified retrospectively from the Royal Victoria Hospital, Belfast, which was the largest volume hospital on the National Hip Fracture Database. Of 2201 hip fractures between 1st August 2008 and 31st December 2010, 97 (4%) intracapsular fractures treated with SHS in adults <65 years were followed for a mean of 2.9 years (range 0-6.6).

RESULTS

Twenty-one (22%) hips were revised to arthroplasty. Avascular necrosis developed in 28 (29%) femoral heads. Eight (8%) fractures proceeded to non-union. Displaced fractures (p<0.001, Fisher's exact [FE]), posterior comminution (p=0.049, FE), chronic respiratory disease (p=0.006, FE) and residual distraction (p=0.011, χ²) were associated with revision to arthroplasty. Multiple regression found displaced fractures (p=0.006) and chronic respiratory disease (p=0.017) significant; in the latter 4 of 6 were revised (67%), including all four patients with chronic obstructive pulmonary disease (COPD). Eleven (11%) individuals required walking aids before injury, which rose to 34 (35%) at one year (p<0.0001, χ²). Eighty-nine (92%) individuals could walk alone outdoors before injury, but only 76 (78%) at one year (p=0.009, χ²).

CONCLUSIONS

Displaced fractures in individuals with chronic respiratory disease should be considered high risk for revision to arthroplasty. Posterior cortex deficiency should be evaluated prior to choice of operation. Fracture biology and revascularisation play a greater role than operation timing. A significant proportion of individuals do not recovery pre-morbid mobility by one year.

NF-YA promotes invasion and angiogenesis by upregulating EZH2-STAT3 signaling in human melanoma cells

The process of angiogenesis is essential for tumor development and metastasis. Vascular endothelial growth factor (VEGF), which is overexpressed in most human cancers, has been demonstrated to be a major modulator of angiogenesis. Thus, inhibition of VEGF signaling has the potential for tumor anti-angiogenic therapy. Signal transducer and activator of transcription-3 (STAT3) is a key regulator for angiogenesis by directly binding to the VEGF promoter to upregulate its transcription. Several factors can enhance STAT3 activity to affect angiogenesis. Here, we found that overexpression of nuclear transcription factor-Y alpha (NF-YA) gene could promote cell invasion and angiogenesis accompanying the increase of STAT3 signaling in human melanoma cells. Moreover, the expression and secretion of VEGF was also found to be upregulated by the overexpression of NF-YA gene in melanoma cells. The STAT3 inhibitor was able to attenuate the upregulation of VEGF induced by NF-YA overexpression. Enhancer of zeste homolog 2 (EZH2), the catalytic subunit of the Polycomb repressive complex 2, enhances STAT3 activity by mediating its lysine methylation. We also showed that NF-YA upregulated the expression of EZH2 and NF-YA‑induced angiogenesis could be inhibited by EZH2 knockdown. Taken together, these findings indicate that overexpression of NF-YA contributes to tumor angiogenesis through EZH2-STAT3 signaling in human melanoma cells, highlighting NF-YA as a potential therapeutic target in human melanoma.

Comprehensive Genome-Wide Transcriptomic Analysis of Immature Articular Cartilage following Ischemic Osteonecrosis of the Femoral Head in Piglets

OBJECTIVE

Ischemic osteonecrosis of the femoral head (ONFH) in piglets results in an ischemic injury to the immature articular cartilage. The molecular changes in the articular cartilage in response to ONFH have not been investigated using a transcriptomic approach. The purpose of this study was to perform a genome-wide transcriptomic analysis to identify genes that are upregulated in the immature articular cartilage following ONFH.

METHODS

ONFH was induced in the right femoral head of 6-week old piglets. The unoperated femoral head was used as the normal control. At 24 hours (acute ischemic-hypoxic injury), 2 weeks (avascular necrosis in the femoral head) and 4 weeks (early repair) after surgery (n = 4 piglets/time point), RNA was isolated from the articular cartilage of the femoral head. A microarray analysis was performed using Affymetrix Porcine GeneChip Array. An enrichment analysis and functional clustering of the genes upregulated due to ONFH were performed using DAVID and STRING software, respectively. The increased expression of selected genes was confirmed by a real-time qRTPCR analysis.

