EPO could be regulated by HIF-1 and promote osteogenesis and accelerate bone repair

Comparison of the effects between catalase and superoxide dismutase on regulating macrophage inflammatory response and protecting osteogenic function of periodontal ligament cells

BACKGROUND

Reactive oxygen species (ROS) have been confirmed closely associated with the pathological process of periodontitis, but the specific roles played by different ROS types are still to be investigated. Catalase (CAT) and Superoxide dismutase (SOD) specifically eliminate hydrogen peroxide (H2O2) and superoxide anion (O2•-), respectively. We for the first time compare the effects and mechanisms of CAT and SOD in protecting periodontal ligament cells (PDLCs) against oxidative damage, reducing the expression of macrophage inflammatory factors, and preserving the osteogenic differentiation function of PDLCs by modulating the inflammatory environment.

METHODS

CAT or SOD in combination with lipopolysaccharide (LPS) were added to the culture medium of RAW 264.7 and PDLCs. The intracellular ROS level, lipid peroxidation and DNA damage were observed by confocal microscope. Inflammation levels were assessed by real-time quantitative polymerase chain reaction (RT-qPCR) and Western blot. A co-culture system of macrophages and PDLCs was established, and the osteogenic differentiation of PDLCs was evaluated by alkaline phosphatase staining, alizarin red S staining, RT-qPCR and Western blot. Finally, differentially expressed genes (DEGs) in CAT and SOD were detected by RNA sequencing and the biological functions and signaling pathways involved were analyzed.

RESULTS

CAT or SOD can effectively inhibit intracellular ROS levels, lipid peroxidation and DNA damage, as well as increase the levels of antioxidative molecules and decrease the levels of inflammatory factors. SOD increased the levels of antioxidative molecules more strongly, while CAT reduced inflammatory factors more effectively. The RNA sequencing results indicate that CAT exhibits stronger inhibitory effects on inflammation-related signaling pathways, which could account for the observed differences.

CONCLUSIONS

In this study, we observed differential antioxidant and anti-inflammatory effects between CAT and SOD, which may be associated with CAT's better inhibition of the activation of inflammatory pathways. Our study will provide scientific references for the future development of highly selective ROS- scavenging antioxidant drugs.

Nanoscale Systems for Local Activation of Hypoxia-Inducible Factor-1 Alpha: A New Approach in Diabetic Wound Management

Chronic wounds in diabetic patients experience significant clinical challenges due to compromised healing processes. Hypoxia-inducible factor-1 alpha (HIF-1α) is a critical regulator in the cellular response to hypoxia, enhancing angiogenesis and tissue restoration. Nevertheless, the cellular response to the developed chronic hypoxia within diabetes is impaired, likely due to the destabilization of HIF-1α via degradation by prolyl hydroxylase domain (PHD) enzymes. Researchers have extensively explored HIF-1α activation as a potential pathway for diabetic wound management, focusing mainly on deferoxamine (DFO) as a potent agent to stabilize HIF-1α. This review provides an update of the other recent pharmacological agents managing HIF-1α activation, including novel PHD inhibitors (roxadustat and daprodustat) and Von Hippel-Lindau protein (VHL) antagonists, which could be potential alternatives for the local treatment of diabetic wounds. Furthermore, it highlights how localized delivery via advanced nanostructures can enhance the efficacy of these novel therapies. Importantly, by addressing these points, the current review can offer a promising area for research. Given that, these novel drugs have minimal applications in diabetic wound healing, particularly in the context of local application through nanomaterials. This gap presents an exciting opportunity for further investigation, as combining these drugs with localized nanotechnology could avoid undesired systemic side effects and sustain drug release within wound site, offering a transformative platform for diabetes wound treatment.

