Decorin inhibits the insulin-like growth factor I signaling in bone marrow mesenchymal stem cells of aged humans.

Aging impairs the IGF-I signaling of bone marrow mesenchymal stem cells (bmMSCs), but the mechanism is unclear. Here, we found that the ability to auto-phosphorylate IGF-I receptor (IGF-IR) in response to IGF-I was decreased in the bmMSCs of aged donors. Conversely, data showed that decorin (DCN) expression was prominently increased in aged bmMSCs, and that under IGF-I treatment, DCN knockdown in serum-starved aged bmMSCs potentiated their mitogenic activity and IGF-IR auto-phosphorylation, whereas DCN overexpression in serum-starved adult bmMSCs decreased both activities. Co-immunoprecipitation assays suggested that IGF-I and DCN bound to IGF-IR in a competitive manner. Online MethPrimer predicted 4 CpG islands (CGIs) in the introns of DCN gene. RT-qPCR and bisulfite sequencing showed that dimethyloxalylglycine, an inhibitor of DNA demethylation, increased DCN mRNA expression and CGI-I methylation in adult bmMSCs, whereas 5-aza-2'-deoxycytidine, a DNA methylation inhibitor, decreased DCN mRNA expression and CGI-I methylation in aged bmMSCs, and ultimately enhanced the proliferation of serum-starved aged bmMSCs under IGF-I stimulation. Thus, IGF-IR could be the prime target of aging in down-regulating the IGF-I signaling of bmMSCs, where DCN could be a critical mediator.

Decorin, a growth hormone-regulated protein in humans.

CONTEXT: Growth hormone (GH) stimulates connective tissue and muscle growth, an effect that is potentiated by testosterone. Decorin, a myokine and a connective tissue protein, stimulates connective tissue accretion and muscle hypertrophy. Whether GH and testosterone regulate decorin in humans is not known. OBJECTIVE: To determine whether decorin is stimulated by GH and testosterone. DESIGN: Randomized, placebo-controlled, double-blind study. PARTICIPANTS AND INTERVENTION: 96 recreationally trained athletes (63 men, 33 women) received 8 weeks of treatment followed by a 6-week washout period. Men received placebo, GH (2 mg/day), testosterone (250 mg/week) or combination. Women received either placebo or GH (2 mg/day). MAIN OUTCOME MEASURE: Serum decorin concentration. RESULTS: GH treatment significantly increased mean serum decorin concentration by 12.7 ± 4.2%; P < 0.01. There was a gender difference in the decorin response to GH, with greater increase in men than in women (∆ 16.5 ± 5.3%; P < 0.05 compared to ∆ 9.4 ± 6.5%; P = 0.16). Testosterone did not significantly change serum decorin. Combined GH and testosterone treatment increased mean decorin concentration by 19.5 ± 3.7% (P < 0.05), a change not significantly different from GH alone. CONCLUSION: GH significantly increases circulating decorin, an effect greater in men than in women. Decorin is not affected by testosterone. We conclude that GH positively regulates decorin in humans in a gender-dimorphic manner.

Identification of quercitrin as a potential therapeutic agent for periodontal applications.

BACKGROUND: Flavonoids are natural phenolic compounds with antioxidant, anti-inflammatory, and antimicrobial capacity. This study aims to investigate the effects of different flavonoids for potential use in periodontal applications. METHODS: Cultures of Staphylococcus epidermidis or primary human gingival fibroblasts (HGFs) were treated with different doses of chrysin, diosmetin, galangin, quercitrin, and taxifolin. The effect of these molecules was evaluated on S. epidermidis growth rate and HGF viability, gene expression, collagen production, reactive oxygen species (ROS) levels, wound healing, and production of matrix metalloproteinase (MMP)-1 and tissue inhibitor of MMP-1 (TIMP1). RESULTS: Among all the screened flavonoids, quercitrin showed the most promising biologic effects, in both HGFs and S. epidermidis. Thus, quercitrin was not toxic for HGFs; increased collagen IIIα1 and decorin levels; downregulated interleukin-6 messenger RNA levels; decreased the expression of profibrotic markers during wound healing; decreased ROS levels in basal and stimulated conditions; and decreased the MMP1/TIMP1 ratio. Quercitrin also decreased the bacterial growth rate. CONCLUSIONS: RESULTS suggest that quercitrin could contribute to protect and recover the integrity of gingival tissues, thus displaying a potential use for periodontal disease treatment or to functionalize dental implant abutments to improve soft tissue integration. Further studies are required to confirm the role of quercitrin in gingival tissues.