RESULTS

Induction of ONFH resulted in the upregulation of 383 genes at 24 hours, 122 genes at 2 weeks and 124 genes at 4 weeks compared to the normal controls. At 24 hours, the genes involved in oxidoreductive, cell-survival, and angiogenic responses were significantly enriched among the upregulated genes. These genes were involved in HIF-1, PI3K-Akt, and MAPK signaling pathways. At 2 weeks, secretory and signaling proteins involved in angiogenic and inflammatory responses, PI3K-Akt and matrix-remodeling pathways were significantly enriched. At 4 weeks, genes that represent inflammatory cytokines and chemokine signaling pathways were significantly enriched. Several index genes (genes that are upregulated at more than one time point following ONFH and are known to be important in various biological processes) including HIF-1A, VEGFA, IL-6, IL6R, IL-8, CCL2, FGF2, TGFB2, MMP1, MMP3, ITGA5, FN and Col6A1 were upregulated in the immature articular cartilage following ONFH. A qRTPCR analysis of selected genes confirmed the upregulated expression observed in the microarray analysis.

CONCLUSION

Immature articular cartilage responds to ONFH by the upregulation of genes involved in hypoxic stress response, angiogenesis, matrix remodeling and inflammation. This study provides novel insights into the multi-faceted role of immature articular cartilage, with inflammation as a key component, following ONFH in piglets.

Hydrogen-rich saline attenuates steroid-associated femoral head necrosis through inhibition of oxidative stress in a rabbit model

A growing body of evidence suggests that hydrogen is a novel, selective antioxidant that exerts a protective effect against organ damage. The present study investigated the effect of hydrogen-rich saline on corticosteroid-induced necrosis of the femoral head in an animal model established using prednisolone. A total of 30 healthy, male, adult New Zealand white rabbits were randomly divided into two groups: Hydrogen-rich saline (treated with hydrogen-rich saline via intraperitoneal injection) and placebo (treated with normal saline). At the set time-points, the structure of the femoral head was examined using a microscope; the concentrations of glutathione (GSH), lipid peroxide (LPO), vascular endothelial growth factor (VEGF) and thrombomodulin (TM) in the plasma were measured and the microvessel density was quantified. The results showed that hydrogen-rich saline significantly decreased the levels of VEGF, TM and LPO and increased the GSH level in steroid-associated necrosis of the femoral head in the rabbit model. A significant increase in the microvessel density was observed in the hydrogen-rich saline group. Histopathological staining confirmed the results of the biochemical analysis. The present study demonstrates that hydrogen treatment may alleviate steroid-associated osteonecrosis by inhibiting oxidative stress. Hydrogen-rich saline may provide an alternative treatment for steroid-associated necrosis of the femoral head.

Neuroleukin/Autocrine Motility Factor Receptor Pathway Promotes Proliferation of Articular Chondrocytes through Activation of AKT and Smad2/3

Cartilage defect is an intractable clinical problem. Therapeutic strategies for cartilage repair are far from optimal due to poor proliferation capacity of chondrocytes. Autologous chondrocyte implantation is a cell based therapy that uses in vitro amplified healthy chondrocytes from the patient. However, chondrocyte dedifferentiation during in vitro culture limits its application. Neuroleukin (NLK) is a multifunctional protein that stimulates cell growth and migration, together with its receptor autocrine motility factor receptor (AMFR, also called gp78). We investigated expression of NLK and AMFR/gp78 during cartilage development in vivo and in cultured articular chondrocytes in vitro, and found the pair associates with chondrocyte proliferation and differentiation. While applied to isolated articular chondrocytes, NLK promotes cell proliferation and secretion of type II collagen, a marker of proliferating chondrocytes. Further work demonstrates that NLK up regulates pAKT and pSmad2/3, but down regulates pSmad1/5. In animals, NLK treatment also promotes chondrocyte proliferation while inhibits terminal differentiation, leading to expanded proliferating zone but decreased prehypertrophic and hypertrophic zones in the growth plate region. NLK is therefore a candidate factor that can be applied in the treatment of cartilage defects.

A Tissue-Engineered Chondrocyte Cell Sheet Induces Extracellular Matrix Modification to Enhance Ventricular Biomechanics and Attenuate Myocardial Stiffness in Ischemic Cardiomyopathy