Impact of hypoxia on alveolar bone dynamics and remodeling

Oxygen is a fundamental requirement for cellular metabolism. Hypoxia is a state of oxygen deprivation of the tissues. Cells develop numerous adaptive mechanisms to survive hypoxic insult. Alveolar bone is a unique structure that encases and protects the tooth. Literature reports that hypoxia, in all forms, impacts alveolar bone health. The hypoxia-inducible pathway appears to play a key role in mediating changes in alveolar bone metabolism. Embryonic hypoxia plays a vital role in craniofacial skeletal development. Further, hypoxia has been anticipated in the repair of extraction sockets. Alveolar bone cells respond distinctly to hypoxic conditions with both beneficial and detrimental effects. Studies have demonstrated enhanced alveolar bone resorption upon hypoxic stimuli. However, hypoxia has also been shown to have potential therapeutic effects on alveolar bone by triggering an angiogenic response. Additionally, the type, duration, and mode of hypoxia are critical in triggering varied responses in alveolar bone metabolism. The main objective of this review is to recapitulate the effects of different types of hypoxia on the tooth supporting apparatus and to analyze some of the presumptive mechanisms underlying hypoxia-induced changes in alveolar bone remodeling.

A Molecular Perspective on HIF-1α and Angiogenic Stimulator Networks and Their Role in Solid Tumors: An Update

Hypoxia-inducible factor-1α (HIF-1α) is a major transcriptional factor, which plays an important role in cellular reprogramming processes under hypoxic conditions, which facilitate solid tumors' progression. HIF-1α is directly involved in the regulation of the angiogenesis, metabolic reprogramming, and extracellular matrix remodeling of the tumor microenvironment. Therefore, an in-depth study on the role of HIF-1α in solid tumor malignancies is required to develop novel anti-cancer therapeutics. HIF-1α also plays a critical role in regulating growth factors, such as the vascular endothelial growth factor, fibroblast growth factor, and platelet-derived growth factor, in a network manner. Additionally, it plays a significant role in tumor progression and chemotherapy resistance by regulating a variety of angiogenic factors, including angiopoietin 1 and angiopoietin 2, matrix metalloproteinase, and erythropoietin, along with energy pathways. Therefore, this review attempts to provide comprehensive insight into the role of HIF-1α in the energy and angiogenesis pathways of solid tumors.

Role of HIF-1α in hypercoagulable state of COPD in rats

OBJECTIVE

To explore the role of HIF-1α in hypercoagulable state of COPD induced by lipopolysaccharide plus smoking in rats. It also has to explore the regulatory mechanism of HIF-1α-EPO/EDN-1/VEGF pathway by using its activator and inhibitor.

METHODS

60 Sprague-Dawley rats (SD rats) were randomly divided into healthy control group, COPD hypercoagulable control group, activator group, and inhibitor group with 15 rats in each group. The healthy control group was fed freely. The other groups were given smoke and lipopolysaccharide by tracheal instillation to establish the experimental animal model of COPD hypercoagulability. After successful modeling, each experimental group was given 0.9 % sodium chloride solution and corresponding drugs by intraperitoneal injection for 7 days. Lung function was detected after drug administration. Hematoxylin-eosin staining was used to observe the pathological changes of lung tissue. Enzyme-linked immunosorbent assay was used to detect serum D-D,F (1 + 2),IL-6,TNF-α. The mRNA expressions of HIF-1α, EPO, EDN-1, and VEGF were detected by RT-PCR. Western-Blot and IHC were used to detect the expression of HIF-1α, EPO, EDN-1, and VEGF in lung tissue of rats.

RESULTS

Compared with the healthy control group, rats in COPD hypercoagulable control group had COPD symptoms/signs, decreased lung function, increased the expression of serum D-D and F (1 + 2), increased the expression of inflammatory factors IL-6,TNF-α, and increased the expression of proteins HIF-1α, EPO, EDN-1 and VEGF. Compared with COPD hypercoagulable control group, lung function in activator group and inhibitor group had no obvious changes. The expressions of serum D-D,F (1 + 2),IL-6,TNF-α in activator group have increased noticeably. The expressions of proteins HIF-1α, EPO, EDN-1, and VEGF have further increased. Compared with COPD hypercoagulable control group, the expression of serum D-D, F (1 + 2), HIF-1α, EPO, EDN-1, and VEGF in the inhibitor group decreased.