Lipopolysaccharide enhances decorin expression through the Toll-like receptor 4, myeloid differentiating factor 88, nuclear factor-kappa B, and mitogen-activated protein kinase pathways in odontoblast cells.

INTRODUCTION: Lipopolysaccharide (LPS) has been shown to regulate the function of odontoblasts. However, the molecular mechanisms of the effect of LPS on odontoblasts are poorly understood. Decorin (DCN), one of the major matrix proteoglycans, is known to affect the mineralization of teeth. In this study, we investigated whether LPS can regulate the expression of DCN in odontoblasts and determined the intracellular signaling pathways triggered by LPS. METHODS: The DCN messenger RNA and protein expression changes in mouse odontoblast-lineage cells (OLCs) were detected by real-time polymerase chain reaction (PCR) analysis and enzyme-linked immunosorbent assay (ELISA). Whether TLR4, myeloid differentiating factor 88 (MyD88), nuclear factor-kappa B (NF-κB), or mitogen-activated protein kinase (MAPK) pathways were involved in the LPS-induced DCN expression was determined by examined real-time PCR, ELISA, and luciferase activity assay. The activation of extracellular signal-regulated kinase (ERK), p38, and JNK in OLCs was measured by Western blot analysis. RESULTS: We found that the mouse OLCs expressed DCN. DCN messenger RNA was rapidly induced by LPS in a time- and dose-dependent manner. Pretreatment with a MyD88 inhibitory peptide, a TLR4 antibody, or a specific inhibitor for NF-κB or I Kappa B alpha (IκBα) significantly inhibited LPS-induced DCN expression. Moreover, the LPS-mediated increase in κB-luciferase activity in OLCs was suppressed by the overexpression of dominant negative mutants of TLR4, MyD88, and IκBα but not by a dominant negative mutant of TLR2. In addition, LPS stimulation activated the ERK, p38, and JNK MAPK pathways. The pretreatment of OLCs with specific inhibitors of the ERK, p38, and JNK MAPK pathways markedly offset the LPS-induced up-regulation of DCN expression. CONCLUSIONS: Our results show that LPS stimulation can up-regulate the gene expression of DCN via the TLR4, MyD88, NF-κB, and MAPK pathways in odontoblast cells.

Gene expression profiling concerning mineralization in human dental pulp cells treated with mineral trioxide aggregate.

INTRODUCTION: This study investigated changes in gene expressions related to mineralization when mineral trioxide aggregate (MTA) is applied in vitro to human dental pulp cells (HDPCs). METHODS: MTA in a Teflon tube (diameter 10 mm, height 2 mm) was applied to HDPCs. Empty tube-applied HDPCs were used as negative control. Total RNA was extracted at 6, 24, and 72 hours after MTA application for microarray analysis. The results were confirmed selectively by performing reverse transcriptase-polymerase chain reaction for genes that showed changes of more than 2-fold or less than half. RESULTS: Of the 24,546 genes, 109 genes were up-regulated more than 2-fold (eg, THBS1, VCAN, BHLHB2, FN1, COL10A1, TUFT1, and HMOX1), and 69 genes were down-regulated below 50% (eg, DCN, SOCS2, and IL8). CONCLUSIONS: These results suggest that rather than being a bio-inert material, MTA affects pulp cells in various ways. MTA appears to affect mineralization and induces slight inflammation and protective role against slight inflammation.