Restoration of normal bone development by human homologue of collagen type II (COL2A1) gene in Col2a1 null mice

Prenatal amoxicillin exposure induces developmental toxicity in fetal mice and its characteristics

Amoxicillin, a widely used antibiotic in human and veterinary pharmaceuticals, is now considered as an "emerging contaminant" because it exists widespreadly in the environment and brings a series of adverse outcomes. Currently, systematic studies about the developmental toxicity of amoxicillin are still lacking. We explored the potential effects of amoxicillin exposure on pregnancy outcomes, maternal/fetal serum phenotypes, and fetal multiple organ development in mice, at different doses (75, 150, 300 mg/(kg·day)) during late-pregnancy, or at a dose of 300 mg/(kg·day) during different stages (mid-/late-pregnancy) and courses (single-/multi-course). Results showed that prenatal amoxicillin exposure (PAmE) had no significant influence on the body weights of dams, but it could inhibit the physical development and reduce the survival rate of fetuses, especially during the mid-pregnancy. Meanwhile, PAmE altered multiple maternal/fetal serum phenotypes, especially in fetuses. Fetal multi-organ function results showed that PAmE inhibited testicular/adrenal steroid synthesis, long bone/cartilage and hippocampal development, and enhanced ovarian steroid synthesis and hepatic glycogenesis/lipogenesis, and the order of severity might be gonad (testis, ovary) > liver > others. Further analysis found that PAmE-induced multi-organ developmental and functional alterations had differences in stages, courses and fetal gender, and the most obvious changes might be in high-dose, late-pregnancy and multi-course, but there was no typical rule of a dose-response relationship. In conclusion, this study confirmed that PAmE could cause abnormal development and multi-organ function alterations, which deepens our understanding of the risk of PAmE and provides an experimental basis for further exploration of the long-term harm.

Molecular mechanism of miR-203a targeting Runx2 to regulate thiram induced-chondrocyte development

Thiram is a kind of organic compound, which is commonly used for sterilization, insecticidal and deodorization in daily life. Its toxicology has been broadly studied. Recently, more and more microRNAs have been shown to participate in the regulation of cartilage development. However, the potential mechanism by which microRNA regulates chondrocyte growth is still unclear. Our experiments have demonstrated that thiram can hamper chondrocytes development and cause a significant increase in miR-203a content in vitro and in vivo trials. miR-203a mimic significantly decrease in mRNA and protein expression of Wnt4, Runx2, COL2A1, β-catenin and ALP, and significantly enhance the mRNA and protein levels of GSK-3β. It has been observed that overexpression of miR-203a hindered chondrocytes development. In addition, Runx2 was confirmed to be a direct target of miR-203a by dual luciferase report gene assay. Transfection of si-Runx2 into chondrocytes reveals that significant downregulation of genes is associated with cartilage development. Overall, these results suggest that overexpression of miR-203a inhibits the expression of Runx2. These findings are conducive to elucidate the mechanism of chondrocytes dysplasia induced by thiram and provide new research ideas for the toxicology of thiram.

Clinical-genetic analysis of selected genes involved in the development of the human skeleton in 128 Czech patients with suspected congenital skeletal abnormalities

BACKGROUND

Congenital skeletal abnormalities are a heterogeneous group of diseases most commonly associated with small or disproportionate growth, cranial and facial dysmorphisms, delayed bone maturation, etc. Nonetheless, no detailed genotype-phenotype correlation in patients with specific genetic variants is readily available. Ergo, this study focuses on the analysis of patient phenotypes with candidate variants in genes involved in bone growth as detected by molecular genetic analysis.

METHODS

In this study we used molecular genetic methods to analyse the ACAN, COL2A1, FGFR3, IGFALS, IGF1, IGF1R, GHR, NPR2, STAT5B and SHOX genes in 128 Czech children with suspected congenital skeletal abnormalities. Pathogenic variants and variants of unclear clinical significance were identified and we compared their frequency in this study cohort to the European non-Finnish population. Furthermore, a prediction tool was utilised to determine their possible impact on the final protein. All clinical patient data was obtained during pre-test genetic counselling.

