Eui-Kyun Park

Polymorphisms in the Matrilin-1 Gene and Risk of Mandibular Prognathism in Koreans

Previous linkage analysis of an Asian population proposed possible candidate genes for mandibular prognathism, such as Matrilin-1 (cartilage matrix protein). To investigate the association between the single-nucleotide polymorphisms (SNPs) in Matrilin-1 and mandibular prognathism, we investigated three sequence variants (-158 T>C, 7987 G>A, 8572 C>T) in 164 mandibular prognathism patients and 132 control individuals with a normal occlusion. The results showed that the 8572 TT genotypes in Matrilin-1 showed increased risk of mandibular prognathism (OR = 9.28, 95% Cl = 1.19~197.57, P < 0.05), whereas the 7987 AA genotype showed a protective effect for mandibular prognathism (OR = 0.16, 95% Cl = 0.05~0.47, P < 0.05). Genotyping results showed that the Matrilin-1 polymorphism haplotype TGC (ht4; 158T, 7987G, and 8572C alleles) had a pronounced risk effect for mandibular prognathism compared with controls (OR = 5.16, 95% Cl = 2.03~13.93, P < 0.01). The results suggest that polymorphisms in Matrilin-1 could be used as a marker for genetic susceptibility to mandibular prognathism.

TGF‐β2 stimulates cranial suture closure through activation of the Erk‐MAPK pathway

Cranial sutures are important growth sites of the skull. During suture closure, the dura mater is one of the most important sources of various positive and negative regulatory signals. Previous results indicate that TGF‐β2 from dura mater strongly accelerates suture closure, however, its exact regulatory mechanism is still unclear. In this study, we confirmed that removal of dura mater in calvarial organ culture strongly accelerates sagittal suture closure and that this effect is further enhanced by TGF‐β2 treatment. TGF‐β2 stimulated cell proliferation in the MC3T3‐E1 cell line. Similarly, it stimulated the proliferation of cells in the sutural space in calvarial organ culture. Furthermore, TGF‐β2‐mediated enhanced cell proliferation and suture closure were almost completely inhibited by an Erk‐MAPK blocker, PD98059. These results indicate that TGF‐β2‐induced activation of Erk‐MAPK is an important signaling component that stimulates cell proliferation to enrich osteoprogenitor cells, thereby promoting their differentiation into osteoblasts to achieve a rapid calvarial bone expansion. J. Cell. Biochem. 98: 981–991, 2006.

Drug delivery from hydroxyapatite-coated titanium surfaces using biodegradable particle carriers.

The goal of this study was to develop a functional titanium (Ti) implant loaded with bioactive molecules using biodegradable polymeric particles as drug delivery carrier for dental applications. In this study, dexamethasone (DEX)-loaded poly(lactic-co-glycolic acid) (PLGA) particles were electrostatically immobilized on a Ti disc surface coated with hydroxyapatite (HA) nanocrystals using a low temperature high speed collision (LTHSC) method. Resorbable blasting media (RBM) Ti discs (S1), HA-Ti discs (S2), and HA-Ti discs treated with DEX-loaded PLGA particles (S3) were fabricated in this study as sample discs. To facilitate surface immobilization, PLGA particles were coated with polyethyleneimine (PEI) to produce a positive surface charge. This modification of PLGA particle surfaces, allowed DEX-loaded PLGA particles to be immobilized on negatively charged S2 disc surface. It was found that DEX-loaded PLGA particles were well dispersed and immobilized onto the S3 disc surfaces. Release profile studies of DEX from S3 discs in a 4-week immersion study indicated an initial burst release followed by sustained release. In vitro evaluation of bone marrow derived mesenchymal stem cells (BMSCs) cultured for 1 and 2 weeks on S3 discs showed greater BMSC differentiation than on S1 or S2 discs, demonstrating that this innovative delivery platform potently induced BMSC differentiation in vitro, and suggesting that it could be exploited for stem cell therapy purposes or to enhance in vivo osteogenesis. In addition, the results of the present study shows that various bioactive molecules that promote bone regeneration can be efficiently incorporated onto HA-Ti surfaces using biodegradable polymeric particles.