CONCLUSION

HIF-1α-EPO/EDN-1/VEGF pathway plays an important role in the hypercoagulable state of COPD. HIF-1α inhibitor can improve airway inflammation and reduce hypercoagulability in COPD model rats.

HIF-1α and periodontitis: Novel insights linking host-environment interplay to periodontal phenotypes

Periodontitis, the sixth most prevalent epidemic disease globally, profoundly impacts oral aesthetics and masticatory functionality. Hypoxia-inducible factor-1α (HIF-1α), an oxygen-dependent transcriptional activator, has emerged as a pivotal regulator in periodontal tissue and alveolar bone metabolism, exerts critical functions in angiogenesis, erythropoiesis, energy metabolism, and cell fate determination. Numerous essential phenotypes regulated by HIF are intricately associated with bone metabolism in periodontal tissues. Extensive investigations have highlighted the central role of HIF and its downstream target genes and pathways in the coupling of angiogenesis and osteogenesis. Within this concise perspective, we comprehensively review the cellular phenotypic alterations and microenvironmental dynamics linking HIF to periodontitis. We analyze current research on the HIF pathway, elucidating its impact on bone repair and regeneration, while unraveling the involved cellular and molecular mechanisms. Furthermore, we briefly discuss the potential application of targeted interventions aimed at HIF in the field of bone tissue regeneration engineering. This review expands our biological understanding of the intricate relationship between the HIF gene and bone angiogenesis in periodontitis and offers valuable insights for the development of innovative therapies to expedite bone repair and regeneration.

Thrombotic Alterations under Perinatal Hypoxic Conditions: HIF and Other Hypoxic Markers

Hypoxia is considered to be a stressful physiological condition, which may occur during labor and the later stages of pregnancy as a result of, among other reasons, an aged placenta. Therefore, when gestation or labor is prolonged, low oxygen supply to the tissues may last for minutes, and newborns may present breathing problems and may require resuscitation maneuvers. As a result, poor oxygen supply to tissues and to circulating cells may last for longer periods of time, leading to life-threatening conditions. In contrast to the well-known platelet activation that occurs after reperfusion of the tissues due to an ischemia/reperfusion episode, platelet alterations in response to reduced oxygen exposition following labor have been less frequently investigated. Newborns overcome temporal hypoxic conditions by changing their organ functions or by adaptation of the intracellular molecular pathways. In the present review, we aim to analyze the main platelet modifications that appear at the protein level during hypoxia in order to highlight new platelet markers linked to complications arising from temporal hypoxic conditions during labor. Thus, we demonstrate that hypoxia modifies the expression and activity of hypoxic-response proteins (HRPs), including hypoxia-induced factor (HIF-1), endoplasmic reticulum oxidase 1 (Ero1), and carbonic anhydrase (CIX). Finally, we provide updates on research related to the regulation of platelet function due to HRP activation, as well as the role of HRPs in intracellular Ca2+ homeostasis.

The Role of HIF-1α in Bone Regeneration: A New Direction and Challenge in Bone Tissue Engineering

The process of repairing significant bone defects requires the recruitment of a considerable number of cells for osteogenesis-related activities, which implies the consumption of a substantial amount of oxygen and nutrients. Therefore, the limited supply of nutrients and oxygen at the defect site is a vital constraint that affects the regenerative effect, which is closely related to the degree of a well-established vascular network. Hypoxia-inducible factor (HIF-1α), which is an essential transcription factor activated in hypoxic environments, plays a vital role in vascular network construction. HIF-1α, which plays a central role in regulating cartilage and bone formation, induces vascular invasion and differentiation of osteoprogenitor cells to promote and maintain extracellular matrix production by mediating the adaptive response of cells to changes in oxygen levels. However, the application of HIF-1α in bone tissue engineering is still controversial. As such, clarifying the function of HIF-1α in regulating the bone regeneration process is one of the urgent issues that need to be addressed. This review provides insight into the mechanisms of HIF-1α action in bone regeneration and related recent advances. It also describes current strategies for applying hypoxia induction and hypoxia mimicry in bone tissue engineering, providing theoretical support for the use of HIF-1α in establishing a novel and feasible bone repair strategy in clinical settings.

