Mastication markedly affects mandibular condylar cartilage growth, gene expression, and morphology

INTRODUCTION

Mandibular growth is believed to be strongly related to mastication. Furthermore, mandibular condylar cartilage is known to be derived from neural crest cells. We examined whether the degree of chewing affects condylar cartilage growth of the mandible.

METHODS

Mice were fed diets with varying hardness. Genes specific to neural crest-derived cells were measured by real-time polymerase chain reaction to compare the expression changes between the mandibular and tibia cartilages. The mandibular condylar cartilage was then evaluated histologically, and proliferation was evaluated using proliferating cell nuclear antigen. Immunostaining was conducted for osteopontin, type X collagen, and Musashi1, and real-time polymerase chain reaction was used to assess the expression levels of osteopontin and type X collagen.

RESULTS

Markers including P75, Wnt-1, Musashi1, and Nestin were upregulated in the mandibular condylar cartilage as compared with the tibial cartilage. Histologic assessment of the mandibular cartilage showed that the hypertrophic chondrocyte zone was statistically significantly thicker in mice fed a hard diet. Chondrocyte proliferation and Musashi1 expression were lower in mice fed a hard diet. After 4 weeks, numerous osteopontin and type X collagen-positive cells were observed in mice fed a mixed diet.

CONCLUSIONS

Mastication affects the balance between differentiation and proliferation in the mandibular condylar cartilage. This phenomenon might be attributed to the presence of neural crest-derived cells.

Expression and clinical significance of Wnt-1 and beta-catenin in nasopharyngeal carcinoma

BACKGROUND AND OBJECTIVE

As signaling molecule and key component of Wnt/beta-catenin signaling pathway respectively, Wnt-1 and beta-catenin are abnormally expressed in several malignancies and correlate with poor prognosis. This study was to investigate the expression and clinical significance of Wnt-1 and beta-catenin in nasopharyngeal carcinoma (NPC).

METHODS

The expression of Wnt-1 and beta-catenin in 111 specimens of NPC was detected by SP immunohistochemistry. Their correlations to relapse-free survival (RFS), metastasis-free survival (MFS) and progression-free survival (PFS) were analyzed.

RESULTS

The high expression of beta-catenin was observed in 64 (57.7%) of the 111 cases. Its high expression rate was significantly higher in advanced NPC than in early stage NPC (63.1% vs. 40.7%, p = 0.041). The RFS, MFS and PFS were lower in high beta-catenin expression group than in low beta-catenin expression group (p < 0.05). Cox regression analysis demonstrated that beta-catenin was related to poor prognosis of NPC patients. The high expression of Wnt-1 was observed in 68 (61.3%) of the 111 cases, but its expression had no effect on RFS, MFS and PFS (p > 0.05).

CONCLUSIONS

Wnt/beta-catenin signaling pathway may be activated abnormally in some NPC patients. beta-catenin may be a prognostic factor of NPC.

Porcupine-mediated lipid-modification regulates the activity and distribution of Wnt proteins in the chick neural tube

A long-term goal of developmental biology is to understand how morphogens establish gradients that promote proper tissue patterning. A number of reports describe the formation of the Wg (Wnt1) gradient in Drosophila and have shown that Porcupine, a predicted membrane-bound O-acyl transferase, is required for the correct distribution of Wg protein. The discovery that Wnts are palmitoylated on a conserved cysteine residue suggests that porcupine activity and Wnt palmitoylation are important for the generation of Wnt gradients. To establish the role of porcupine in Wnt gradient formation in vertebrates, we tested the role of porcupine/Wnt palmitoylation in human embryonic kidney 293T cells and in the chick neural tube. Our results lead us to conclude that: (1) vertebrate Wnt1 and Wnt3a possess at least one additional site for porcupine-mediated lipid-modification; (2)porcupine-mediated lipid-modification of Wnt proteins promotes their activity in 293T cells and in the chick neural tube; and (3) porcupine-mediated lipid-modification reduces the range of activity of Wnt1 and Wnt3a in the chick neural tube. These findings highlight the importance of porcupine-mediated lipid modifications in the formation of vertebrate Wnt activity gradients.

Syndecan-1 and Wingless-type protein-1 in human ameloblastomas

BACKGROUND

Aberrant Wingless type 1 glycoprotein (Wnt) pathway in ameloblastomas and a role of syndecan-1 (SDC1) in activating Wnt signalling were perspected. SDC1 shifting from epithelium to stroma was reported in invasive non-odontogenic neoplasms. The aim of this study was to reveal the role of SDC1 and Wnt1 in intraosseous ameloblastomas (IA(s)).

METHODS

SDC1 and Wnt1 expressions were investigated in 29 ameloblastoma subtypes and seven tooth buds.

RESULTS

SDC1 immunostaining strongly depicted stromal cells, extracellular matrix (ECM) and basement membranes of ameloblastomas. It also showed epithelial tumour cells in the acanthomatous and plexiform subtypes, and it often occurred in stellate reticulum cells and basal ameloblasts of tooth buds. Parallel Wnt1 expression occurred in ameloblastomatous epithelial cells, but it was common in basal cells of tooth buds too. Statistically, a significant correlation was found between the percentage of IA(s)-bearing SDC1-positive stromal cells and ECM and the percentage of IA(s)-bearing Wnt1-positive epithelial cells.

CONCLUSIONS

A role of SDC1 in stromal cells and ECM can be hypothesized as a critical factor for carcinogenesis and local invasiveness of IA(s).

Development of leiomyosarcoma of the uterus in MMTV-CR-1 transgenic mice

Overexpression of Cripto-1 (CR-1) in FVB/N mice using the MMTV-LTR promoter results in increased mammary tumourigenesis in these female transgenic mice (MMTV-CR-1). Here, we characterize uterine tumours that developed in 15/76 (19.7%) of MMTV-CR-1 female nulliparous or multiparous mice during 24 months of observation compared with 0/33 (0%) of FVB/N normal control mice observed during the same time period (p < 0.01). The uterine tumours collected from the MMTV-CR-1 mice were classified as leiomyosarcomas and found to express the CR-1 transgene by polymerase chain reaction analysis and immunohistochemistry. Detection by western blot analysis showed higher levels of phosphorylated (P) forms of c-src, Akt, GSK-3beta, and dephosphorylated (DP)-beta-catenin in lysates from MMTV-CR-1 uterine leiomyosarcomas in comparison with lysates from normal control FVB/N uteri. Immunostaining showed increased nuclear localization of beta-catenin in the MMTV-CR-1 uterine leiomyosarcomas. Increased immunostaining for CR-1 was detected in 9/13 (69.2%) cases of human leiomyosarcoma compared with staining in 3/15 (20%) human leiomyoma sections. Stronger immunostaining for P-src, P-Akt, P-GSK-3beta and increased nuclear localization of beta-catenin was also seen in human leiomyosarcomas in comparison with leiomyomas. Normal human uterine smooth muscle (UtSM) cells treated with exogenous soluble rhCR-1 showed increased levels of P-src, P-Akt, P-GSK-3beta and dephosphorylated (DP)-beta-catenin and increased proliferation (p < 0.05) and migration (p < 0.01) in comparison with untreated control UtSM cells. Inhibitors against c-src, Akt or beta-catenin, individually or in combination, significantly reduced CR-1-induced migration. These results suggest a role for CR-1 during uterine tumourigenesis either directly by activating c-src and Akt and/or via cross-talk with the canonical Wnt signalling pathway, as suggested by the increased expression of P-GSK-3beta, DP-beta-catenin, and increased nuclear localization of beta-catenin in human and MMTV-CR-1 mice leiomyosarcomas.