There exists a substantial body of work describing cardiac support devices to mechanically support the left ventricle (LV); however, these devices lack biological effects. To remedy this, we implemented a cell sheet engineering approach utilizing chondrocytes, which in their natural environment produce a relatively elastic extracellular matrix (ECM) for a cushioning effect. Therefore, we hypothesized that a chondrocyte cell sheet applied to infarcted and borderzone myocardium will biologically enhance the ventricular ECM and increase elasticity to augment cardiac function in a model of ischemic cardiomyopathy (ICM). Primary articular cartilage chondrocytes of Wistar rats were isolated and cultured on temperature-responsive culture dishes to generate cell sheets. A rodent ICM model was created by ligating the left anterior descending coronary artery. Rats were divided into two groups: cell sheet transplantation (1.0 × 10(7) cells/dish) and no treatment. The cell sheet was placed onto the surface of the heart covering the infarct and borderzone areas. At 4 weeks following treatment, the decreased fibrotic extension and increased elastic microfiber networks in the infarct and borderzone areas correlated with this technology's potential to stimulate ECM formation. The enhanced ventricular elasticity was further confirmed by the axial stretch test, which revealed that the cell sheet tended to attenuate tensile modulus, a parameter of stiffness. This translated to increased wall thickness in the infarct area, decreased LV volume, wall stress, mass, and improvement of LV function. Thus, the chondrocyte cell sheet strengthens the ventricular biomechanical properties by inducing the formation of elastic microfiber networks in ICM, resulting in attenuated myocardial stiffness and improved myocardial function.

Osteonecrosis of the femoral head: treatment with ancillary growth factors

Osteonecrosis (ON) of the femoral head, also known as avascular necrosis (AVN) of the femoral head, is a progressive disease that predominantly affects younger patients. During early stage of ON, decompression of the femoral head has been commonly used to improve pain. The decompression has been augmented with nonvascularized or vascularized bone grafts, mesenchymal stems cells, and growth factors. The use of adjuvant growth factors to supplement the core decompression has mainly been limited to animal models in an attempt to regenerate the necrotic lesion of ON. Factors utilized include bone morphogenetic proteins, vascular endothelial growth factors, hepatocyte growth factors, fibroblast growth factors, granulocyte colony-stimulating factors, and stem cells factors. In animal models, the use of these factors has been shown to increase bone formation and angiogenesis. Although promising, the use of these growth factors and cell-based therapies clinically remains limited.

Association between VEGF -634G/C polymorphism and osteonecrosis of the femoral head susceptibility: a meta analysis

BACKGROUND

VEGF plays an important role in bone formation and repair. However, the effects of VEGF -634G/C polymorphisms on the pathogenesis of osteonecrosis of the femoral head (ONFH) were not conclusive. Our research was aimed to further analyze the association of VEGF -634G/C polymorphism with ONFH risk.

METHODS

The relevant articles were searched in PubMed, Elsevier, EMBASE, Web of Science and Chinese National Knowledge Infrastructure (CNKI) database. And a total of 692 cases and 875 controls were included. Pooled odds ratios (ORs) with 95% confidence intervals (CIs) were calculated to assess the correlation of VEGF -634G/C polymorphism and ONFH susceptibility. Chi-square based Q-statistic test was used to evaluate heterogeneity among the studies. The random-effects model or fixed-effects model was used depending on heterogeneity.

RESULTS

The sensitivity analysis and publication bias test indicated that our results were stable and credible. And the results suggested that VEGF -634G/C polymorphism was significantly related with increased risk for ONFH in Asian population (CC versus GG: OR=1.34, 95% CI=1.02-1.76).

CONCLUSION

The results indicated that VEGF -634G/C polymorphism might serve as genetic-susceptibility factor for ONFH.

Summary of the various treatments for osteonecrosis of the femoral head by mechanism: A review

Osteonecrosis of the femoral head (ONFH), also known as femoral head avascular necrosis, is a pathological state with a number of possible etiologies including steroid administration, alcohol abuse, traumatic events, vascular injury and idiopathic origins. ONFH causes a reduction in the vascular supply to the subchondral bone of the femoral head, which results in osteocyte death and the collapse of the articular surface. Treatments for ONFH include non-weight-bearing therapy, physical support, the promotion of osteoclast apoptosis, and the reduction of osteoblast and osteocyte apoptosis. The aim of the present review was to summarize the treatments for ONFH by mechanism from a new perspective and to describe the condition with an emphasis on treatment options.

2'-Epi-uscharin from the latex of Calotropis gigantea with HIF-1 inhibitory activity

Two stereoisomeric cardenolides, uscharin (1) and a new compound, 2′-epi-uscharin (2), were isolated from the latex of Calotropis gigantea (Asclepiadaceae). Their structures were fully elucidated based on their spectroscopic data, X-ray crystallographic data and chemical evidences. Both epimers (1 and 2) exhibited strong inhibitory effects on HIF-1 activity with different magnitudes. Compound 1 showed much more potent activity than 2 and digoxin, a well-known HIF-1 inhibitor. Discrepancy in potencies between 1 and 2 revealed the contribution of a β-configuration of 2′ hydroxyl moiety for HIF-1 inhibitory activity. This is a first report of the activity of HIF-1 inhibition of thiazoline ring-containing cardenolides.