Oxygen-Generating Biomaterials for Translational Bone Regenerative Engineering

Successful regeneration of critical-size defects remains one of the significant challenges in regenerative engineering. These large-scale bone defects are difficult to regenerate and are often reconstructed with matrices that do not provide adequate oxygen levels to stem cells involved in the regeneration process. Hypoxia-induced necrosis predominantly occurs in the center of large matrices since the host tissue's local vasculature fails to provide sufficient nutrients and oxygen. Indeed, utilizing oxygen-generating materials can overcome the central hypoxic region, induce tissue in-growth, and increase the quality of life for patients with extensive tissue damage. This article reviews recent advances in oxygen-generating biomaterials for translational bone regenerative engineering. We discussed different oxygen-releasing and delivery methods, fabrication methods for oxygen-releasing matrices, biology, oxygen's role in bone regeneration, and emerging new oxygen delivery methods that could potentially be used for bone regenerative engineering.

Conditioned medium of PC‑3 prostate cancer cells affects microRNA and mRNA profiles in mechanically strained osteoblasts

Bone is the main site of metastasis from prostate cancer; therefore, it is important to investigate the microRNAs (miRNAs) and mRNA associated with bone metastases from prostate cancer. Since an appropriate mechanical environment is important in the growth of bone, in the present study, the miRNA, mRNA, and long non-coding RNA (lncRNA) profiles of mechanically strained osteoblasts treated with conditioned medium (CM) from PC-3 prostate cancer cells were studied. MC3T3-E1 osteoblastic cells were treated with the CM of PC-3 prostate cancer cells and were simultaneously stimulated with a mechanical tensile strain of 2,500 µε at 0.5 Hz; the osteoblastic differentiation of the MC3T3-E1 cells was then assessed. In addition, the differential expression levels of mRNA, miRNA and lncRNA in MC3T3-E1 cells treated with the CM of PC-3 cells were screened, and some of the miRNAs and mRNAs were verified by reverse transcription-quantitative PCR (RT-qPCR). The signal molecules and signaling pathways associated with osteogenic differentiation were predicted by bioinformatics analysis. The CM of PC-3 prostate cancer cells suppressed osteoblastic differentiation of MC3T3-E1 cells. A total of seven upregulated miRNAs and 12 downregulated miRNAs were selected by sequencing and further verified using RT-qPCR, and related differentially expressed genes (11 upregulated and 12 downregulated genes) were also selected by sequencing and further verified using RT-qPCR; subsequently, according to the enrichment of differentially expressed genes in signaling pathways, nine signaling pathways involved in osteogenic differentiation were screened out. Furthermore, a functional mRNA-miRNA-lncRNA regulatory network was constructed. The differentially expressed miRNAs, mRNAs and lncRNAs may provide a novel signature in bone metastases of prostate cancer. Notably, some of the signaling pathways and related genes may be associated with pathological osteogenic differentiation caused by bone metastasis of prostate cancer.

Hypoxia-Inducible Factors Signaling in Osteogenesis and Skeletal Repair

Sufficient oxygen is required to maintain normal cellular and physiological function, such as a creature’s development, breeding, and homeostasis. Lately, some researchers have reported that both pathological hypoxia and environmental hypoxia might affect bone health. Adaptation to hypoxia is a pivotal cellular event in normal cell development and differentiation and in pathological settings such as ischemia. As central mediators of homeostasis, hypoxia-inducible transcription factors (HIFs) can allow cells to survive in a low-oxygen environment and are essential for the regulation of osteogenesis and skeletal repair. From this perspective, we summarized the role of HIF-1 and HIF-2 in signaling pathways implicated in bone development and skeletal repair and outlined the molecular mechanism of regulation of downstream growth factors and protein molecules such as VEGF, EPO, and so on. All of these present an opportunity for developing therapies for bone regeneration.