The role of lysyl oxidase-like 2 in the odontogenic differentiation of human dental pulp stem cells

Adult human dental pulp stem cells (hDPSCs) are a unique population of precursor cells those are isolated from postnatal dental pulp and have the ability to differentiate into a variety of cell types utilized for the formation of a reparative dentin-like complex. Using LC-MS/MS proteomics approaches, we identified the proteins secreted from the differentiating hDPSCs in mineralization media. Lysyl oxidase-like 2 (LOXL2) was identified as a protein that was down-regulated in the hDPSCs that differentiate into odontoblast-like cells. The role of LOXL2 has not been studied in dental pulp stem cells. LOXL2 mRNA levels were reduced in differentiating hDPSCs, whereas the levels of other LOX family members including LOX, LOXL1, LOXL3, and LOXL4, are increased. The protein expression and secretion levels of LOXL2 were also decreased during odontogenic differentiation. Recombinant LOXL2 protein treatment to hDPSCs resulted in a dose-dependent decrease in the early differentiation and the mineralization accompanying with the lower levels of odontogenic markers such as DSPP, DMP-1 and ALP. These results suggest that LOXL2 has a negative effect on the differentiation of hDPSCs and blocking LOXL2 can promote the hDPSC differentiation to odontoblasts.

Reciprocal interactions of Fgf10/Fgfr2b modulate the mouse tongue epithelial differentiation

The molecular mechanisms for epithelial differentiation have been studied by observing skin development in embryogenesis, but the early signaling modulations involved in tongue epithelial differentiation are not completely understood. Based on the gene expression patterns of the Fgf signaling molecules and previous results from Fgf10 and Fgfr2b knockout mice, it was hypothesized that there would be fundamental signaling interactions through the epithelial Fgfr2b and its mesenchymal ligand Fgf10 to regulate tongue epithelium differentiation. To elucidate these reciprocal interactions in tongue epithelial differentiation, this study employed an in vitro tongue organ culture system with antisense-oligodeoxynucleotides (AS-ODNs) and recombinant protein-soaked bead implantation for the loss-of-function and gain-of-function studies. Functional analysis of Fgf signaling revealed precise reciprocal interactions, which showed that mesenchymal Fgf10 rather than Fgf7 modulates tongue epithelial differentiation via Fgfr2b in a temporal- and spatial-specific manner.

Polycan suppresses osteoclast differentiation and titanium particle-induced osteolysis in mice

Particle-induced osteolysis is a major issue, and it is most likely the result of enhanced osteoclast activation in the pathogenesis of various skeletal diseases. This study investigated whether the inhibitory effect that Polycan has on osteoclast differentiation can be used to treat osteolysis induced by titanium (Ti) particles. To this end, the effects of Polycan were examined in terms of the cytotoxicity, osteoclast differentiation, cytokine expression, and Ti-induced calvarial osteolysis. Polycan had no significant cytotoxic effects on bone marrow macrophages (BMMs) but instead increased BMM proliferation. High levels of interleukin (IL)-6, IL-12, and macrophage colony-stimulating factor (M-CSF) were expressed in BMM cells in the presence of Polycan, suggesting that Polycan drives the differentiation of BMMs into M1 macrophages. Polycan significantly inhibited osteoclast differentiation induced by M-CSF and the receptor activator of nuclear factor kappa-B ligand (RANKL). The expression levels of the osteoclast marker genes significantly decreased, and Polycan induced and maintained the expression of IL-12, which suppressed osteoclast differentiation. In contrast, the RANKL signaling pathway was not inhibited by Polycan. An in vivo calvarial osteolysis model revealed that Polycan significantly decreased the osteoclast numbers and suppressed osteolysis. Our results suggest that the natural compound Polycan is a good candidate for therapeutic intervention against enhanced osteoclast differentiation and Ti particle-induced osteolysis.

03-P080 Reciprocal Fgf signalling interactions modulate differentiation of mouse tongue epithelium

naling pathway. For this, we focused on Pea3/Ets (Pea3, Erm, Er81), a subfamily of Ets transcription factors, since it has been suggested that Pea3/Ets is a direct transcriptional target of Fgf signaling. We first checked that Pea3 and Erm are expressed in the midbrain and the hindbrain around stage10 of the chick embryos. We then obtained results that Pea3 and Erm expressions are regulated by Fgf-Ras/ERK signaling; Pea3/Erm were induced after misexpression of Fgf8 and repressed by misexpression of dominant-negative form of Ras. In order to examine function of Pea3/Erm in the isthmus, we constructed dominant-negative form of Pea3 (Pea3-DN) and misexpressed it in the mesencephalon and the metencephalon at st.9 chick embryos. Surprisingly, Shh was ectopically induced at Pea3DN expressing sites in the midbrain and hindbrain. Oculomotor neurons that differentiate in the ventral midbrain differentiated ectopically in the dorsal side of the midbrain. It is speculated that Fgf signaling is involved in not only caudorostral axis formation, but also ventro-dorsal axis formation of the midbrain by repressing Shh through Pea3/Ets transcription factors.