Effects of hypoxia environment on osteonecrosis of the femoral head in Sprague-Dawley rats

Identification of microtubule-associated biomarker using machine learning methods in osteonecrosis of the femoral head and osteosarcoma

Background

This study aims to explore the microtubule-associated gene signatures and molecular processes shared by osteonecrosis of the femoral head (ONFH) and osteosarcoma (OS).

Methods

Datasets from the TARGET and GEO databases were subjected to bioinformatics analysis, including the functional enrichment analysis of genes shared by ONFH and OS. Prognostic genes were identified using univariate and multivariate Cox regression analyses to develop a risk score model for predicting overall survival and immune characteristics. Furthermore, LASSO and SVM-RFE algorithms identified biomarkers for ONFH, which were validated in OS. Function prediction, ceRNA network analysis, and gene-drug interaction network construction were subsequently conducted. Biomarker expression was then validated on clinical samples by using qPCR.

Results

A total of 14 microtubule-associated disease genes were detected in ONFH and OS. Subsequently, risk score model based on four genes was then created, revealing that patients with low-risk exhibited superior survival outcomes compared with those with high-risk. Notably, ONFH with low-risk profiles may manifest an antitumor immune microenvironment. Moreover, by utilizing LASSO and SVM-RFE algorithms, four diagnostic biomarkers were pinpointed, enabling effective discrimination between patients with ONFH and healthy individuals as well as between OS and normal tissues. Additionally, 21 drugs targeting these biomarkers were predicted, and a comprehensive ceRNA network comprising four mRNAs, 71 miRNAs, and 98 lncRNAs was established. The validation of biomarker expression in clinical samples through qPCR affirmed consistency with the results of bioinformatics analysis.

Conclusion

Microtubule-associated genes may play pivotal roles in OS and ONFH. Additionally, a prognostic model was constructed, and four genes were identified as potential biomarkers and therapeutic targets for both diseases.

LncAABR07053481 inhibits bone marrow mesenchymal stem cell apoptosis and promotes repair following steroid-induced avascular necrosis

The osteonecrotic area of steroid-induced avascular necrosis of the femoral head (SANFH) is a hypoxic microenvironment that leads to apoptosis of transplanted bone marrow mesenchymal stem cells (BMSCs). However, the underlying mechanism remains unclear. Here, we explore the mechanism of hypoxic-induced apoptosis of BMSCs, and use the mechanism to improve the transplantation efficacy of BMSCs. Our results show that the long non-coding RNA AABR07053481 (LncAABR07053481) is downregulated in BMSCs and closely related to the degree of hypoxia. Overexpression of LncAABR07053481 could increase the survival rate of BMSCs. Further exploration of the downstream target gene indicates that LncAABR07053481 acts as a molecular "sponge" of miR-664-2-5p to relieve the silencing effect of miR-664-2-5p on the target gene Notch1. Importantly, the survival rate of BMSCs overexpressing LncAABR07053481 is significantly improved after transplantation, and the repair effect of BMSCs in the osteonecrotic area is also improved. This study reveal the mechanism by which LncAABR07053481 inhibits hypoxia-induced apoptosis of BMSCs by regulating the miR-664-2-5p/Notch1 pathway and its therapeutic effect on SANFH.

A review of the skeletal effects of exposure to high altitude and potential mechanisms for hypobaric hypoxia-induced bone loss

Mountaineering and exposure to high altitude result in physiological adaptations to the reduced inspiratory oxygen availability. Acute mountain sickness (AMS), high altitude pulmonary edema (HAPE), and high altitude cerebral edema (HACE) are well-described harmful effects of exposure to high altitude. Common to AMS, HAPE, and HACE are distinct clinical signs and symptoms of impaired function. However, several studies have suggested that high altitude might result in a substantial bone loss, which usually does not produce any apparent symptoms. This review aims to provide a comprehensive overview of, and map current knowledge of the skeletal effects of hypobaric hypoxia and high altitude. PubMed and Embase were searched from inception to September 6, 2021, to identify studies investigating the skeletal effects of exposure to hypobaric hypoxia and high altitude. Three hundred sixty titles and abstracts were screened, and 20 full-text articles were included (16 in vivo studies and four real-world human studies). In rodents, simulated high altitude up to 2900 m did not result in any adverse skeletal effects. In contrast, studies exposing animals to very high altitude (3500-5500 m) reported substantial reductions in BMD, cortical morphology, and bone strength, as well as deteriorated trabecular microstructure. Detrimental microstructural effects were also reported in rats exposed to simulated extreme altitude (6000 m). Finally, real-world human studies in mountaineers suggested high altitude exposure reduced bone mineral density (BMD) and that the harmful skeletal effects of hypobaric hypoxia were not entirely recovered after 12 months. In conclusion, in vivo and real-world studies demonstrated high altitude exposure results in adverse skeletal effects. The underlying mechanism for hypobaric hypoxia-induced bone loss is not elucidated.

Integrating Transcriptome-Wide Association Study and mRNA Expression Profiling Identifies Novel Genes Associated With Osteonecrosis of the Femoral Head

Objective

This study aims to identify novel candidate genes associated with osteonecrosis of the femoral head (ONFH).

Methods

A transcriptome-wide association study (TWAS) was performed by integrating the genome-wide association study dataset of osteonecrosis (ON) in the UK Biobank with pre-computed mRNA expression reference weights of muscle skeleton (MS) and blood. The ON-associated genes identified by TWAS were further subjected to gene ontology (GO) analysis by the DAVID tool. Finally, a trans-omics comparative analysis of TWAS and genome-wide mRNA expression profiling was conducted to identify the common genes and the GO terms shared by both DNA-level TWAS and mRNA-level expression profile for ONFH.

Results

TWAS totally identified 564 genes that were with P_TWAS value <0.05 for MS and blood, such as CBX1 (P_TWAS = 0.0001 for MS), SRPK2 (P_TWAS = 0.0002 for blood), and MYO5A (P_TWAS = 0.0005 for blood). After comparing the genes detected by TWAS with the differentially expressed genes identified by mRNA expression profiling, we detected 59 overlapped genes, such as STEAP4 [P_TWAS = 0.0270, FC (fold change)_mRNA = 7.03], RABEP1 (P_TWAS = 0.010, FC_mRNA = 2.22), and MORC3 (P_TWAS = 0.0053, FC_mRNA = 2.92). The GO analysis of TWAS-identified genes discovered 53 GO terms for ON. Further comparing the GO results of TWAS and mRNA expression profiling identified four overlapped GO terms, including cysteine-type endopeptidase activity (P_TWAS = 0.0006, P_mRNA = 0.0227), extracellular space (P_TWAS = 0.0342, P_mRNA = 0.0012), protein binding (P_TWAS = 0.0112, P_mRNA = 0.0106), and ATP binding (P_TWAS = 0.0464, P_mRNA = 0.0033).

Conclusion

Several ONFH-associated genes and GO terms were identified by integrating TWAS and mRNA expression profiling. It provides novel clues to reveal the pathogenesis of ONFH.