Erythropoietin Activates Autophagy to Regulate Apoptosis and Angiogenesis of Periodontal Ligament Stem Cells via the Akt/ERK1/2/BAD Signaling Pathway under Inflammatory Microenvironment

Background. Angiogenic tissue engineering is a vital problem waiting to be settled for periodontal regeneration. Erythropoietin, a multieffect cytokine, has been reported as a protective factor for cell fate. According to our previous study, erythropoietin has a significantly angiogenic effect on periodontal ligament stem cells. To further explore its potential effects and mechanism, we studied biological behaviors of periodontal ligament stem cells under inflammatory microenvironment induced by different concentrations (0, 10, 20, 50, and 100 ng/mL) of tumor necrosis factor-α (TNF-α) and examined how different concentrations (0, 5, 10, 20, and 50 IU/mL) of erythropoietin changed biological behaviors of periodontal ligament stem cells. Materials and Methods. Cell Counting Kit-8 was used for cell proliferation assay. Annexin V-PI-FITC was used for cell apoptosis through flow cytometry. Matrigel plug was adopted to measure the angiogenic capacity in vitro. RNA sequencing was used to detect the downstream signaling pathway. Quantitative real-time polymerase chain reaction was conducted to examine mRNA expression level. Western blot and immunofluorescence were applied to testify the protein expression level. Results. Periodontal ligament stem cells upregulated apoptosis and suppressed autophagy and angiogenesis under inflammatory microenvironment. Erythropoietin could activate autophagy to rescue apoptosis and angiogenesis levels of periodontal ligament stem cells through the Akt/Erk1/2/BAD signaling pathway under inflammatory microenvironment. Conclusions. Erythropoietin could protect periodontal ligament stem cells from inflammatory microenvironment, which provided a novel theory for periodontal regeneration.

Hypoxia mimetics restore bone biomineralisation in hyperglycaemic environments

Diabetic patients have an increased risk of fracture and an increased occurrence of impaired fracture healing. Diabetic and hyperglycaemic conditions have been shown to impair the cellular response to hypoxia, via an inhibited hypoxia inducible factor (HIF)-1α pathway. We investigated, using an in vitro hyperglycaemia bone tissue engineering model (and a multidisciplinary bone characterisation approach), the differing effects of glucose levels, hypoxia and chemicals known to stabilise HIF-1α (CoCl2 and DMOG) on bone formation. Hypoxia (1% O2) inhibited bone nodule formation and resulted in discrete biomineralisation as opposed to the mineralised extracellular collagen fibres found in normoxia (20% O2). Unlike hypoxia, the use of hypoxia mimetics did not prevent nodule formation in normal glucose level. Hyperglycaemic conditions (25 mM and 50 mM glucose) inhibited biomineralisation. Interestingly, both hypoxia mimetics (CoCl2 and DMOG) partly restored hyperglycaemia inhibited bone nodule formation. These results highlight the difference in osteoblast responses between hypoxia mimetics and actual hypoxia and suggests a role of HIF-1α stabilisation in bone biomineralisation that extends that of promoting neovascularisation, or other system effects associated with hypoxia and bone regeneration in vivo. This study demonstrates that targeting the HIF pathway may represent a promising strategy for bone regeneration in diabetic patients.

HIF signaling: A new propellant in bone regeneration

Bone tissue destruction leads to severe pain, physical flaws, and loss of motility. Bone repair using biocompatible and osteo-inductive scaffolds is regarded as a viable and potential therapeutic approach. However, for large-scale bone regeneration, oxygen and nutrient supply have become limiting factors. Further, a considerable need exists for recruited cell activities and blood vessel growth. Hypoxia-inducible factor (HIF) signaling pathways induced by hypoxia are involved in angiogenesis and osteogenesis. As an important transcription factor, HIF-1 functions by modulating vital genes, such as VEGF, PDK1, and EPO, and is a crucial regulator that influences the final fate of bone regeneration. Collectively, to achieve better osteogenesis results, the in-depth molecular mechanisms that underpin the links between materials, cells, and HIF signaling pathways must be determined. This review aimed to provide an in-depth insight into recent progress in HIF-regulated bone regeneration. Hypoxia and cellular oxygen-sensing mechanisms and their correlations with osteogenesis were determined, and recent studies on hypoxia-inducing and hypoxia-mimicking strategies were briefly described. Finally, the potential applications of HIF signaling in bone regeneration were highlighted. This review provides theoretical support for establishing a novel and viable bone repair strategy in the clinic by harnessing HIF signaling.

