Differential Expression of Amelogenin, Enamelin and Ameloblastin in Rat Tooth Germ Development

Tooth development shows dynamic morphological changes from the stages of cap to hard tissue formation and is strictly regulated during development. In the present study, we compared expression and localization of 3 major enamel matrix proteins in rats: amelogenin, enamel and ameloblastin. DD-PCR and RT-PCR revealed differential expression of the major proteins from the cap stage to root stage. Immunofluorescence staining results indicated that amelogenin was not detected in either inner enamel epithelium or reduced enamel epithelium, but highly immunoreactive in preameloblasts and ameloblasts; in addition, it was sporadically expressed in preodontoblasts abutting preameloblasts. Ameloblastin expression was also observed in not only differentiated ameloblasts but also osteoblasts. Immunoreactivity to ameloblastin in ameloblasts was strong in Tomes' processes. Enamelin was exclusively localized along the entire newly formed and maturing enamel. Enamelin was largely localized in near Tomes' processes and enamel rods in maturing enamel. Alendronate treatment resulted in down-regulation of amelogenin and ameloblastin at both transcription and translation levels; whereas, enamelin expression was unchanged in response to the treatment. These results suggested that amelogenin, ameloblastin and enamelin might be implicated in cell differentiation, adhesion of ameloblasts to enamel and enamel crystallization during enamel matrix formation, respectively.

Effects of CoCl2 on Osteogenic Differentiation of Human Mesenchymal Stem Cells

OBJECTIVE: To investigate the effects of the hypoxia inducible factor-1 (HIF-1) activation-mimicking agent cobalt chloride (CoCl2) on the osteogenic differentiation of human mesenchymal stem cells (hMSCs) and elucidate the underlying molecular mechanisms. STUDY DESIGN: The dose and exposure periods for CoCl2 in hMSCs were optimized by cell viability assays. After confirmation of CoCl2-induced HIF-1alpha and vascular endothelial growth factor expression in these cells by RT-PCR, the effects of temporary preconditioning with CoCl2 on hMSC osteogenic differentiation were evaluated by RT-PCR analysis of osteogenic gene expression, an alkaline phosphatase (ALP) activity assay and by alizarin red S staining. RESULTS: Variable CoCl2 dosages (up to 500 microM) and exposure times (up to 7 days) on hMSC had little effect on hMSC survival. After CoCl2 treatment of hMSCs at 100 microM for 24 or 48 hours, followed by culture in osteogenic differentiating media, several osteogenic markers such as Runx-2, osteocalcin and osteopontin, bone sialoprotein mRNA expression level were found to be up-regulated. Moreover, ALP activity was increased in these treated cells in which an accelerated osteogenic capacity was also verified by alizarin red S staining. CONCLUSIONS: The osteogenic differentiation potential of hMSCs could be preserved and even enhanced by CoCl2 treatment.

Focal adhesion linker proteins expression of fibroblast related to adhesion in response to different transmucosal abutment surfaces

PURPOSE: To evaluate adherence of human gingival fibroblasts (HGFs) to transmucosal abutment of dental implant with different surface conditions with time and to investigate the roles of focal adhesion linker proteins (FALPs) involved in HGFs adhesion to abutment surfaces. MATERIALS AND METHODS: Morphologies of cultured HGFs on titanium and ceramic discs with different surface were observed by scanning electron microscopy. Biocompatibility and focal adhesion were evaluated by ultrasonic wave application and cell viability assay. FALPs expression levels were assessed by RT-PCR and western blot. RESULTS: There seemed to be little difference in biocompatibility and adhesion strength of HGFs depending on the surface conditions and materials. In all experimental groups, the number of cells remaining on the disc surface after ultrasonic wave application increased more than 2 times at 3 days after seeding compared to 1-day cultured cells and this continued until 7 days of culture. FALPs expression levels, especially of vinculin and paxillin, also increased in 5-day cultured cells compared to 1-day cultured fibroblasts on the disc surface. CONCLUSION: These results might suggest that the strength of adhesion of fibroblasts to transmucosal abutment surfaces increases with time and it seemed to be related to expressions of FALPs.

