The modulation of hypoxia-inducible factor-1α/plasminogen activator inhibitor-1 axis in human gingival fibroblasts stimulated with cyclosporine A

Pathogenesis of Enamel-Renal Syndrome Associated Gingival Fibromatosis: A Proteomic Approach

The enamel renal syndrome (ERS) is a rare disorder featured by amelogenesis imperfecta, gingival fibromatosis and nephrocalcinosis. ERS is caused by bi-allelic mutations in the secretory pathway pseudokinase FAM20A. How mutations in FAM20A may modify the gingival connective tissue homeostasis and cause fibromatosis is currently unknown. We here analyzed conditioned media of gingival fibroblasts (GFs) obtained from four unrelated ERS patients carrying distinct mutations and control subjects. Secretomic analysis identified 109 dysregulated proteins whose abundance had increased (69 proteins) or decreased (40 proteins) at least 1.5-fold compared to control GFs. Proteins over-represented were mainly involved in extracellular matrix organization, collagen fibril assembly, and biomineralization whereas those under-represented were extracellular matrix-associated proteins. More specifically, transforming growth factor-beta 2, a member of the TGFβ family involved in both mineralization and fibrosis was strongly increased in samples from GFs of ERS patients and so were various known targets of the TGFβ signaling pathway including Collagens, Matrix metallopeptidase 2 and Fibronectin. For the over-expressed proteins quantitative RT-PCR analysis showed increased transcript levels, suggesting increased synthesis and this was further confirmed at the tissue level. Additional immunohistochemical and western blot analyses showed activation and nuclear localization of the classical TGFβ effector phospho-Smad3 in both ERS gingival tissue and ERS GFs. Exposure of the mutant cells to TGFB1 further upregulated the expression of TGFβ targets suggesting that this pathway could be a central player in the pathogenesis of the ERS gingival fibromatosis. In conclusion our data strongly suggest that TGFβ -induced modifications of the extracellular matrix contribute to the pathogenesis of ERS. To our knowledge this is the first proteomic-based analysis of FAM20A-associated modifications.

Hypoxia stimulates collagen hydroxylation in gingival fibroblasts and periodontal ligament cells

BACKGROUND

Cellular responses to hypoxia regulate various biological events, including angiogenesis and extracellular matrix metabolism. Collagen is a major component of the extracellular matrix in periodontal tissues and its coordinated production is essential for tissue homeostasis. In this study, we investigated the effects of hypoxia on collagen production in human gingival fibroblasts (HGFs) and human periodontal ligament cells (HPDLs).

METHODS

HGFs and HPDLs were cultured under either normoxic (20% O₂ ) or hypoxic (1% O₂ ) conditions. Nuclear expression of hypoxia-inducible factor-1α (HIF-1α) was determined by western blotting. Peri-cellular expression of type I collagen was examined by immunocytochemistry analysis. Synthesis of type I collagen was evaluated by measuring the concentration of procollagen type I C-peptide (PIP) in culture supernatant using enzyme-linked immunosorbent assay. Expression of collagen hydroxylase enzymes prolyl 4-hydroxylase alpha polypeptide 1 (P4HA1) and 2-oxoglutarate 5-dioxygenase 2 (PLOD2) was determined by RT-qPCR and western blotting. The roles of these enzymes were analyzed using siRNA transfection.

RESULTS

Cultivation under hypoxic conditions stimulated type I collagen production via HIF-1α in both cell types. Interestingly, hypoxic conditions did not affect collagen 1a1 or 1a2 gene expression but upregulated that of P4HA1 and PLOD2. Additionally, suppressing P4HA1 significantly decreased the levels of hypoxia-induced procollagen type I C-peptide, a product of stable triple helical collagen, in the supernatant. In contrast, PLOD2 suppression decreased cross-linked collagen expression in the pericellular region.

CONCLUSION

Our results suggest that hypoxia activates collagen synthesis in HGFs and HPDLs by upregulating hydroxylases P4HA1 and PLOD2 in an HIF-1α-dependent manner.

The regulation of Oct4 in human gingival fibroblasts stimulated by cyclosporine A: Preliminary observations

Background/purpose

Oct4, a key transcription factor, could reprogram human somatic fibroblasts into embryonic stem cell-like pluripotent cells. The exact mechanism of cyclosporine A (CsA)-induced gingival overgrowth is still unclear. The aim of this study was to investigate the effects of CsA on the expression of Oct4 in cultured human gingival fibroblasts (HGFs) in vitro.