Recombinant human erythropoietin accelerated the proliferation of non-small cell lung cancer cell lines and reduced the expression of VEGF, HIF-1α, and PD-L1 under a simulated hypoxic environment in vitro

Background

As erythropoietin (EPO) has been used to treat anemia in cancer patients, negative controversy has continued. Unfortunately, its effects on non-small-cell lung carcinoma (NSCLC) cell lines are uncertain and the phenomenon of inducing immune escape of tumor cells remains to be explored. This study aimed to provide an important basis for the application of exogenous EPO in the treatment of tumor-associated anemia.

Methods

Cells were cultured in 1% O2, 5% CO2, and 94% N2 to simulate a hypoxic environment of the tumor. A549 cell line (lower expression EPOR) and NCI-H838 cell line (higher expression EPOR) were treated with 2 and 8 U/ml recombinant human EPO (rhEPO). CCK-8 method was used to determine the logarithmic growth phase of the cells and to detect cell proliferation. The expression levels of VEGF, HIF-1α, and PD-L1 were determined by western blot. One-way ANOVA was used for statistical analysis between groups, with p < 0.05 indicating a significant difference.

Results

Hypoxia itself could decrease the survival rate of NSCLC cells. Under the hypoxic condition, rhEPO induced tumor cells proliferation, especially in the NCI-H838 cell line, where 2 U/ml rhEPO increased the total number of surviving cells (Hypoxia + rhEPO 2 U/ml vs. Hypoxia, p < 0.05). Western blot analysis showed that hypoxia upregulated the expression of VEGF, HIF-1α, and PD-L1 in NSCLC cell lines (Normoxia vs. Hypoxia, p < 0.05), but may not be dependent on the expression levels of EPOR. RhEPO decreased the expression levels of VEGF and HIF-1α. In the A549 cell line, it depended on the concentration of rhEPO and was particularly obvious in HIF-1α (Hypoxia vs. Hypoxia + rhEPO 2 U/ml vs. Hypoxia + rhEPO 8 U/ml, p < 0.05). A low concentration of rhEPO may not reduce VEGF expression. In the NCI-H838 cell line, the effect of rhEPO on VEGF was more obvious, but it may be independent of rhEPO concentrations. The downregulation of PD-L1 expression by rhEPO was only presented in the A549 cell line and required higher rhEPO concentrations (Hypoxia + rhEPO 8 U/ml vs. Hypoxia&Hypoxia + rhEPO 2 U/ml, p < 0.05).

Conclusion

The effect of prolonged high concentrations of rhEPO under hypoxic conditions resulted in accelerated cells proliferation of non-small-cell lung cancer and was independent of EPOR expression levels on the cell lines surface. Hypoxia resulted in increased expression of VEGF, HIF-1α, and PD-L1 on the NSCLC cell lines. Under normoxic conditions, rhEPO did not affect the expression of VEGF, HIF-1α, and PD-L1; but under hypoxic conditions, the application of rhEPO reduced the expression of VEGF, HIF-1α, and PD-L1, producing an impact on the biological behavior of tumor cells.