CsA Affects the Rat Submandibular Glands via Regulating the CypA Expression

The effects of the an immunosuppressive drug cyclosporine A (CsA), on the salivary gland are largely unknown, even though clinical trials for the stimulation of salivation using CsA have been attempted. Cyclophilin A (CypA) is known to be a binding protein for CsA. CypA has cell proliferation and tissue matrix change activities. In our present study, the presence of CypA in the gland and effects of CsA on CypA expression were investigated by immunohistochemistry, immunoblotting and RT-PCR analyses. CypA was immunohistochemically detected in various kinds of ducts in the submandibular glands of Sprague Dawley rats. The CypA mRNA level was highest at postnatal day 1 and gradually decreased in a time-dependent manner up to adulthood. The expression of CypA increased after a 10 day subcutaneous administration of CsA in postnatal day 1 rats. Surgical sections of the chorda-lingual nerve with impaired salivation showed no changes in CypA expression. A cell proliferation assay using PCNA anti-serum showed increased cell division following CsA treatment. These results suggest that CsA and CypA may act on ductal cells to regulate saliva composition rather than salivation levels.

Expression of Deleted in Colorectal Cancer in the Rat Trigeminal Ganglia

The deleted in colorectal cancer (DCC) protein mediates attractant responses to netrin during axonogenesis. In the rat trigeminal ganglia (TG), axons must extend toward and grow into the trigeminal nerve to innervate target tissues such as dental pulp. Our present study aimed to investigate the expression of DCC in the TG. Four developmental timepoints were assessed in the experiments: postnatal days 0, 7 and 10 and adulthood. RT-PCR and western blotting revealed that the expression of DCC mRNA and protein does not significantly change throughout development. Immunohistochemistry demonstrated that DCC expression in the TG was detectable in the perikarya region of the ganglion cells during development. Nerve injury at 3 and 5 days after the mandibular nerve had been cut did not induce altered expression of DCC mRNA in the TG. Moreover, DCC-positive cell bodies also showed similar immunoreactive patterns after a nerve cut injury. The results of this study suggest that DCC constitutively participates in an axonogenesis attractant in ways other than expression regulation.

Expression of Tissue Inhibitors of Metalloproteinases in Developing Rat Tooth Germs / 체질인류학회지

Tissue inhibitors of metalloproteinases (TIMPs) are a family of secreted molecules that were identified as natural inhibitors of matrix metalloproteinases (MMPs). Tooth histomorphogenesis and cytodifferentiation are accompanied by rapid changes in cellular organization and remodeling of the extracellular matrix, in which MMPs and TIMPs might be expected to play significant roles. This study examined the expression and localization of TIMP-1 and TIMP-2 during the molar development of rats. The expression patterns of TIMPs were determined from Sprague-Dawley rat pups including the developing molars using RT-PCR, western blot and immunofluorescent staining. Gene and protein quantification analyses showed that both TIMPs increased from the cap stage to the root stage tooth germs. In contrast, the immunofluorescent data showed that they were expressed slight differentially. TIMP-1 was strongly expressed in secretory ameloblasts and moderate immunoreactivity was observed along the basement membrane. TIMP-2 expression was also detected in the basement membrane. Although strong immunoreactivity was observed in the secretory ameloblasts and enamel matrix itself, differentiated odontoblasts showed weak reactivity. However, little reactivity for both TIMPs were detected in the cap stage tooth germs and surrounding tissues. These distinct temporospatial expression patterns of TIMPs suggest that the TIMPs may play a variety of roles including dental hard tissue formation during molar tooth development.

MMP-2 and MMP-9 are Differentially Involved in Molar Growth

Matrix metalloproteinases (MMPs) have been implicated in tissue development and re-modeling. Dynamic morphological changes of tooth germs reflect involvement of these enzymes during odontogenesis. The present study was performed to investigate expression and localization of MMP-2 and MMP-9, which have been known to have type IV collagenase activities, in rat tooth germs at different developmental stages. MMP-2 expression was increased gradually in the tooth germs from cap to crown staged germs at both transcription and translation levels. The localization of this molecule was detected in secretory ameloblasts and preameloblasts. The strong immunoreactivities were occasionally seen along the basement membrane between ameloblasts (or preameloblasts) and odontoblasts (preodontoblasts). However, weak reactivity was detected in odontoblasts and reduced enamel epithelium. The level of MMP-9 expression in the tooth germs was higher in cap stage than in crown staged germs at both transcription and translation levels. They were strongly expressed in both ameloblasts and odontoblasts. Even though reduced enamel epithelium after enamel formation and inner enamel epithelium at the cap stage exhibited weak reactivity, strong reactivity was detected in dental follicles and perifollicular tissues surrounding cap staged germs. These results suggested that MMP-2 may involve degradation of the basement membrane during hard tissue formation, whereas MMP-9 might be involved in remodeling of follicular tissues.

