Immunohistochemical localization of tenascin-C in rat periodontal ligament with reference to alveolar bone remodeling

Downregulation of Yap1 during limb regeneration results in defective bone formation in axolotl

The Hippo pathway plays an imperative role in cellular processes such as differentiation, regeneration, cell migration, organ growth, apoptosis, and cell cycle. Transcription coregulator component of Hippo pathway, YAP1, promotes transcription of genes involved in cell proliferation, migration, differentiation, and suppressing apoptosis. However, its role in epimorphic regeneration has not been fully explored. The axolotl is a well-established model organism for developmental biology and regeneration studies. By exploiting its remarkable regenerative capacity, we investigated the role of Yap1 in the early blastema stage of limb regeneration. Depleting Yap1 using gene-specific morpholinos attenuated the competence of axolotl limb regeneration evident in bone formation defects. To explore the affected downstream pathways from Yap1 down-regulation, the gene expression profile was examined by employing LC-MS/MS technology. Based on the generated data, we provided a new layer of evidence on the putative roles of increased protease inhibition and immune system activities and altered ECM composition in diminished bone formation capacity during axolotl limb regeneration upon Yap1 deficiency. We believe that new insights into the roles of the Hippo pathway in complex structure regeneration were granted in this study.

Polarization of human gingival fibroblasts by Th1-, Th2-, Th17-, and Treg-derived cytokines

BACKGROUND AND OBJECTIVE

The purpose of this study was to evaluate whether gingival fibroblasts (GFs) can be differently activated and polarized into distinct functional subtypes by T-helper (Th) cytokines.

METHODS

Gingival fibroblasts were stimulated with interferon (IFN)-γ, interleukin (IL)-4, IL-17, and transforming growth factor (TGF)-β, representative cytokines of Th1, Th2, Th17, and regulatory T cells, respectively, and the gene expression profiles were analyzed by microarray. Differentially expressed genes (DEGs) in GFs stimulated by 4 cytokines were screened, and a gene ontology (GO) analysis of the DEGs was conducted. To confirm the reliability of the microarray results, the DEGs that showed the largest differences compared with non-stimulated GFs were further analyzed by RT-PCR. To evaluate the effect of polarization on GFs responses to lipopolysaccharide (LPS), GFs stimulated by 4 cytokines were further stimulated with Escherichia coli LPS and mRNA levels of several genes were analyzed using RT-PCR.

RESULTS

Differentially expressed genes by 4 Th cytokines were enriched in different GO terms, and the patterns of gene expression on GFs were shown functionally different. GFs stimulated with IFN-γ (GF(IFN-γ)) up-regulated the expression of chemokines (chemokine (C-X-C motif) ligand (CXCL)9, -10, -11, chemokine (C-C motif) ligand (CCL)8), molecules involved in antigen presentation, complement component 3 (C3), and other immune response-related molecules, whereas they down-regulated the expression of several types of collagen, extracellular matrix (ECM) components, and DNA replication and nuclear protein-related molecules. By contrast, GF(IL-4) up-regulated the expression of ECM components, cell adhesion molecules, and tissue development-related molecules and down-regulated the expression of chemokines (CXCL10 and CXCL8) and adaptive immune response-related molecules. GF(IL-17) up-regulated the expression of chemokines and other molecules for neutrophil infiltration and activation, the pro-inflammatory cytokine IL-6, and C3. GF(TGF-β) up-regulated the expression of cell growth-related molecules, ECM components, several types of collagen, and cell adhesion molecules and down-regulated the expression of molecules related to complement activation and bacterial recognition. GFs stimulated by 4 cytokines responded differently to LPS.

CONCLUSION

These results show that Th cytokines can polarize GFs into cells with functionally distinct features: immune-activating but tissue-destructive GF(IFN-γ), tissue-reparative, and immune-inhibiting GF(IL-4), highly pro-inflammatory GF(IL-17), and potent tissue-reparative GF(TGF-β).

Comparative proteomics analysis of teleost intermuscular bones and ribs provides insight into their development

BACKGROUND

Intermuscular bones (IBs) and ribs both are a part of skeletal system in teleosts, but with different developing process. The chemical composition of fish IBs and ribs as well as the underlying mechanism about their development have not been investigated. In the present study, histological structures showed that one bone cavity containing osteoclasts were existed in ribs, but not in IBs of Megalobrama amblycephala. We constructed the first proteomics map for fish bones including IBs and ribs, and identified the differentially expressed proteins between IBs and ribs through iTRAQ LC-MS/MS proteomic analysis.

RESULTS

The proteins extracted from IBs and ribs at 1- to 2-year old M. amblycephala were quantified 2,342 proteins, with 1,451 proteins annotated with GO annotation in biological processes, molecular function and cellular component. A number of bone related proteins as well as pathways were identified in the study. A total of 93 and 154 differently expressed proteins were identified in comparison groups of 1-IB-vs-1-Rib and 2-IB-vs-2-Rib, which indicated the obvious differences of chemical composition between these two bone tissues. The two proteins (vitronectin b precursor and matrix metalloproteinase-2) related to osteoclasts differentiation were significantly up-regulated in ribs compared with IBs (P < 0.05), which was in accordance with the results from histological structures. In comparison groups of 1-IB-vs-2-IB and 1-Rib-vs-2-Rib, 33 and 51 differently expressed proteins were identified and the function annotation results showed that these proteins were involved in regulating bone development and differentiation. Subsequently, 11 and 13 candidate proteins in comparison group of 1-IB-vs-1-Rib and 1-IB-vs-2-IB related to bone development were validated by MRM assays.

CONCLUSIONS

Our present study suggested the different key proteins involved in the composition of fish ribs and IBs as well as their growth development. These findings could provide important clues towards further understanding of fish skeletal system and the roles of proteins playing in regulating diverse biological processes in fish.

Tenascin C affects mineralization of SaOS2 osteoblast-like cells through matrix vesicles

Tenascin C (TNC) is an extracellular matrix glycoprotein involved in osteogenesis and bone mineralization. In a previous study, we identified TNC protein located in the matrix vesicles (MVs) of osteoblasts. MVs are determinant in the mineralization formation. Therefore, we hypothesize whether TNC can modulate osteoblast mineralization via MVs. In this study, we demonstrated that the expression level of TNC was increased with osteoblast differentiation of osteoblast-like SaOS2 cells, and down-regulation of TNC expression by siRNA could significantly inhibit SaOS2 differentiation toward osteoblasts and mineralization as evidenced by decreases in ALP activity, mineralized nodule formation, calcium deposition, and down-regulation of osteogenic marker genes ALP, and COL1A1. Furthermore, we validated that TNC located in the MVs of mineralized SaOS2 cells, and that down-regulation of TNC could decrease MVs mineralization ability in vitro, and the decrease of MVs mineralization ability was not associated with annexins. In conclusion, in this study, we extended the role of TNC during osteogenesis previous progresses, and that supported TNC as an important functional MVs component in modulating osteoblast mineralization.