Multi-functional osteoclasts in matrix-based tissue engineering bone

The repair of bone defects, especially for the large segment of bone defects, has always been an urgent problem in orthopedic clinic and attracted researchers' attention. Nowadays, the application of tissue engineering bone in the repair of bone defects has become the research hotspot. With the rapid development of tissue engineering, the novel and functional scaffold materials for bone repair have emerged. In this review, we have summarized the multi-functional roles of osteoclasts in bone remodeling. The development of matrix-based tissue engineering bone has laid a theoretical foundation for further investigation about the novel bone regeneration materials which could perform high bioactivity. From the point of view on preserving pre-osteoclasts and targeting mature osteoclasts, this review introduced the novel matrix-based tissue engineering bone based on osteoclasts in the field of bone tissue engineering, which provides a potential direction for the development of novel scaffold materials for the treatment of bone defects.

Impact of High-Altitude Hypoxia on Early Osseointegration With Bioactive Titanium

Nowadays, the bone osseointegration in different environments is comparable, but the mechanism is unclear. This study aimed to investigate the osseointegration of different bioactive titanium surfaces under normoxic or high-altitude hypoxic environments. Titanium implants were subjected to one of two surface treatments: (1) sanding, blasting, and acid etching to obtain a rough surface, or (2) extensive polishing to obtain a smooth surface. Changes in the morphology, proliferation, and protein expression of osteoblasts on the rough and smooth surfaces were examined, and bone formation was studied through western blotting and animal-based experiments. Our findings found that a hypoxic environment and rough titanium implant surface promoted the osteogenic differentiation of osteoblasts and activated the JAK1/STAT1/HIF-1α pathway in vitro. The animal study revealed that following implant insertion in tibia of rabbit, bone repair at high altitudes was slower than that at low altitudes (i.e., in plains) after 2weeks; however, bone formation did not differ significantly after 4weeks. The results of our study showed that: (1) The altitude hypoxia environment would affect the early osseointegration of titanium implants while titanium implants with rough surfaces can mitigate the effects of this hypoxic environment on osseointegration, (2) the mechanism may be related to the activation of JAK1/STAT1/HIF-1α pathway, and (3) our results suggest the osteogenesis of titanium implants, such as oral implants, is closely related to the oxygen environment. Clinical doctors, especially dentists, should pay attention to the influence of hypoxia on early osseointegration in patients with high altitude. For example, it is better to choose an implant system with rough implant surface in the oral cavity of patients with tooth loss at high altitude.

The Expression Regulatory Network in the Lung Tissue of Tibetan Pigs Provides Insight Into Hypoxia-Sensitive Pathways in High-Altitude Hypoxia

To adapt to a low-oxygen environment, Tibetan pigs have developed a series of unique characteristics and can transport oxygen more effectively; however, the regulation of the associated processes in high-altitude animals remains elusive. We performed mRNA-seq and miRNA-seq, and we constructed coexpression regulatory networks of the lung tissues of Tibetan and Landrace pigs. HBB, AGT, COL1A2, and EPHX1 were identified as major regulators of hypoxia-induced genes that regulate blood pressure and circulation, and they were enriched in pathways related to signal transduction and angiogenesis, such as HIF-1, PI3K-Akt, mTOR, and AMPK. HBB may promote the combination of hemoglobin and oxygen as well as angiogenesis for high-altitude adaptation in Tibetan pigs. The expression of MMP2 showed a similar tendency of alveolar septum thickness among the four groups. These results indicated that MMP2 activity may lead to widening of the alveolar wall and septum, alveolar structure damage, and collapse of alveolar space with remarkable fibrosis. These findings provide a perspective on hypoxia-adaptive genes in the lungs in addition to insights into potential candidate genes in Tibetan pigs for further research in the field of high-altitude adaptation.

Network Pharmacology-Based Investigation on the Anti-Osteoporosis Mechanism of Astragaloside IV