The Epithelial-Mesenchymal Transition During Tooth Root Development

Hertwig's epithelial root sheath (HERS) consists of bilayered cells derived from the inner and outer dental epithelia and plays important roles in tooth root formation as well as in the maintenance and regeneration of periodontal tissues. With regards to the fate of HERS, and although previous reports have suggested that this entails the formation of epithelial rests of Malassez, apoptosis or an epithelialmesenchymal transformation (EMT), it is unclear what changes occur in the epithelial cells in this structure. This study examined whether HERS cells undergo EMT using a keratin-14 (K14) cre:ROSA 26 transgenic reporter mouse. The K14 transgene is expressed by many epithelial tissues, including the oral epithelium and the enamel organ. A distinct K14 expression pattern was found in the continuous HERS bi-layer and the epithelial diaphragm were visualized by detecting the beta-galactosidase (lacZ) activity in 1 week postnatal mice. The 2 and 4 week old mice showed a fragmented HERS with cell aggregation along the root surface. However, some of the lacZ-positive dissociated cells along the root surface were not positive for pan-cytokeratin. These results suggest that the K14 transgene is a valuable marker of HERS. In addition, the current data suggest that some of the HERS cells may lose their epithelial properties after fragmentation and subsequently undergo EMT.

Feasibility of CD147 for an Eruption-Related Molecule during Rat Molar Development / 체질인류학회지

Understanding the genetic control of tooth eruption is one of the major issues in tooth development. Thus far, it is known that eruption-related molecules are secreted from follicular cells surrounding the germs and are related mainly to osteoclast formation. This study examined the involvement of CD147 and its downstream molecules in the eruption of rat developing molars using immunohistochemistry, RT-PCR and histomorphometry. CD147 was expressed differentially in the cap (3rd molar germs) and root formation (2nd molar germs) stages in tooth development. CD147 was localized immunohistochemically in the follicular cells and osteoclasts as well as in the ameloblasts and odontoblasts. The expression pattern of CD147 and mmps was investigated because CD147 is an mmp inducer. The expression of both mmp-2 and -9 increased at the root formation stage compared to that at the cap stage and increased in a stage dependent manner. However, the level of mmp-13 was not changed notably. The histomorphometrical study suggested that the number of osteoclasts that appeared occlusal to the molar germs for the resorption of alveolar bone increased significantly during development. These results suggest that CD147 may play an important role in the formation of the eruption pathway along with the mmps.

Effects of Chorda-lingual Denervation on NOS Expression in the Rat Submandibular Gland / 체질인류학회지

Nitric oxide (NO) gas has been recognized to diffuse readily across the membrane and bind directly to molecule (s) inside target cells. In the salivary gland, eNOS and nNOS are constitutively expressed. iNOS was also reported to express in neoplastic salivary tissues. Regarding the role of NO in the salivary gland, it has been suggested that it may control blood flow to the glands and furthermore involve in growth and development of the gland. The present study hypothesized that denervation of parasympathetic secretomotor fibers may lead to salivary secretion dysfunction, changing NOS expression. The gland weight on the denervated side significantly decreased from 3 days after the denervation, comparing the control (p.0.01). Some atrophic and hyperchromatic changes, but no inflammatory reactions were found for the whole period of the experiment. All three kinds of NOS were mainly expressed in the ducts of the gland in both the control and experimental sides. Immunoreactivities of nNOS and eNOS were not noticeably different from those of the control. However, iNOS was also detected in ducts in the normal submandibular gland by immunohistochemical staining. The iNOS expression increased more than 2 times at denervated side of the gland than the control. These results suggest that NOS isoforms, especially iNOS following chorda-lingual denervation may lead to matrix loss or cell death in the salivary gland.

A Case of Generalized Putular Psoriasis after Varicella Infection

Generalized pustular psoriasis is the most servere form of psoriasis. This disorder is characterized by pustular skin lesions general symptoms such as high fever, weakness and peripheral blood leukocytosis. We have experienced a case of generalized pustular psoriasis after suffering from chickenpox which was diagnosed by clinical symptoms and pathologic features from a skin biopsy. This 4-year-old male patient was managed by local and oral corticosteroid therapy with excellent outcome. A brief review of the related literature is also included.