Materials and methods

The effects of CsA on HGFs were used to elucidate whether Oct4 expression could be induced by CsA by using quantitative real-time reverse transcription-polymerase chain reaction and western blot. Cell growth in CsA-treated HGFs with Oct4 lentiviral-mediated shRNAi knockdown was evaluated by tetrazolium bromide reduction assay.

Results

CsA was found to upregulate Oct4 transcript in a dose-dependent manner (p < 0.05). CsA also dose-dependently increased Oct4 protein expression (p < 0.05). The lentivirus expressing sh-Oct4 successfully prevented the CsA-induced Oct4 mRNA and protein in HGFs (p < 0.05). However, knockdown of Oct4 was insufficient to inhibit CsA-stimulated cell growth in HGFs. Furthermore, double knockdown with pluripotency-associated transcription factor Nanog showed that the down-regulation of Oct4/Nanog by lentiviral infection significantly inhibited CsA-stimulated cell growth (p < 0.05).

Conclusion

Taken together, CsA was first found to upregulate Oct4 mRNA and protein expression in HGFs. The silencing Oct4 could not suppress cell growth unless Nanog was repressed simultaneously.

Hypoxia and HIF-1α Regulate Collagen Production in Keloids

Keloids are reactive or spontaneous fibroproliferative dermal tumors characterized by the exaggerated and uncontrolled accumulation of extracellular collagen. Current approaches to mitigate keloidogenesis are largely procedural in nature. However, a better understanding of its biological drivers may lead to novel targeted treatments for keloids. Through whole-genome expression analysis, we found that an HIF-1α transcriptional footprint is preferentially upregulated (activation score = 2.024; P = 1.05E-19) in keloid fibroblasts compared with normal dermal fibroblasts. We verified that HIF-1α protein is more strongly expressed in keloid specimens compared with normal skin (P = 0.035) and that hypoxia (1% O₂) leads to increased collagen, especially in the extracellular compartment. Collagen levels were reduced uniformly by selective HIF-1α inhibitor CAY10585. Our results indicate that collagen secretion may be intimately linked to a hypoxic microenvironment within keloid tumors and that HIF-1α blockade could be a novel avenue of treatment for these tumors.

Upregulation of embryonic stem cell marker Nanog in human gingival fibroblasts stimulated with cyclosporine A: An in vitro study

Background/purpose

Gingival overgrowth is a common side effect of medication with the immunosuppressant cyclosporine A (CsA). This study proposed to verify whether Nanog, an embryonic stem cell marker, contributes to gingival overgrowth stimulated with CsA in human gingival fibroblasts (HGFs).

Materials and methods

The effect of CsA on HGFs was used to elucidate whether Nanog expression could be induced by CsA using quantitative real-time reverse transcription-polymerase chain reaction and Western blotting. Cell growth in CsA-treated HGFs with Nanog lentivirus-mediated short hairpin RNA interference knockdown was evaluated by tetrazolium bromide reduction assay.

Results

CsA upregulated Nanog transcript in HGFs in a dose-dependent manner (P < 0.05). CsA was also shown to increase Nanog protein expression in HGFs in a dose-dependent manner (P < 0.05). In addition, downregulation of Nanog by lentiviral infection significantly inhibited CsA-stimulated cell growth in HGFs (P < 0.05).

Conclusion

CsA upregulated Nanog expression and cell growth in HGFs, while silencing Nanog effectively reversed these phenomena. Nanog may act as a major switch in the pathogenesis of CsA-induced gingival overgrowth.

Effects of fibroblast growth factor-2 on cell proliferation of cementoblasts

Background/purpose

Fibroblast growth factor (FGF)-2 is known as a signaling molecule that induces tissue regeneration. Little is known about the effect of FGF-2 on cementoblasts for periodontal and periapical regeneration. The aim of this study was to investigate the effects of FGF-2 on murine immortalized cementoblast cell line (OCCM.30).

Materials and methods

Cell growth and proliferation was judged by using alamar blue reduction assay. Flow cytometry analysis was used to evaluate Stro-1 positive cells expression with or without FGF-2. Western blot was used to evaluate the expression of phosphorylated serine–threonine kinase Akt (p-Akt) and extracellular signal-regulated protein kinase (p-ERK) in cementoblasts.

Results

FGF-2 was found to increase cell growth in a dose-dependent manner (P < 0.05). The concentration of 10 ng/mL FGF-2 enhanced cell proliferation in a time-dependent manner (P < 0.05). In addition, 10 ng/mL FGF-2 significantly increased the number of Stro-1 positive cells in the first 24 hours (P < 0.05). Moreover, 10 ng/mL FGF-2 was found to upregulate p-Akt and p-ERK in a time-dependent manner (P < 0.05).