Astragaloside IV is the main active ingredient of Astragalus membranaceus. Studies have found that it can promote the proliferation of osteoblasts and can antagonize the apoptosis of mouse osteoblasts induced by hydrogen peroxide, but its molecular mechanism for the treatment of osteoporosis is still not clear. First, we used 3 online platforms: CTD, PharmMapper and SwissTargetPrediction to retrieve the targets of Astragaloside IV, and collected osteoporosis-related targets. Next, we used Cytoscape 3.7.2 software to construct a visual network diagram of PPI and further screened the key genes of Astragaloside IV in the treatment of osteoporosis using cluster analysis. Finally, after the receptor and ligand were docked, the binding activity was assessed by docking score. We obtained 102 overlapping targets of Astragaloside IV and osteoporosis. According to the node degree value in the PPI network, the top 10 genes were PIK3CA, MAPK1, SRC, STAT3, VEGFA, HSP90AA1, RELA, AKT1, IGF1, EGFR, of which SRC, AKT1, PIK3CA could bind stably to Astragaloside IV. KEGG pathway enrichment results showed that Astragaloside IV treated osteoporosis through 10 main pathways, including PI3K-Akt signaling pathway, FoxO signaling pathway, MAPK pathway, and so on. The classification of these pathways belongs to signal transduction, immune system, development and regeneration and endocrine system. Astragaloside IV is significantly related to several pathways involved in osteoporosis, such as PI3K-Akt, FoxO signaling pathway and MAPK pathway. SRC, AKT1, and PIK3CA can bind stably with Astragaloside IV, and they may be hub genes for the treatment of osteoporosis.

Characteristics of Tibetan pig lung tissue in response to a hypoxic environment on the Qinghai-Tibet Plateau

To adapt to the plateau environment, Tibetan pigs' lungs have developed a unique physiological mechanism during evolution. The vascular corrosion casting technique and scanning electron microscopy were used to understand arterial architecture. Blood physiological index and quantitative real-time PCR (qRT-PCR) were used for assessing whether the lung can regulate the body through anatomical, physiological and molecular mechanisms to adapt to hypoxic environments. Our study showed that the lungs of Tibetan pigs were heavier and wider and that the pulmonary arteries were thicker and branched and had a denser vascular network than those of Landrace pigs. The hemoglobin (HGB), mean corpuscular hemoglobin concentration (MCHC) values of high-altitude pigs were significantly higher than those of low-altitude pigs. The expression levels of HIF- 1α , EPAS1, EPO and VEGF, but not those of eNOSand EGLN1, were significantly higher in the lungs of high-altitude pigs than in those from pigs at a lower altitude ( P<0.05 ). These findings and a comprehensive analysis help elucidate the pulmonary mechanism of hypoxic adaptation in pigs.

Skeleton-vasculature chain reaction: a novel insight into the mystery of homeostasis

Angiogenesis and osteogenesis are coupled. However, the cellular and molecular regulation of these processes remains to be further investigated. Both tissues have recently been recognized as endocrine organs, which has stimulated research interest in the screening and functional identification of novel paracrine factors from both tissues. This review aims to elaborate on the novelty and significance of endocrine regulatory loops between bone and the vasculature. In addition, research progress related to the bone vasculature, vessel-related skeletal diseases, pathological conditions, and angiogenesis-targeted therapeutic strategies are also summarized. With respect to future perspectives, new techniques such as single-cell sequencing, which can be used to show the cellular diversity and plasticity of both tissues, are facilitating progress in this field. Moreover, extracellular vesicle-mediated nuclear acid communication deserves further investigation. In conclusion, a deeper understanding of the cellular and molecular regulation of angiogenesis and osteogenesis coupling may offer an opportunity to identify new therapeutic targets.

Hypoxia-Inducible Factor-1: A Potential Target to Treat Acute Lung Injury

Acute lung injury (ALI) is an acute hypoxic respiratory insufficiency caused by various intra- and extrapulmonary injury factors. Presently, excessive inflammation in the lung and the apoptosis of alveolar epithelial cells are considered to be the key factors in the pathogenesis of ALI. Hypoxia-inducible factor-1 (HIF-1) is an oxygen-dependent conversion activator that is closely related to the activity of reactive oxygen species (ROS). HIF-1 has been shown to play an important role in ALI and can be used as a potential therapeutic target for ALI. This manuscript will introduce the progress of HIF-1 in ALI and explore the feasibility of applying inhibitors of HIF-1 to ALI, which brings hope for the treatment of ALI.