RESULTS

Pathogenic variants were identified in the FGFR3, GHR, COL2A1 and SHOX genes in a total of six patients. Furthermore, we identified 23 variants with unclear clinical significance and high allelic frequency in this cohort of patients with skeletal abnormalities. Five of them have not yet been reported in the scientific literature.

CONCLUSION

Congenital skeletal abnormalities may lead to a number of musculoskeletal, neurological, cardiovascular problems. Knowledge of specific pathogenic variants may help us in therapeutic procedures.

Collagen- and hyaluronic acid-based hydrogels and their biomedical applications

Hydrogels have been widely investigated in biomedical fields due to their similar physical and biochemical properties to the extracellular matrix (ECM). Collagen and hyaluronic acid (HA) are the main components of the ECM in many tissues. As a result, hydrogels prepared from collagen and HA hold inherent advantages in mimicking the structure and function of the native ECM. Numerous studies have focused on the development of collagen and HA hydrogels and their biomedical applications. In this extensive review, we provide a summary and analysis of the sources, features, and modifications of collagen and HA. Specifically, we highlight the fabrication, properties, and potential biomedical applications as well as promising commercialization of hydrogels based on these two natural polymers.

Inner histopathologic changes and disproportionate zone volumes in foetal growth plates following gestational hypoglycaemia in rats

Maternal hypoglycaemia throughout gestation until gestation day (GD)20 delays foetal growth and skeletal development. While partially prevented by return to normoglycaemia after completed organogenesis (GD17), underlying mechanisms are not fully understood. Here, we investigated the pathogenesis of these changes and significance of maternal hypoglycaemia extending beyond organogenesis in non-diabetic rats. Pregnant rats received insulin-infusion until GD20 or GD17, with sacrifice on GD20. Hypoglycaemia throughout gestation increased maternal corticosterone levels, which correlated with foetal levels. Growth plates displayed central histopathologic changes comprising disrupted cellular organisation, hypertrophic chondrocytes, and decreased cellular density; expression of pro-angiogenic factors, HIF-1α and VEGF-A increased in surrounding areas. Disproportionately decreased growth plate zone volumes and lower expression of the structural protein MATN-3 were seen, while bone ossification parameters were normal. Ending maternal/foetal hypoglycaemia on GD17 reduced incidence and severity of histopathologic changes and with normal growth plate volume. Compromised foetal skeletal development following maternal hypoglycaemia throughout gestation is hypothesised to result from corticosterone-induced hypoxia in growth plates, where hypoxia disrupts chondrocyte maturation and growth plate structure and volume, decreasing long bone growth. Maternal/foetal hypoglycaemia lasting only until GD17 attenuated these changes, suggesting a pivotal role of glucose in growth plate development.

Mandibular Distraction in a Patient With Type II Collagenopathy

Kniest dysplasia is an extremely rare form of type II collagenopathy associated with cleft palate, micrognathia, shortened trunk, arms and legs, and club foot. The authors present a case of an infant with this disorder who also had micrognathia and respiratory distress for which mandibular distraction was performed. Although abnormal collagen and impaired endochondral ossification is noted with Kniest dysplasia, adequate bone formation was observed across the distraction gap. Nonetheless, despite stable mandibular advancement, failure to consider concomitant restrictive lung disease resulted in tracheostomy dependence. The authors demonstrate that while successful bone regeneration can be achieved through distraction of intramembranous facial bones, discretion must still be employed in patients with collagenopathies.

Multigenic Delineation of Lower Jaw Deformity in Triploid Atlantic Salmon (Salmo salar L.)

Lower jaw deformity (LJD) is a skeletal anomaly affecting farmed triploid Atlantic salmon (Salmo salar L.) which leads to considerable economic losses for industry and has animal welfare implications. The present study employed transcriptome analysis in parallel with real-time qPCR techniques to characterise for the first time the LJD condition in triploid Atlantic salmon juveniles using two independent sample sets: experimentally-sourced salmon (60 g) and commercially produced salmon (100 g). A total of eleven genes, some detected/identified through the transcriptome analysis (fbn2, gal and gphb5) and others previously determined to be related to skeletal physiology (alp, bmp4, col1a1, col2a1, fgf23, igf1, mmp13, ocn), were tested in the two independent sample sets. Gphb5, a recently discovered hormone, was significantly (P < 0.05) down-regulated in LJD affected fish in both sample sets, suggesting a possible hormonal involvement. In-situ hybridization detected gphb5 expression in oral epithelium, teeth and skin of the lower jaw. Col2a1 showed the same consistent significant (P < 0.05) down-regulation in LJD suggesting a possible cartilaginous impairment as a distinctive feature of the condition. Significant (P < 0.05) differential expression of other genes found in either one or the other sample set highlighted the possible effect of stage of development or condition progression on transcription and showed that anomalous bone development, likely driven by cartilage impairment, is more evident at larger fish sizes. The present study improved our understanding of LJD suggesting that a cartilage impairment likely underlies the condition and col2a1 may be a marker. In addition, the involvement of gphb5 urges further investigation of a hormonal role in LJD and skeletal physiology in general.