Conclusion

Taken together, FGF-2 could increase cementoblast growth, proliferation, and Stro-1 positive cells. These enhancements are associated with the upregulation of p-Akt and p-ERK expression. The application of FGF-2 may provide benefit for periodontal and periapical regeneration during the early phase of wound healing.

Upregulation of Slug expression by cyclosporine A contributes to the pathogenesis of gingival overgrowth

BACKGROUND/PURPOSE

Gingival overgrowth occurs as a side effect of systemic medication with immunosuppressant cyclosporine A (CsA). Slug, a master regulator of epithelial-mesenchymal transition, is dramatically upregulated in a variety of fibrotic diseases. The aim of this study is to investigate the role of epithelial-mesenchymal transition marker Slug in the pathogenesis of CsA-induced gingival overgrowth.

METHODS

Clinically healthy gingiva and CsA-induced gingival overgrowth specimens were analyzed by immunohistochemistry. The effect of CsA on normal human gingival fibroblasts (HGFs) was used to elucidate whether Slug expression could be affected by CsA by real-time reverse transcription-polymerase chain reaction and western blot. Cell proliferation in CsA-treated HGFs with Slug lentiviral-mediated shRNAi knockdown was evaluated by tetrazolium bromide reduction assay.

RESULTS

Slug expression was higher in CsA-induced gingival overgrowth specimens than in clinical healthy gingiva (p < 0.05). Slug expression was significantly higher in CsA-induced gingival overgrowth specimens with higher levels of inflammatory infiltrates (p < 0.05). CsA was found to increase Slug transcript and protein expression in HGFs in a dose-dependent manner (p < 0.05). In addition, knockdown of Slug significantly suppressed CsA-induced cell proliferation in HGFs (p < 0.05).

CONCLUSION

Taken together, upregulation of Slug in HGFs stimulated by CsA may play an important role in the pathogenesis of CsA-induced gingival overgrowth.

[Xenon: From rare gaz to doping product]

Doping is defined as the use of processes or substances to artificially increase physical or mental performance. Xenon is a noble gas used as an anesthetic and recently as a doping agent. Xenon is neuroprotective as an antagonist of NMDA glutamate receptors. Xenon stimulates the synthesis of erythropoietin (EPO) by increase of hypoxia inducible factor (HIF). Xenon would be a new doping product, maintaining doping methods ahead of detection.

Hypoxic regulation of plasminogen activator inhibitor-1 expression in human buccal mucosa fibroblasts stimulated with arecoline

BACKGROUND

Oral submucous fibrosis (OSF) is regarded as a pre-cancerous condition with fibrosis in oral subepithelial connective tissue. Hypoxia-inducible factor (HIF)-1α regulates a wide variety of profibrogenic genes, which are closely associated with tissue fibrosis. The aim of this study was to compare HIF-1α expression in normal buccal mucosa tissues and OSF specimens and further explore the potential mechanisms that may lead to the induction of HIF-1α expression.

METHOD

Twenty-five OSF specimens and six normal buccal mucosa were examined by immunohistochemistry. The expression of HIF-1α from fibroblasts cultured from OSF and normal buccal mucosa was measured by Western blot. Arecoline, a major areca nut alkaloid, was challenged to normal buccal mucosa fibroblasts (BMFs) to elucidate whether HIF-1α expression could affect by arecoline. In addition, the effects of arecoline on plasminogen activator inhibitor (PAI)-1 expression were evaluated in environmental hypoxia.

RESULTS

HIF-1α expression was significantly higher in OSF specimens and expressed mainly by fibroblasts, epithelial cells, and inflammatory cells. Fibroblasts derived from OSF were found to exhibit higher HIF-1α protein expression than BMFs (P < 0.05). Arecoline was found to upregulate HIF-1α protein in a dose-dependent manner (P < 0.05). Hypoxia increased arecoline-induced PAI-1 protein expression than normoxic conditions (P < 0.05).

CONCLUSION

These results suggest that HIF-1α expression is significantly upregulated in OSF tissues from areca quid chewers, implying a potential role as a biomarker for local tissue hypoxia. The activation of HIF-1α may promote fibrogenesis by an increase of PAI-1 expression and a subsequent elevation of extracellular matrix production in oral submucosa leading to fibrosis.