Identification of co-expression modules and pathways correlated with osteosarcoma and its metastasis.

BACKGROUND: Osteosarcoma is the most common bone tumor that occurs in children. METHODS: To identify co-expression modules and pathways correlated with osteosarcoma and its clinical characteristics, we performed weighted gene co-expression network analysis (WGCNA) on RNA-seq data of osteosarcoma with 52 samples. Then we performed pathway enrichment analysis on genes from significant modules. RESULTS: A total of 5471 genes were included in WGCNA, and 16 modules were identified. Module-trait analysis identified that a module involved in microtubule bundle formation, drug metabolism-cytochrome P450, and IL-17 signaling pathway was negatively correlated with osteosarcoma and positively correlated with metastasis; a module involved in DNA replication was positively correlated with osteosarcoma; a module involved in cell junction was positively correlated with metastasis; and a module involved in heparin binding negatively correlated with osteosarcoma. Moreover, expression levels in four of the top ten differentially expressed genes were validated in another independent dataset. CONCLUSIONS: Our analysis might provide insight for molecular mechanisms of osteosarcoma.

Investigating age­induced differentially expressed genes and potential molecular mechanisms in osteosarcoma based on integrated bioinformatics analysis.

Osteosarcoma (OS) is the most common primary bone malignancy. It predominantly occurs in adolescents, but can develop at any age. The age at diagnosis is a prognostic factor of OS, but the molecular basis of this remains unknown. The current study aimed to identify age­induced differentially expressed genes (DEGs) and potential molecular mechanisms that contribute to the different outcomes of patients with OS. Microarray data (GSE39058 and GSE39040) obtained from the Gene Expression Omnibus database and used to analyze age­induced DEGs to reveal molecular mechanism of OS among different age groups (<20 and >20 years old). Differentially expressed mRNAs (DEMs) were divided into up and downregulated DEMs (according to the expression fold change), then Gene Ontology function enrichment and Kyoto Encyclopedia of Genes and Genomes pathway analysis were performed. Furthermore, the interactions among proteins encoded by DEMs were integrated with prediction for microRNA­mRNA interactions to construct a regulatory network. The key subnetwork was extracted and Kaplan­Meier survival analysis for a key microRNA was performed. DEMs within the subnetwork were predominantly involved in 'ubiquitin protein ligase binding', 'response to growth factor', 'regulation of type I interferon production', 'response to decreased oxygen levels', 'voltage­gated potassium channel complex', 'synapse part', 'regulation of stem cell proliferation'. In summary, integrated bioinformatics was applied to analyze the potential molecular mechanisms leading to different outcomes of patients with OS among different age groups. The hub genes within the key subnetwork may have crucial roles in the different outcomes associated with age and require further analysis.

Galectin-3 deficiency protects lipopolysaccharide-induced chondrocytes injury via regulation of TLR4 and PPAR-γ-mediated NF-κB signaling pathway.

The aim of the present study was to identify the functional role of galectin-3 (Gal-3) in lipopolysaccharide (LPS)-induced injury in ATDC5 cells and to explore the probable molecular mechanisms. Here, we identified that LPS is sufficient to enhance the expression of Gal-3 in ATDC5 cells. In addition, repression of Gal-3 obviously impeded LPS-stimulated inflammation damage as exemplified by a reduction in the release of inflammatory mediators interleukin (IL)-1ß, IL-6, and tumor necrosis factor-α, as well as the production of nitric oxide and prostaglandin E2 (PGE2) concomitant with the downregulation of matrix metalloproteinases (MMP)-13 and MMP-3 expression in ATDC5 cells after LPS administration. Moreover, ablation of Gal-3 dramatically augmented cell ability and attenuated cell apoptosis accompanied by an increase in the expression of antiapoptotic protein Bcl-2 and a decrease in the expression of proapoptotic protein Bax and caspase-3 in ATDC5 cells subjected with LPS. Importantly, we observed that forced expression of TLR4 or blocked PPAR-γ with the antagonist GW9662 effectively abolished Gal-3 inhibition-mediated anti-inflammatory and antiapoptosis effects triggered by LPS. Mechanistically, depletion of Gal-3 prevents the NF-κB signaling pathway. Taken together, these findings indicated that the absence of Gal-3 exerted chondroprotective properties dependent on TLR4 and PPAR-γ-mediated NF-κB signaling, indicating that Gal-3 functions as a protector in the development and progression of osteoarthritis.

Retinoic acid retards fetal and hindlimb skeletal development asymmetrically in a retinoic acid-induced clubfoot model.

Retinoic acid (RA) has been shown to induce congenital clubfoot in animal models, but it is unknown whether the effect of RA on the formation of clubfoot in vivo results from generalized growth retardation or from the specific effects of hindlimb skeletal development. Our experimental research was based on a clubfoot model treated by maternal administration of RA (120, 130 or 140 mg/kg body weight) as an intragastric dose on embryonic day 10 (E10), and a control group was administered with an equivalent dose of solvent. Prenatal RA exposure reduced fetal body weight, length and skeletal ossification of the hindlimb compared with the control fetuses in a dose-dependent manner. The normal development curves indicated that the RA-exposed fetuses showed delayed increase in body weight and skeletal ossification development. However, there was no uniform effect on the skeletons of the hindlimb, not least retardation in ossification and induction malformation on the talus and calcaneus. Our results demonstrated that prenatal RA exposure had retardation effects on the developing hindlimb skeleton that was independent of those on the overall fetal growth. The normal skeletal ossification showed that the talus and calcaneus were poorly ossified and they were delayed by almost one day in the RA 120 mg/kg group. Therefore, during the susceptible stages, different regions of the limb bud responded differently to the teratogenic effects of RA.

Quantitative evaluation in vivo of the degree of differentiation of hindlimb cartilage in a rat clubfoot model.

The Limb Morphogenetic Differentiation Scoring system introduced by Neubert and Barrach in 1977 has been used in drug testing as a measure of the degree of cartilage growth inhibition especially for forelimb in vitro. There is no scoring system to quantify the degree of hindlimb bud cartilage differentiation in vivo. A total of 60 female Sprague-Dawley rats weighing 220-250 g were assigned at random to six control groups and six experimental groups on day 0 of pregnancy. The experimental groups were treated with all-trans-retinoic acid (ATRA). A new limb morphogenetic differentiation scoring system was developed and used to quantify the degree of development of the hindlimb buds from the fetuses at embryonic days E13 to E18. The differentiation of cartilages assessed by the new scoring system showed a statistically significant difference between the experimental group and the control group from E13 to E18 (T-test, p < 0.05). Cartilage growth (the proximodistal length) in the control group increased gradually from E14, reaching its peak at E17, but in the experimental group the growth at E13, E16, E17, and E18 was significantly shorter (p < 0.05). In conclusion, the new limb morphogenetic differentiation scoring system described here can be used to quantify the degree of inhibition of the hindlimb bud development by teratogenic drugs or materials, and morphogenetic differentiation in vivo.