Developmental effects related to angiogenesis and osteogenic differentiation in Salmon larvae continuously exposed to dioxin-like 3,3',4,4'-tetrachlorobiphenyl (congener 77)

We have studied the effects of dioxin-like 3,3',4,4'-tetrachlorobiphenyl (PCB-77) on developmental effects related to angiogenesis and osteogenesis during early life-stages of salmon. Larvae were kept at 6°C and continuously exposed to waterborne PCB-77 (1 or 10 ng/L) initiated at the egg stage or 416-day degrees (dd) and throughout yolk-sac stage (716 dd) and for a total duration of 50 days (or 300 dd). Gene transcription analysis was performed on whole larvae total RNA at 548, 632, 674 and 716 dd using real-time PCR. Bone morphogenetic protein (bmp2 and bmp4), transforming growth factor β (TGF-β), estrogen receptors (ERα and ERβ), runx2, sox9 and collagen type 2 alpha 1 (col2a1) and vascular endothelial growth factor (VEGF) genes were studied. Effect on VEGF gene transcription was related to observation of heart rate, arrhythmia and anemia, demonstrating effects on vascular system development. Alizarine-red staining and quantification of ossified bone structures showed that PCB-77 produced concentration-dependent increases in the rate of osteogenic tissue formation. PCB-77 produced increases in col2a1 and runx2 transcription with subsequent induction of chondrogenesis and osteogenesis, respectively. The transcription of TGF-β gene was associated with ERβ transcription. Transcripts of AhR gene battery were differentially modulated by PCB-77 and these effects were dependent on concentration and larval age. Evidence of vascular system disruption by PCB-77 was observed as cardiac edema, anemia and arrhythmia in exposed individuals and as decreased level of VEGF gene transcription at early age. In general, our data indicate that PCB-77 produced developmental effects related to angiogenesis and osteogenic differentiation and disruption of vascular system development.

Bone growth retardation in mouse embryos expressing human collagenase 1

Cellular growth and differentiation are readouts of multiple signaling pathways from the intercellular and/or extracellular milieu. The extracellular matrix through the activation of cellular receptors transmits these signals. Therefore, extracellular matrix proteolysis could affect cell fate in a variety of biological events. However, the biological consequence of inadequate extracellular matrix degradation in vivo is not clear. We developed a mouse model expressing human collagenase (matrix metalloproteinase-1, MMP-1) under the control of Col2a1 promoter. The mice showed significant growth retardation during embryogenesis and a loss of the demarcation of zonal structure and columnar array of the cartilage. Immunological examination revealed increased degradation of type II collagen and upregulation of fibronectin and alpha(5)-integrin subunit in the transgenic cartilage. The resting zone and proliferating zone of the growth plate cartilage exhibited a simultaneous increase in bromodeoxyuridine (BrdU)-incorporated proliferating cells and terminal deoxynucleotidyl transferase-mediated X-dUTP nick-end labeling-positive apoptotic cells, respectively. Chondrocyte differentiation was not disturbed in the transgenic mice as evidenced by normal expression of the Ihh and type X collagen expression. These data demonstrate that type II collagen proteolysis is an important determinant for the skeletal outgrowth through modulation of chondrocyte survival and cartilagenous growth.

Skeletal abnormalities and ultrastructural changes of cartilage in transgenic mice expressing a collagen II gene (COL2A1) with a Cys for Arg-alpha1-519 substitution

OBJECTIVE

To examine the mechanism by which the Arg-->Cys 519 mutation causes the clinical phenotype employing transgenic mice that express the mutated human COL2A1.

METHODS

A DNA construct under the control of a COL2A1 specific promoter was prepared from genomic DNA isolated from fibroblasts from the proband with primary generalized osteoarthritis (OA) associated with a mild chondrodysplasia. Transgenic mice were obtained by injection of the constructs into pro-nuclei of fertilized eggs from the FVB/N inbred mouse strain. Transgenic mice harboring two alleles of the mutated human COL2A1 were examined for morphological abnormalities and for alterations of their skeletal development. Ultrastructural examination was performed to identify changes in the organization and density of collagen II fibrils in articular cartilage of the transgenic mice.

RESULTS

Transgenic mice harboring two alleles of the mutated human collagen gene were smaller than their normal littermates, had a cleft palate, and disorganized growth plate. Electron microscopy of articular cartilage showed a decreased density of collagen II fibrils and revealed chondrocytes with dilated Golgi cysternae.

CONCLUSIONS

Expression of a COL2A1 with an Arg-->Cys 519 substitution in transgenic mice causes retardation of skeletal development and ultrastructural alterations in articular cartilage with a profound reduction of the density of the collagen II fibrils in the tissue. These alterations may be responsible for the phenotype of precocious generalized OA and chondrodysplasia displayed by patients harboring this COL2A1 mutation.

Candidate genes for osteoporosis. Therapeutic implications

Osteoporosis, which afflicts 10 million Americans, is a complex disease characterized by decreased bone mass, microarchitectural deterioration of bone tissue, and an increase in fracture risk. Family and twin studies have established a genetic contribution to the etiology of osteoporosis. The biological candidate genes of osteoporosis can be ordered into 5 categories: (i) calcium homeostasis; (ii) hormonal dysfunction; (iii) osteoblast and osteoclast development and regulation; (vi) cartilage matrix metabolism; and (v) lipoprotein metabolism. In addition, genome-wide scans have identified a number of chromosomal regions harboring genes that influence bone mineral density. Moreover, the drug responses to various treatments of osteoporosis are reported to be modulated by DNA polymorphisms of the vitamin D receptor gene, the estrogen receptor 1 gene, and the transforming growth factor beta 1 gene. With the rapid advancement of the Human Genome Project and biotechnology, it will be possible to carry out parallel analyses of large numbers of candidate genes for osteoporosis and to calculate a patient's individual fracture risk in the context of specific environmental influences. This will eventually lead to more advanced diagnostic methods and more efficacious drugs targeting osteoporosis.

Premature vertebral endplate ossification and mild disc degeneration in mice after inactivation of one allele belonging to the Col2a1 gene for Type II collagen

STUDY DESIGN

Skeletal tissues of mice with an inactivated allele of the Col2a1 gene for Type II collagen ("heterozygous knockout") were studied.

OBJECTIVE

To determine whether a heterozygous inactivation of the Col2a1 gene has a role in the etiology of spine disorders such as disc degeneration.

SUMMARY OF BACKGROUND DATA

Mutations in the COL2A1, COL11A1, COL11A2, and COL9A2 genes have been linked to spine disorders. However, the mechanism by which genetic factors lead to disc degeneration still are largely unknown.

METHODS

Spine tissues were studied using radiograph analyses; conventional, quantitative, and polarized light microscopy; immunohistochemistry for the major extracellular components, and in situ hybridization for procollagens alpha1(I) and alpha1(II). Voluntary running activity also was monitored in half of the mice.

RESULTS

As the findings showed, 1-month-old heterozygous knockout mice had shorter limb bones, skulls, and spines, as well as thicker and more irregular vertebral endplates, which calcified earlier than in the control mice. They also had a lower concentration of glycosaminoglycans in the anulus fibrosus, in the endplates, and in the vertebral bone than the controls. These features in the heterozygous knockout mice were compensated by the age of 15 months. However, the long bones and skulls of the mature heterozygous mice remained shorter than those of the controls. Gene-deficient mice used the running wheel less. However, physical exercise did not induce any marked structural changes in the skeleton.

CONCLUSION

Mice with heterozygous knockout of Col2a1 show subtle early skeletal manifestations that bear some resemblance to those of human spine disorders.